CA2237464A1 - Network protocol for wireless broadband isdn using atm - Google Patents
Network protocol for wireless broadband isdn using atm Download PDFInfo
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- CA2237464A1 CA2237464A1 CA002237464A CA2237464A CA2237464A1 CA 2237464 A1 CA2237464 A1 CA 2237464A1 CA 002237464 A CA002237464 A CA 002237464A CA 2237464 A CA2237464 A CA 2237464A CA 2237464 A1 CA2237464 A1 CA 2237464A1
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- base station
- frame
- atm
- cell
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/204—Multiple access
- H04B7/212—Time-division multiple access [TDMA]
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/04—Wireless resource allocation
- H04W72/044—Wireless resource allocation based on the type of the allocated resource
- H04W72/0446—Resources in time domain, e.g. slots or frames
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing
- H04Q11/0428—Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
- H04Q11/0478—Provisions for broadband connections
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/54—Store-and-forward switching systems
- H04L12/56—Packet switching systems
- H04L12/5601—Transfer mode dependent, e.g. ATM
- H04L2012/5603—Access techniques
- H04L2012/5604—Medium of transmission, e.g. fibre, cable, radio
- H04L2012/5607—Radio
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/54—Store-and-forward switching systems
- H04L12/56—Packet switching systems
- H04L12/5601—Transfer mode dependent, e.g. ATM
- H04L2012/5638—Services, e.g. multimedia, GOS, QOS
- H04L2012/5646—Cell characteristics, e.g. loss, delay, jitter, sequence integrity
- H04L2012/5652—Cell construction, e.g. including header, packetisation, depacketisation, assembly, reassembly
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/54—Store-and-forward switching systems
- H04L12/56—Packet switching systems
- H04L12/5601—Transfer mode dependent, e.g. ATM
- H04L2012/5672—Multiplexing, e.g. coding, scrambling
Abstract
A networking protocol for wireless point (base station) to multipoint (user) networks where the users are stationary, which utilizes time division multiplexing in the direction of base station to user; i.e. the downstream direction; and time division multiple access in the direction from the user to the base station; i.e. the upstream direction. Time slots in the upstream and downstream directions carry ATM cells. Users maintain time slot synchronization to within 2 modulation symbols by monitoring downstream receptions (11) and central processing unit (7) tracks time slot assignments and handles in-band signaling while segmentation and reassembly (6) handles treatment of the ATM cells.
Description
CA 02237464 1998-0~-12 W O 97/21285 PCTrUS96/19341 NETWORK PROTOCOL FOR WIRELESS BROADBAND ISDN USING ATM
BACKGROUND OF THE INVENTION
The recent allocation of frequencies by the FCC at 2.5 G~Iz and 28 GHz has enabled the delivery of broadband-ISDN services to residential and commercial users through wireless means. Broadband ISDN typically uses ATM
as the link layer of the network protocol. ATM is a switch-oriented link protocol where each user has a dedicated connection to the switch and the switch manages bandwidth contention by multiple users by queues input cells until they can be delivered to the app~ iate output. In a wireless point to multipoint system, theanalog of the switch resides in a base station, and the link to the switch is a shared medium hy all users whose access to that m~ m must be controlled. Therefore, for wil,less point to multipoint systems there is the additional need for m~-linm access control which is not required in ordinary ATM nelwo ~.
The medium access control requirements for wireless point to multipoint systems where the users are stationary are unique compared to other wireless nelwo~k~ such as wireless local area networks (LANs) as specified by the lEEE
802.11 standard. A wireless point to multipoint system can take advantage of thestationary nature of users enabling the use of highly directional s~nt~.nn~ at the user stations. However, the base station will still employ broad bearn ~nt~nn~
and will thus have multiple user ~ ;ons received simulLalleously. Medium access control will be nece~ ly to ensure that mutual illl~,lr~,~Gnce by multiple user tr~n~mi~sion impinging on the base station antenna is elimin~te~
There are numerous MAC protocols currently in use by both wired and wireless standards. In Ethernet, where the cabling is a shared m~ m, carrier-sense multiple access is employed, which is essentially a listen before talk approach. In wi~less LANs, such as that specified by the lEEE 802.11 standard, SUBSTITUTE SHEET (RULE 26~
CA 02237464 1998-0~-12 W O 97/21285 PCT~US96/19341 medium access control is also managed through carrier-sense multip]e access.
This is possible because portable user terminals will each typically have an omnidirectional ~ntenn~ so that each user t~rmin~l can receive tr~nsmissions from other users and ascertain whether the frequency ch~nnel is available. This is not possible with wireless point to multipoint systems where st~tion~ry users employdirectional antennas, as they cannot receive tr~n~mi.~sions from other users.
An additional complication in wide area wireless point to multipoint systems, is that the two way range differential beLweell users close to the basestation and those distant to the base station can be much larger than a modulation symbol.
The object of this invention is a netwo~ lg protocol which provides bandwidth to users on an on-dçm~n(l basis, which controls access by users to theshared wireless medium, which is bandwidth efficient, and which can be implemented with the minimnm of hd~dwalt; cost.
SUBSTITUTE SHEET (P~ULE 2~
W O 97~1285 PCTAUS96/19341 DESCRIPTION
S~ l&l,~ of the Invention A networking protocol for wireless point (base station) to multipoint (user) networks where the users are stationary which utilizes time-division multiplexing in the direction of the base station to the user, heretofore called the dowll~tlcalll direction, and time-division multiple access in the direction of the user to the base station, heretofore called the u~llealu direction, where mediumaccess control actively assigns time slots in the u~ alu direction to accommodate varying demands for bandwidth by multiple users, where U~ u frame timing is synchronized to the duwn~ ,alll frame timing, where time slots carry individual ATM cells, where the first time slot of the dowllsL~ ll frame carries a frame start ATM cell, where U~)S~ llll time slot syncl~luni~alion is m~int~ined to within ~2 modulation symbols through timing control from the base station to the user, where random access time slots are used for control plane requests by users entering the network and users in standby mode seeking to begin a session, where polling is used for management plane functions and responses by users are on a polling response time slot.
Fe~llul es of the I~ ..t-G..
A networking protocol ~or wireless point (base station) to multiport (user) networks with stationary users utilizing high gain directional ~ntenn~ where:
1. Means for tr~n~mi.c.sion convergence layer is provided through SUBSTITUTE SHEET (RULE 26) CA 02237464 1998-0~-12 a) Time-division multiplexing is utilized in the direction of the base station to the user, heretofore called the downstream direction;
b) Time-division multiple access is used in the direction of the user to the base station, heretofore called the u~ ,am direction;
c) Time slots in the upbli~,alll direction have two preamble bytes, one ATM cell, and a one byte guard band;
d) Time slots in the downstream direction have one sync byte, one ATM cell, and no guard band;
e) Up~llGall- frame timing is synchronized to the downstream frame timing, where the first time slot of the dowllslleal.l frame carries a frame start ATM cell which is defined by a unique reserved VPI/VCI;
f) Frame periods in both the upbll~alll and dowllbllGam directions are approximately but not greater than six milli~e.conds in length to allow delivery of voice traffic with minim-lm latency.
BACKGROUND OF THE INVENTION
The recent allocation of frequencies by the FCC at 2.5 G~Iz and 28 GHz has enabled the delivery of broadband-ISDN services to residential and commercial users through wireless means. Broadband ISDN typically uses ATM
as the link layer of the network protocol. ATM is a switch-oriented link protocol where each user has a dedicated connection to the switch and the switch manages bandwidth contention by multiple users by queues input cells until they can be delivered to the app~ iate output. In a wireless point to multipoint system, theanalog of the switch resides in a base station, and the link to the switch is a shared medium hy all users whose access to that m~ m must be controlled. Therefore, for wil,less point to multipoint systems there is the additional need for m~-linm access control which is not required in ordinary ATM nelwo ~.
