CA1187942A - Non-orthogonal mobile subscriber multiple access system - Google Patents
Non-orthogonal mobile subscriber multiple access systemInfo
- Publication number
- CA1187942A CA1187942A CA000435412A CA435412A CA1187942A CA 1187942 A CA1187942 A CA 1187942A CA 000435412 A CA000435412 A CA 000435412A CA 435412 A CA435412 A CA 435412A CA 1187942 A CA1187942 A CA 1187942A
- Authority
- CA
- Canada
- Prior art keywords
- signal
- noise
- communications system
- code
- interfering
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7097—Interference-related aspects
- H04B1/7103—Interference-related aspects the interference being multiple access interference
- H04B1/7107—Subtractive interference cancellation
- H04B1/71075—Parallel interference cancellation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
- H04B1/12—Neutralising, balancing, or compensation arrangements
- H04B1/123—Neutralising, balancing, or compensation arrangements using adaptive balancing or compensation means
Abstract
Abstract of the Disclosure An adaptive interference cancelling system for multi-bit spread spectrum noise codes wherein a plurality of users in a mobile subscriber access system each operates with a different noise code. Each user receives a composite signal which includes a desired noise coded signal from another user plus any unwanted interference noise coded signals from other like users in relatively close proximity. The RF demodulator or front end section of each user receiver is coupled to a bank of matched filters which selectively detect and identify any interfering codes. These interfering codes are then regenerated devoid of the desired signal to provide a coherent replica of the interference signal.
The received composite signal and the coherent replica of one or more interference signals are applied to individual signal subtractor circuits which operate to cancel the interfering noise coded signals leaving the desired signal to be subsequently matched filter detected free of interference from other users.
The received composite signal and the coherent replica of one or more interference signals are applied to individual signal subtractor circuits which operate to cancel the interfering noise coded signals leaving the desired signal to be subsequently matched filter detected free of interference from other users.
Description
This :invention relates gene.rally to noise eode communi-catiolls sys-tems and more partieularly to a non-orthogonal eode divi.sion multiple aceess communieations system.
Multiple aeeess communieations systems uti.l.izing noise coded si.cJnals are ~ell known. Typieal e~amples oi sueh multiple accessinc3 communi.eations systems are shown and described in:
U S. Paten-t 3,908,088, enti-tled, "Time Division Mul.tiple Aeeess Commllnica-tions Sys-tem", which i.ssued to Fran~ S Gut.leber, the present i.nventor, on September 23, 1.975; U.S. Patent ~},2:15,244, :l0 entitled, "Self-Adaptive Mobi].e Subseriber Aeeess System Employin~
T:ime Divisi.on ~ultiple Aeeessing", whieh issued to Frank S. Gutleber on July 29, 1980; and U.S. Patent 4~301,530, entitled, "0r-thogollal Spread Speetrum Time Division Multiple Aeeessiny ~lobile Sub-scriber Access System", whie~ issued to Frank S Gutleber on November 17, 19~1.
What is si.gnifieant about the systems diselosed in the aforementioned paten-t:s is that they employ pairs of mul-tiple~ed noise codes vf the type termed eode mates having au-toeorrelation Lunctions which upon deteetion p.rovide an impulse autocorrelation fullction and wherein the configurations deseribed enab:le random access or direet e~all-up to be aceomplished ~li.th minimal ~7~
interference between users. The codes utilized ~re called noise codes because the infornrlation to be corrlmunicated :is cod~d with a cligital code that is "noise like" in that it will compress to an impu:Lse when detected wi,th a matchecl filter.
The utiliza-tion of different noise codes for a plurality of users in a nonsynchronous mobile subscriber multiple access sys-tem has been found to be heretofore less than adequa-te because oE self-interference between users. Such a system is referred to as a non-orthogonal system. Although each interLerence signal is reduced by the time-bandwidth product, interfering ~Isers in c~lvse proximity make for intolerable systern opera-tion~
Accordingly, it is an object of the present invention to provide an improved non-orthogorlal noise code communications sys-tem.
