CA2210792A1 - Cellular communication system with dynamically modified data transmission parameters - Google Patents

Abstract

An apparatus and process for improving the performance of a cellular communication system using direct sequence spread spectrum techniques. The apparatus and process enable dynamic modification of communication system parameters including PN code length, chipping rate and modulation technique for transmission of a data packet. Modification is based on proximity of the transmitter and receiver, transmitter and receiver capabilities, and other factors. The system evaluates tradeoffs between data transmission speed and communication range to improve system performance.

Description

W O 97/21294 PCT~US96/19336 Ti~le: CELLULAR COMMUNICATION SYSTEM WITH DYNAMICALLY MODIFIED
O DATA T~ANSMISSION PARAMt It~:l;
CROSS-REFERENCE TO RELATED APPLICATION
~ This application is a Continuation-in-Part of Serial No. 08t523,942, filed September 6, 1995, entitled CELLULAR COMMUNICATION SYSTEM WITH DYNAMICALLY MODIFIED
DATA TRANSMISSION PARAMETERS, the entirety of which is incorporated herein by reference.
TECHNICAL FIELD
This invention relates generally to the field of wireless data communication systems and, in particular, to a direct sequence spread spectrum cellular comm~",icd~ion system which dy"al":~-'ly modifies data l~a,lsl";ssion pa~d",etera to enhance system pe,ror",d"ce.
BACKGROVND ART
In recent years, the use of cellular communication systems having mobile terminals which communicate with a hardwired network, such as a local area network (LAN) and a wide area network ~\/VA~I), has become widespread. Retail stores and warehouses, for example, may use cellular commu"icdlions systems to track inventory and (t~ lenisl- stock. The lldnspo, l~lion industry may use such systems at large outdoor storage facilities to keep an accurate account of incoming and outgoing shi~ur"er,l~. In manufacturing facilities, such systems are useful fortracking parts, cGrll~JlEted products and defects.
A typical cellular commu"i~ "Dn system includes a number of fixed base stations interconnected by a cable medium to form a hardwired network. The hardwired network is often referred to as a system backbone. Also included in many cellular communication systems are i"te"ne.liale base stations which are not directly connected to the hardwired network. I"ler"~e.3idLe base stations, often referred to as ~ ~less base stations, increase the area within which base stations connected to the hardwired network can communicate with mobile terminals. Unless otherwise ill~ ed, the terrn "base station" will hen;:inarler refer to both base stations hardwired to the network and wireless base s~a~ions.
Associated with each base station is a geographic cell. A cell is a geographic area in which a base station has sumcient signal strength to lldns,,,il data to and receive data from a mobile terrninal with an acce,ui ' !e error rate. The error rate for transmitted data is defined as the ratio of the number of l, dl 1~ i data bits received in error to the total number of bits lldllsn,ilLed. It is economically inefficient to design a communications system with a "zero"
error rate. Rather, depending on the requ;,t:",enls of users of the system, an acceplable _ _ _ _ . ,, CA 022l0792 l997-07-l8 W O 97/212g4 PCT~US96/19336 error rate is determined. For example, an acce,utable error rate may be set at a maximum error correcting rate capabiiity of an error correcting code utilized by the system.
The shape of each cell is primarily determined by the type of antenna associaled with a given base station. For instance, base stations which communicate with mobile terminals 5 often have omnidirectional type dr,lennas which provide for generally circular shaped cells and allowfor a wide area of coverage. In many instances, however, the cell of a base station is not co", I Is'y sy""~l,ical because physical structures within the cell may partially block data signals emanating from the base station or create "dead spots" where no signals can pass. Further, the cell size may be decreased by machinery located in the vicinity of the 10 base station which generdles excessive noise levels that degrade a signal transmitted by the base station. Undesirable signals that i"Le,rer~ with the l,dr,s",;asion and reception of a lldns"i d signal are collectively referred to as noise signals. A useful quantitative measure of relative noise in a communication system is the signal-to-noise ratio (SNR). The SNR is the ratio of the amplitude of a desired signal at any given time to the amplitude of noise signals at that same time.
Generally, when a mobile terminal is powered up, it "registers" with a base station through which the mobile terminal can rll~illlaill wireless communication with the network. In order to register, the mobile terminal must be within the cell range of the base station and the base station must likewise be situated within the effective cell range of the mobile ter",;.,al. It is 20 generally not F~ ~ ' le to have one base station service a large area by itself. This is due to transmission power reslri~lions goveMed by the FC~ and the fact that the extra hardware needed to provide a mobile terminal with such a large cell range would add siy"irical,lly to the size and weight of the mobile terminal thereby making it less desirable to use. Thus, cellular communication systems generally have several base stations spaced apart such that 25 the c ~ /c cell area coverage of the base sldlions is sufficient to cover the entire area in which a mobile terminal may roam. As the location of the mobile terminal changes, the base station with which the mobile terminal was originally regisLered may fall outside of the geographic cell range of the mobile terminal. Therefore, the mobile terminal may "de-register" with the base station it was originally registered to and register with another base 30 station which is within its communication range.
When designing a cellular commu, . Iion system for a region, an approp, idle number of base stations must be selected and their locdlions detemmined to assure cell coverage for the region. Each additional base station i~,a~ases the cost of the communication system by the incremental cost of the base station itself and inst~ tion fees. Both the cost of the base 35 station and the installation costs are often great. When hardwiring a new base station to the W O 97/21294 PCTrUS96/19336 network both a data line and a power line must be provided. The data line allows the base station to lldlls,l~il and receive inror,lldlion from the system backbone while the power line provides continual power to support the operdlions of the base station. Although wireless ~ base stations do not require data lines since all data is comml."i . ~ted ~ lessly, they do require power. Howevers providin~ power lines to wireless base stations can often be difficult. This is especially true in the co"~,on situation where a wireless base station is situated in a large outdoor storage facility having a concrete foundation, such as areas near a shipyard or loading dock. Typically electrical outlets are not readily ~ccesc;l.!e in such areas and therefore power lines must be supplied to the w; ~less base station from the network or elsewhere. Power lines could be located on the surface of the concrete fo~" ,ddlion however this provides an undesirable obsta~!e that must be avoided by heavy loading vehicles typically found operating at such facilities. Consequently a trench is often created through the conulele in order to house the power lines. Unfortunately, providing such a trench adds a si!J"iric~nl amount of extra time and cost to the instP"~tion process. Another method of supplying power to wireless base stations could involve suspending power lines from power poles. I lolLEvcr, this method has been Found irnpl~usi~'e given the difficulty involved with erecting such power poles in the concrete fou"ddlion. As a result there is a strong need in the art for a manner of supplying power to a wireless base station that is not unduly bul densol "e or costly.
Wireless commu,.i~ ~ ~n systems such as those described above often involve spread spectrum (SS) technology. A SS communication system is one in which the transmitted frequency spectrum or bandwidth is much wider than absolutely necessary. Wideband frequency modulation (FM) is an example of an analog SS communicalion system. With regard to a digital SS commu--icdlion system the tldns""ssion bandwidth required by the 2~ baseband mod~ tion of a digital signal is expanded to a wider bandwidth by using a much faster switching rate than used to represent the original bit period. Operationally, prior to l,dr,s",;ssion each original data bit to be l,dns",illed is converted or coded to a sequence of "sub bits" often ,t:r~r,ed to as "chips" ~having logic values of zero or one) in accoldance with a conversion algorill"". The coding algorithm is usually termed a spreading function.
Depending on the sprt:ad;.,g function the original data bit may be converted to a sequence of five ten or more chips. The rate of trans",;ssion of chips by a l,dns",iller is defined as the"chi,~p;"g rate".
A SS communication system l,ans",ils chips at a wider signal bandwidth (broadband signal) and a lower signal amplitude than the corresponding original data would have been transmitted at b~ceb~nd. At the receiver a despreading function and a democll~tor are e" '~ ~ed to convert or decode the lldllall ,ilLed chip code sequence back to the originai data on baseb~l Id. The receiver, of course, must receive the broadband signal at the ll dnsl I ,iller chipping rate.
An advantage of a SS communication system is that the l ~,u, ~sentalion and communication of an original data bit as a sequence of chips over a wide bandwidth in lieu of ll~llallliUillg the original data bit over a narrow bandwidth generally results in a lower error rate at the receiver. This is especially true in transmission env;,on"lerlls characterized by noise having high amplitude and short duration i.e., "spike" noise. The probability of a receiver extracting and correctly interpreting a data bit represented by a l,dn:jr"illed sequence of chips interspersed with random, uncorrelated noise spikes is greater than the probability of the receiver extracting and correctly interpreting a trans" "ssion of single bits interspersed with such random noise spikes.
In essence a SS communicdlion system utilizes increased bandwidth and a coding scheme to reduce error rate vis-à-vis a conventional b~seb~nd system. The reduction in error rate results in an improved output SNR at the receiver. For any comm~",icalion system the dirre,t:nce between output SNR and input SNR is defined as the processing gain of the system. In a SS communication system the plucess;l,g gain of the system is the ratio of the l,d"~",;J~ion code rate to the original inror,,,c,lion bit rate. For ex2~""~1c, assume that the SS
coding scheme utilizes a sequence of ten chips to represent one original data bit. If the ten chips are transmitted at a chipping rate such that their collective duration is equal to a single bit period at baseband then the processing gain of the SS system is appru~i" .,;ely equal to ten. Communication range is determined by a fully prucessed SNR at a receiver. The fuliy processed SNR is the processi"g gain ~c5Or: led with SS comm~"i~ation techniquescombined with the received signal ~ ngll,.
The coding scher"e of a SS digital communication system utilizes a pseudo-randombinary sequence (PRSB). One type of a digital SS communication system is known as a direct sequence spread spectrum (DSSS) system. In a DSSS system coding is achieved by converting each original data bit (zero or one) to a predetermined repetitive pseudo noise (PN) code. A type of PN code is illustrated in Figure 1. For this example the digital data signal 110 is made up of a binary "1" bit and a "0" bit. A PN code 120 rep~ser,li-,g the digital data si~nal 110 is co",~u,i~ed of a sequence of ten sub bits or chips, namely, "1", "0" "1" "1"
"û", "1", "1", "1", "0", "1".
The digital data signal 110 is coded or spread by modulo 2 multiplying (e.g., via an "EXCLUSIVE NOR" (XNOR) function) of the digital data signal 110 with the PN code 120.
If the data bit is a "1" then the resulting spread data signal (PN coded signal) in digital forrn _ corresponds to the PN code 120. However if the data bit to be coded is a "0" then the spread data signal in digital form will correspond to a code 130. As can be seen the code 130 is the inverse of PN code 120. That is the PN code and its inverse are used to represent data bits "1" and 0" respectively.
A PN code length refers to a length of the coded sequence (the number of chips) for each original data bit. As noted above the PN code length effects the processing gain. A longer PN code yields a higher prucessi,)g gain which results in an illcreased commu"i~ alion range.
The PN code chipping rate refers to the rate at which the chips are t~ns",itled by a transmitter system. A receiver system must receive, demodulate and despr~ad the PN
1~ coded chip sequence at the chipping rate utilized by the l~nsn~iller system. At a higher chipping rate, the receiver system is allotted a smaller amount of time to receive, demodulate and despread the chip sequence. As the chipping rate increases so to will the error rate.
Thus, a higher chipping rate effectively reduces communication range. Converselydecreasing the chi,l.pi,lg rate increases communication range.
The spreading of a digital data signal by the PN code does not effect overall signal strength (or power~ the data being l,dns",illed or received. ~lowever, by spreading a signal the amplitude at any one point typically will be less then the original (non-spread) signal.
It will be c"~,uleNal~:d that increasing the PN code length or decreasing the ch:rp:.lg rate to achieve a longer comm~",icdlion range will result in a slower data trans",ission rate.
Correspondingly de~ a:,;"g the PN code length or increasing the chipping rate will increase data transmission rate at a price of reducing communication range.
Figure 1A schematically illustrates a transmitter system or assembly 100 of a DSSS
system. Original data bits 101 are input to the transmitter system 100. The l,dns",iller system includes a mod~ or 102 a spreading function 104 and a ll~llalllil filter 106. The modulator 102 modulates the data onto a carrier using for example a binary phase shift keying (BPSK) modnl~ion techl,: le The BPSK modulation tecl~n:que involves Irdns",;.li"g the carrier in-phase with the os~ il' ';ons of an oscillator or 180 degrees out-of-phase with the oscillator depending on whether the transmitted bit is a "0" or a "1". The spr~adi"g function 104 converts the modulated original data bits 101 into a PN coded chip sequence, also referred to as spread data. The PN coded chip sequence is transmitted via an a"lenna so as to represent a l,dns",illed PN coded sequence zs shown at 108.
Figure 1A also illustrates a receiver system or assel"l~ly, shown generally at 150. The receiver system 150 includes a receive filter 152 a despreading function 154 a bandpass filter 156 and a demodulator 158. The PN coded data 108 is received via an antenna and is filtered by the filter 152. Thereafter, the PN coded data is decoded by a PN code W O 97/21294 PCT~US96/19336 despreading function 154. The decoded data is then filtered and demodulated by the hlter 156 and the demodulator 158 respectively to reconstitute the original data bits 101. To receive the lldnsn,illed spread data, the receiver system 150 must be tuned to the same predetermined carrier frequency and be set to demodulate a BPSK signal using the same 5 predetermined PN code.
More sper;ri~lly to receive a SS t,d"s",;ision signal the receiver system must be tuned to the same frequency as the transmitter assembly to receive the data. Furthermore, the receiver assembly must use a demodulation technique which corresponds to the particular modulation technique used by the transmitter assembly (i.e. same PN code length same 10 chipping rate BPSK). Because mobile ten"i"als cornmunicate with a cGr"n,on base station each device in the cellular network must use the same carrier frequency and modul~tion techn,~ue.
A drawback associated with current cellular commu"icalion systems is that PN code parameters such as PN code length and chi,upill9 rate must be selected to provide 15 performance based on average communication range and average noise condilions. The data rate/range tradeoff leads to a cell size/throughput tradeoff in the commu~ ,ic~lion system.
The rate that each transr"ission occurs will limit the size of each cell. Thus it would be desi, to have a cellular communication system wherein PN code pa,d",eter modulation complexity and other lldnslllillillg and receiving pd,d",ete,~ could be dyllalll:- ~y modified 20 for each transn,ission based on dijldnce between the t,dns-"ill~r and receiver and noise conditions such that an improved data transl";ssion rate for that l.d"~",iss;on could be achieved thereby enhancing system performance.
SUMMARY OF THE INVENTION
The present invention includes an apparatus and a process for enhancing the 25 pe, ru", ldnce capabilities of a cellular commu" ion system utilizing DSSS techniques. The cellular communication system of the present invention includes a plurality of mobile terminals and a plurality of base stations. The base stations may be connected to a hardwired network backbone or serve as wireless base stations. Each base station can transmit and receive data in its respective cell. For a ~iven communication between a mobile 30 terminal and a base station the mobile terminal and the base station can adjust the PN code length and the chipping rate depending on communication condilions to increase the transmission rate while retaining an acceptable error rate. Moreover the system also provides that system components can adjust between other cellular communication system l,dn~""ssion pa,dm~le,~i such as between dirrerenl mod~ tion schemes andlor dirrel~nl W O 97/21294 PCT~US96/19336 transmitter power levels in conjunction with PN code adjusl"lents to further enhance the performance capabilities of the system.
Each base station and mobile terminal of the cellular communication system or network of the present invention includes a l,~ns",iller system and a receiver system. Furthermore each l,c,na,,,iller system and receiver system preferably is c~p~lc of respectively, transmitting or receiving PN coded signals formed with PN codes having different code lengths and chipping rates. Accordingly, as conditions of the wireless communication link between the base station and mobile terminal change, the present invention advantageously may adjust the PN code values to obtain the best available data rate possible for the current range and noise conditions thereby opli",i~il,g the pelrur"lance capabilities of the cellular communication system as a whole.
In a first illustrative example, when a mobile terminal and a base station are located in relativeiy close ,u~u~ ity to each other the system in acco, clance with the present invention may select and utilize a short PN code length (e.g. eleven chips per original data bit) resulting in a relatively fast data transmission rate. The short PN code length will result in a relatively low processing gain and a corresponding decreased communication range.
However because the base station and mobile temminal are close in proximity, the decreased communication range does not sig"iricanlly increase the error rate. If the mobile terminal moves away from the base station such that the terminal is outside a comm~",ic~lion range or cell when communicating using the short PN code length, the cellular communication system of the present invention lecoylli~es the changing condilions and the base station and mobile terminal suitably increase the Pl\l code length (e.g., to twenty-two chips per original data bit) to provide for a higher processing gain and thereby greater commu"icalions range.
The greater processing gain afforded by the longer PN code length reduces the data I,~"~n,;~ion rate. Despite the slower trans",;ssion rate between the mobile station terminal and the base station however, the overall exchange of data between the base station and all other mobile lelllli-lals will not be err~ ted unless this base station is operating close to full capacity. The~rur~: in most i, lalal ,ces the reduced trans" ,;ssion rate between a specific mobile terminal and a base station should have little effect on the communication system as a whole.
~ On the other hand when a mobile terminal and a base station are in need of a fast data ll~n~ sion rate and con.litions oll le~ pemmit the mobile unit and base station according - to the present invention may select a PN code having a relatively rapid ~I,ipp;"g rate value (e.g. 22 MHz). If the specl,~l bandwidth needs to be decreased due to, arnon~ other reasons excessive noise on closely situated frequency bands the mobile units and base CA 022l0792 l997-07-l8 W O 97/21294 PCT~US96tl9336 stations may decrease the chipping rate (e.g. to 11 MHz) to decrease the required lldnal~ sion bandwidth. In this case the data transmission rate is reduced co"",~ensurate with the narrower bandwidth.
In a second embodiment of this invention, each base station and mobile terminal of a 5 cellular comm~l~icdlion system or network may or may not be C~F- le of varying their ~pecIi~/e chlpplng rates and PN code lengths. Therefore a cellular network is provided in which PN code values are dynamically modified based on the r~r~hilities of the respective trans",ille,~ and receivers.
For example a base station capable of dynamically varying PN code values may be 10 communicating with a closely positioned mobile terminal which ll~llsr~,ils and l~ceive3 data only at a single, predetermined PN code length and chipping rate. Although a shorter PN
code length could be selected based on the close range, the mobile terminal may be incapable of supporting the shorter PN code length. Therefore, the PN code length sup,oo, led by the mobile terminal is utilized.
In another aspect of the present invention ad.liti,~ndl system modulation pd,d"leter~ may be altered by system cor"~onents to optimize the data transmission ratelrange tradeoff for each communication. For example in a situation where a high data l,~"s"~ission rate is required, a base station may select to use a high order modu! ~ion scheme, for example, 16 QAM 32 QAM, etc. In a situation where an increased cell size, lower l,ahs",iller power 20 and/or a lower data error rate is required the base station may select a lower order modulation scheme (e.g. BPSK QPSK etc.).
In yet another aspect of the present invention Irans",ission power is also sele~ Q by system components. Thus in a situation where a strong PN coded signal is neces~it~ted becauce the mobile terminal is relatively distant from the base station the present invention 25 may select to use a hi~h powerleveLto llc~n~ il the PN Goded siyna!. Ccr.versely i~ the battery of a mobile terminal is running low the present invention may select a lower power level to l,d"~n the PN coded signal in order to conserve the battery's energy. Also where the mobile terminal is located in very close plu~illlily to the base station the present invention may select to use an even lower power level to t, ansmil the PN coded signals back 30 and forth between the commu"icdlion devices so that the receivers of each device are not saturated.
In yet a further aspect of the present invention the system components may also select to Lldns,),il and receive PN coded signals using a variety of antennas having different gain and directivity ~;hald~ s. For e,~d",ple where a base station is positioned in the center 35 of a cell, the present invention may select to use an or"".li,c:clional antenna so that the base station may Llc"s",il and receive signals in all directions. In another example, where a base station is to communicate a longer .li .lance, the present invention may select to use a yagi directional antenna so that the base station may lldnsnlil a signal with a higher gain.
According to another feature of the invention, the wireless base sldlions may be sllpplied 5 power through a solar power system having solar panels, charging circuitry and a battery system. This obviates the need for l~ ~ncl ~ ~9 in order to bury power lines and/or suspending power lines as ~icclle7sed above in connection with conventional practices.
According to one aspect of the invention, a cellular comm-",icdlion system is provided which includes: a plurality of base stations coupled to a system bachL one, each of the base stations col",uriai"g a base station receiver system for receiving wireless commun;cdlions and a base station lra,)s",iller system for l~dns",illing wireless commu"i- "ons; and a plurality of mobile temminals each for communicating with the system backbone by way of at least one of the plurality of base stations, each of the plurality of mobile terminals having a mobile temminal l~dnall liller for lldns" ,;;li"g ~ less communications to the at least one of the 15 plurality of base stations and a mobile terminal receiver system for receiving w..~less communications from the at least one of the plurality of base stations; wherein, with respect to at least one of the mobile terminals, at least one of the mobile terminal transmitter system and the mobile terminal receiving system wirelessly communicates with the at least one of the plurality of base stations by selectively l,dns",itli"g or receiving data according to any of 20 a plurality of different PN code pa,d",atera.
According to another aspect of the present invention, a cellular comm~",icalion system is provided which indudes: a plurality of base stations co~pied to a system backbone, each of the base stations COIII,uliaillg a base station receiver system for receiving wireless communications and a base station l, ansl "iller system for transmitting wireless 25 communications; and a plurality of mobile terminals each for communicating with the system backbone by way of at least one of the plurality of ~ase stations, each of the plurality of mobile terminals having a mobile terminal transmitter for l,dns"~ilLi"g u:.~lesscommunications to the at least one of the plurality of base stations and a mobile terminal receiver system for receiving wireless commu,.i_dliorls from the at least one of the plurality 30 of base ~.lalions; whereinl with respect to at least one of the mobile terminals, at least one ~ of the mobile temminal t, dnSI "iller system and the mobile terminal receiving system wirelessly communicates with the at least one of the plurality of base stations by selectively Indns"lilli"g or receiving data accG,ding to any of a plurality of .lirrt:rt:nl trans,l,;ssion pdldllleler:> based on communications received from the mobile terminal.