The medium access control requirements for wireless point to multipoint systems where the users are stationary are unique compared to other wireless nelwo~k~ such as wireless local area networks (LANs) as specified by the lEEE
802.11 standard. A wireless point to multipoint system can take advantage of thestationary nature of users enabling the use of highly directional s~nt~.nn~ at the user stations. However, the base station will still employ broad bearn ~nt~nn~
and will thus have multiple user ~ ;ons received simulLalleously. Medium access control will be nece~ ly to ensure that mutual illl~,lr~,~Gnce by multiple user tr~n~mi~sion impinging on the base station antenna is elimin~te~
There are numerous MAC protocols currently in use by both wired and wireless standards. In Ethernet, where the cabling is a shared m~ m, carrier-sense multiple access is employed, which is essentially a listen before talk approach. In wi~less LANs, such as that specified by the lEEE 802.11 standard, SUBSTITUTE SHEET (RULE 26~
CA 02237464 1998-0~-12 W O 97/21285 PCT~US96/19341 medium access control is also managed through carrier-sense multip]e access.
This is possible because portable user terminals will each typically have an omnidirectional ~ntenn~ so that each user t~rmin~l can receive tr~nsmissions from other users and ascertain whether the frequency ch~nnel is available. This is not possible with wireless point to multipoint systems where st~tion~ry users employdirectional antennas, as they cannot receive tr~n~mi.~sions from other users.
An additional complication in wide area wireless point to multipoint systems, is that the two way range differential beLweell users close to the basestation and those distant to the base station can be much larger than a modulation symbol.
The object of this invention is a netwo~ lg protocol which provides bandwidth to users on an on-dçm~n(l basis, which controls access by users to theshared wireless medium, which is bandwidth efficient, and which can be implemented with the minimnm of hd~dwalt; cost.
SUBSTITUTE SHEET (P~ULE 2~
W O 97~1285 PCTAUS96/19341 DESCRIPTION
S~ l&l,~ of the Invention A networking protocol for wireless point (base station) to multipoint (user) networks where the users are stationary which utilizes time-division multiplexing in the direction of the base station to the user, heretofore called the dowll~tlcalll direction, and time-division multiple access in the direction of the user to the base station, heretofore called the u~llealu direction, where mediumaccess control actively assigns time slots in the u~ alu direction to accommodate varying demands for bandwidth by multiple users, where U~ u frame timing is synchronized to the duwn~ ,alll frame timing, where time slots carry individual ATM cells, where the first time slot of the dowllsL~ ll frame carries a frame start ATM cell, where U~)S~ llll time slot syncl~luni~alion is m~int~ined to within ~2 modulation symbols through timing control from the base station to the user, where random access time slots are used for control plane requests by users entering the network and users in standby mode seeking to begin a session, where polling is used for management plane functions and responses by users are on a polling response time slot.
Fe~llul es of the I~ ..t-G..
A networking protocol ~or wireless point (base station) to multiport (user) networks with stationary users utilizing high gain directional ~ntenn~ where:
1. Means for tr~n~mi.c.sion convergence layer is provided through SUBSTITUTE SHEET (RULE 26) CA 02237464 1998-0~-12 a) Time-division multiplexing is utilized in the direction of the base station to the user, heretofore called the downstream direction;
b) Time-division multiple access is used in the direction of the user to the base station, heretofore called the u~ ,am direction;
c) Time slots in the upbli~,alll direction have two preamble bytes, one ATM cell, and a one byte guard band;
d) Time slots in the downstream direction have one sync byte, one ATM cell, and no guard band;
e) Up~llGall- frame timing is synchronized to the downstream frame timing, where the first time slot of the dowllslleal.l frame carries a frame start ATM cell which is defined by a unique reserved VPI/VCI;
f) Frame periods in both the upbll~alll and dowllbllGam directions are approximately but not greater than six milli~e.conds in length to allow delivery of voice traffic with minim-lm latency.
2. Means for physical medium dependent layer where:
a) The downstream in continuous-carrier, without pulse-shape filtering, with frequency channels symbol synchronous and spaced 1 TD apart where TD is the period of a downstream modulation symbol;
SUBSTITUTE SH~ (Rl~LE 26) WO 97/2128~; PCT/US96/19341 b) The up~,LIcalll is burst-mode with 25% excess bandwidth root raised cosine filtered with frequency channels spaced 1.25/TU
apart where TU is the period of an upstream modulation symbol;
c) QPSK or ~Itf rn~tely 16 QAM modulation is employed on the upsl~eanl and the downstream;
d) A concatenated (60, 54) Reed-Solomon over GF(256) and rate 7/8 convolutional code is used on the downstream; and e) A (59.53) Reed-Solomon code over GF(256) is used on the alll.
a) The downstream in continuous-carrier, without pulse-shape filtering, with frequency channels symbol synchronous and spaced 1 TD apart where TD is the period of a downstream modulation symbol;
SUBSTITUTE SH~ (Rl~LE 26) WO 97/2128~; PCT/US96/19341 b) The up~,LIcalll is burst-mode with 25% excess bandwidth root raised cosine filtered with frequency channels spaced 1.25/TU
apart where TU is the period of an upstream modulation symbol;
c) QPSK or ~Itf rn~tely 16 QAM modulation is employed on the upsl~eanl and the downstream;
d) A concatenated (60, 54) Reed-Solomon over GF(256) and rate 7/8 convolutional code is used on the downstream; and e) A (59.53) Reed-Solomon code over GF(256) is used on the alll.
3. Means for control plane functions is provided through:
a) In-band ~ign~ling through ATM cells with reserved VPIlVCIs so that the requi~ lenl, for acquisition, de.m~ iQn, and forward error correction are uniform across the data, control, and management planes of the network protocol;
b) Tr~n.cmi~ion convergence layer medium access control which actively assigns time slots in the upstream direction to accommodate varying demands for bandwidth by multiple users;
c) Continuous time slots at the beginning of the u~ am frame are used for entry into the network by users whose two-way range timing has not been resolved to avoid mutual interference, where users entering the network remain on the net entry time slots until their timing is aligned by means described in claim 1;
SUBSTITUTE SHEET (RULE 26) W O 97/21285 PCT~US96/19341 d) Session requests are performed on a contention basis through random access of the net entry time slots;
e) Carrying control plane acknowleclgm~nt of service requests in the payload of the frame start ATM cell in dow,l~L,c;alll frame.
a) In-band ~ign~ling through ATM cells with reserved VPIlVCIs so that the requi~ lenl, for acquisition, de.m~ iQn, and forward error correction are uniform across the data, control, and management planes of the network protocol;
b) Tr~n.cmi~ion convergence layer medium access control which actively assigns time slots in the upstream direction to accommodate varying demands for bandwidth by multiple users;
c) Continuous time slots at the beginning of the u~ am frame are used for entry into the network by users whose two-way range timing has not been resolved to avoid mutual interference, where users entering the network remain on the net entry time slots until their timing is aligned by means described in claim 1;
SUBSTITUTE SHEET (RULE 26) W O 97/21285 PCT~US96/19341 d) Session requests are performed on a contention basis through random access of the net entry time slots;
e) Carrying control plane acknowleclgm~nt of service requests in the payload of the frame start ATM cell in dow,l~L,c;alll frame.