Anotller object of the present invention is to provide a code division rnultiple access noise code corNmunications system.
Still another object o:E the present invention is to provide mealls for cancelling noise coded interfeL-ence in a non--orthogonal code division mult;ple access system.
And yet another object o the present i,nventiotl is to provide a code d:ivision multiple acces,s systern which ellables a large qualltitV of users to operate in the sarne confined ~eogra-phical area without incurrinc3 unacceptable mutual interference.
~ccordingly~ these and other objects are achieved in a coc1e division multiple access communications systelrl including a plurality oE users wherein each user employs a clifr'erent noise code which is modulated on an RF carrier. Each user uti:L;~es ~1~37~ ~
radio apparatus which is adapted to yenerate, transmit~ receive and cletect multi-bit digital noise codes while operating within the same RF` frequency band. The receiver portion of each user appara-tus is adapted to receive a desired noise coded signa:L from another user but addi.tionally includes an adaptive in-te:rference cancelling system comprised of a plurality of matched filters coupled to the front end or ~F demodulator sec-tion which operate -to detect and identify any undesired and thus interfering noise codes coming from other close proximity users alony wlth the d~sired signal. The matched filters are coupled to respective noise code generators which provide a coherent replica of the respective inter:Eerence code but one devoid of the desired signal The~ replica signal is then fed to signal s~tractor means along wi.th a composite input received signal which includes both the desired signal and any interference signal. The subtractor cir-cuitxy operates to cancel the interference signal(s) leaving the desired noise coded signal to be matched fi].ter detected free of interference.
Particular embodiments of the invention will be described in conjunction wi-th the accompanying drawings in which:
Fiyure 1 is a simplified illustration of a non-orthogonal ground mobi:Le access system employi.ng code division multiple accessing;
Figure 2 is a functional block diagram of the trans-mitter po.rtion oE apparatus for use with the comrnunications system shown in Figure l; and Figure 3 is a Eunctional block diagrarn o:E the receiver portion of apparatus ~or use with the communications system shown in Figure 1 and illustrating the preferred el~odimer~t of the subject invent.ion.
Referring now to the drawings and more particul.arly to E'igure 1, there is illustrated a multiple access syst:em such as a mobile subscriber access noise coded communications systern e~lploying code division multiple access (CDMA). Each user Nos.
1, 2, ~. n-l and n operates with and accordingly generates a dif~erellt cespective multi-bit binary digi.tal noise code 1 ~.. n of -the same numbe.r of bits of the sp:read spectrum type.
Moreover, the codes generated are utili~ed to modulate ~F f:re-quency carriers in the same frec~uency band and as a consetluence sel.F-~intel-:Eerence between the various users normally exi.sts for ~hose users which are geoyraphicall~ relatively close to one another. Since the rms value o~ the crosscorrelation :Eunction of difEerent noise codes will be suppressed by the time-b~ndwi.dth product, users of the system that are not in close proximity'to one another would receive or cause a ne~ligible deyree of intter-ference -to any other specific user havlng a receiver responsi.ve to more codes operable in the aforementioned same frequency band.
Those use:rs that are i.n close proximity, howeve.r, wil.l :interfere with each other since the ],arge increase in the amplit~ude or level of the interference due to the short range diffe.rence between a desir.ed and int.erfering source of .noise code cor~lunications signals ~Jould overcome the i.nterference suppression associated ~ith t:he margi.n of an n bit noise code. As an example, if an interfering user has a 10/1 range advantacle, the received signal of the in-t:erferiny user would be lO0 times or 20dh strongel~ than a desired received .signal which is received in a composite signal includirlg the interEering signal. If the sys-tem shown in Figure l is irnplemerlted with radio apparatus, e.y, transceivers wherein each transcei~er employed a lO0 bit noise cvde, then the gain margin advantage o~ 100/l or 20db would be completely nullified and the output signal to interference rati.o would be unity or Odb which is totally inadequate.