CA 02210792 1997-07-lX

W O 97t21294 PCTAJS96/19336 According to still another aspect of the present invention a cellular communication system is provided which inciudes: a plurality of base stations coupled to a system backbone each of the base alalionâ coi"~ l isi"g a base station receiver system for receiving wireless communications and a base station transmitter system for 1~ dnsmilling w;. ~iesscommunications; and a plurality of mobile terl";.,als each for communicating with the system backbone by way of at least one of the plurality of base stations each of the plurality of mobile ter",;.~als having a mobile ter"lil,al ll;3nal"iller for lldnSII ,itli"g w;.~less commu"icalions to the at least one of the plurality of base ~l~lions and a mobile ter",inal receiver system for receiving wireless commu~ ~ic~lions from the at least one of the plurality of base stations; wherein, with respect to at least one of the mobile te",~;"als at least one of the mobile terminal l~d"s"~iller system and the mobile terminal receiving system wirelessly communicates with the at least one of the plurality of base stations by seledively transmitting or receiving data according to any of a plurality of different ll~nsn,iasion parameters; and wherein at least another one of the mobile terminals cannot vary any of its transmission pdl dl) ,et~ra.
In acco~ "ce with yet another aspect of the invention, a cellular communication system is provided which includes: a plurality of base stations coupled to a system b~rkhone each of the base stations col"~,iaing a base station receiver system for receiving wireless communications and a base station transmitter system for transmitting wireless commu,.:~ na, and a plurality of mobile terminals each for commu, :-~ li"g with the system backbone by way of at least one of the plurality of base stations each of the plurality of mobile terminals having a mobile terminal l, ~nsn ,itler for transmitting wireless communications to the at least one of the plurality of base stations and a mobile terminal receiver system for receiving wireless commu"icalions from the at least one of the plurality of base stations;whereinl with respect to the at least one base station at least one of the base station l, ~nsn lilLer system and the base station receiving system ~ Iessly communicates with one of the mobile terminals by selectively trans",illing or ~eceiv;"g data accordi.,g to any of a plurality of dirr~n nl PN code pa,d",elers.
According to but another aspect a cellular communication system is provided which 3~ includes: a plurality of base stations coupled to a system bachl-one each of the base stations con ,,ona;"g a base station receiver system for receiving wireless communications and a base station transmitter system for llanalllittillg wireless communicaliolls; and a plurality of mobile terminals each for communicating with the system backbone by way of at least one of the plurality of base stations, each of the plurality of mobile terrrlinals having a mobiie terminal l, dnal I lill~:~ for l, dnal, liLlil ,g ~ Icss communications to the at least one of the plurality of base stations and a mobile terminal receiver system for receiving ~,vii~less commu,,icc,lions from the at least one of the plurality of base stations; wherein, with respect to the at least one base station, at least one of the base station l,dns",ilLer system and the base station receiving system wi ~les~ly communicates with one of the mobile terminals by selectively l, dns",illing 5 or receiving data according to any of a plurality of different trans~";ssion pa,dn)eter~.
In accordance with still another aspect, a cellular commun ~ n system is provided which includes: a plurality of base stations coupled to a system bacl~bone, each of the base stations co"~ i..g a base station receiver system for rt:ceiv;l,g wireless communications and a base station transmitter system for transmitting wireless communications; and a plurality of mobile temminals each for communicating with the system backbone by way of at least one of the plurality of base stations, each of the plurality of mobile terminals having a mobile terminal transmitterfor lldns",iLli"g wireless communications to the at least one of the plurality of base sldlions and a mobile terminal receiver system for receiving wireless communications from the at least one of the plurality of base sldlions1 wherein, with respect to the at least one base station, at least one of the base station transmitter system and the base station receiving system wirelessly communicates vvith one of the mobile terminals by selectively Ll dnsmilling or receiving data accor.J;. ,g to any of a plurality of different lldlls",;Jsion pal~nl~ r~, and wherein at least another one of the base stations cannot vary any of its l,dns",ission paldlllt:lera.
According to yet another aspect, a mobile terrninal for use in a cellular commu"icd~;on system having at least one base station coupled to a system backbone is provided, the mobile terminal including: a lldnslllillillg system for wirelessly comm-."icaling data to the base station; and a receiving system for wirelessly receiving data from the base station, wherein at least one of the transmitting system and the receiving system wirelessly communicates with the base station by selectively llans",illi"g or receiving data acco,~ g to any of a plurality of ~Jirr~ dllalll;ssion paldllleler~ based on communicdLions received from the at least one of the plurality of base stations.
In ac~,u,ddnce with still another aspect, a base station coupled to a system backbone for use in a cellular communication system is provided, the base station including: a l~nsr"illi"g system for wirelessly commu"ic~li"g data to a mobile terminal included in the cellular communication system; and a It:C~;J;I 19 system for wirelessly receiving data from the mobile terminal; wherein at least one of the transmitting system and the receiving system ~ lessly communicates with the mobile temminal by selectively transmitting or receiving data according to any of a plurality of different l,ansmission paldmetel~ based on communications received from the at least one of the plurality of base stations.

According to still another aspect, a method of wireless communication between a mobile terminal and a base station in a cellular communication system is provided, including the steps of: the mobile ter",il,al transmitting data to the base station accGrdi"g to a first lrdl)sn,;s:~iun pd,d,l,eter and determining if the data has been validly received; and the mobile terminal automatically l, al ,~millil ~9 data to the base station acco, di. ,9 to a second l,d"~",;;,~ion pdldlll~terwhich is different from the first transmission p~,d",eler if the data is determined not to have been validly received.
According to yet another aspect, a wireless base station for use in a ceilular comm~ n system having a system backbone is provided, cor,,,urising: a communication 10 system for pel rul "~;"9 t~ r~less communications with devices in the cellular commu"icdlion system, including communicating with the system backbone by way of wireless communications: and a power supply for providiny power to operate the wireless base station, the power supply including a solar power device for deriving the power from solar energy.
In accordance with but another aspect of the in\rention, a wireiess base station for use in a ceilular communic~lion network having a system backbone is provided, including: a communication system for performing wireless communications with devices in the cellular commu"icdLion network, said communication system receiving and l,dns~"illi"g wireless communication between a first device and a second device in the cellular communication 20 network; and an error correction system for correcting data errors in the wireless commu":- 'ion received by the communication system prior to the commu".~~ n system l,~n~ll,illi"g the wireless communication.
In accordance with still yet another aspect of the invention, a wireless base station for use in a cellular commu"icd~ion system is provided, including: a t,dnsceiving system for 25 perfomming 11~ ,35 communications with devices in the cellular communication system, said transceiving system being adapted for receiving and l,dns",illi"g wireless commu"icdlion between a first device and a second device in the cellular communication system; said I,d,)scoiv;ng system having a first antenna, a second antenna and antenna selection circuitry, wherein said anl~n"a s~ ,lion circuitry selects one of said first antenna and second antenna 30 for at least one of said receiving and llans",illi"g wireless commu"icdlion.
The drorementioned features and other aspects of the present invention are described in more detail in the detailed desc, i~lion and accGr"pal,ying drawings which follow.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic representation of a PN coded signal for data bits "0" and "1";