4. Means for management plane functions are provided through:
a) In-band signaling through ATM cells with reserved VPI/VCIs so that the requirements for acquisition, demodulation, and f~)l w~d error correction are uniform across the data, control, and management planes of the n~,twolh protocol;
b) Polling users by the base station, with users responding on dedicated time slots in the u~ t;anl frame;
c) Carrying management plane polling requests in the payload of the frame start ATM cell in the dowllsL-.ialll frame carries;
d) U~llt,a,l, time slot synchronization is m~int~in~d to within ~2 modulation symbols through timing control from the base station to the user and through slaving the user transmit symbol clock to its received symbol clock in the tr~n~mi~sion convergence layer;
e) Upstream power control is employed to ensure adequate received signal strength at the base station while ,..in;.,.i,.;~ adjacent cell hltelrelellce.
a) In-band signaling through ATM cells with reserved VPI/VCIs so that the requirements for acquisition, demodulation, and f~)l w~d error correction are uniform across the data, control, and management planes of the n~,twolh protocol;
b) Polling users by the base station, with users responding on dedicated time slots in the u~ t;anl frame;
c) Carrying management plane polling requests in the payload of the frame start ATM cell in the dowllsL-.ialll frame carries;
d) U~llt,a,l, time slot synchronization is m~int~in~d to within ~2 modulation symbols through timing control from the base station to the user and through slaving the user transmit symbol clock to its received symbol clock in the tr~n~mi~sion convergence layer;
e) Upstream power control is employed to ensure adequate received signal strength at the base station while ,..in;.,.i,.;~ adjacent cell hltelrelellce.
5. Ha,dwa,e and software means for impl~ ;"~ above claims in the base station including:
SUBSTITUTE SHEET (RUl~
W O 97/21~8S PCT~US96/19341 a) means for routing of in-band .cign~ling ATM cells by the ATM
switching device to and from the central ~ c~;ng unit;
b) means for m~a~llring timing offsets by s~bs~ ~ ;hers through counting periods of the reference symbol clock from a master frame epoch to the detectlon of the Barker sequence of the received tr;ln~mix.~ion from the user;
c) means for ll~ea~ulillg received signal level via bit error rate estimation for closed loop power control of the user tr~nxmitter.
SUBSTITUTE SHEET (RUl~
W O 97/21~8S PCT~US96/19341 a) means for routing of in-band .cign~ling ATM cells by the ATM
switching device to and from the central ~ c~;ng unit;
b) means for m~a~llring timing offsets by s~bs~ ~ ;hers through counting periods of the reference symbol clock from a master frame epoch to the detectlon of the Barker sequence of the received tr;ln~mix.~ion from the user;
c) means for ll~ea~ulillg received signal level via bit error rate estimation for closed loop power control of the user tr~nxmitter.
6. Haldw~ and software means for implementing above claims in the user e4uipll~ellt including:
a) means for routing in-band .ci~n~ling ATM cells to and from the ATM switching or segmentation and re~cxrlllhly device to the user e~ iplllent central proc~s~ing unit;
b) ad3usting l~ X-~ r power based on received power level and power control comm~ntls via in-band .~i~n~1in~ ATM cells from the base station;
c) means for slaving the transmit symbol clock reference to the received symbol clock reference;
d) means for adjusting the lldn~lllit symbol clock timing to minimi7.e interference to other users.
SUBSTITUTE SHEET (RUL~ 26) WO 97/21285 PCTrUSg6119341 DESCRIPTION OF THE DRAWINGS
The above and other objects, advantages and features of the invention will become more clear when considered with the following specification and attached drawings, wherein:
Figure 1 shows the protocol stack for the invention according to the convention of the OSI Reference Model, Figure 2 illustrates the two way turnaround effect of range from the base station which causes the need for large guard bands between user tr~n.cmi~sions, 1 being the nearby user and 2 being the distant user, Figure 3 is a block diagram of user or subscriber station har~lw~G
architecture, and Figure 4 is a block diagram of a base station h~dw~e arçhit.o.chlre.
DETAILED DESCI~IPTION OF THE INVENTION
It is well known that asynchronous transfer mode is the candidate network link protocol for broadband integrated services digital network (B-ISDN) which is typically defined as bit rates in excess of that of the y~ y rate interface ISDN
(PRI-ISDN) of 1.544 Mbps. Physical layer standards have been developed or are being developed for using ATM over synchronous optical network (SONET) at rates of 155 and 622 Mbps, over category 3 twisted pair at 25 Mbps, and over category 5 twisted pair at 45 Mbps and 100 Mbps. In each of these cases, however, the network topology is switch-oriented where each user has a fi~.r1iC~tf~ connection to an input port of the switch, and the switch buffers input cells until they can be routed to an output port of the switch. This is a classical star configuration.
SUBSTITUTE SHEET (RU~ E 26) CA 02237464 1998-0~-12 W O 97/21285 PCT~US96/19341 Tn a wireless point to multipoint system, where the users each employ a narrowbeam antenna, and the switch resides in a centrally-located base station which employs a broad beam antenna, in which multiple users lie in its beam, thewireless medium becomes a shared medium. While the point to multipoint nature of the system appears to be a star topology, because the wireless m~ m is shared, it is actually a bus or ring configuration. Hence, a m~ m access controlprotocol needs to be defined.
The networl~ protocol stack is as shown in Figure 1, and comprises the physical layer of the OSI Reference Model. Within the physical layer there is the physical m~dinm dependent layer which involves the modulation, forward error correction, and filt~in~ of the signal that is l~ ed over the wireless medium. The tr~nemieeion convergence layer comprices time-multiple access, the frame structure, and the time slot skucture within each frame.
The control plane functions at the tr~nemieeion convergence layer include those functions necess~ry for controlling access to the wireless Illedium through assignment of time slots. This function must interface to a higher level controlplane functions such as the lTU Q.293 1 signaling standard, the ATM Forum User Network Interface, and LAN Fm~ tion clients.
The m:ln~gem.~nt plane functions at the tr~nemieeion convel~,ence layer involve timing control to minimi7e guard band times between time slots. At the physical layer, the management functions involve controlling the user tr~n~emit~er power to ensure an adequate received signal level at the base station but not too strong as to cause adjacent cell interference, where cell refers to a cell in a cellular distribution system, not an ATM cell. Additionally, the management plane ~unctions include controlling the user's lfallsll~iL frequency so that it does not interfere with users on adjacent frequency ch~nnele, which is described in detail in a separate patent application.
SUBSTITUTE SWEET (RUI E 26) W O 97/21285 PCT~US96/19341 NETWORK PROTOCOL STACK
Tr~n~ ton Co~ g~..ceLayer Downstream Since the downstream data origin:~tes from the same source and is continuous carrier, different ATM virtual circuits are time-division multiplexedonto a single RF carrier. The forrnat is shown in Table 1. The Sync Byte is usedto synchronize the deinterleaver and the Reed-Solomon decoder in the user demodulator.
Table 1: Downstream Time Slot Structure 2 1 3 1.. 1 54 55 56 57 58 59 60 SyncATM Check Check Check ~heck Check Check ByteCell Byte 1 Byte 2 Byte 3 Byte4 Byte5 Byte6 3.4.1. 1.2 UPSTRl~AM
Since the u~ cal~l data ori~in~tes from different sources, each with different symbol timing and center frequency offsets, the u~ l will be time-division multiple access. The format is shown in Table 2.