Further as shown in Figure l, in the deplo~nent of ~ser communications apparatus lOl, 102, ... lOn, user No. 2 cor~lunica-ting with user ~o. 1 would be interfer.ed with by code 3 :Erorn user No. 3 as well as code 5 from user No. 5 in a standard non--or-thoyonal CD~A system~ In a like manner, users 3 and 5 would be inter~ered with by the code from user No. 2 and codes 3 or 5 as the case may be. The interfering regions are indicated by the loops identified by reference numerals l'~, 14 and 16, The present invention is directed to a CDMA system involving a plurality of user comrnunications apparatus operating with spread spectrum noise codes. The receiver portion of each apparatus includes an adaptive interference cancelling system which is responsive to all the codes of the other users :Eor cancelling undesired close proximity user interference which affects the desired reception from another user.
Referring now to Figure 2, each user communications apparatus a]so includes a transmitter portion 18 which in lts broadest aspects is comprised of a noise code yenerator 20 coupled to a l through n code selector 22. The noi.se code selected and generated is fed to transmitter apparatus 24 which 94:2 i.s coupled t.o a radiating antenna ~6 which is adapte(3 to radiate a noise code modulatecl i~ signal to another user apparatus ~lich includes a :recei~7er portion 28, the details of which are shown in Fi~ure 3.
Referri.ng now to Figure 3, a receiving antenna 30 i.s coupled to a receiver front end sect:ion 32 which is adap-ted to demodulate tne RF signal recei.ved from the transmitter 1.8 Erom another communicating user and provide an output at circul.t node 34 which is a composite noise coded signal including not only the desired signal, but also any other interfering noise coded siynals received from other usexs in close proxi.mity.
Adaptive inter:Eerence cancelling circuitry 33 follows the rece.i.ver RF demodulator section 32 and is comprised of a bank i.eO a plurality l, 2 ..~ n of like circuits 36l, 362 - ~ 36n which are respective:Ly adapted to de-tect a mutually different unwanted inteLfering noise coae signal and regenerate it again free of the desired signal. More particularly, each circui.t 36l~ 362, 36n is comprised of a ma-tched filter 38 which is coupled to circuit node 34. Each matched filter 38 is operable to detect a particular noise code of codes l through n and establish the precise tirne of its arrival. Since the codes utilized by the various users l ... n are comprised of spread spectrum noise codes, the matched filter 38 will compress the code and provide a high amplitude impulse output ln a wel]. known fashiorl which is Eed to a video detector circuit 40 which is adapted to enhance the interfering siynal by the time bandwidth product or equival.-ently the number of noise code bits so that positi.ve detection and identification oE strong interference signals is providedO
-- , --~7~ ~
The cletected compxessed signal from the de-tector 40 is ne~t fed to a noise code generator 42 which is oper.able to coherently rec~enerate the same code structure detected; however, it is -to-tally free of any other interfexing code signal as well as the desixed siynal. The code c3enerated in each of t.he circuits 361, 3~2 36n is next fed to one of a plurali.ty of casca~ed ox tandemly connected signal subtractor cixcuits 441~ 442 -~44n wherein a particular regenerated noise code is subtracted fxom a cornposite siynal appearing at circuit node 34. The com-posite signal appearing at circuit node 34 is coupled to the firstsiynal subtractor 441 shown in Figure 3 by means of a time delay circuit 46 ~hich provides a ti.me delay of ~ to compensate Eor the delay introduced when compressing noise coded signals in the appxop:riate matched filter 33 and regenerating the respective intereriny codes in the code generator 42. A vaxiable gain amplifier 461, 462, 46n is furthermore coupled between the noise codes circuits 361, 362 and 36n and their respective subtractor circuits 441~ 442 and 44n to set the amplitude of the yenerated code equal to its respective value at: the output of the front end section of the receiver 32.