Figure 1A is a schematic represelllalioll of a transmitter system and a receiver system of a DSSS comm~ Don system;
Figure 2 is a scl)er"dlic ,~:p,~ser,laliol- of a cellular commul~icalion system of the present invention;
5Figure 3A is a sc;he"ldlic representation of a data packet including a header portion and ~ a data portion;
Figure 3B is a detailed block didyldlll of an exemplary embodiment of a mohile terminal in accoldance with the present invention;
Figure 3C is a detailed block cliag~ a"~ of an exemplary embodiment of a base station in accordance with the present invention;
Figure 4A is a flowchart illustrating a mobile terminal registering with and ascertaining a data communications rate for communicating with a base station;
Figure 4B is the process as described in Figure 4 wherein at least one of the base stations that the mobile terminal is attempting to registerwith is a w;.~less base station;
Figure 5 is a system flowchart illu~llalillg a mobile terminal setting communicdlion pardn,eter~ to correspond to a selected data commul,icalions rate with a base station;
Figure 6A is a scll~llldlic represer,ldlion of a portion of a cellular commul~i- lion system of the present invention;
Figure 6B is a block didyldln of a solar powered wireless base station in accGrdallce with the present invention;
Figure 7A is a block diagram of one embodiment of a transmitter system of the present invention;
Figure 7B is a block diay,dln of another embodi",enl of a transmitter system of the present invention;
25Figure 7C is a block diagram of another embodiment of a transmitter system of the present invention;
Figure 7D is a block Jiay,d", of a non-conl,." hle l,dnsl,liller of the present invention;
Figure 7E is a block diay, dn l of a co"l, ullablE transmitter of the present invention;
Figure 8A is a block diagram of one embodiment of a receiver system of the present 30invention suitabie for use within a base station or a mobile terminal;
Figure 8B is a block didyldln of another embod;,neni of a receiver system of the present invention suitable for use within a base station or a rnobile terminal;
Figure 8C is a block didyldlll of another embodiment of a receiver system of the present invention suit~le for use within a mobile terminal with one conll~,'l~ le receiver;
Figure 8D is a block did91dlll of a non-cGr,llu''~ receiver of the present invention; and W O 97/21294 PCT~JS96/19336 Figure 8E is a block diagram of a controllable receiver of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Figure 2 sche",~lically illustrates a cellular communication system, shown generally at 200 in accGrdance with the present invention. The cellular commu"icalion system 200 may 5 be one of several types including a local area network (LAN) or a wide area network ~WAN).
The cellular communication system 200 of this e,~:r",~lary e~ol~odi",el,l has a network 250 which fomms a hardwired data commu": .ic n path. The hardwired data communication path may be made of a twisted pair cable shielded coaxial cable or fiber optic lines for i":,lance and is often referred to as the system backbone 26Q. Connected to the system backbone 260 is a base station 210 which is ~ra~lc of dynamically modifying one or more of its data l~ans",ission pa,~r"ete,~i in accor-lance with this invention. Also connected to the system backbone 260 is a conventional base station 211 having generally fixed data l,cns~,,issio pa~d",ete,~. Each base station 210 211 wirelessly communicates with other devices in the system 200 via an omnidirectional antenna 290 which allows for a generally spherical area of coverage. D~ 1ion~1 yagi type dl ,lennas or other fomms of a- ,lennas could also readily be used as will be dp,~ ,idled. The antenna 290 allows each base station 210 211 to transmit and receive data within a respective geog, c,~ hic cell. As is discussed below the cell size is the geographic area in which a device can communicate with another device in a cellular commu"ic~lion system 200. The present invention permits the base station 210 to adjust effectively its cell size in order to better opli",i~e overall system pelrGr"~dnce. The adjustability of the cell size of base station 210 is sche"~dLically illustrated by curved lines labeled 212 214 216 (cor,~sponding to a fast mid and slow data t(ans",ission rate rt:spe~lively~. Conventiol1~1 base station 211 has a fixed cell 218 associated with it wherein cell 218 is of the mid cell size in this particular embodiment. The cellular communication system 200 generally will have several dynamic base ~lali~ns 210 and/or several conv~nLional base stations 211 spaced apart along the system backbone 260. However for purposes of illustration and si.ll~ . ity, only one of each is shown in this embodiment.
Other components of the system 200 that may be wired to the backbone 260 include a client/server network co",posed of a work station (client) 270 such as an IBM col"~.ali~le personal computer, and a server 280 such as an IBM RS/6000. A network controller 220 may also be wired to the backbone 260 to control the flow of data between the base station 210 and other cG"".onents wired to the backbone 260. The network cGnl,.l er 220 may communicate with the co, nponents wired to the backbone 260 using a variety of protocols such as the Ethemet protocol or the Token Ring protocol.

W O 97/21294 PCT~US96/19336 In order to expand the effective communication range of base stations 2iO, 211 col"lecled to the network, several wireless base stations designated 215a, 215b, and 215c are included in the cellular communication system 200. When referenced c~lle~ /ely, wireless base stations 215a, 215b, and 215c will her~inafter be ~efe~ed to as ~ .~IESS base station 215. Each wireless base station 215 is shown to have a power supply 217. The power supply 217 may be hardwired to an existing power source via power lines or, it may be an auxiliary power source in accoldance with the invention. Such an auxiliary power source may use solar power, as is described below, or it may use other natural energy sources such as wind or water.
In this particular embodiment, each wireless base station 215 is shown to have connected to it both an omnidirectional antenna 290 and a yagi type directed antenna 292. The omnidire-;tiondl antennas 290 allow for a spherical area of coverage, whereas the yagi type antennas 292 allow for a more elongated, ellirtic~l shaped cell coverage. The yagi type antennas 292 are cor,l"~only used when communication is maintained with another device having a fixed location in order to allow for longer distance coverage. Similar to the base station 210 "le"lioned above, each wireless base station 215 of this invention can vary its cell size to allow for optimal settings. For exd",; le, wireless base station 215a is shown to have an omnidirectional antenna 290 which provides for cell area coverage illustrated by circular lines 222, 224, 226 and a yagi type anlenl-a 292 which aliows for directed cell area coverage illustrated by elliptical lines 232, 234, 236. In other embo.li"lenls, it is likely that a wireless base station may be configured to operate with one antenna. Although not completely shown or labeled forthe sake of ~implicily, wireless base sldlions 215b and 215c have similar cell area coverage.
The cellular communication system 200 also includes one or more mobile te" "i"als each Z5 referred to gene,dlly as a mobile terminal 230. The mobile ter",inals 230 are each c ,G ' le of dynamically modifying theirdata llan~l";ssiol1 p~,dn,eler~ in accordance with the invention as is described more fully below. In this particular embodiment, three mobile terminals designated 230a, 230b, 230c are communicating with devices connected to the net~,vork 250.
Also shown within the cellular communicdlion system is a conventional mobile terminal 231 3~ with generally fixed pdldnlt lt:r~. The mobile terminals 230, 231 are c~r~lE of roaming from cell to cell and using a ~t:yi~L~alion and derey;~l,dlion process to assure a single entry point to the backbone 260, as is described in more detail below. The mobile terminals 230, 231 - may include a hand held or arm mounted portable computer, or a portable data form reader mounted to a vehicle, for example.

PCT~US96/19336 Connected to each mobile terminal 230, 231 is an omnidirectional antenna 290.
Omnidirectional antennas allow for a generaliy spherical cell area coverage which is ogen beneficial for roaming mobile terminals, however other types of al,Lennas could readily be used. In acco~dd"ce with the exemplary embodiment of this invention described herein, each mobile terminal 230 has an adjustable cell size as is representatively indicated by cells 242, 244, and 246 (corresponding to fast, mid, and slow data ll~ns,l,;ssion rate, respectively~ as illustrated with respect to mobile terminal 230a. The cell coverage of the mobile terminals 230b, 230c, and conventional mo~ile terminal 231 are not shown in Figure 2 for sake of clarity. I{owever, in order to n~ai-~lai" proper communication with a particular base station 210, 211, or215 it is not enough that the mobile terminal be within the cell area coverage of the base station, but rather, the base station must also be within the cell area coverage of the mobile terminal as will be app, ~:cidled.
For example, in this particular embodiment, mobile terminal 230a is shown to be within the cell area coverage 218 of base station 211. However, in order to Illdinldill proper bid;lt:.ilional communication and registerwith base station 211, the base station 211 must also be within the cell area coverage of the mobile terminal 230a. As shown, at the fastest data lldn:,lll;ssiun rate, mobile terminal 23ûa only has t,d"s",;s~ion capabilities within cell 242 which is not suffident to communicate with base station 211. Thel eron, the mobile terminal 230a must communicate at the mid or slow rate corresponding to cell coverage 244, 246 respectively. At these rates, the base station 211 falls wlthin the trans"lis:,ion range of mobile terrninal 230a. Thus, reyial,dlion and commu"icalion can be readily maintained.
In many instances, a mobile terminal may register with a wireless base station 215 in order to gain access to the network 25û. Similar to that ~ cussed above, both the mobile terminal and the vl~ ~I~SS base station must be within each others trans",;;,sion range in order to allow for proper commu"~ n to take place. As is disc~ lcsed below, each wireiess base station 215 will form a permanent path to the network 250 through which all commun ~;on with registered mobile terminals take place. In this particular embod;."enl, u~ less base station 215b has forrned a per",anenl path to the network 250 through wireless base station 215a and base station 210. Thus, if mobile terminal 230c is registered with w;r~less base station 215b then all commu";_dlion between the mobile le"ni"al 230c and the network 25û
wiil follow this path.
T,d":"";;,:.ic,ns between the devices in the cellular commu~,icalion system 200 p~c:r~rdbly occur in a packet format 300 (Figure 3) using Spread Spectrum wireless commu"icdlion techniques, as described in the Background section. Although this particular embodiment describes a Direct Sequence Spread Spectrum (DSSS), a frequency hopping system or a hybrid system using direct sequence or frequency couid be readily employed. In order to accol"",oddle varying cell sizes in a DSSS system as rfiscussed above, the mobile terminals 230 and the base stations 210, 215 are capable of varying PN code pard,nale,:~ such as PN
code length and chipping rates, and modulation complexity for example. The effect of varying each of these par~lllt:lela will now be fliscussed in coniunction with their effect on cell - size and overall system pe, run"al)ce.
As indicated previously in the background section, a longer PN code length results in a higher processing gain and correspondingly increases a communication range between a mobile terminal 230 and a base station 210, 215. On one hand, a high p~ucessi"g gain may 10 advant~geously be utilized to perrnit data ll dns miaSiOIl between the mobile terminal 230 an the base station 210, 215 that would otherwise be out of the commu";cdlion range. However, the i"cl~ased communication range arro,ded by the high p,ucessi,~g gain results in a reduced data l,dns",;ssion rate (where the data l,d"s",;ssion rate is measured in terms of original data bits transmitted per unit time). On the other hand, a lower processing gain may be utilized 15 to achieve a fasterdata l,dn~i",;~sion rate between a mobile terminal 230 and a base station 210, 215 which are nearby. The lower processing gain, however, reduces the commu~,i,;dlion range between the mobile terminal 230 and the base station 210, 215.
The chipping rate refers to the rate at which chips are transmitted by the system component sending a data l, dns" ,ission. A system component receiving the data 20 (,dnsm;ssion must receive, demodulate and despread the PN coded chip sequence at the chipping rate utilized by the sending component. At a higher Cll;~ ping rate, the receiver system is allotted a smaller amount of time to receive, demodulate and despread the chip sequence. As the chipping rate increases so to will the error rate. Thus, a higher chipping rate effectively reduces the communication range. Conversely, decreasing the chipping rate 25 increases the commu"icdlion range.
In addition to modifying the PN code length and chipping rate, the modulation co" ~ ly may be varied. A BPSK mocl~ ion scheme, which provides for modulating the carrier to one of two phases, may be used to l,dns",il one bit at a time over the wireless commu": ":n link, while a QPSK modulation scheme, which provides for modulating the carrier to one of 30 four phases may be used to transmit data at a faster rate, two bits at a time, over the link.
- While QPSK will result in a faster data rate, it is more sensitive to noise and more errors may occur ber~uce the receiver must operate within a 90 degree phase deci~ion angle rather than - 180 degrees associdled with BPSK. Thus, a greater lld~slnission range can also be accomplished by using a BPSK modulation complexity over a QPSK modulation co"l~,leAily W O 97121294 PCT~US96/19336 since BPSK moduiation has a higher tolerance to noise and allows for better opportunities to clecode each bit.
While the rate/range tradeoff still applies to each individual l,dns",ission, the system 20Q
allows an individual mobile terminal 23~ and an individual base station 210, 215 to opli",i,e 5 the p~ucessillg gain and data l, dns",;ssion rate tradeoff for a given data l,dns,),;~sion. This over.iu",es the cell si e/llllùughput tradeoff limitation. It will be apparent that the system 200, by providing the base stations 210, 215 and the mobile terminals 230 with the abiiity to dynamically modify the PN code length, ch rp ng rate, and/or modulation cor" 'e: :ly effectively provides a base station 210,215 with an adjustable cell size as il,dic~led in Figure 2. For instance, the cell size i,ldicaled by the curved line 212 of base station 210 would correspond to a data lrdnsn,ission characterized by a low processing gain and a high data lldnsl";saiol1 rate. The cell size indicated by the curved line 214 would correspond to a data transnlission characterized by an i,lI~ lediale processing gain and intermediate data transm;ssion rate. Finally, the cell size indicated by the curved line 216 would correspond 15 to a data l,d"a"~;ssion characterized by a high processing gain and a low data trana,n;ssiûn rate. The present system 200 can have exceptionally large cells while only sacrificing throughput to the extent mobile terminals on the fringe of ~ ,eulive base station cells require the higher processing gain for error free communication.
O,uti",i~dlion of a wireless communication link occurs when all pald-"elera are set such 20 that data is llarlslllilled at the fastest possible rate to the system backbone 260 at or below an "a''__r h's~ error rate given the c~r~i,i'ilies of the communicating system components, the range of data lld,lalll;~sion and the alllbieni noise conditions. However, in obtaining this optimum setting, tradeoffs will occur as disr~ucsed above.
One advantage of dyllan.:_~lly altering the commullicdlion pard",e(ers to optimize 2~ p~,ru""a"ce is that mobile terminals 230 close to a base station 210, 215 may l,dns"~iI data rapidly thereby reducing total air time usage. Additionally, fewer base stations will likely be needed to cover a given service region, thereby reducing the overall cost aCsor -led with the cellular communication system. Without the ability to dy"a",:--"y alter commu" cdlion pa,a."ete,a, the base station cell sizes remain constanl. Thus, it will be necessaly to ensure 3~ that there are a sufficient number of base stations located so as to cover the entire service region. It should be evident in such situations that, unless each base station is preset to lld"all,il at its lowest possible data commu" "on rate, the base station cell size will be less than a cell size defined by its maximum range capabilities. However, given the rate/range tradeof~ (as discu-ssed above), it would be exl,~r"ely inefficient usage of air time to set the 35 slowest rate on most base stations, which consequently would correspond to a need for a W O 97/21294 PCT~US96/19336 greater number of base stations in order to cover any ~iven area. Additionally, by having this dynamic altering ability, base stations may be able to adjust for additional noise introduced into their communicating area. Without this ability, newly introduced noise could result in reduced range or "dead spots" where a mobile terminal can no longer communicate with any 5 preexisting base station.
In order to allow for o~li" ,i~dlion of a cellular commu, licalion system, each base station 210, 215 in the c~l;en~,uldly embodiment is capable of communicating with a plurality of mobile ter",;.,als 230 at three different data rates, fast, mid and slow. In other e",bodin,er.ts, a variety of rates variably adjustable between the slowest and fastest rate could be used.
10 Because of the rate/range tradeoff, the fast rate can only be used to communicate with mobile terminals 230 located relatively close to a base station 210, 215. A cell 212 (Figure 2), for example, in which the fast rate can be used is referred to as the near zone. The mid data rate can be used to communicate with mobile terminals 230 which are more distant from the base station 210, 215. For exan', IE, in cell 214 the mid data rate can be used, but not 15 the fast data rate. Finally, a mobile terrninal 230 that is even more distant from a base station 210, 215 requires data l,dns",ission at the slow data rate.
In this particular embodiment, the fast data rate includes use of an 11 chip PN code and a QPSK modulation CO~ y. The chipping rate can be set to 11 MHZ to provide a 2MB/sec data rate. The mid data rate includes use of an 11 chip code and a BPSK
20 mod~ ~'~tion complexity. An 11 MHZ chipping rate will provide a 1 MB/sec data rate. The slow data rate includes a 22 chip code and a BPSK mocl~ tion complexity. The 11 MHZ chipping rate provides a 1/2 MB/sec data rate. Table 1 below SU"""dli~s such pa,d",eteri. It will be appreciated, of course, that such values are exe,n,ulaly and are not intended to limit the scope of the invention.
TABL~ I
Data Rate PN Code Length Chip Rate (MHZ) Mcr~~ation - ~ - (chips) Fast 11 11 QPSK
Mid 11 11 BPSK
Slow 22 11 BPSK

To eliminate the need for each system cor"~onenl (mobile terminal 230 or base station 210, 215) to have a receiver system capable of simultaneously iistening for data L,dn~"-illed at all three data rates, a network protocol provides for a more si""~liried receiver system.