SUBSTITUTE St~'LET ~RUl~ 26) W O 97/21285 PCT~US96/19341 The start of the do~ .l,ca--- frame is delinez-t~d by a Frame Start ATM
cell in the first time slot. This Frame Start ATM cell carries a reserved VP~VCIheader which can be routed by the segmentation and re?l~emhly ASIC to the host processor in the user equipment. This will reset the ~ ,alll frarne time slot count in the user processor, enabling the ul)sll~,alll frame timing to be synchronized to the downstream frarne timing.
The payload of the frame start cell will contain fields for resolving Table 3: Downstream Frame Structure Frame Time Time Time Time Time ... Time ~ Time Time Sta~t Slot I Slot2 Slot3 Slot4 Slot5 SlotN-2 SlotN-1 SlotN
Table 4: Frame Start CeU Payload N N+l ¦ .. ¦ M M+l ¦ ~-- ¦ P P+l ¦ ... ¦ 48 ~ -r. Su~ ,. IDs S~ D~ . Timing, Reserved Avdlli~ility/ for Polling r~ u~ .y, and Power A~hnu~
The up~.lle~lll frame structure is shown in Table 5. There will be contiguous time slots at the beginning of the frame for random access by users attempting to either enter the network during a power up, or by users allelllL)tillg to switch to an active state from an inactive state, or by users needing controlsignaling during an active state.
Table 5: Upstream Frame Structure Random Random Random Polling Polling Time Time Access I Access 2 Access N Response I Response M Slot I Slot M
Physical Medium D~yi ~nt Layer Dowll.ll~;anl SUBSTITUTE SHEET ~RULE 26) The modulation parameters are shown in Table 6.
Since all frequency channels in the dow.lsllt;alll direction originate from the same source, the downstream can be continuous carrier with each ~requency channel symbol synchronous. By maintaining the data on each frequency ch~nn~.l to be symbol synchronous, it enables the frequency channels to be spaced 1/TD
apart where TD is the period of a d~wll~LI~a-ll modulation symbol. This obviatesthe need for spectral-shape filtering on each frequency eh:lnn~l to reduce its spectral occupancy.
Table 6: Downstream Modulation Parameters Pulse-Shape Filtering None Modulation ~/4 QPSK
Convolutional Encoding Rate 7/8 Interleaving Forney Method, Depth = 12 Reed-Solomon Encoding ~60,54) Table 7: Typical Downstream Data Rate QPSK Modulation Symbol Rate 34.000 Mbaud Coded Symbol Rate 68.000 Msps Convolutional Coded Symbol Rate 61.200 Msps Bit Rate 53.550 Mbps ATM Rate 52.558 Mbps ATM Cell Rate 0.124 M Cells/Sec ATM Cells per Frame 743.000 Frame Period 5.994 ms SUBSTITUTE SHEET (RULE 26) W O 97~1285 PCT~US96/19341 U~ ,alll The modulation ~ar~ll~ters are shown in Table 8.
Table 8: Upstream Modulatio n Parameters Pulse-Shape Filtering a = 0.25 Root-Raised Cosine Modulation ~/4 QPSK
Convolutional Encoding None Interleaving None Reed-Solomon Encoding (59,53) Table 9: Typ~cal Upstream Data Ra~e QPSK Modulation Symbol Rate 2.607 Mbaud Time Slot Symbol Rate 5.213 Msps Coded Symbol Rate 4.961 Mbps ATM Rate 4.456 Mbps ATM Cell Rate 0.011 M CellslSec ATM Cells per Frarne 63.000 Frame Period 5.994 ms MANAGEMENT PLANE
Net Entry Upon power up, the user will acquire the d-~w~ le~ll frame tirning and begin processing the Contention Availability Acknowledgm~n~ field of the Frame Start cell payload. When the contention time slots are available, a null user IDwill be contained in the field. The user will then transmit a single Net Entry SUBSTITUTE SHEET (RUEE ~6) CA 02237464 1998-0~-12 W O 97121285 PCT~US96/19341 ATM cell on the Contention time slot in the next upstream frame. A Net entry ATM cell will be de~lned by a reserved VPI/VCI in the cell header, plus additional information in the payload cont~ining the user ID. If the Net Entry ATM cell is successfully received by the base station, the base station will acknowledge by responding with the user's ID in the Contention Availability/Acknowledge field of the frame start cell in the next frame. The field will also contain timing, frequency, and power adjustments.
The user will continue to lla~ lil Net Entry ATM cells on the C~ontention time slots until its timing, frequency, and power are within prescribed limits at which time it will be commanded to a standby state freeing up the Contention time slots for another user.
In the case of a collision on the Contention time slots, the base station will not acknowledge any user and the Frame Start cell will continue to indicate thatthe Contention time slots are available by containing the null user ID. The users will then perform any number of well known algo~ ms~ such as randomly back off based on the user lD, to determine how many frames they wait before retr~n~mi~sion.
Network M&A.~ .e.,~
During operation, inactive users will have to be periodically polled to ensure that their time slot timing, transmit frequency, and tr~n~mit power are suitable to ~ t~ reliable co-------~,ic~tion. This is neces~h- y as the propagation characteri~tics will change over time; for in~t~n~e if it begins to rain. With approximately 250 users per coverage area, polling one user per frame, each userwould be polled every 1.5 seconds. The number of users polled per frame will depend on user density, coverage area, and data rates employed when the system is deployed.
SUBSTITUTE StlEET ( ~ULE 26) CA 02237464 1998-0~-12 The polling sequence is described. In the Frame Start cell, user IDs are placed in the Polling ~leld. During the next frame, these polled subscribers respond on the Polling Response time slots. The base station cO~ ules the correction factors for timing, frequency, and power control and sends them in the Subscriber Adjustment ~leld of the Frame Start cell in the next frame.
If a user fails to respond to a poll, the Subscriber Adju~ field will be null for that user. The base station will then wait until the next cycle, after it polls all other users, before polling the user again, so that other users are polled at the regular interval. After a certain number of polls where the user fails to respond, the network manager will consider that user in a power down state. That user will have ~e,ro~lll Net entry to return to the standby state.
CONTROL PLANE
When a user in the standby state wishes to begin a session, it will transmit a Session Request ATM cell on the Contention time slots when available. Again the Session Request ATM cell will have a reserved VPI/VC~ in the cell header with the cell payload cont~ining the type of request and the user lD. The Tr~n~mi~ion Convergence Call Processing agent in the base station will then interface with the necessaly higher level control plane functions to complete the session initi~ tion.
Depending on the level of int~-a~;lion required to initiate the session, the user may only have to send the single Session Request cell, or the user may haveto be assigned a traffic time slot to complete the ~i~n~ling functions.