I-t can be seen, therefore, that a coherent .eplica of any un~anted interference code is generated and appropria-tely fed to one of the subtractor circuits 441~ 442 44n which a;l.so recei~es a composite signal consisting of both -the desired siynal and -the i.nterference signal, but due to the subtractive process, the output of the last subtractor circuit 44n comprises a siqnal free of interference signals which is then fed to a matched filter 48 that is matched to the code structu:ce of the :~8~79~
desi--ed signal, which is compressed thereby and :Fed to a detector 50. The detector 50 provides an out.put signal that is n times g:reater than any residual unwanted interference signal -that may stil.l e.xi.st after su~tracting all of the relatively strong inter:~erence signals out of the recei.ved composite signal '~PE~earing at circuit node 34 While Figure 3 discloses a bank of matched filters and code generators commonly connected to circ~it node 34, it may he desirable to additionally include means, not shown, 1.0 at -the output of the receiver front end section 3~ to sequentially search rnost or all of the codes utili~ed by the system to provi.de a correct mat.ch for a mat.ched filter.
Whi.le the adapti~e interference cance:l:Ling system shown in Figure 3 can utilize any class of noise code, t.he use of mul.tiple~ed noise codes such as disclosed in the aforementioned U.S. Paten-ts 3,908,088;`4,215,244; and 4,301,530 of~er substantial advantages in that they not only compress to a Iobe-less impulse, but the quantity of these unique cocles is extremely large for moderate time~bandwidth produc-ts.
Fur-thermore, they are relatively easy to generate and compress and the apparatus required is relativel.y small in size, nec31igible in weight and low in cost. In an appli.cat.ion of multip]exed cocles involving relatively strong mu]tipath in-terEerence signals~ each interfering signal will be isolatecl when the composite s.iynal is detected in the matched fil.ter s:ince the codes compress to a lobeless impulse when ].inearly added together. The composite compressed signal plllS multipath .interLerence signals would therefore automatically regenerate the original coded signal plus the mult.ipath signal in a single code generator and provide cancel.lation of the composite interfering signal with a single amplitude adjustment.
Having thus shown and described what is at pLesent considered to be the preferred embodiment of the invention, it should be understood that the same has been made by way of illustration and not o~ limitation and accordingly, all modifications, alterations and changes coming within -the spirit and scope of the invention as defined in the following claims are herein meant to be included.
Multiple aeeess communieations systems uti.l.izing noise coded si.cJnals are ~ell known. Typieal e~amples oi sueh multiple accessinc3 communi.eations systems are shown and described in:
U S. Paten-t 3,908,088, enti-tled, "Time Division Mul.tiple Aeeess Commllnica-tions Sys-tem", which i.ssued to Fran~ S Gut.leber, the present i.nventor, on September 23, 1.975; U.S. Patent ~},2:15,244, :l0 entitled, "Self-Adaptive Mobi].e Subseriber Aeeess System Employin~
T:ime Divisi.on ~ultiple Aeeessing", whieh issued to Frank S. Gutleber on July 29, 1980; and U.S. Patent 4~301,530, entitled, "0r-thogollal Spread Speetrum Time Division Multiple Aeeessiny ~lobile Sub-scriber Access System", whie~ issued to Frank S Gutleber on November 17, 19~1.
What is si.gnifieant about the systems diselosed in the aforementioned paten-t:s is that they employ pairs of mul-tiple~ed noise codes vf the type termed eode mates having au-toeorrelation Lunctions which upon deteetion p.rovide an impulse autocorrelation fullction and wherein the configurations deseribed enab:le random access or direet e~all-up to be aceomplished ~li.th minimal ~7~
interference between users. The codes utilized ~re called noise codes because the infornrlation to be corrlmunicated :is cod~d with a cligital code that is "noise like" in that it will compress to an impu:Lse when detected wi,th a matchecl filter.
The utiliza-tion of different noise codes for a plurality of users in a nonsynchronous mobile subscriber multiple access sys-tem has been found to be heretofore less than adequa-te because oE self-interference between users. Such a system is referred to as a non-orthogonal system. Although each interLerence signal is reduced by the time-bandwidth product, interfering ~Isers in c~lvse proximity make for intolerable systern opera-tion~
Accordingly, it is an object of the present invention to provide an improved non-orthogorlal noise code communications sys-tem.