_ _ _ . _ . . _ _ _ _ _ _ . . ..... . . . ... . ...... . . .. ..

W O 97/21294 PCTnJS96/19336 The preferred network protocol inco~,,ordLes a combination of positive and negative acknowledgment signals used by a responding component. The achr~o~,edgment signals provide information to a transmitting component that allows the l,dt-s,niffi"g col"ponent to change its paldmele,a in a manner which optimizes the communicdlion link. A positive 5 acknowledgment signal is returned to the transmitting component when the receiving cG~ unenl properly received all of the transmitted data. Thus, a positive acknowledgment signal informs the transmitting cor,,,uoner,l that its current transmitting pa,d",eter settings are sumcient to allow for commuoicdlion. However based on the i"fo""alion given in the acknowledgment, more optimal settings may be avallable. A negative aulu,o~edgrnent 10 signal is used when the receiving component only partially received the transmitted data. A
negative acknowledgment signal informs the trans"-illi~g col~,.)onent that its current transmitting pard",eler settings are not sufficient to allow for proper communication.
cr the lldnslllillillg component can use the inrc,r"lalion given in this acknowledy"~en signal to change its pdldl I lel~la (if possible) to allow for cor~ te and optimal communication to take place.
In the piere"~d embodiment of this system 200 it is desirable to enable the mobile terminal 230 to choose the data rate or data rates used for the packet. Base slaliuns 210 hardwired to the system backbone 260 and ~ less base stations 215 are p~uyldlllllled to respond to the mobile terminal at the same rate or rates. Therefore, the mobile terminal ~t:ceiver system will be able to anticipate the rate of the incoming signats at any one time.
The base station 210 215, on the other hand will not know which data rate the mobile terminal 230 will choose or which of several mobile terminals will l,dns",il a packet.
17~elt:rur~: the base station 210 215 would ordinarily be required to simultaneously be able to detect all three data rates. To provide for a more simplified base station 210 215 receiver system however the network protocol requires all packets to begin with a header 302 (Figure 3A) l,dns"~ilLed at the mid or slow data rate. Therefore the base station 210 215 need only listen for the mid or slow rates as is explained more fully below in connection with Figures 3B and 3C.
Re~.,i"g to Figure 3A each packet 300 pl~re,ably includes overhead bits in the form of a header 302 and a plurality of data bits 304. While the entire packet 300 may be trans" lilLed at the fast mid or slow rate the protocol of this specific embo-li",ent provides for the header to be lldllar~lrt:d at the mid or slow rate while the data portion is transferred at the fast mid or slow rates. Any co", i. ,dlion of these varying rates in a single packet may be r~fer,cd to as a packet rate. The header 302 may include receiver system setup data signifying the data rate at which the data bits 304 will be transmiffed. The packet 300 may contain -CA 022l0792 l997-07-l8 W O 97/21294 PCT~US96/19336 sy, ,ch~rii~clion bits (not shown) between the header and data portion to provide the receiver time to reconfigure itself to the data l, dns",;;,sion rate for the data bits 304.
A conventional mobile terminal 231 which cannot change its pard"~ele,~ need only be configured in the exemplary embodt,l,el)L to operate at the mid rates by preselecting its one non-a~usPhle PN chip code length chaldLlerisLic value to 11 chips and its modulation complexity to BPSK. Accordingly, the header and data of a packet 300 are always I,dnsrnilled by the mobile terminal 231 to the base station at the mid data rates.
~er~use the mobile terminals 230 may transmit headers 302 of the packets 300 to the base station 210, 215 at either the mid rate or the slow rate the modulation co,n, ' . :ty of the header is always BPSK. Therefore, the receiver system of base stations that communicate with the mobile terminals 230 are configured initially to receive BPSK signals, in that it distinguishes between the two possible phases of the carrier frequency. However, the mid data rate has an 11 chip PN code length and the slow data rate has a 22 chip PN code length. Therefore, the base station must be able to determine which of the two Pl\ codes is in use to determine whether the header 302 is being transmitted at the mid or slow data rates. Consequently, as described below in conne~;lion with Figure 3C the base station 210 includes at least two PN decodel ~ serving as cor, t:lalion channels, one to cGr, ~ildle when an 11 chip PN code length is used and the second configured to detect and decode a 22 chip PN code length. In l~aponse to a header 302 indicating that the accor"panying data bits 304 of the packet 300 are to be communicated using the fast data rate, the base station 210 ,~icorlliyures to receive QPSK mod~ on and the incoming data is cor, ~ildled with an 11 chip PN code as discussed below.
Wireless base stations 215 which do not directly communicate with mobile terminals generally do not have to continuously be able to detect dirre~ir,l data rates. I l~tLt-ivcr, due to their start up pcoceduce~ as is ~~isc~csed belowj they are configured so as to be ab!e to receive inro,l"~lion at .lirrerenl rates. Further, wireless base stations such as base station 215a in Figure 2 may optionally be configured to communicate with mobile terminals as well as serve as an intemmediate link between other wireless base stations and the network. For instance, a manual switch (not shown) may be attached to the w:.~less base station and 3~ control whether the wireless base station responds ~o a request to register signal sent from a mobile terminal. Alternatively, the ~ less base station could be configured such that a ,IJlV91dlll stored in the memory of the wireless base station allows reyiaL,dlion with mobile temminals only when the ~ less base station is also able to effectively support loading from other ~ less base sldlions which may have Itiy;aler~id with it. The leg;~ lion prucess CA 02210792 1997-07-lX

W O 97/21294 PCT~US96/19336 between a wlreless base station 215 and another base station 210, 211 or a wireless base station 215 and a mobile terminal 230, 231 is discu~sed below.
Regardless of whether or not a wireiess base station is configured to permit regial~Lion with mobile terminals, the commun~ n path between the wireless base station 215 and the other base stations 210, 211 is a fixed path. Therefore, in order to set up a permanent communication path, at start up each wireless base station sends out a request to register with a base station closerto the system backbone. The request to l~y;sler is initially sent at the fastest speed. If a response is received at the fast rate, the wireless base station will establish a pe,ll,~nelll communication link with the responding base station. If no response is received, the wireless base station will send out a request to lcyialer at a slower speed.
This process will continue until a permanent commu~ic~lion link is created. If at any time, more then one base station responds to the ~ less base station's request to register, the ~.~less base station will select one of the responding base slalions to be its permanent link to the backbone based on pr~deterll,i, ,ed criteria such as system load, for example.
It should be readily understood that there can be several embodi",ents of the mobile terminal 230 of the present invention. Different embodiments may have different limitations on the paldlll~:tela used to vary the processing gain. For eXdlll,'E, a first embodiment may be capable of varying PN code length and mod~ ion complexity in accordal1ce with all three data rates. In another more limited embodiment, the mobile le, lll;nal 230 may be ~a, ' le of varying the mod~ ;on complexity but not the chip PN code length. When such e",bodi,nenl is set for an 11 chip PN code, it is capable of the fast and mid data rates.
The network of this invention can also support conventional base slalions 211 and base stations 210, 215 with limited ability to alter code length or mod~lation coll,l.lexily. The capabilities of both the mobile terminal 230 and the base station 210, 21~ limit the data rates that the mobile tellni-lal 230 can choose. The base station may include its rate capabilities in fhe "OK to register" packet, often, ~ :fel, ed to as the "router idenliricalion" packet, and the mobile terrninal 230 will comply with the base station's rate li,.,ikllions when choosing a data rate.
In summary, the preferred en,bodi",ent of the cellular communication system 200 of the present invention utilizes a packet structure with a mid or slow data rate used for the header 302 and a fast, mid or slow data trans"l;ssion rate used for the data bit portion 304 of the packet 300. The mobile terminal 230 chooses the packet data trans,ll;~sion rates and the base station lespollse packet will use the same rates. At start up, wireless base stations 215 ~e~ a permanerll link to the system backbone 260 and mai"lair~ conal~nl optimal commun: - n with hardwired base stations 210 or other wireless base stations 21 ~ situated closer to the backbone 260.
P<erel,il,g nowto Figure 3B, a detailed block ciiayldlll of an exemplary embodiment of a mobile temlinal 230 is shown in accGrcidnce with the present invention. The mobile terminal 230 inciudes the aror~:l"enlioned antenna 290 which is used both for l,dnsr"illi"g and receiving data. The antenna 290 is connected to the anlenna terminal of a receive/l,dns"liL
switch 305. The receive/l,dnsr"il switch 305 can be any type switch for switching the antenna 290 between a transmitting mode and a receiving mode, for example a PlN-diode based single pole-double throw (SPDT) type switch as is known. Signals received by the antenna 290 are coupled via the switch 305 to the input of an RF down-conversion circuit 306. The RF down-conversion circuit 306 typically includes a mixer and can be of any known sl ~ t-~'e design for outputting the data signal onto line 307.
The mobile terminal 230 includes a bank 308 of PN code spread spectrum decoders,each r~spe.,li~/ely being of con\,~:nlional design. In the exemplary embodiment, the bank 308 includes PN code spread spectrum decoders 308a, 308b and 308c each respectively configured for decoding or despreading signals received at the fast, mid and slow data rates.
For e~cdll'~ le, decoder 308a is conhgured to decode PN coded data having an 11 chip PN
code length and a chipping rate of 11 MHZ. The decoder 308a generally includes a mixer 309a which mixes the received PN coded data with a signal PN, representing the 11 chip PN
code at the 11 MHZ chipping rate. The output of the mixer 309a is provided to an il Itesl dlor 310a which inleyldles the signal to produce a decoded data output on line 311. The output of the integrator 310a is also fed back to a timing cor,ll-'ler 312 which produces the app,up(id~e decoding signal PN1 and adjusts the timing thereof based on the output of the illleg, dlur 310a in order to obtain optimum co" t:idlion with the data received by the decoder.
Similarly, the decoder 308b is configured for receiving data ll dnsn ,illed at the mid data rate. Since the mid data rate in the exemplary embodiment also uses a PN code length of 11 and a chipping rate of 11 MHZ, the construction of the decoder 308b can be identical to that of the decoder 308a. In fact, decoder~ 308a and 308b in this particular embodiment can be one and the same as will be appreciated. Nevertheless, the decoder 308b similarly includes a mixer 309b, an integrator 310b, and receives an appo,p,idle timing signal PN2 from the timing corilluller 312. The decoder 308c also includes a mixer 309c and an integrator 310c, but is configured to receive a timing signal PN3 from the timing conll-"er 312 corresponciing to a PN code length of 22 at a chi~,p;.,g rate of 11 MHZ.
A mic,uco"l,-ller 313 included in the mobile terminal 230 is p~oy,d"",led to carry out the 3~ various control and ,u,ucessi"g opertllions described herein. For t xdll,~oie, the mic, ucorll,ùller W O 97/21294 PCTrUS96/19336 313 controls a switch 314 which determines whetherthe mobile terminal 230 is set to receive data at the fast, mid or slow data rate by respectiveiy coupling the PN coded signal on line 307 to any of decoders 308a-308c. Similariy, the microcontroller 313 conl, ~,ls a switch 315 which deler",;.,es what type of further demodulation is peiro""ed on the data signal. More specifically, the mobile terminal includes an array of select~hle demodulators 316.
Demosi~ ors 316a and 316b are con\r~nlional and perform BPSK and QPSK demodulation, respectively. Depending on whether the mobile terrninal 230 is to be set to receive data at the fast, mid or slow data L,dnsl"ission rate, the mic,uconl,-l'er 313 adjusts the position of switch 315 accordi,lyly. If the mobile terminal 230 intends to receive data at the fast data rate, the switch 315 couples the output from the decoder bank 308 to QPSK demodulator 316b. On the other hand, if the mobile terminal 230 is to receive data at the mid or slow data rates, the switch 315 connects the signal on line 311 to the BPSK demodulator 316a. The data which is output from the demodulators 316a,316b is then provided on the RECEIVE
DATA line to the ,I,i.,,ucontroller 313 for apl.lupriate processing based on the given ~p,~licalion.
In orderforthe mobile terminal 230 to transmit data, the ,,,;u,ucoi,l,~ller 313 provides data to be l~dlls",;;led onto a TRANSMIT DATA line. The TRANSMIT DATA line is connected to a cor,l,."-')ls switch 317 which determines the manner in which the lldnSl~ data is modulated. More specifically, the mobile terminal 230 includes a bank of mod~ tors 318 including BPSK and QPSK modulators 318a and 31 ~b, respectively. In the event data is to be lldlls",iLIt:d by the mobile terminal 23~ at the fast rate, the microcontroller 313 causes the switch 317 to couple the lldns",il data to the input of the QPSK modulator 318b.Altematively, if the data is to be transmitted at the mid or slow rates, the data is connected to the input of the BPSK modulator 31~a via the switch 317.
Th.e BPSK o. QPSK m"~ ~'~d data ~Crom modulators 318z, 318b is outpu: orlto line 319 which serves as the input for a plugldllllll-~le PN encoder 320 included in the mobile terminal 230. ~pe~ifir~lly, the PN encoder 320 includes a pluyldlllllldble PN code sequencer 321 which provides the appru,uridle PN code for mixing (via mixer 322) with the data on line 319 to be PN code modulated. The proyldrllllldbie PN code sequencer 321 can be any 3Q digital logic circuit desiyl ,ed to generate a PN code sequence at the desired chip length and chipping rate. The plUUldllllll :'P' PN code sequencer321 of this embodiment utilizes a shift register to create the necessary PN codes. The pluy,d"""able PN code sequencer 321 leceivc~ as control inputs a PN code select signal from the microcor,l,.llor 313 via line 323, and a chip rate select signal provided from a timing cor,l,ullEr 324 via line 329. The PN code select signal defines the particular PN code to be used which, in the exer"pla~y embodiment is either an 11 chip or 22 chip code. The chip rate select signal from the timing conl, ~I'er 324 determines the chipping rate of the PN code sequence produced by the sequencer 321. In the exer",uld,y embodiment, the chip rate select signal causes the PN code sequence output from the programmable PN code sequencer 321 to have a chipping rate of 11 MHZ at all 5 times but another embodiment could include varying the chipping rate as wiil be appreciated.
~ The timing conl~ùller 324 like the timing controller 312 is connected to the microconl~l'er 313 and is conlr l'ed thereby.
Accordingly when the mobile terminal 230 l,dns",il~ data at the fast or mid rates the microconl,- ler 313 provides a PN code select signal on line 323 indicating that the 10 programmable PN code sequencer 321 is to generate a PN code sequence having a PN
code length of 11 and a chipping rate of 11 MHZ. When the mobile terminal 230 lldllSllliL~
data at the slow rate, the microconl(."nr 313 provides a PN code select signal to the p~uyldlllnl: o PN code sequencer 321 indicating that the pruy,d"""able PN code sequencer 321 is to generate a PN code sequence having a PN code length of 22 and a chipping rate of 11 MHZ. The output of the p~uy~dr~llllable PN code sequencer 321 is provided to mixer 322 where it is mixed with the data on line 319 to produce a PN spread spectrum signal on line 329. The spread spectnum signal is then input to a conventional RF up-conversion circuit 326 which mixes the signal onto an RF carrier prior to being provided to an RF output ampliher 327. The RF signal is amplified by the amplifier 327, and the output of the amplifier ~0 is provided to the lldns,l,iL terminal of the switch 305. During a transmit mode the microcontroller 313 causes the switch 305 to couple the output of the amplifier 327 to the dnlenl1a 290 so that the signal is ll dl lall."' ~ During the receive mode of course the switch 305 is cor,l,. ed by the microcontroller 313 to couple the signal from the antenna 290 to the RF down conversion circuit 306.
The RF output amplifier 327 in the prefer,t:d embo.li",enl has an adjustable gain which is contr~l'ed by the ".:. ucor,l,uller 313 via line 328. In the event the microcor,l,uller 313 elects to i"u,~ase the power level at which the RF signal is llarlslnilled from the dnlenna 290 the microconl,ullEr 313 can increase the gain of the ar"plirier 327. Conversely, if the mic,uuo.,l,. ~r 313 elects to reduce the lldl ,s.nit power level the microcor l,~ ~ r 313 reduces the gain of the al" ';rier 327.
In addition to the above described receiver and transmitter systems the mobile terminal 230 includes a memory 330 which stores for ex~",,..lc, code which is executed by the mic, ucor,t, . . r 313 for carrying out the functions described herein. It will be readily a,t~part:nl to those having ordinary skill in the art of ~l upr~cessor proU~d~"ling how the 35 microconl,.'ler 313 can be prog.d,"",ed in order to carry out such functions based on the .