HARDWARE AND SOFTWARE IMPLEMENTATIONS
User E~
Figure 3 shows the block diagram for the subscriber e4ui~lllc;nt which implements the wireless networ~c protocol. An RF transceiver (1) interf~t~es with SUBSTll~TE SHEFr (P~ULE ~6) W O 97/21285 PCT~US96/19341 the antenn~ and performs signal amplifieation, downeonversion from RF to baseband, and the gain eontrol to provide proper levels into the analog to digital (AID) eonverter (2). The digital demodulator (3) reeovers the earrier and symboltiming of input signal and passes soft-deeision demodulation data to the forwarderror eorreetion deeoder (4). the digital demodulator recovers the input signal symbol t}ming by eontrolling the phase of the A/D eonverter sample eloek via a data transition tracking loop fed back to a voltage-controlled oseillator ~not shown for elarity~. The digital demodulator also eontrols the gain in the downeonverter stage of the RF transeeiver via a gain eontrol voltage. The fc,l w~d error eorreetion deeoder performs eonvolutional deeoding via the Viterbi algorithm and Reed-Solomon deeoding and passes recovered ATM eells to the "~ ioneonvergeneetransceiver(5). Thetr~n.cmi.e~ioncon~ genec transeeiver deteets the frame start ATM eell and eounts time slots within the frame to filter out ATM cells which are not intP.ncled for the user. ATM cells intenfled for the user are passed to the segment~tion and l~asse,.~hly (SAR) deviee (6) whieh eon~L~ s higher level pae~ets to be passed to the data interfaces. In-band ATM si~n~lin~ eells are passed direetly to the eentral ~luces.~;..g unit (7) whieh interprets the eomm~n(lc In the transmit direet;on, the central proce.csing unit m~int~in.c a time slot map whieh is loaded into the tr~ncmicsion eonvergenee tlallscGivt;r. As higher level packets from the data interfaces are segmented into ATM eells, the tr~ncmicsion eonvergenee lldnsceiver loads them into the preseribed time slots of the up~lean~ frame. In-band si~n~lin~ eells, either session requests or responses to polling are passed from the eentral proceccing unit to the seg".~.~.lh~ion and ~asselllbly device for insertion into the upstream frame.
Alternately, the trAncmi~cion eonvergence transceiver ean reeognize and direct in-band cign~lin~ ATM cells to and from the eentral proc~ccing unit and bypass the SAR device, or the tr~n.cmic.cion eon~v~rgellce transeeiver and the SAR
may be eombined into a single deviee.
SUBSTITUTE SHEEr (RULE 26) CA 02237464 1998-0~-12 W O 97/21285 PCT~US96~9341 ATM cells packaged onto the U~)SLI~ l frame are passed to the fo~ ~d error correction encoder (8) which then sends the serial stream to the modulator(9) for modulation onto a carrier. The symbol timing of the modulator is coherently referenced to the recovered receive symbol timing via a frequency synthesizer or numerically controlled oscillator (NCO) (10). The symbol timing can be adjusted to ensure time slot alignm~nt by a clock swallower circuit (t 1) or other means. The modulated signal is then frequently converted to the desired RFfrecluency by the RF transceiver. The output power level is controlled by the CPU from measur~lllellLs of received power level from the AGC feedback from the digital demodulator to the RF transceiver and from the bit error rate estimator in the forward error correction device.
Base Station E4..;~ ..t Figure 4 shows the block diagram for the base station e.~..;p.~.~nt- An RF
transceiver (1) interfaces with the ~ntenn~ and p.,lrOlllls signal arnplification, downconversion forrn R~ to baseband, and the gain control to provide proper levels into the analog to digital ~A/D) convtller (2). The digital demodulator (3) recovers the carrier and symbol timing of input signal and passes soft-decision demodulated data to the forward error correction decoder (4). The forward error correction decoder performs convolutional decoding via the Viterbi algorithm andReed-Solomon decoding and passes recovered ATM cells to the ATM switch (5).
Ln-band ATM ~i~n~lin~ cells are passed dlrectly to the central proce~in~ unit (6) which interprets the l~-lue~ts and polling lc;~pollses.
When the base station polls a user for status and health, it will read the user's timing offset from the timing counter ~7), and the user's frequency offset and signal level from the digital ~lemod~ tQr. Corrections to these are assembled into an in-band ATM cell and passed to the ATM switch for insertion into the SUBSTITUTE SHEET (RULE 26) CA 02237464 1998-0~-12 WO 97/21285 PCT~US96/19341 down~,L,eam frame. Time slots in the downstream frames are ~llled with cells by the ATM switch according to typical scll~d-lling functions of switches with the exception that the ATM switch inserts the frame start cell received from the central processing unit and exact Intervals. The ATM cells are then forward error correction encoded (8) and modulated (9) to form the downstream RF. The RF
transceiver upconverts the downstream signals to radio frequency. The central processing unit adjusts the transmit power level according to bit error rate measurements fed back from the subscriber to the hub station in the u~sll~,a network management polling response ATM cells.
VARIATIONS
The following variations should be obvious to a trained observer and are also claimed:
1. Use of ~l~ernSlte data rates resulting in a different number of time slots per frame.
2. Use of means other than ATM switch for routing in-band signaling ATM cells to the CPU in the base station.
3. Use of means other than SAR device for routing in-band ~ign:~ling ATM cells to the CPU in the user e(l..;p...~-~t 4. Location of the contention cells and polling ~ onse cells within the upstream frame. Depending on plOCÇ'jSi~-g capability, it may be advantageous to place the polling response time slot in the middle of the upstream frame, so that the subscriber can respond within the same frame period.
SUBSTITUTE SHEET (RULE 26) W O 97/21285 PCT~US96119341 5. Use of alternate circuits for adjusting the user transmit time slot timing with respect to implementing a nelwulh protocol for wireless broadband-ISDN. Use of alternate circuits for unrelated applications in not cl~imf~cl, . Other measures of received power level by the user e~ui~ ent such as monitoring AGC settings, bit error rates prior to ful vvcu-l error correction decoding, etc.
While the invention has been described in culme-;lion with preferred embo-1im~nt~, it will be appreciated that various other modifications and adaptations of this invention will be obvious to those skilled in the art.
WHAT IS CLAIMED IS:
SUBSTITUTE SHEET ~RULE 26)
a) means for routing in-band .ci~n~ling ATM cells to and from the ATM switching or segmentation and re~cxrlllhly device to the user e~ iplllent central proc~s~ing unit;
b) ad3usting l~ X-~ r power based on received power level and power control comm~ntls via in-band .~i~n~1in~ ATM cells from the base station;
c) means for slaving the transmit symbol clock reference to the received symbol clock reference;
d) means for adjusting the lldn~lllit symbol clock timing to minimi7.e interference to other users.
SUBSTITUTE SHEET (RUL~ 26) WO 97/21285 PCTrUSg6119341 DESCRIPTION OF THE DRAWINGS
The above and other objects, advantages and features of the invention will become more clear when considered with the following specification and attached drawings, wherein:
Figure 1 shows the protocol stack for the invention according to the convention of the OSI Reference Model, Figure 2 illustrates the two way turnaround effect of range from the base station which causes the need for large guard bands between user tr~n.cmi~sions, 1 being the nearby user and 2 being the distant user, Figure 3 is a block diagram of user or subscriber station har~lw~G
architecture, and Figure 4 is a block diagram of a base station h~dw~e arçhit.o.chlre.
DETAILED DESCI~IPTION OF THE INVENTION
It is well known that asynchronous transfer mode is the candidate network link protocol for broadband integrated services digital network (B-ISDN) which is typically defined as bit rates in excess of that of the y~ y rate interface ISDN
(PRI-ISDN) of 1.544 Mbps. Physical layer standards have been developed or are being developed for using ATM over synchronous optical network (SONET) at rates of 155 and 622 Mbps, over category 3 twisted pair at 25 Mbps, and over category 5 twisted pair at 45 Mbps and 100 Mbps. In each of these cases, however, the network topology is switch-oriented where each user has a fi~.r1iC~tf~ connection to an input port of the switch, and the switch buffers input cells until they can be routed to an output port of the switch. This is a classical star configuration.
SUBSTITUTE SHEET (RU~ E 26) CA 02237464 1998-0~-12 W O 97/21285 PCT~US96/19341 Tn a wireless point to multipoint system, where the users each employ a narrowbeam antenna, and the switch resides in a centrally-located base station which employs a broad beam antenna, in which multiple users lie in its beam, thewireless medium becomes a shared medium. While the point to multipoint nature of the system appears to be a star topology, because the wireless m~ m is shared, it is actually a bus or ring configuration. Hence, a m~ m access controlprotocol needs to be defined.