Anotller object of the present invention is to provide a code division rnultiple access noise code corNmunications system.
Still another object o:E the present invention is to provide mealls for cancelling noise coded interfeL-ence in a non--orthogonal code division mult;ple access system.
And yet another object o the present i,nventiotl is to provide a code d:ivision multiple acces,s systern which ellables a large qualltitV of users to operate in the sarne confined ~eogra-phical area without incurrinc3 unacceptable mutual interference.
~ccordingly~ these and other objects are achieved in a coc1e division multiple access communications systelrl including a plurality oE users wherein each user employs a clifr'erent noise code which is modulated on an RF carrier. Each user uti:L;~es ~1~37~ ~
radio apparatus which is adapted to yenerate, transmit~ receive and cletect multi-bit digital noise codes while operating within the same RF` frequency band. The receiver portion of each user appara-tus is adapted to receive a desired noise coded signa:L from another user but addi.tionally includes an adaptive in-te:rference cancelling system comprised of a plurality of matched filters coupled to the front end or ~F demodulator sec-tion which operate -to detect and identify any undesired and thus interfering noise codes coming from other close proximity users alony wlth the d~sired signal. The matched filters are coupled to respective noise code generators which provide a coherent replica of the respective inter:Eerence code but one devoid of the desired signal The~ replica signal is then fed to signal s~tractor means along wi.th a composite input received signal which includes both the desired signal and any interference signal. The subtractor cir-cuitxy operates to cancel the interference signal(s) leaving the desired noise coded signal to be matched fi].ter detected free of interference.
Particular embodiments of the invention will be described in conjunction wi-th the accompanying drawings in which:
Fiyure 1 is a simplified illustration of a non-orthogonal ground mobi:Le access system employi.ng code division multiple accessing;
Figure 2 is a functional block diagram of the trans-mitter po.rtion oE apparatus for use with the comrnunications system shown in Figure l; and Figure 3 is a Eunctional block diagrarn o:E the receiver portion of apparatus ~or use with the communications system shown in Figure 1 and illustrating the preferred el~odimer~t of the subject invent.ion.
Referring now to the drawings and more particul.arly to E'igure 1, there is illustrated a multiple access syst:em such as a mobile subscriber access noise coded communications systern e~lploying code division multiple access (CDMA). Each user Nos.
1, 2, ~. n-l and n operates with and accordingly generates a dif~erellt cespective multi-bit binary digi.tal noise code 1 ~.. n of -the same numbe.r of bits of the sp:read spectrum type.
Moreover, the codes generated are utili~ed to modulate ~F f:re-quency carriers in the same frec~uency band and as a consetluence sel.F-~intel-:Eerence between the various users normally exi.sts for ~hose users which are geoyraphicall~ relatively close to one another. Since the rms value o~ the crosscorrelation :Eunction of difEerent noise codes will be suppressed by the time-b~ndwi.dth product, users of the system that are not in close proximity'to one another would receive or cause a ne~ligible deyree of intter-ference -to any other specific user havlng a receiver responsi.ve to more codes operable in the aforementioned same frequency band.
Those use:rs that are i.n close proximity, howeve.r, wil.l :interfere with each other since the ],arge increase in the amplit~ude or level of the interference due to the short range diffe.rence between a desir.ed and int.erfering source of .noise code cor~lunications signals ~Jould overcome the i.nterference suppression associated ~ith t:he margi.n of an n bit noise code. As an example, if an interfering user has a 10/1 range advantacle, the received signal of the in-t:erferiny user would be lO0 times or 20dh strongel~ than a desired received .signal which is received in a composite signal includirlg the interEering signal. If the sys-tem shown in Figure l is irnplemerlted with radio apparatus, e.y, transceivers wherein each transcei~er employed a lO0 bit noise cvde, then the gain margin advantage o~ 100/l or 20db would be completely nullified and the output signal to interference rati.o would be unity or Odb which is totally inadequate.