W O g7/21294 PCT~US96tl9336 description provided herein. Furthermore, the memory 33Q may inciude ~pplic;,lion code, data, etc., as is conventional. The mobile terminal 230 also includes a user input 331 such as a keypad, touch display, LCD, etc., which can be used for inputting or viewing illron,,dlion.
The mobile terminal 230 includes a power supply 332 which provides the power foropel~li"g the mobile terminal 230. Typically, the power supply 332 consisLs of a battery pack which is either ~ la-u' 'e omechd~ ~I t, The output of the power supply 332 is n~onilored by a power level detector 333 which measures the uoltage andlor current delivered by the power supply 332 to the mobile temminal 230. In the exemplary embodiment, the power level detector 333 detects if the voltage provided by the power supply 332 falls below a pledele~ ined I hleal~ If this occurs, the power level detector 333 provides a signal to the microconl~-ller 313 to inform the microcGnl,.'ler 313 that the power level is low. The miclucol,L,l I'er 313 may then take p,edelér,llined action such as reducing the l,dnslnil power level by reducing the gain of the al~ ier 327, thus reducing power consumption.
Furthermore, the mobile te"nif,al 230 includes a signal level detector circuit 335 which detects the signal level of the signal received via the anlenna 290 from a base station, for example. In the ,~, e~en ed embodiment, the signal level detector 335 is designed to provide an output signal to the mi-;~uCollb~" ~r 313 in the event the signal level of the received signal exceeds a predetermined level (thereby indicating the base station is in close pru,~i",ity).
Upon receiving such a signal, the microconlrollEr 3l3 may elect to reduce the gain of the amplifier327 fortransl"illi"g inr(""~aLion back to the base station. This enab'~s the mobile terminal 230 to conserve power andlor avoid saturating the front end of the base station 210.
Regarding the base station 210, Figure 3C shows an exemplary er"bodi",ent havingvarious aspects of the present invention. The base station 210 is driven by a microcontroller generally desiylldled 350. As discussed above, the base station 210 may include two or more dirrere"l antennas 290 and 292. AddiLionally, the base station 210 may include antenna selection circuitry which in this embodiment is generally represented by a rll: uconlputer 350, and a switch 351. The Ill: uco.ll,uller 350 determines which anlenna is utilized during any particular l,d":"";ssion or reception by way of the switch 351 cûn~ led by the microconl,.'ler 350. The state of the switch 351 delel",i.,es which of the antennas 290t292 is selectively coupled to the antenna terminal of the receiveltransmit switch 352.
The receiveltransmit switch 352 is identical in operation to the switch 305 described in conne-,tion with the mobile terminal in Figure 3B. The output of the receive/l,~ns",il switch 352, i.e.t the receive temminalt is connected to the input of an RF down-conversion circuit 353.
The ope, tllion of the RF down-conversion circuit 353 is identical to that of the cor, espondit ~g 3~ RF down-conversion circuit 306 in the mobile ter",;.lal 230.

WO 97/21~94 PCT/US9G/19336 Thus, RF signals which are received by the base station 210 from a mobile unit 230 are received via either antenna 290 or 292, and are input to the RF down-conversion circuit 353 via the receive/l~ans,l"t switch 352. Like the l,dnsil,iLLer system in the mobile terminal 230, the base station includes a bank 354 of PN code spread spectrum decoders 354a-354c.
Each are of conventional design and together with timing conl",llcr 355 are idenlical in operation to the decoders 30Ba-308c and timing controller 312 in the mobile terminai 230, respectively. In other words, the decoders 354a and 354b are each configured accor.li"g to conventional techniques to decode a PN coded spread spectrum signal having a PN code length of 11 and a chipping rate of 11 MHZ. Decoder 354c is configured to decode a PN
coded signal having a PN code length of 22 and a chipping rate of 11 MHZ. Each decoder generally includes a mixer 355 and an il llegldlu, 356, and receives appropriate timing signals ~PN1-PN3) and control via the timing cor,L~ r 355.
Unlike the mobile terminal 230, however, the transmitter system of the base station 210 does not include a switch for selecting which of the decoders 354a-354c receive the output from the RF down-conversion circuit 353. This is because in the exemplary embodiment it is p,~dete,l,lined that the mobile terminal 230 will know that data validly received from the base station will initially be l,~nsl"itled at a particular rate as rliscussed more fully below.
Hence, the r": uco~ lll u" -r 313 in the mobile terminal 230 knows initially how to set switches 314 and 315 such that the data is decoded in accor.lance with the particular data rate. The base station 210, on the other hand, does not always know the trans",;ssion rate at which data will be received. Consequently, the output from the RF down-conversion circuit 353 is input to each of the decoders 354a-354c in parallel. The outputs of each of the decoders 354a-354c are provided to a circuit 357 for selacli"g the output from the decoders 354a-354c which exhibits the best co" ~ :lalion between the signal which is received by the decoder and the particular PN code sequence and rate for which it is designed. As will be appr~ciated by those having ordinary skill in the art, the decoder which receives the PN coded spread spectrum signal having a data transr";ssion rate corresponding to the that for which the decoder is designed, will exhibit the best cor,~lalion at its output. The circuit 357 can be a logic array and/or a switch or multiplexer which autoll,aticdlly couples the output of the decoder354a-354c exl,il,ili,lg the best co,le:laliol- onto line 358. In addition, the circuit 357 is desiy,led to provide an output to the mic,ucollll-'ler 350 via line 359 indicating the PN code length and the chipping rate of the received signal by virtue of knowing which decoder 354a-354c produced the best cor, ~Idlion. In other words, if the decoder 354a provides the best correlation7 it is known that the data l,dns"liss7ion rate of the received signal is fast. If the decoder 354b provides the best co"t:ldlion, it is known that the data transmission rate is mid.

W O 97/21294 PCTrUS96/19336 Finally, if the decoder 354c provides the best co~ lalion, it is known that the data trans,),;ssion rate is slow.
The output on line 358 from the circuit 357 is connected to the pole of switch 361. The n,ic,ucontroller 350 controls the position of the switch 361 so as to determine w;,~lher the decoded spread spectrum signai on line 358 is input to a BPSK demodulator 362a or a QPSK
demodul~tor 362b. Thus, if the signal received from the mobile terminal is at the mid or slow data rate as determined by the circuit 357 initially at least, the microcor,l,.l'er 350 causes the switch to couple the signal on line 358 to the input of the BPSK demod~ tor 362a. On the other hand, if the signal received from the mobile terminal is at the fast rate, the mic,u~,lll-" ~ 350 causes the switch 361 to couple the signal on line 358 to the input of the QPSK demod~ or 362b. The BPSK and QPSK demodulators 362a and 362b, respectively,are conventional in design. The output of each demodulator 362a,362b is connected to a RFCEIVF DATA line which provides the demodulated data to the data input of the mic,ucor,l,.ller 350.
It will be appreciated that in the present embodiment, decoders 354a and 354b for the fast and mid data rates are each configured for processing a PN code having a code length of 11 and a chipping rate of 11 MHZ. Hence, whether the data received by the base station 210 has been transmitted at the fast rate or the mid rate, the outputs of both decoders 354a and 354b should show good cor,eldlion. Consequently, the decoders 354a and 354b can either be combined into a co""l,on unit or the circuit 357 can be desi~u,ned to select one of the two by default in the event both show good corl~elalion. In either case, however, the illrc"."~lion provided to the ", ucont,." Ir 350 from the circuit 357 via line 359 distinguishes only whether the data l,d"~",;ssion is at the slow rate or is at a mid/fast rate. The circuit 357 cannot distinguish between the mid and fast rates based only on the outputs of the decoders 354a and 354b. As a result, the "llo""al or default position of the switch 361 is in the position whereby the signal on line 358 is coupled to the input of the BPSK demodl~ln~or 362a. According to the tA~ Jlaly embodiment as desc,il.ed herein, the mobile terminals are configured to initially lldns",il the header portion 302 of the packet at the mid or slow data lldn:.lll;;.aion rate. Consequently, the data will be co"t:clly demodulated. Ther~arLerl i"for",dlion contained in the data packet received from the mobile terminal will provide the ucGnl~l'er 350 with i"fol",dlion as to the app,u,~(idLe data trans",isâion rate.The l~d"a- "itlel system of the base station 210 is functionally e~uivalent to the ll dn~" liller system of the mobile terminal 230 described above. In otherwords, data to be l,d"s",illed is output from the ".: ucor-l.uller 350 onto the TRANSMIT DATA line. The data on the TRANSMIT DATA line is selectively conl1ecied via switch 365 to either the input of BPSK

modui-~for 366a or the input of QPSK moduiator 3B6b. In the event data is to be l~nsn,illed at the fast rate, the ",:_,uconl~ r 350 causes the switch 365 to couple the data to be Il dl l'~rl ~ ~illed to the QPSK modulator 366b. If data is to be transmitted at the mid or slow rates the microconl~ller 350 causes the switch 365 to couple the data on the TRANSMIT DATA
line to the BPSK modulator 366a.
Like the mobile terminal 230, the base station 210 includes a proy, dmlll l'~ le PN encoder 320 which is identical in construction and operation. Consequently, the details thereof will not be ,~:peaLed for sake of brevity. It suffices to say that when the base station 210 elects to l,~ns",il data at the fast or rate the microcontroller 350 provides to the p, ugl dlllll ,able PN
code sequencer 321 a PN code select signal identifying the PN code with a code length of 11. In addition the microcontroller 350 provides a chip rate select signal via the timing cor,l,~ 'ler 324 to the p,uy,~""": e PN code sequencer 321, the chip rate select signal being rq~senldli~/e of a chipping rate of 11 MHZ. When the base station is to ll~n~.llil data at the slow rate the microcontroller 350 provides the same chip rate select signal representative of 11 MHZ; however the PN code select signal provided by the ": uconlio ler 35û has a code length of 22 rather than 11. The prog~ able PN code sequencer 321 in turn, generates a PN code sequence with the ap~" upn~le PN code and chipping rate which is then mixed via the mixer 322 with the mod~ ted outputs from the BPSK and QPSK modu~ t~rs 366a 366b.
The resultant PN spread spectrum signal is then output on line 329 so as to be an input to the RF up-conversion circuit 368. Like the RF up-conversion circuit 326 in the mobile temminal the circuit 368 is convenlional in design and mixes the PN spread spectrum signal onto an RF carrier. The output of the RF up-conversion circuit 326 is provided to the input of an adjustable gain RF output amplifier 369. The output of the amplifier 326 is coupled to the transmit terminal of the receive/transmit switch 352 such that the spread spectrum RF
signal can be transmitted via one of the anlennas 2~0 or 292.
The gain of the RF output amplifier 369 is cor,Lf :. ed by the microcohl,.ller 350 so as to increase or de~,~ase the l~ns",il power level of the base station 210. For example the base station 210 includes a signal level detector circuit 370. The signal level detector circuit 370 detects the level of the signal received via the output of the receive/l~dr,s"~it switch 352 for ~ example. If the signal level is below a predeterl"i,led threshold for example indic~li"g that the mobile te""i"al is far away the signal level detector circuit 370 sends a 'low power' ~ control signal to the microconl,-l'or 350. The microconl,.llcr 35û may in turn increase the gain of the amplifier 369. In addition, or in the altemative; the microcor,l, .llor 350 may switch from the antenna 29û to the higher gain anLenna 292 via the switch 351. If the signal level CA 022l0792 l997-07-l8 W O 97/21294 PCT~US96/19336 det~cted by the signai level detector circuit 370 is above another pledeler~ ed Ihl~sho'~', thereby indicating that the mobile terminal is close, the signal level detector circuit 370 provides a "high power" control signal to the microcor,l,."er 350. In response, the mic~ uconlruller 350 can reduce the gain of the RF output amplifier 369 so as to avoid the 5 possi~ility of saturating the front end of the mobile terminal. In ad~ilion, or in the allt:",ali~re, the m _ ucor~ r 350 may cause the base station 210 to switch from a higher gain antenna to a lower gain antenna via the switch 351.
The base station 210 also includes a memory 370 serving as system memory for themicruconl,ullPr 350 and which is subalah~ially idenlical in function to the memory 330 10 described above in connection with the mobile terminal. In addition, the base station may include a user i"le,~ace 372 such as a keypad, display, etc.
Also included in the base station 210 is a power supply 374 for providing the necessary power for ope,dli"g the device. In the conventional case, the power supply can be based on power received from conventional power lines (not shown). I lo~levcr, it will be apprt:ciated 15 that all or part of the features shown in Figure 3C also apply to the above rfisc~lcsed \r::n,less base stations 215. Hence the power supply 374 can also be a solar powered, rechd,~oahle battery based system as is r~iscll~sed below in more detail in relation to Figure 6B.
Furthermore, in another embod;."ent of the invention, the base station includes an error correction circuit as part of the receiver system as lepr~sented by phantom box 378.
20 Particularly in the case where the base station is a w:.~less base station 215, it is desi,dijle to include an errorco,lt:clion circuit 378 for reducing errors in the received data. The circuit 378 can be of conver,liol,al design, but it is preferdl)ly included in wireless base stations 215 which are used as repeater ald~ions. As is discussed more fully below, it is significant that wi.~less base stations 215 which serve as repeaters include such an error correction circuit 25 378. In this manner, the total number of errors which occur during multiple hops can be decl eased.
Although the above e~"l,odi",enla of the mobile terminal 230 and the base stations 210,215 where des.;,ibed as using the same ch;~pi.lg rate regardless of whether the data is being lldnalllit~ed at a fast, mid or slow rate, it will be appr~:..idLed that another embodiment 30 may involve adjusting the chipping rates via the appropriate timing cohl,-"or. Similarly, although the above embodiments are designed primarily using discrete hardware com~.onenla, it will be appreciated that the majority of functions can be carried out pr""dl ily via software without departing from the scope of the invention. Also, although the receiver system in both the mobile terminal 230 and the base station 210,215 was described as a 35 bank of decode,a operating in parallel, it will be appreciated that another embodiment of the W O 97/21294 PCTnUS96/19336 invention may use a serial type receiver which adjusts the timing of the PN signal provided to the mixer until a valid signal is found.
Furthermore, the exemplary embodiment utilized BPSK and QPSK modulation techniques. Nevertheless, other modulation techniques can be substituted or added as 5 conditions dictate. For example, a QAM modulation scheme may be utilized in ad-lilion to BPSK and QPSK. Hence, the present invention is not intended to be limited to any particular combination necessarily. Figures 7A-7E and 8A-8E discussed below illustrate additional embod;."enLs of the present invention.
The above ~iiccussion of Figures 3B and 3C describes in detail exemplary hardware configurations of the mobile terminals 230 and base stations 210,215. The following description explains in more detail the relevant protocols involved.
Figure 4A is a flowchart that represents the process by which a mobile terminal 230 registers with a base station 210 halJw~ d to the backbone and selects an initial data rate to be used for communicdli, ,9 with the base station. The Figure 4A flow chart is based on situations where all responding base stations 210 are hardwired to the backbone 260 while Figure 4B shows the steps taken when one or more responding base stations are wireless.
At step 410 in Figure 4A, the mobile terminal 230 sets its initial rate at which it will aUempt to register with one of the base stations. The initial rate set may simply default to a fast rate or be set in acco~dance with the rate at which previous communications have occurred or be 20 set by any other criteria including a l,dns",;~sioll rate known to be within the capability of certain base stations. At step 420, the mobile terminal 230 broadcasts a request to register a packet known as the "find router" packet to any base station 210, 211, 215 available to receive the broadcast. The "find router" packet includes i"for")dlion illdicdli"g to any base stations 210, 211, 215 within receiving range of the broadcast that the particular mobile 25 temminal 230 is seeking to register with a base station. The base stations which receive the packet, in turn, are pluyldnlmed to lldllslllil a "router identification" packet to any mobile terminals 230 from which they receive a "find router" packet. These "router idenlir,cdlion"
packets include i,,~u,,,,alion as to fhe identity of the base station, the amount of use (or "load") on the base station, and an indication of the relative location of the base station in the 30 system 200. The i"ro""-dlion related to the location of the base station indicates to the ~ mobile temminal how many "hops" the responding base station is from the system backbone 260. Base stations hardwired to the network are consideled a single "hop" for the mobile terminal, whereas each addilional wireless base station 215 used to access the n~lworh adds a "hop" through which the mobile terminal must communicate in order to access the 35 backbone 260.