The networl~ protocol stack is as shown in Figure 1, and comprises the physical layer of the OSI Reference Model. Within the physical layer there is the physical m~dinm dependent layer which involves the modulation, forward error correction, and filt~in~ of the signal that is l~ ed over the wireless medium. The tr~nemieeion convergence layer comprices time-multiple access, the frame structure, and the time slot skucture within each frame.
The control plane functions at the tr~nemieeion convergence layer include those functions necess~ry for controlling access to the wireless Illedium through assignment of time slots. This function must interface to a higher level controlplane functions such as the lTU Q.293 1 signaling standard, the ATM Forum User Network Interface, and LAN Fm~ tion clients.
The m:ln~gem.~nt plane functions at the tr~nemieeion convel~,ence layer involve timing control to minimi7e guard band times between time slots. At the physical layer, the management functions involve controlling the user tr~n~emit~er power to ensure an adequate received signal level at the base station but not too strong as to cause adjacent cell interference, where cell refers to a cell in a cellular distribution system, not an ATM cell. Additionally, the management plane ~unctions include controlling the user's lfallsll~iL frequency so that it does not interfere with users on adjacent frequency ch~nnele, which is described in detail in a separate patent application.
SUBSTITUTE SWEET (RUI E 26) W O 97/21285 PCT~US96/19341 NETWORK PROTOCOL STACK
Tr~n~ ton Co~ g~..ceLayer Downstream Since the downstream data origin:~tes from the same source and is continuous carrier, different ATM virtual circuits are time-division multiplexedonto a single RF carrier. The forrnat is shown in Table 1. The Sync Byte is usedto synchronize the deinterleaver and the Reed-Solomon decoder in the user demodulator.
Table 1: Downstream Time Slot Structure 2 1 3 1.. 1 54 55 56 57 58 59 60 SyncATM Check Check Check ~heck Check Check ByteCell Byte 1 Byte 2 Byte 3 Byte4 Byte5 Byte6 3.4.1. 1.2 UPSTRl~AM
Since the u~ cal~l data ori~in~tes from different sources, each with different symbol timing and center frequency offsets, the u~ l will be time-division multiple access. The format is shown in Table 2.
SUBSTITUTE St~'LET ~RUl~ 26) W O 97/21285 PCT~US96/19341 The start of the do~ .l,ca--- frame is delinez-t~d by a Frame Start ATM
cell in the first time slot. This Frame Start ATM cell carries a reserved VP~VCIheader which can be routed by the segmentation and re?l~emhly ASIC to the host processor in the user equipment. This will reset the ~ ,alll frarne time slot count in the user processor, enabling the ul)sll~,alll frame timing to be synchronized to the downstream frarne timing.
The payload of the frame start cell will contain fields for resolving Table 3: Downstream Frame Structure Frame Time Time Time Time Time ... Time ~ Time Time Sta~t Slot I Slot2 Slot3 Slot4 Slot5 SlotN-2 SlotN-1 SlotN
Table 4: Frame Start CeU Payload N N+l ¦ .. ¦ M M+l ¦ ~-- ¦ P P+l ¦ ... ¦ 48 ~ -r. Su~ ,. IDs S~ D~ . Timing, Reserved Avdlli~ility/ for Polling r~ u~ .y, and Power A~hnu~
The up~.lle~lll frame structure is shown in Table 5. There will be contiguous time slots at the beginning of the frame for random access by users attempting to either enter the network during a power up, or by users allelllL)tillg to switch to an active state from an inactive state, or by users needing controlsignaling during an active state.
Table 5: Upstream Frame Structure Random Random Random Polling Polling Time Time Access I Access 2 Access N Response I Response M Slot I Slot M
Physical Medium D~yi ~nt Layer Dowll.ll~;anl SUBSTITUTE SHEET ~RULE 26) The modulation parameters are shown in Table 6.
Since all frequency channels in the dow.lsllt;alll direction originate from the same source, the downstream can be continuous carrier with each ~requency channel symbol synchronous. By maintaining the data on each frequency ch~nn~.l to be symbol synchronous, it enables the frequency channels to be spaced 1/TD
apart where TD is the period of a d~wll~LI~a-ll modulation symbol. This obviatesthe need for spectral-shape filtering on each frequency eh:lnn~l to reduce its spectral occupancy.
Table 6: Downstream Modulation Parameters Pulse-Shape Filtering None Modulation ~/4 QPSK
Convolutional Encoding Rate 7/8 Interleaving Forney Method, Depth = 12 Reed-Solomon Encoding ~60,54) Table 7: Typical Downstream Data Rate QPSK Modulation Symbol Rate 34.000 Mbaud Coded Symbol Rate 68.000 Msps Convolutional Coded Symbol Rate 61.200 Msps Bit Rate 53.550 Mbps ATM Rate 52.558 Mbps ATM Cell Rate 0.124 M Cells/Sec ATM Cells per Frame 743.000 Frame Period 5.994 ms SUBSTITUTE SHEET (RULE 26) W O 97~1285 PCT~US96/19341 U~ ,alll The modulation ~ar~ll~ters are shown in Table 8.
Table 8: Upstream Modulatio n Parameters Pulse-Shape Filtering a = 0.25 Root-Raised Cosine Modulation ~/4 QPSK
Convolutional Encoding None Interleaving None Reed-Solomon Encoding (59,53) Table 9: Typ~cal Upstream Data Ra~e QPSK Modulation Symbol Rate 2.607 Mbaud Time Slot Symbol Rate 5.213 Msps Coded Symbol Rate 4.961 Mbps ATM Rate 4.456 Mbps ATM Cell Rate 0.011 M CellslSec ATM Cells per Frarne 63.000 Frame Period 5.994 ms MANAGEMENT PLANE
Net Entry Upon power up, the user will acquire the d-~w~ le~ll frame tirning and begin processing the Contention Availability Acknowledgm~n~ field of the Frame Start cell payload. When the contention time slots are available, a null user IDwill be contained in the field. The user will then transmit a single Net Entry SUBSTITUTE SHEET (RUEE ~6) CA 02237464 1998-0~-12 W O 97121285 PCT~US96/19341 ATM cell on the Contention time slot in the next upstream frame. A Net entry ATM cell will be de~lned by a reserved VPI/VCI in the cell header, plus additional information in the payload cont~ining the user ID. If the Net Entry ATM cell is successfully received by the base station, the base station will acknowledge by responding with the user's ID in the Contention Availability/Acknowledge field of the frame start cell in the next frame. The field will also contain timing, frequency, and power adjustments.
The user will continue to lla~ lil Net Entry ATM cells on the C~ontention time slots until its timing, frequency, and power are within prescribed limits at which time it will be commanded to a standby state freeing up the Contention time slots for another user.
In the case of a collision on the Contention time slots, the base station will not acknowledge any user and the Frame Start cell will continue to indicate thatthe Contention time slots are available by containing the null user ID. The users will then perform any number of well known algo~ ms~ such as randomly back off based on the user lD, to determine how many frames they wait before retr~n~mi~sion.
Network M&A.~ .e.,~
During operation, inactive users will have to be periodically polled to ensure that their time slot timing, transmit frequency, and tr~n~mit power are suitable to ~ t~ reliable co-------~,ic~tion. This is neces~h- y as the propagation characteri~tics will change over time; for in~t~n~e if it begins to rain. With approximately 250 users per coverage area, polling one user per frame, each userwould be polled every 1.5 seconds. The number of users polled per frame will depend on user density, coverage area, and data rates employed when the system is deployed.