Further as shown in Figure l, in the deplo~nent of ~ser communications apparatus lOl, 102, ... lOn, user No. 2 cor~lunica-ting with user ~o. 1 would be interfer.ed with by code 3 :Erorn user No. 3 as well as code 5 from user No. 5 in a standard non--or-thoyonal CD~A system~ In a like manner, users 3 and 5 would be inter~ered with by the code from user No. 2 and codes 3 or 5 as the case may be. The interfering regions are indicated by the loops identified by reference numerals l'~, 14 and 16, The present invention is directed to a CDMA system involving a plurality of user comrnunications apparatus operating with spread spectrum noise codes. The receiver portion of each apparatus includes an adaptive interference cancelling system which is responsive to all the codes of the other users :Eor cancelling undesired close proximity user interference which affects the desired reception from another user.
Referring now to Figure 2, each user communications apparatus a]so includes a transmitter portion 18 which in lts broadest aspects is comprised of a noise code yenerator 20 coupled to a l through n code selector 22. The noi.se code selected and generated is fed to transmitter apparatus 24 which 94:2 i.s coupled t.o a radiating antenna ~6 which is adapte(3 to radiate a noise code modulatecl i~ signal to another user apparatus ~lich includes a :recei~7er portion 28, the details of which are shown in Fi~ure 3.
Referri.ng now to Figure 3, a receiving antenna 30 i.s coupled to a receiver front end sect:ion 32 which is adap-ted to demodulate tne RF signal recei.ved from the transmitter 1.8 Erom another communicating user and provide an output at circul.t node 34 which is a composite noise coded signal including not only the desired signal, but also any other interfering noise coded siynals received from other usexs in close proxi.mity.
Adaptive inter:Eerence cancelling circuitry 33 follows the rece.i.ver RF demodulator section 32 and is comprised of a bank i.eO a plurality l, 2 ..~ n of like circuits 36l, 362 - ~ 36n which are respective:Ly adapted to de-tect a mutually different unwanted inteLfering noise coae signal and regenerate it again free of the desired signal. More particularly, each circui.t 36l~ 362, 36n is comprised of a ma-tched filter 38 which is coupled to circuit node 34. Each matched filter 38 is operable to detect a particular noise code of codes l through n and establish the precise tirne of its arrival. Since the codes utilized by the various users l ... n are comprised of spread spectrum noise codes, the matched filter 38 will compress the code and provide a high amplitude impulse output ln a wel]. known fashiorl which is Eed to a video detector circuit 40 which is adapted to enhance the interfering siynal by the time bandwidth product or equival.-ently the number of noise code bits so that positi.ve detection and identification oE strong interference signals is providedO
-- , --~7~ ~
The cletected compxessed signal from the de-tector 40 is ne~t fed to a noise code generator 42 which is oper.able to coherently rec~enerate the same code structure detected; however, it is -to-tally free of any other interfexing code signal as well as the desixed siynal. The code c3enerated in each of t.he circuits 361, 3~2 36n is next fed to one of a plurali.ty of casca~ed ox tandemly connected signal subtractor cixcuits 441~ 442 -~44n wherein a particular regenerated noise code is subtracted fxom a cornposite siynal appearing at circuit node 34. The com-posite signal appearing at circuit node 34 is coupled to the firstsiynal subtractor 441 shown in Figure 3 by means of a time delay circuit 46 ~hich provides a ti.me delay of ~ to compensate Eor the delay introduced when compressing noise coded signals in the appxop:riate matched filter 33 and regenerating the respective intereriny codes in the code generator 42. A vaxiable gain amplifier 461, 462, 46n is furthermore coupled between the noise codes circuits 361, 362 and 36n and their respective subtractor circuits 441~ 442 and 44n to set the amplitude of the yenerated code equal to its respective value at: the output of the front end section of the receiver 32.