W O 97121294 PCT~US96/19336 At step 430 the mobile te"~;nal 230 waits for a preset period of time and determines whether a "router identification" signal has been received from at least one base station 210 211 215. If no "router idenLiricdlion" is received then the mobile terminal 230 proceeds to step 440. At step 440 it is deten~,i"ed whether the particular embodiment of the mobile terminal 230 in use has the capability of commun~ n at a slower rate. If it is possible then at step 450 data transmission rate pa,dl"eter~ within the mobile terminal 230 are changed to slowthe data tldnsn,;ssion rate thereby inc;rtasi"g the signal range, and proceeds back to step 420 and alle,,,,ul~ to registerwith a base station 210 at the slower l,ansr"ission rate.
If it is not possible to slow the commw,icdlion rate, then the mobile ter",;"al proceeds back to step 420 where it ,~ ns",il:, its "find router."
If, at step 430, the mobile terminal 230 receives a "router ider,lilicc,lion'' signal then the terminal proceeds to step 460. At step 460 the mobile terminal 230 determines if the responding base station 210 is acceplable. When all the responding base stations 210 are hardwired to the backbone 260 (i.e. a com 'etely single "hop" network) then there are two in~lances when the responding base station 210 would be acceptable~ when the request to register signal was sent at the fastest rate or (2) when the request to register was not sent at the fastest rate, however there was no acceplance at an already ~lle,r",led faster rate.
If the mobile lellll;ndl 230 receives more then one acceptable "router idenlificalior," packet in step 460 then the mobile terminal 230 is prus~,~,,,,,,ed to evaluate the packets accor-ling to predetermine oriteria in order to select a base station 210 with which to register. Such predetermined criteria may be based on for example which base station 210 exhibits the lowest load. The mobile terminal 230 will then proceed to step 480 where it will register with the base station 210 selected.
If the responding base station 210 is not acceptable then the mobile terminal 230 will pruceecJ to step 470 where the mobile terminal pdl ~11 ,alers are modifled to send the "request to ,~g;Jl~," at a faster rate and then proceeds back to step 420 where it cller,,pls to register at the faster rate. The purpose of the step 420 is to help optimize the system by ensuring that the base station with the strongest signal is being used.
In a multiple "hop" cellular communication systern 200 having one or more v~ less base sldlions respondi,19 to a mobile terminal's 230 "flnd router" packet determining w~ ll,er a given base station 210 is accep -~'e is slightly more complex. Fig. 4B depicts the steps taken by a mobile terrninal when at least one wireless base station 215 responds to the mobile temminal's '~ind router" packet. As shown in Fig. 4B steps 41 OB through 450B remain unchanged from corresponding steps 410 through 450 in the process desclibed above 3~ dealing with the situation where all responding ba5e stations are hardwired to the network.

CA 022l0792 l997-07-l8 W O 97/21294 PCT~US96/1933~

I lu.vevcr in this situation determining whether to register with a given base station it is not enough that the mobile ten~,i"al is commu"icaling at the fastest possible rate with any base station. What must be dete"";. ,ed is at what speed the mobile terminal 230 must transmit infor"~lion in order to register with a base station 210 215 which will provide the fastest 5 "overall" I,ans",;ssion time to the network. When wireless base stations 215 are involved the overall time it takes a mobile terminal 230 to access the network will include the time it takes to send a packet from the mobile terminal 230 to the wireless base station 215, processing ~or queuing) time for the wireless base station 215 and the time it takes the wireless base station to send the packet to the network. For instance, if a mobile terminal 230 is communicating with a wireless base station 215 at the fastest pOC~ ' !e rate a further inquiry must be made to determine what speed the wireless base station 215 is communicating with the network. If the wireless base station 215 is communicating at a slow speed with the network it may be more optimal for the mobile terminal 230 to reduce its own communicating pa,t""eter- and attempt to directly communicate with a base station 210 15 hardwired to the network. If this is done, the time it takes to send the i,,ru,,,,alion to the w:.~less base station 215 plus the processing time needed by the wireless base station is eliminated.
In order to account for these extra parameters ~ssoci-ted with wireless base stations 215 lookup tables may be maintained within the memory of each mobile terminal 230. The 20 lookup tables are set up to allow the mobile terminals 230 the ability to dele" ";~ ,e the overall time itwould take to send i"~ur",~lion to the network via a given route. An example lookup table may be as follows:

CA 022l0792 l997-07-l8 W O g7/21~94 PCT~US96/19336 Assume time for High speed= x Medium speed= 2x slow speed = 4x and queuing time = .1x W;~ SS base Wiireless base U~,';._less base sta~ion to ~e~ r~ s~ation to l~etvi~lh slaiio~. to ek~l~Tk - Hi~h = Medium ~ Slow Mobile to wireless: Time equals: Time equals: Time equals:
....
base shLi~,lt = x+x+.1x = 2.1x x+2x+.1x = 3.1x x+4x+.1x = 5.1x High Mohile to wireless Time equals: Time equals: Time equals:
. ~ . : . , . ::
base.. ale.lio.l - 2x+x+. 1x = 3.1x 2x~2x+. 1x = 4.1x 2x+4x ~ .1x = 6.1x ~ Med..:: .
Mobile to wireless Time equals: Time equals: Time equals:
base sldliol~ - 4x+x+.1x = 5.1x 4x+2x+.1x = 6.1x 4x+4x+.1x = 8.1x S~ow .