SUBSTITUTE StlEET ( ~ULE 26) CA 02237464 1998-0~-12 The polling sequence is described. In the Frame Start cell, user IDs are placed in the Polling ~leld. During the next frame, these polled subscribers respond on the Polling Response time slots. The base station cO~ ules the correction factors for timing, frequency, and power control and sends them in the Subscriber Adjustment ~leld of the Frame Start cell in the next frame.
If a user fails to respond to a poll, the Subscriber Adju~ field will be null for that user. The base station will then wait until the next cycle, after it polls all other users, before polling the user again, so that other users are polled at the regular interval. After a certain number of polls where the user fails to respond, the network manager will consider that user in a power down state. That user will have ~e,ro~lll Net entry to return to the standby state.
CONTROL PLANE
When a user in the standby state wishes to begin a session, it will transmit a Session Request ATM cell on the Contention time slots when available. Again the Session Request ATM cell will have a reserved VPI/VC~ in the cell header with the cell payload cont~ining the type of request and the user lD. The Tr~n~mi~ion Convergence Call Processing agent in the base station will then interface with the necessaly higher level control plane functions to complete the session initi~ tion.
Depending on the level of int~-a~;lion required to initiate the session, the user may only have to send the single Session Request cell, or the user may haveto be assigned a traffic time slot to complete the ~i~n~ling functions.
HARDWARE AND SOFTWARE IMPLEMENTATIONS
User E~
Figure 3 shows the block diagram for the subscriber e4ui~lllc;nt which implements the wireless networ~c protocol. An RF transceiver (1) interf~t~es with SUBSTll~TE SHEFr (P~ULE ~6) W O 97/21285 PCT~US96/19341 the antenn~ and performs signal amplifieation, downeonversion from RF to baseband, and the gain eontrol to provide proper levels into the analog to digital (AID) eonverter (2). The digital demodulator (3) reeovers the earrier and symboltiming of input signal and passes soft-deeision demodulation data to the forwarderror eorreetion deeoder (4). the digital demodulator recovers the input signal symbol t}ming by eontrolling the phase of the A/D eonverter sample eloek via a data transition tracking loop fed back to a voltage-controlled oseillator ~not shown for elarity~. The digital demodulator also eontrols the gain in the downeonverter stage of the RF transeeiver via a gain eontrol voltage. The fc,l w~d error eorreetion deeoder performs eonvolutional deeoding via the Viterbi algorithm and Reed-Solomon deeoding and passes recovered ATM eells to the "~ ioneonvergeneetransceiver(5). Thetr~n.cmi.e~ioncon~ genec transeeiver deteets the frame start ATM eell and eounts time slots within the frame to filter out ATM cells which are not intP.ncled for the user. ATM cells intenfled for the user are passed to the segment~tion and l~asse,.~hly (SAR) deviee (6) whieh eon~L~ s higher level pae~ets to be passed to the data interfaces. In-band ATM si~n~lin~ eells are passed direetly to the eentral ~luces.~;..g unit (7) whieh interprets the eomm~n(lc In the transmit direet;on, the central proce.csing unit m~int~in.c a time slot map whieh is loaded into the tr~ncmicsion eonvergenee tlallscGivt;r. As higher level packets from the data interfaces are segmented into ATM eells, the tr~ncmicsion eonvergenee lldnsceiver loads them into the preseribed time slots of the up~lean~ frame. In-band si~n~lin~ eells, either session requests or responses to polling are passed from the eentral proceccing unit to the seg".~.~.lh~ion and ~asselllbly device for insertion into the upstream frame.
Alternately, the trAncmi~cion eonvergence transceiver ean reeognize and direct in-band cign~lin~ ATM cells to and from the eentral proc~ccing unit and bypass the SAR device, or the tr~n.cmic.cion eon~v~rgellce transeeiver and the SAR
may be eombined into a single deviee.
SUBSTITUTE SHEEr (RULE 26) CA 02237464 1998-0~-12 W O 97/21285 PCT~US96~9341 ATM cells packaged onto the U~)SLI~ l frame are passed to the fo~ ~d error correction encoder (8) which then sends the serial stream to the modulator(9) for modulation onto a carrier. The symbol timing of the modulator is coherently referenced to the recovered receive symbol timing via a frequency synthesizer or numerically controlled oscillator (NCO) (10). The symbol timing can be adjusted to ensure time slot alignm~nt by a clock swallower circuit (t 1) or other means. The modulated signal is then frequently converted to the desired RFfrecluency by the RF transceiver. The output power level is controlled by the CPU from measur~lllellLs of received power level from the AGC feedback from the digital demodulator to the RF transceiver and from the bit error rate estimator in the forward error correction device.
Base Station E4..;~ ..t Figure 4 shows the block diagram for the base station e.~..;p.~.~nt- An RF
transceiver (1) interfaces with the ~ntenn~ and p.,lrOlllls signal arnplification, downconversion forrn R~ to baseband, and the gain control to provide proper levels into the analog to digital ~A/D) convtller (2). The digital demodulator (3) recovers the carrier and symbol timing of input signal and passes soft-decision demodulated data to the forward error correction decoder (4). The forward error correction decoder performs convolutional decoding via the Viterbi algorithm andReed-Solomon decoding and passes recovered ATM cells to the ATM switch (5).
Ln-band ATM ~i~n~lin~ cells are passed dlrectly to the central proce~in~ unit (6) which interprets the l~-lue~ts and polling lc;~pollses.
When the base station polls a user for status and health, it will read the user's timing offset from the timing counter ~7), and the user's frequency offset and signal level from the digital ~lemod~ tQr. Corrections to these are assembled into an in-band ATM cell and passed to the ATM switch for insertion into the SUBSTITUTE SHEET (RULE 26) CA 02237464 1998-0~-12 WO 97/21285 PCT~US96/19341 down~,L,eam frame. Time slots in the downstream frames are ~llled with cells by the ATM switch according to typical scll~d-lling functions of switches with the exception that the ATM switch inserts the frame start cell received from the central processing unit and exact Intervals. The ATM cells are then forward error correction encoded (8) and modulated (9) to form the downstream RF. The RF
transceiver upconverts the downstream signals to radio frequency. The central processing unit adjusts the transmit power level according to bit error rate measurements fed back from the subscriber to the hub station in the u~sll~,a network management polling response ATM cells.
VARIATIONS
The following variations should be obvious to a trained observer and are also claimed:
1. Use of ~l~ernSlte data rates resulting in a different number of time slots per frame.
2. Use of means other than ATM switch for routing in-band signaling ATM cells to the CPU in the base station.
3. Use of means other than SAR device for routing in-band ~ign:~ling ATM cells to the CPU in the user e(l..;p...~-~t 4. Location of the contention cells and polling ~ onse cells within the upstream frame. Depending on plOCÇ'jSi~-g capability, it may be advantageous to place the polling response time slot in the middle of the upstream frame, so that the subscriber can respond within the same frame period.
SUBSTITUTE SHEET (RULE 26) W O 97/21285 PCT~US96119341 5. Use of alternate circuits for adjusting the user transmit time slot timing with respect to implementing a nelwulh protocol for wireless broadband-ISDN. Use of alternate circuits for unrelated applications in not cl~imf~cl, . Other measures of received power level by the user e~ui~ ent such as monitoring AGC settings, bit error rates prior to ful vvcu-l error correction decoding, etc.
While the invention has been described in culme-;lion with preferred embo-1im~nt~, it will be appreciated that various other modifications and adaptations of this invention will be obvious to those skilled in the art.