I-t can be seen, therefore, that a coherent .eplica of any un~anted interference code is generated and appropria-tely fed to one of the subtractor circuits 441~ 442 44n which a;l.so recei~es a composite signal consisting of both -the desired siynal and -the i.nterference signal, but due to the subtractive process, the output of the last subtractor circuit 44n comprises a siqnal free of interference signals which is then fed to a matched filter 48 that is matched to the code structu:ce of the :~8~79~
desi--ed signal, which is compressed thereby and :Fed to a detector 50. The detector 50 provides an out.put signal that is n times g:reater than any residual unwanted interference signal -that may stil.l e.xi.st after su~tracting all of the relatively strong inter:~erence signals out of the recei.ved composite signal '~PE~earing at circuit node 34 While Figure 3 discloses a bank of matched filters and code generators commonly connected to circ~it node 34, it may he desirable to additionally include means, not shown, 1.0 at -the output of the receiver front end section 3~ to sequentially search rnost or all of the codes utili~ed by the system to provi.de a correct mat.ch for a mat.ched filter.
Whi.le the adapti~e interference cance:l:Ling system shown in Figure 3 can utilize any class of noise code, t.he use of mul.tiple~ed noise codes such as disclosed in the aforementioned U.S. Paten-ts 3,908,088;`4,215,244; and 4,301,530 of~er substantial advantages in that they not only compress to a Iobe-less impulse, but the quantity of these unique cocles is extremely large for moderate time~bandwidth produc-ts.
Fur-thermore, they are relatively easy to generate and compress and the apparatus required is relativel.y small in size, nec31igible in weight and low in cost. In an appli.cat.ion of multip]exed cocles involving relatively strong mu]tipath in-terEerence signals~ each interfering signal will be isolatecl when the composite s.iynal is detected in the matched fil.ter s:ince the codes compress to a lobeless impulse when ].inearly added together. The composite compressed signal plllS multipath .interLerence signals would therefore automatically regenerate the original coded signal plus the mult.ipath signal in a single code generator and provide cancel.lation of the composite interfering signal with a single amplitude adjustment.
Having thus shown and described what is at pLesent considered to be the preferred embodiment of the invention, it should be understood that the same has been made by way of illustration and not o~ limitation and accordingly, all modifications, alterations and changes coming within -the spirit and scope of the invention as defined in the following claims are herein meant to be included.
Claims (18)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A non-orthogonal code division multiple access communications system for a plurality of users, comprising:
a plurality of user communications apparatus, one for each user;
each said user apparatus including means for generating and transmitting a mutually different noise coded signal to another said user apparatus;
each said user apparatus further including, means for receiving a composite noise coded signal including a desired noise coded signal transmitted from a predetermined said user apparatus and any undesired interfering noise coded signal trans-mitted from at least one other said user apparatus, a plurality of noise code selective circuit means in separate separate paths for detecting said interfering noise coded signal included in said composite signal, respective circuit means coupled to said plurality of noise code selective circuit means for regenerating a replica of said interfering noise coded signal detected devoid of said desired noise coded signal, signal combiner means coupled to said composite signal received and said replica signals and being responsive thereto to operably cancel, by the process of subtraction, said interfering signal from said composite signal and leaving said desired signal, and detector means coupled to said signal combiner means for detecting said desired signal free of undesired interference.
a plurality of user communications apparatus, one for each user;
each said user apparatus including means for generating and transmitting a mutually different noise coded signal to another said user apparatus;
each said user apparatus further including, means for receiving a composite noise coded signal including a desired noise coded signal transmitted from a predetermined said user apparatus and any undesired interfering noise coded signal trans-mitted from at least one other said user apparatus, a plurality of noise code selective circuit means in separate separate paths for detecting said interfering noise coded signal included in said composite signal, respective circuit means coupled to said plurality of noise code selective circuit means for regenerating a replica of said interfering noise coded signal detected devoid of said desired noise coded signal, signal combiner means coupled to said composite signal received and said replica signals and being responsive thereto to operably cancel, by the process of subtraction, said interfering signal from said composite signal and leaving said desired signal, and detector means coupled to said signal combiner means for detecting said desired signal free of undesired interference.
2. The communications system as defined by claim 1 wherein said noise coded signal comprises a multi-bit digital spread spectrum code.