The values from this lookup table can be compared with the amount of time it would take 15 if the mobile terminal 230 communicated directly with a hardwired base station 210, or the lookup table could be used to COIllpalë the total time it would take to communicate via two different wireless base station paths. In the prerelled embod;."enl the processor of the mobile terminal 230 would be proy,d"""ed to opli",i,e communication time given these tions. As shown in Fig. 4B in achieving these optimal settings the mobiie terminal 20 at step 460B would initially determine if le9i~lel il l9 with one of the currently responding base stations would necess~rily allow for an optimal setting. Such may be the case if the mobile terminal is ll dn~l l litlil ,9 at the fastest rate to a base station hardwired to the b~r.khone. If the optimal setting is possible then at step 500B registration is conri""ed with this base station.
If more then one responding base station would provide optimal settings, then one base 25 station would be -~le~;t~d based on the mobile terminals predeler".;.,ed criteria as ~liscussed above.
If at step 4~0B it is not pD-~'-''' to definitively select an optimal responding base station then at step 470B the responding base station providing the best time is stored in memo~.
At step 480B if the mobile terminal has sent out ley; lldliol1 requests at all three speeds then 30 the mobile terminal co" If ~leS the best responding base station times from each of the three ,eg;~llalion bruadc~st~. Following this co",,.~a,ison the mobile te""i"al goes to step 500B
where it selects the most optimal base station. If at step 480B the mobile terminal has not sent out rég;;~ll diions at all three speeds then the ll dnSI I ~;5sion speed of the mobile tel 1 l l;l ,al CA 022l0792 l997-07-l8 W O97/21294 PCTrUS96/19336 is adjusted to transmit at a faster rate if possible or eise at the slowest rate and the mobile terminal proceeds back to step 420. In this manner the fastest path to the network is e~ hed by reviewing the overall l,dns",ission time to the network at difr~:n:nl rates.
Each wireless base station 210 transmits reyi~l,dlion i"ro""c,lion to base stations with 5 which it formed a pen"ane"l link as is discussed above. Regi ,l, ~lion update packets are sent out periodically by each wireless base station to each base station 210 forming a link to the system backbone 260. Upon receiving the reyi~lldlion update packet each base station adds the mobile terminals indicated in the update packet into their own rey;~l~lion table. In this manner, base stations hardwired to the network will know which p~ketc to 10 copy off of the system backbone 260 and transmit to the mobile terminal via the permanent link formed with the wireless base station(s).
Whenever i"ror",dlion packets are wirelessly transmitted there is a real possibility of errors occurring within the packet. In situations where wireless base stations are used as intermediate links between the network and a mobile terrrlinal the possi~ility of errors 15 occurring sig"i~ical,lly i"c,~ases since the ir,for"lalion is being wirelessly ll~ns",illad and received multiple times depending on the number of wireless base stations involved.
Therefore under the present invention each wireless base station has an error cor,~clion circuit 378 (Figure 3C~ which is used to correct errors in the i"forl,l~lion packet received prior to retransmitting the packet. In this manner, stacked errors which occur from the, ~pe~l~d 20 ~ less ll~ns"~ia~ion of data is better avoided.
Once the mobile terminal 230 is reg;sl~, ~d and an initial data rate is set all communication between the base stations 210 215 and the mobile terminal 230 may take place at that data rate. Periodically the mobile terminal 230 may attempt to re-register at a faster data rate. Alternatively the mobile terminal may vary the commu":- -n rate while 25 already rag; ,lt:rt:d. Figure 5 is a flowchart which represents this process. Step 510 ,~p,~senls the mobile terminal setting the commu":-~'ion parameters to correspond to the data rate at which it will attempt commu"i- lion with the base station 210 215. The initial setting may be a default rate a rate previously used a rate at which the mobile terminal 230 has recently i"lel~ eplad a trans",ission from the base station or a rate set by some other 3~ criteria. At step 52Q the mobile terminal 230 transmits a "find router packet at the rate set.
~ At step 530 the mobile terminal 230 then waits to receive a "router idenliricalion response signal from the base station 210. The base station 210 will send the response signal at the same data rate or rates used by the mobile terminal 230. If no response signal is received by the mobile terminal 230 it can be concluded that the base station 210 215 did not receive 35 the trans",;ssion, or the transmission was not received error free. The,t:for~ the mobile W O 97/21294 PCT~US96/19336 the mobile terminal 230 and the base station 210, it shouid be appreciated that several wireless base stations 210 could be used in a row to further extend communicating range.
As desc,ilJed above in the background section, ~rl~r,li",es there are problems a~sori~t~d with nunning power lines from the system backbone 260 to the wireless base station 215. To 5 avoid these problems, this invention utilizes a solar powering system 630 to provide power to the wireless base station 215. In other embodiments, wind, water or other natural energy resources could be used. Referring to Figure 6A, the solar powering system 630 includes solar panels 640, charging circuitry 650, and a battery system 660. The charging circuitry 650 is coupled to the solar panels 640 and the battery system 660 and serves to regulate the 10amount of power fed into the battery system 660 at any given time. The battery system 660 is coupled to the wireless base station 215 and provides power independent of any power supplied through the system backbone 260. It should be appreciated that in another embodiment the v~ leis base station 215 may connect directly to the charging circuitry 650 or the solar panel B40 itself.
15In this particular embodiment, a photovoltaic solar panel 640 having a number of cells 641 is used as shown in ~igure 6B. The cells 641 are textured and have an anti-reflection coating in order to better absorb energy from the sun. The overall size of the solar panel 640 is app~u~ lat~ly five s~uare feet. The solar panel 640 should be of a type which can sufficiently ,~cl,a,ye the battery system 660 within a ,~ason~' lo amount of time determined 20 by the e:,li",dled amount of sun light expected in a given area. For example, in particularly sunny areas such as a desert it may be sufficient to have smaller or fewer solar panels 640 which recharge the battery system 660 at a slower rate since it is expected that the sun's energy can be captured by solar panels 640 during a large part of the day. By conl,~:.l, in areas where it may be cloudy during a greater portion of the day, larger solar panels 640 25 capable of ,~uI,~rui"9 the battery system 660 in a shorter period of time may be necesc~ry in order to ensure the solar powering system 630 remains reliable throughout various weather cor,di~ions. In many typical climates having semi-unprec ~hlc weather condilions, a solar panel 640 such as the model M5~ produced by Siemens of Camarillo, CA may be used. It is e:,li",~led that this particular solar panel is c~p~hle of fully recharging the battery system 30 660, des~,ibed in more below, affer receiving c,pp,u~ ly twenty four hours of full sun light.
It should be ~.,u" :-,ialed, however, that full sun light is not necessary to recharge the battery system as the solar panels can still capture solar energy at a slower rates when conditions do not allow for full sun light to be received.
The purpose of the battery system 660 is to store energy captured by the solar panels 3~ 640 for later use. In this particular embodiment, two 12-volt lead acid gel cell batteries be obtained. The r~ g is a ~iscuscion which generally describes dirre,t:nL embodi",enls of a transmitter system and a receiver system for use in the mobile terminals and base stations.
The transmitter system generally desig"dled 610 of the present invention may be 5 i". -~: "enled in a number of embodiments. For example"t r~"i"9 to Figures 7A, 7B, and 7C, these embodi",enls may include two or more non-col,l,ullabie trans",ill~r~. 710a, a conl,." ' 'e l, dns",iller 71 Ob and a comb;nalion of a non-conl~ ullable l,dns",iller 710a and a controllable l,d"s",illar 710a. A non-c~ le transmitter 710a as shown in Figure 7D
for example and described in further detail below is a transmitter which is typically used in con\,~r,lional base stations 211 and conventional mobile terminals 231 because it is c~r~hle of transmiffing PN coded signals formed with PN codes having only one preselected non-adjustable value of each characteristic. On the other hand a conl~llable lld~1.",iller 710b as shown in Figure 7E and desc,il ed in more detail below is a l,dns",iller r~r~hle of lldl lal"itli"g PN coded signals formed with PN codes having a piurality o~ adjustable values for one or more modulation chardcleri~.lics.
Figure 7A illustrates one of the embodiments of the transmitter system 61 0. For this embodiment the l,~ns",;tler system 610 includes a plurality of non-co"l,."--ble l,dns,niLlers 710a a mic~up~ucessor73û and an antenna 750. Each non-controllable transmitter 710a is capable of l,d"~.",;:~i.,g at a packet rate that is different than the values selected for each of the other non-co,-l,- '-' le lldl ~ .IIlitlt:l . 71ûa. As is ~iscussed above the header portion 31û
and the data portion 32û of the packet 3û0 may be sent at dirre~t nt data tran .n,;ssion rates and therefore each packet rate It:p~t:senl . a dirrt,~nl co"lbi"alion of these possibilities.
Once a packet rate has been de~er",;.,ed ~via the processes described with reference to Figures 4 and 5) a " ,: - uprucessor 730 will prepare for transmission by selecting the non-2~ co"l, . '-' le t,dnsmiller 71 0a ~p~'- le of transmitting at this rate.
Figure 7B illustrates another embodil"enL of the l,ans",illar system 610. This embodiment is very similarto the l,dns",illar system 61û shown in Figure 7A. I loN_vcr, this transmittersystem 610 includes a cor,l,."~'~'e l,dns",iller 71ûb as opposed to a plurality of non-conlll "-hletransmitters 71Oa. ~hus, in preparing fortransmission the r";_,up,ucessor 730 will make adjusl."er,l~. to the conl(o!l ' ;e l,dnsn,iller 710b such that it is r.~r: ' 'e of - lldnsmilli"g at the given packet rate.
~igure 7C illustrates yet another embod;menl of the transmitter system 610. Thisembodiment is also very similar to the transmitter systems 610 illustrated above in Figures 7A and 7B. I IOJ ~Jcr this l,dns",illar system 61û includes a non-controllable l,dns",iLIer 3~ 71ûa and a CGIIll'~ '- 'e l~dnsmiller 71ûb. In preparing for 1, dl)srlli~.sion~ the microprocessor W O 97/21294 PCT~U~96/19336 conne- Led in series are used to fomm the battery system 660. Each battery is rated to provide 90 amp-hours of power. At this rate it is estimated that at full charge the battery system containing these two bdlLeries could supply appro~il"alely nine days of continuous power to the wireless base station 215 without any recharging. A variety other balle~ies ~ '19 of 5 supplying varying amounts of power could readily be used.
The charging circuitry 650 reg~ tes the amount of energy fed into the battery system 660 and ",on .~ the power level of the battery system 660. In order to perform these functions the charging circuitry 650 includes voltage regulating circuitry 651 and current ",onilori"g circuitry 652. The voltage regulating circuitry 651 connects the solar panels to the battery system 660 and provides CO~ dlll voltage to the battery system 660 during l~cl)a,y;"g. The ~l~onito~i"g circuitry 652 regl~l~tes when recharging is to occur and is therefore connecled to the voltage regulating circuitry 651. The Illonilori,,g circuitry is further connected to the output of the battery system 660 in order to monitor the amount of power being drained by the v.:. ~ less base station 215. The n lonitol il Ig circuitry 652 is set to allow solar based energy to enterthe battery system 660 for recharging when the ll,oniluril,g circuitry 650 senses the battery system 660 has dropped below a charge resumption set point. In this particular embodiment the charge resumption set point is set at 18 volts which represents a lower end voltage level at which the wireless base station can still operate properly. Charging circuitry 650 such as the Automatic Sequencing Charger (AS~) produced by Specialty Concepts Inc of Canoga Park, CA could be used in this invention.
The amount of power consumed by a typical wireless base station 215 will greatly vary by the amount of activity being processed. It is esli",~led that the amount of power needed to run an ~; ~less base station in its idle state is .25 amps at 22 volts. During an active state such as when the v~ less base station is transmitting or receiving inror"~lion app~u,d",dlely .5 amps is needed at the same voltage level. In any event by utilizing the solar powering system 630 the power requirements for the W;~IeJS base station 215 of this exen")lary embodiment will be met.
Generally as des.;,ii,ed above the lransl"iller system 610 and the receiver system 620 of the base stations 210, wireless base station 215 and mobile terminal 230 will adjust their paldr"~le,s in order to opli",i~e the system 200. Thus the following sections describe in detail a variety of embodiments which the transmitter system 610 and receiver system 620 may use in adjusting these data rates.
Figures 3B and 3C liiscussed above illustrate only one example of embodi",en~s of a mobile terminal 230 and a base station 210 21~ in accG,-lance with the invention. There are in fact, a variety of ways in which similar flexibiiity in the data l~ dnSIl l;ssion chara~;Leri:,lics can W O 97/21294 PCTnUS96/19336 terminal 230 dLLt~ .L~ to il,~;lease the range and accuracy by using a siower data rate. Step 540 represents the mobile terminal deter,l,i,ling whether a slower rate is possible. If the determination results in a positive answer, the mobile terminal 230 varies comm~",icalion parameters to slow the rate at step 550 and rel,;an:,",ils at step 520. If a slower rate is not possible, the mobile terminal 230 simply retums to step 520 to attempt another ll ans",;ssion.
To avoid an endless loop at the slowest data rate, the mobile terminal 230 may attempt to register with another base station (as rliscussed earlier) when communication is no longer possible with the present base station 210 or 215.
If, at step 530, a response signal is received within a preset period of time, then the mobile terminal 230 proceeds to step 560. At step 560, the mobile terminal 230 determines whether the response signal was received error free. If not, then the mobile terminal p~g, ~:sses to step 540 where it deter" ,;. ~es if a slower data rate is possible. However, if the onse signal is received error free, then the mobile terminal proceeds to step 570 where it dete"";.,es whether a faster commul,icdLion rate with the base station 210 or 215 is possible. If it is possible, then at step 580 one or more communication pa, dr"~ler:, within the mobile terminal 230 are changed to increase the communicalion rate with the base station.
The new pa~an,ele,~ are set at step 510 for use when l,ans",iLLi"g the next packet. If, however, at step 570, it is not possible to increase the commu"icdliol1 rate between the mobile temminal and the base station, then the mobile terminal will simply keep the currently set commu"icdLion pa~d"~etel:, at step 510.
As an illustrative example of a cellular commun5cdLion system in accorciance with this invention, Figure 6A shows a mobile temminal 230 communicating with a device on the system backbone 260. The mobile terminal is regijLert:d to a wireless base station 215 which has formed a pe", Idl lel IL link to the system ba-,hbol1e through ~ase station 210. Both the wireless base station 215 and the hardwired base station 210 have the ability to dynamicaily alter paldlllelel~ such as moch ~ ion complexity, PN code iength, and/or ~,h ,~p..lg rate in order to optimize data l,dnsr";ssion as discucsed above. The wireless base station 215 in~(eases the geoyld~h:- area in which the mobile temminal 230 can travel and still Illdil ll~;ll contact with devices on the system backbone 260. In order to further increase the distance from which the wireless base station 215 can communicate with the base station 210, an o""~idi, t:ctional type al,lenna is directed toward the base station 210. In other embodiments, the two a"~n,1as could be dlldcl ,ed to the wireless base station, wherein one antenna is a yagi type directed a"Lenna for communicating with the hardwired base station, and a second antenna is a omnidirectional type antenna for receiving and tldns",iLLi"g to the mobile terminal 230.
Although oniy one w,:.~lcss base station 210 is shown to act as an intermediate link between 730 will first look to see if any non-conl,~ le l,dns",iller 710a is c~r~h e of sending at the given packet rate and if so the "ic, oprocessor 730 selects this transmitter. However if no such non-controllable transmitter exists, then the ,,,iu,up,ucessor 730 will adiust the controllable l,~ns~r,iller 710b to send at the given packet rate.
Following the selE- Jiol1 or adjustment of the proper transr~liller in any of the embodi",enls shown above (7A 7B 7C), the n,iu~uprùcessor 730 may also adjust other communication parameters ~i.e. antenna type, signal power, etc.) prior to transn.;ssion. Once all of these additional char.duleristics are adjusted for the trans~iller selected prepares to l,~nsi"il according to the pd,d",t:lera set.
Figures 7D and 7E are block diagrams of the non-conl~ l,ans",iller 710a and the conl,."~hle transmitter 710b. Referring to Figure 7D the non-cs,-l~ 'e lidnsn,iller 710a generally includes a static PN code sequencer 713 a mixer 714 and a modulator 716. The mixer 714 receives the data to be transn,illed and mixes the data with a PN code received from the static PN code sequencer 713, which is a PN code sequencer c~rah'e of sequencing a PN code having only constant parameters (i.e. chip code length chipping rate...etc.). The mixer 714 then mixes the data with the PN code to form the PN coded signa.
and fo;wards the PN coded signal to the mod~ ~lator 716. The modulator 716 then modulates the PN coded signal onto a ca,Tier frequency with, for exar, I"le a BPSK or QPSK modulation cor" e :'y type.
Refe lillg to Figure 7E the co"l,."~'~'~ I,dns"~ 3r 710b generally includes an adjustable PN code sequencer 712, a mixer 714 and a modulator 716. In operdlion, the ~-~just~l-le PN
code sequencer 712 which is a PN code sequencer ca~arle of adjusting a PN code to a variety of pa,d",eler5 receives a signal from the microprocessor 730 indicating the pa~d",~t~ a to be set. This signal is then used to adjust the PN code values of the PN code sequencer 712 accordi, lgly. The PN code sequencer 712 then fo~ rda to the mixer 714 a PN code having the pdldlll~:lela select~n' The mixer 714 receives data to be l,.d"s",illed and mixes the data with the PN code received from the adjustable PN code sequencer 712. The mixer 714 then mixes the data with the PN code to form the PN coded signal and forwards the PN coded signat to the mod~ tnr 716. The mo~ or 716 then modulates the PN coded signal onto a carrier frequency with one of the modulation complexities.
~csoci~ted vvith each l,d,1smiller system 610 is a receiver system 620 using the same ~":_n"a 750 and ~ uprucessor 730. I lo.r:_vcr unlike the l,~ns",iller systems a receiver system is required to maintdi" certain characteristics when housed in a base station 210 which are not neces~ .,y for receiver systems housed in mobile terminals. The reason for the difference is that base station receivers, under this embodiment are initially required to CA 022l0792 l997-07-l8 W O 97/21294 PCT~US96/19336 handle packets being sent at either the mid or slow packet rates (i.e. BPSK modulation and either an 11 or 22 chip PN code length, see above). Thus, in order to handle either instance, the base station receiver system must have at least two correlators to account for the ~ different chip code lengths. A mobile terminai 230, on the other hand, initiates the 5 communication with a base station 210 at a specific rate and any responding base station ~ must reply at the same rate. Therefore, the mobile terminal receiver will not have to "guess"
as to which rate the base station will respond and only needs one cor,tlalor to effectively communicate.
Similar to the transmitter system 610, the receiver system 620 of the present invention may also be i",, !en,enled in a multitude of embodiments with the only l~sl,iution being that receiver systems for base stations must have at least two separate corl ~lclora, one of which is c~r~l~le of handling a slow packet data tran~"~;ssion rate and one of which is caF ~ le of handling a mid packet data transmission rate. As described below, each receiver typically has only one coll~,l.,tor acso~ ed with it and, therefore, the receiver system 620 must have at least two receivers within it. However, since the initial packet is always sent at the BPSK
rate (i.e. mid or slow rates) only one demodulator is needed to handle this initial data. If it is indicated that further data will be sent at the fast packet rate, then a second demod~'q~nr capable of har,dli,.g a QPSK modulation complexity would be necess~ry.
Figures 8A and 8B showtypical embodi,l,er,ls of the receiver system 620 of the present invention which may be used within a base station 210 or a mobile terminal 230. For i"~ldnce, Figure 8A shows the receiver system 620 with a combination of two or more non-cor"lc"~''e receivers 810a, while Figure 8B shows the receiver system 620 havingcombination of a con~ ''E receiver 810b and a non-co"l,ullable receiver 810a. Asdescribe below, non-cGr,l,~ 1E receivers 810a are ones which do not have the capability of changing their own p~ to receive packets at data communication rates other then the rate preset within the particular non-conl,.l'nhle receiver. The co"ll."-hle receivers 810b, on the other hand, have at least some c~r~l~ilily to vary their receiving pclldllletel:~ to be able to receive parkets at more then one data communication rate.
In o,u~,~tion, when only non-conll~!l ' le receivers 810a are used in the receiver system 3~) 620 (see Figure 8A), the ",: uplucessor 730 will simply select the non-controllable receiver 810a c~pr' 1~ of handling the packet to be received. If no such non-conL,~ le receiver 81ûa exists, then the receiver system 620 would not be c- p-~le of receiving this packet. If, - however, both a non-co~ "~'~'e receiver 810a and a conl,.l'-hle receiver 810b exist in the same leceiver system 620 (see Figure 8B), then the ",i-,,oprocessor 730 first determines 35 ~hetl,erthe non-cor,lf "-'lle receiver 810a is c~r~hle of handling the packet to be received.

-CA 022l0792 l997-07-l8 W O 97/21294 PCT~US96/19336 If so, the microprucessor 730 selects this non-controllable receiver 810a. If the non-cor,l,~"~hle receiver 810a is not capable of handling the packet, then the microprocessor 730 wili simply adjust the controllable receiver 810b such that it is capable of receiving the ~n~ d paclcet. Following this selection/adjustment process, the microprocessor 730 may also make adjusll"er,la to other pal~r"aters which may help the rec~ivi~,g process (i.e., changes to the antenna, battery power, etc.).
As indicated above, since the mobile terminal 230 does not require two cor, ~IdlOl a, it is possible that only one receiver is used within the mobile terminal. Therefore, Figure 8C
depicts another embodiment which is available for the mobile terminal only. In this embodi",enl, the receiver system 620 utilizes only one conl,~ '2 receiver 810b which is continually adjusted by the mic~op~ucessor 130 to receive packets at the desired rate.
Figures 8D and 8E further describe the non-conl,."~'lle receiver 810a and the controllable receiver 810b, respectively. Referring to Figure 8D, the non-conl~ ' le receiver 810a generally includes a demodulator 814, a static PN code sequencer 817 and 1~ a correlator 819. In operation, the particular non-conl,ullable receiver 810a has been selected by the tll _ uprocessor 730 because of its capability of receiving a packet having certain values which correspond to those values transmitted from a transmitter systsm 610.
The demodulator 814 receives the modulated PN coded signal from the t,~"a",illersystem 610. The demodulator 814 demodulates the PN coded signal from the carrierfrequency and forwards the PN coded signal to the colleldlor 819. The co"~ or 819 also receives a PN code received from the static PN code sequencer 817, which is a PN code sequencer c~p ~le of sequencing a PN code having only conslanl values. The co"~ lor 819 then uses the PN code to co"~laLe the data (extract or decode the data) from the PN
coded signal.
Referring to Figure 8E, as described above, the receiver system 62~ may also include a controllable receiver 810b which may be used instead of or in conjunction with the non-conl,. " ' le receivers 810a. The cG"I,ullaLle ~t:ceiver 810b is similar to the non-conl, ullable receiver 810a but is addilionally capable of receiving PN coded signals formed with PN codes having different values.
The controllable receiver 810b includes a demodulator 814, a filter (preferably a baseband filter) 816, an adjustable PN code sequencer 818 and a cor,clalor 819. In ope,~tion, the dem~d~'~'or 814 l~ceives the mod~ P-d PN coded signal from the t,~ns",iller system 610. The demodulator 814 demodulates the PN coded signal from the carrierfrequency and folwards the PN coded signal to the filter 816. Prior to receiving the PN coded signal, the filter 816 receives the PN code chipping rate value signal from the ~ uprucessor CA 022l0792 l997-07-l8 W O 97/21294 PCT~US96/19336 730 and adjusts its spectral bandwidth based on the PN code chipping rate value received.
Upon receipt of the PN coded signal the filter 816 then filters the PN coded signal and fonNards the filtered PN coded signal to the cGr,~l~lor 819. Additionally, the adjustable PN
code sequencer 818 may also be feed through the filter 816 prior to entering the cor,t:lalor 819.
Prior to receiving the filtered PN coded signal~ the conelc,lor 819 receives a PN code length signal form the ",:_,uplucessor 730 and adjusts itself accordingly to cG~ lale a PN
code having the PN chip code length value. In another e~bodin,enl, the col,~lalor 819 is actually a plurality of cor,~lalors 819 and the microprocessor 730 selects the co" lalor 819 capable of correlating a PN code having the sele~Pd PN code length value.
Upon receipt of the PN coded signal, the cor,eldlor 819 also l~ceives a PN code from the adjustable PN code sequencer 818 which is a PN code sequencer ~r~hlQ Of adjusting a PN
code to a variety of values received form the ~ up~ucessor 730. The cor,~6~or 819 then uses the PN code to co,relale (decode) the data from the P~ coded signal.
Another embodiment of the cellular comm-".ir -n system 200 of the present invention includes a mobile terminal 230 andlor base station 210 that can vary its l,~ns"~illing par~"leters but not its receiving pa,amelera. Conversely, such a system 200 may have a mobile terminal 230 and/or a base station 210 that can vary only its receiving pa,a")elers but not its lldnsl,,illi,,~ p~,amelers.
What has been des~.,ibed above are prere"~d embodiments of the present invention. It is, of course, not possible to describe every conceivable co",b;nalion of components or ll,~lhodologies for purposes of describing the present invention but one of ordinary skill in the art wiil recognize that many further co",i i"alions and permutations of the present invention are pos- ' le.

Claims

1. A cellular communication system, comprising:
a plurality of base stations coupled to a system backbone, each of the base stations comprising a base station receiver system for receiving wireless communications and a base station transmitter system for transmitting wireless communications; and a plurality of mobile terminals each for communicating with the system backbone by way of at least one of the plurality of base stations, each of the plurality of mobile terminals having a mobile terminal transmitter for transmitting wireless communications to the at least one of the plurality of base stations and a mobile terminal receiver system for receiving wireless communications from the at least one of the plurality of base stations;
wherein, with respect to at least one of the mobile terminals, at least one of the mobile terminal transmitter system and the mobile terminal receiving system wirelessly communicates with the at least one of the plurality of base stations by selectively transmitting or receiving data according to any of a plurality of different PN code parameters.
2. The cellular communication system of claim 1, wherein the mobile terminal transmitting system of the at least one mobile terminal is controllable to select any of a plurality of different data transmission rates.
3. The cellular communication system of claim 2, wherein any of the plurality of different data transmission rates is selected by way of at least one of selecting among different PN code lengths and selecting among different chipping rates.
4. The cellular communication system of claim 1, wherein the mobile terminal transmitting system of the at least one mobile terminal is controllable based oncommunications received from the at least one of the plurality of base stations.5. The cellular communication system of claim 4, wherein the controllable mobile terminal transmitting system is configured to transmit initially at a first data transmission rate and, based on communications received from the at least one of the plurality of base stations, to transmit subsequently at a second data transmission rate.
6. The cellular communication system of claim 1, wherein the mobile terminal receiving system of the at least one mobile terminal is controllable to select any of a plurality of different data transmission rates.
7. The cellular communication system of claim 6, wherein any of the plurality of different data transmission rates is selected by way of at least one of selecting among different PN code lengths and selecting among different chipping rates.

8. The cellular communication system of claim 1, wherein the base station transmitting system and the base station receiving system of the at least one of the plurality of base stations have generally fixed PN code parameters.
9. The cellular communication system of claim 1, wherein at least one of the base station transmitting system and the base station receiving system of the at least one of the plurality of base stations wirelessly communicates with the at least one mobile terminal by selectively transmitting or receiving data according to any of a plurality of different PN code parameters.
10. The cellular communication system of claim 9, wherein the base station transmitting system of the at least one base station is controllable to select any of a plurality of different data transmission rates.
11. The cellular communication system of claim 10, wherein any of the plurality of different data transmission rates is selected by way of at least one of selecting among different PN code lengths and selecting among different chipping rates.
12. The cellular communication system of claim 10, wherein the base station transmitting system is controllable based on communications received from the at least one of the plurality of mobile terminals.
13. The cellular communication system of claim 1, wherein at least one of the plurality of base stations is coupled to the system backbone by way of a wireless connection.
14. A cellular communication system, comprising:
a plurality of base stations coupled to a system backbone, each of the base stations comprising a base station receiver system for receiving wireless communications and a base station transmitter system for transmitting wireless communications; and a plurality of mobile terminals each for communicating with the system backbone by way of at least one of the plurality of base stations, each of the plurality of mobile terminals having a mobile terminal transmitter for transmitting wireless communications to the at least one of the plurality of base stations and a mobile terminal receiver system for receiving wireless communications from the at least one of the plurality of base stations;
wherein, with respect to at least one of the mobile terminals, at least one of the mobile terminal transmitter system and the mobile terminal receiving system wirelessly communicates with the at least one of the plurality of base stations by selectively transmitting or receiving data according to any of a plurality of different transmission parameters based on communications received from the at least one of the plurality of base stations.

15. The cellular communication system of claim 14, wherein the mobile terminal transmitting system of the at least one mobile terminal is controllable to select any of a plurality of different data transmission rates.
16. The cellular communication system of claim 15, wherein any of the plurality of different data transmission rates is selected by way of at least one of selecting among different PN code lengths selecting among different chipping rates, and selecting among different modulation schemes.
17. The cellular communication system of claim 14, wherein the mobile terminal receiving system of the at least one mobile terminal is controllable to select any of a plurality of different data transmission rates.
18. The cellular communication system of claim 17, wherein any of the plurality of different data transmission rates is selected by way of at least one of selecting among different PN code lengths, selecting among different chipping rates, and selecting among different modulation schemes.
19. The cellular communication system of claim 14, wherein the plurality of different transmission parameters comprise different power levels at which data is transmitted.
20. The cellular communication system of claim 14, wherein the base station transmitting system and the base station receiving system of the at least one of the plurality of base stations have generally fixed transmission parameters.
21. The cellular communication system of claim 14, wherein at least one of the base station transmitting system and the base station receiving system of the at least one of the plurality of base stations wirelessly communicates with the at least one mobile terminal by selectively transmitting or receiving data according to any of a plurality of different transmission parameters.
22. The cellular communication system of claim 21, wherein the plurality of different transmission parameters comprise different power levels at which data is transmitted.
23. The cellular communication system of claim 21, wherein the plurality of different transmission parameters comprise different antennas used to receive or transmit data.
24. The cellular communication system of claim 14, wherein at least one of the plurality of base stations is coupled to the system backbone by way of a wireless connection.
25. A cellular communication system comprising:
a plurality of base stations coupled to a system backbone, each of the base stations comprising a base station receiver system for receiving wireless communications and a base station transmitter system for transmitting wireless communications; and a plurality of mobile terminals each for communicating with the system backbone by way of at least one of the plurality of base stations, each of the plurality of mobile terminals having a mobile terminal transmitter for transmitting wireless communications to the at least one of the plurality of base stations and a mobile terminal receiver system for receiving wireless communications from the at least one of the plurality of base stations;
wherein, with respect to at least one of the mobile terminals, at least one of the mobile terminal transmitter system and the mobile terminal receiving system wirelessly communicates with the at least one of the plurality of base stations by selectively transmitting or receiving data according to any of a plurality of different transmission parameters; and wherein at least another one of the mobile terminals cannot vary any of its transmission parameters.
26. The cellular communication system of claim 25, wherein the mobile terminal transmitting system of the at least one mobile terminal is controllable to select any of a plurality of different data transmission rates.
27. The cellular communication system of claim 25, wherein the mobile terminal receiving system of the at least one mobile terminal is controllable to select any of a plurality of different data transmission rates.
28. A cellular communication system, comprising:
a plurality of base stations coupled to a system backbone, each of the base stations comprising a base station receiver system for receiving wireless communications and a base station transmitter system for transmitting wireless communications; and a plurality of mobile terminals each for communicating with the system backbone by way of at least one of the plurality of base stations, each of the plurality of mobile terminals having a mobile terminal transmitter for transmitting wireless communications to the at least one of the plurality of base stations and a mobile terminal receiver system for receiving wireless communications from the at least one of the plurality of base stations;
wherein, with respect to the at least one base station, at least one of the base station transmitter system and the base station receiving system wirelessly communicates with one of the mobile terminals by selectively transmitting or receiving data according to any of a plurality of different PN code parameters.
29. The cellular communication system of claim 28, wherein the at least one basestation is coupled to the system backbone by way of a wireless connection.

30. The cellular communication system of claim 28 wherein the base station transmitting system of the at least one base station is controllable to select any of a plurality of different data transmission rates.
31. The cellular communication system of claim 30, wherein any of the plurality of different data transmission rates is selected by way of at least one of selecting among different PN code lengths and selecting among different chipping rates.
32. A cellular communication system, comprising:
a plurality of base stations coupled to a system backbone, each of the base stations comprising a base station receiver system for receiving wireless communications and a base station transmitter system for transmitting wireless communications; and a plurality of mobile terminals each for communicating with the system backbone by way of at least one of the plurality of base stations each of the plurality of mobile terminals having a mobile terminal transmitter for transmitting wireless communications to the at least one of the plurality of base stations and a mobile terminal receiver system for receiving wireless communications from the at least one of the plurality of base stations;
wherein with respect to the at least one base station at least one of the base station transmitter system and the base station receiving system wirelessly communicates with one of the mobile terminals by selectively transmitting or receiving data according to any of a plurality of different transmission parameters based on communications received from the mobile terminal.
33. The cellular communication system of claim 32 wherein the base station receiving system of the at least one base station is controllable to select any of a plurality of different data transmission rates.
34. The cellular communication system of claim 33, wherein any of the plurality of different data transmission rates is selected by way of at least one of selecting among different PN code lengths and selecting among different chipping rates.
35. The cellular communication system of claim 32 wherein the at least one base station is coupled to the system backbone by way of a wireless connection.
36. The cellular communication system of claim 32 wherein the base station transmitting system of the at least one base station is controllable to select any of a plurality of different data transmission rates.
37. The cellular communication system of claim 32 wherein any of the plurality of different data transmission rates is selected by way of at least one of selecting among different PN code lengths, selecting among different chipping rates, and selecting among different modulation schemes.

38. A cellular communication system, comprising:
a plurality of base stations coupled to a system backbone, each of the base stations comprising a base station receiver system for receiving wireless communications and a base station transmitter system for transmitting wireless communications; and a plurality of mobile terminals each for communicating with the system backbone by way of at least one of the plurality of base stations, each of the plurality of mobile terminals having a mobile terminal transmitter for transmitting wireless communications to the at least one of the plurality of base stations and a mobile terminal receiver system for receiving wireless communications from the at least one of the plurality of base stations;
wherein, with respect to the at least one base station, at least one of the base station transmitter system and the base station receiving system wirelessly communicates with one of the mobile terminals by selectively transmitting or receiving data according to any of a plurality of different transmission parameters; and wherein at least another one of the base stations cannot vary any of its transmission parameters.
39. The cellular communication system of claim 38, wherein the base station transmitting system of the at least one base station is controllable to select any of a plurality of different data transmission rates.
40. The cellular communication system of claim 38, wherein the base station receiving system of the at least one base station is controllable to select any of a plurality of different data transmission rates.
41. A mobile terminal for use in a cellular communication system having at least one base station coupled to a system backbone, the mobile terminal comprising:
a transmitting system for wirelessly communicating data to the base station; anda receiving system for wirelessly receiving data from the base station, wherein at least one of the transmitting system and the receiving system wirelessly communicates with the base station by selectively transmitting or receiving data according to any of a plurality of different transmission parameters based on communications received from the base station.
42. The mobile terminal of claim 41, wherein the transmitting system is controllable to select any of a plurality of different data transmission rates.
43. The mobile terminal of claim 42, wherein any of the plurality of different data transmission rates is selected by way of at least one of selecting among different PN code lengths, selecting among different chipping rates, and selecting among different modulation schemes.

44. The mobile terminal of claim 41, wherein the transmitting system is controllable based on communications received from the base station.
45. The mobile terminal of claim 41, wherein the plurality of different transmission parameters comprise different power levels at which data is transmitted.
46. A base station coupled to a system backbone for use in a cellular communication system, the base station comprising:
a transmitting system for wirelessly communicating data to a mobile terminal included in the cellular communication system; and a receiving system for wirelessly receiving data from the mobile terminal;
wherein at least one of the transmitting system and the receiving system wirelessly communicates with the mobile terminal by selectively transmitting or receiving data according to any of a plurality of different transmission parameters based on communications received from the mobile terminal.
47. The base station of claim 46, wherein the base station is coupled to the system backbone by way of a wireless connection.
48. The base station of claim 46, wherein the transmitting system is controllable to select any of a plurality of different data transmission rates.
49. The base station of claim 48, wherein any of the plurality of different datatransmission rates is selected by way of at least one of selecting among different PN code lengths, selecting among different chipping rates, and selecting among different modulation schemes.
50. The base station of claim 46, wherein the transmitting system is controllable based on communications received from the mobile terminal.
51. The base station of claim 46, wherein the plurality of different transmission parameters comprise different power levels at which data is transmitted.
52. A method of wireless communication between a mobile terminal and a base station in a cellular communication system, comprising the steps of:
the mobile terminal transmitting data to the base station according to a first transmission parameter and determining if the data has been validly received; and the mobile terminal automatically transmitting data to the base station according to a second transmission parameter which is different from the first transmission parameter if the data is determined not to have been validly received.
53. The method of claim 52, wherein the difference between the first transmission parameter and the second transmission parameter relates to at least one of PN code length, chipping rate, and modulation scheme.

54. The method of claim 52, further comprising the steps of the mobile terminal transmitting information to the base station regarding a desired data transmission rate, and the base station automatically adjusting a transmission parameter in order to receive data from the mobile unit at the desired data transmission rate.
55. The method of claim 54 wherein the base station adjusts at least one of a PNcode length a chipping rate and a modulation scheme.
56. A wireless base station for use in a cellular communication system having a system backbone, comprising:
a communication system for performing wireless communications with devices in the cellular communication system including communicating with the system backbone by way of wireless communications: and a power supply for providing power to operate the wireless base station, the power supply including a solar power device for deriving the power from solar energy.
57. The wireless base station of claim 56 the power supply further comprising a battery system which is charged by the solar power device.
58. The wireless base station of claim 57, the power supply further comprising current monitoring circuitry for monitoring the current delivered to the battery system from the solar power device.
59. The wireless base station of claim 57 the power supply further comprising voltage regulating circuitry for regulating the voltage delivered to the battery system from the solar power device.
60. A wireless base station for use in a cellular communication network having asystem backbone, comprising:
a communication system for performing wireless communications with devices in the cellular communication network said communication system receiving and transmitting wireless communication between a first device and a second device in the cellular communication network; and an error correction system for correcting data errors in the wireless communication received by the communication system prior to the communication system transmitting the wireless communication.
61. A wireless base station for use in a cellular communication network comprising:
a communication system for performing wireless communications with devices in the cellular communication network said communication system being adapted for receiving and transmitting wireless communication between a first device and a second device in the cellular communication network; said communication system having a first antenna, a second antenna and antenna selection circuitry, wherein said antenna selection circuitry selects one of said first antenna and second antenna for at least one of said receiving and or transmitting wireless communication.