3. The communications system as defined by claim wherein said noise coded signal of each said user apparatus comprises a mutually different digital noise code of the same number of bits.
4. The communications system as defined by claim 3 wherein each said plurality of noise code selective circuit means for detecting said interfering noise coded signal includes matched filter circuit means, said matched filter circuit means being operable to compress a predetermined one of a plurality of interfering noise coded signals, and wherein said respective circuit for regenerating a replica of said interfering noise coded signal comprises noise code generator means operable to coherently generate the same code compressed by the respective matched filter circuit means.
5. The communications system as defined by claim 4 wherein said signal combiner means comprises signal subtractor circuit means.
6. The communications system as defined by claim 5 and additionally including time delay circuit means coupling said composite signal to said signal subtractor circuit means for compensating for a delay introduced by said matched filter circuit means and said noise code generator means.
7. The communications system as defined by claim 6 and additionally including respective signal detector means coupled between each said matched filter circuit means and said noise code generator means.
8. The communications system as defined by claim 7 and additionally including signal amplifier means coupled between each said code noise generator means and said subtractor means to make the amplitude of each replicated interfering noise coded signal substantially equal to the amplitude of said interfering noise coded signal in said composite signal.
9. The communications system as defined by claim 3 wherein said plurality of noise code selective circuit means for detecting said interfering noise coded signal comprises a plurality of like circuits which are operable to detect selected ones of the different noise codes of said plurality of user apparatus.
10. The communications system as defined by claim 3 wherein said plurality of noise code selective circuit means for detecting said interfering noise coded signal comprises a plurality of like circuits which are operable to detect and regenerate substantially all of the different noise codes of said plurality of user apparatus.
11. The communications system as defined by claim 8 wherein said plurality of said like circuits is comprised of a bank of matched filters each operable to compress a predetermined interfering noise coded signal.
12. The communications system as defined by claim 11 and wherein said respective circuit means for regenerating a replica signal comprises noise code signal generator means operable to coherently generate the noise coded signal compressed by the respective said matched filter coupled thereto.
13. The communications system as defined by claim 12 wherein said signal combiner means comprises a plurality of inter-coupled signal subtractors respectively coupled to said composite signal and to a mutually different replica noise coded signal whereby selective interference noise coded signal cancellation occurs in each signal subtractor.
14. The communications system as defined by claim 13 wherein said plurality of signal subtractors are coupled in a cascade circuit connection.
15. The communications system as defined by claim 14 and additionally including time delay circuit means coupling said composite signal to said cascade connected plurality of signal subtractors for compensating for a delay introduced by said bank of matched filters and the respective noise code signal generator means.
16. The communications system as defined by claim 15 and additionally including respective detector means interposed between each matched filter of said bank of matched filters and the respective noise code signal generator means coupled thereto and signal amplifier means coupled between each said noise code signal generator means and one respective signal sub-tractor of said plurality of signal subtractors, said signal amplifier means making the amplitude of the respective regenerated noise code substantially equal to the amplitude of the respective interfering noise coded signal in said composite signal.
17. The communications system as defined by claim 1 wherein said noise coded signal is comprised of a pair of multi-plexed noise codes.
18. The communications system as defined by claim 1 wherein said pair or noise codes are of the type which compress to a lobeless impulse.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/439,232 US4470138A (en) | 1982-11-04 | 1982-11-04 | Non-orthogonal mobile subscriber multiple access system |
| US439,232 | 1982-11-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1187942A true CA1187942A (en) | 1985-05-28 |
Family
ID=23743858
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000435412A Expired CA1187942A (en) | 1982-11-04 | 1983-08-26 | Non-orthogonal mobile subscriber multiple access system |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4470138A (en) |
| CA (1) | CA1187942A (en) |
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-
1982
- 1982-11-04 US US06/439,232 patent/US4470138A/en not_active Expired - Fee Related
-
1983
- 1983-08-26 CA CA000435412A patent/CA1187942A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4470138A (en) | 1984-09-04 |
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