WHAT IS CLAIMED IS:
SUBSTITUTE SHEET ~RULE 26)
Claims (14)
1. In an RF communication system for controlling communication between a base station and a plurality of stationary user stations, said base station and each said user stations having an RF transceivers and each said stationary users having a high gain directional antenna, the improvement comprising, in combination:
means for effecting time-division multiplexed communications from said base station to said stationary users, means for providing time division multiple access time slot communications from each said stationary user, respectively, to said base station including means for actively assigning time slots to each said user and means for synchronizing frame timing from each said user transceiver, respectively, with frame timing between said base station to said stationary users, each said time slot carries one asynchronous transfer mode (ATM) cell and wherein the first of time slots in the communication between said base station and said carries a frame start ATM cell.
means for effecting time-division multiplexed communications from said base station to said stationary users, means for providing time division multiple access time slot communications from each said stationary user, respectively, to said base station including means for actively assigning time slots to each said user and means for synchronizing frame timing from each said user transceiver, respectively, with frame timing between said base station to said stationary users, each said time slot carries one asynchronous transfer mode (ATM) cell and wherein the first of time slots in the communication between said base station and said carries a frame start ATM cell.
2. In an RF communication system for controlling communication between a base station and a plurality of stationary user stations, said base station and each said user stations having an RF transceivers and each said stationary users having a high gain directional antenna, the improvement comprising, in combination:
means for effecting time-division multiplexed communications in the downstream direction from said base station to said stationary users, time slots in said down stream direction having one sync byte, one ATM cell, and no guard time (band), means for providing time division multiple access time slot communications in the upstream direction from each said stationary user, respectively, to said base station including means for actively assigning time slots to each said user and means for synchronizing frame timing from each said user transceiver, respectively, with frame timing between said base station to said stationary users, time slots in said upstream direction having two preamble bytes, one ATM cell, and a one byte guard time (band), each said time slot being divided into asynchronous transfer mode (ATM) cells and wherein the first of time slots in the communication between said basestation and said carries a frame start ATM cell.
means for effecting time-division multiplexed communications in the downstream direction from said base station to said stationary users, time slots in said down stream direction having one sync byte, one ATM cell, and no guard time (band), means for providing time division multiple access time slot communications in the upstream direction from each said stationary user, respectively, to said base station including means for actively assigning time slots to each said user and means for synchronizing frame timing from each said user transceiver, respectively, with frame timing between said base station to said stationary users, time slots in said upstream direction having two preamble bytes, one ATM cell, and a one byte guard time (band), each said time slot being divided into asynchronous transfer mode (ATM) cells and wherein the first of time slots in the communication between said basestation and said carries a frame start ATM cell.
3. The RF communication defined in claim 2 wherein the frame periods in both the upstream and downstream directions are approximately but not greater than six milliseconds in length to allow delivery of voice traffic with minimum latency.
4. The RF communication system defined in claim 2 incorporating:
a) The downstream is continuous-carrier, without pulse-shaping filtering, with frequency channels symbol synchronous and spaced 1/TD apart where TD is the period of a downstream modulation symbol;
b) The upstream is burst-mode with 24% excess bandwidth root raised cosine filtered with frequency channels spaced 1.25/ TD
apart where TD is the period of an upstream modulation symbol;
c) QPSK or alternately 16 QAM modulation is employed on the upstream and the downstream;
d) A concatenated (60.54) Reed-Solomon over GF(256) and rate 7/8 convolutional code is used on the downstream and e) A (59.53) Reed-Solomon code over GF(256) is used on the upstream.
a) The downstream is continuous-carrier, without pulse-shaping filtering, with frequency channels symbol synchronous and spaced 1/TD apart where TD is the period of a downstream modulation symbol;
b) The upstream is burst-mode with 24% excess bandwidth root raised cosine filtered with frequency channels spaced 1.25/ TD
apart where TD is the period of an upstream modulation symbol;
c) QPSK or alternately 16 QAM modulation is employed on the upstream and the downstream;
d) A concatenated (60.54) Reed-Solomon over GF(256) and rate 7/8 convolutional code is used on the downstream and e) A (59.53) Reed-Solomon code over GF(256) is used on the upstream.
5. The RF communication system defined in claim 2 further incorporating:
Means for control plane functions through:
a) In-band signaling through ATM cells with reserved VPI/VCIs so that the requirements for acquisition, demodulation, and forward error correction ale uniform across the data, control, and management planes of the network protocol;
b) Transmission convergence layer medium access control which actively assigns time slots in the upstream direction to accommodate varying demands for bandwidth by multiple users;
c) Contiguous time slots at the beginning of the upstream frame are used for entry into the network by users whose two-way range timing has not been resolved to avoid mutual interference, where users entering the network remain on the net entrey time slots until their timing in aligned;
d) Session requests are performed on a contention basis through random access of the net entry time slots;
e) Carrying control plane acknowledgment of service requests in the payload of the frame start ATM cell in the downstream frame.
Means for control plane functions through:
a) In-band signaling through ATM cells with reserved VPI/VCIs so that the requirements for acquisition, demodulation, and forward error correction ale uniform across the data, control, and management planes of the network protocol;
b) Transmission convergence layer medium access control which actively assigns time slots in the upstream direction to accommodate varying demands for bandwidth by multiple users;
c) Contiguous time slots at the beginning of the upstream frame are used for entry into the network by users whose two-way range timing has not been resolved to avoid mutual interference, where users entering the network remain on the net entrey time slots until their timing in aligned;
d) Session requests are performed on a contention basis through random access of the net entry time slots;
e) Carrying control plane acknowledgment of service requests in the payload of the frame start ATM cell in the downstream frame.
6. The RF communication system defined in claim 2 further incorporating:
Means for management plane functions provided through:
a) In-band signaling through ATM cells with reserved VPI/VCIs so that the requirements for acquisition, demodulation, and forward error correction are uniform across the data, control, and management planes of the network protocol;
b) Polling users by the base station, with users responding on dedicated time slots in the upstream frame;
c) Carrying management plane polling requests in the payload of the frame start ATM cell in the downstream frame;
d) Upstream time slot synchronization is maintained to within ~2 modulation symbols through timing control to correct range difference from the base station to each user and through slaving the user transmit symbol clock to its received symbol clock;
e) Upstream power control is employed to ensure adequate received signal strength at the base station while minimizing adjacent cell interference.
Means for management plane functions provided through:
a) In-band signaling through ATM cells with reserved VPI/VCIs so that the requirements for acquisition, demodulation, and forward error correction are uniform across the data, control, and management planes of the network protocol;
b) Polling users by the base station, with users responding on dedicated time slots in the upstream frame;
c) Carrying management plane polling requests in the payload of the frame start ATM cell in the downstream frame;
d) Upstream time slot synchronization is maintained to within ~2 modulation symbols through timing control to correct range difference from the base station to each user and through slaving the user transmit symbol clock to its received symbol clock;
e) Upstream power control is employed to ensure adequate received signal strength at the base station while minimizing adjacent cell interference.
7. The RF communication system defined in claim 2, said base station including:
a) means for routing of in-band signaling ATM cells by the ATM
switching device to and from the central processing unit;
b) means for measuring timing offsets by subscribers through counting periods of the reference symbol clock from a master frame epoch to the detection of the Barker sequence of the received transmission from the user;
e) means for measuring received signal level via bit error rate estimation or relative received power level for closed loop power control of the user transmitter.
a) means for routing of in-band signaling ATM cells by the ATM
switching device to and from the central processing unit;
b) means for measuring timing offsets by subscribers through counting periods of the reference symbol clock from a master frame epoch to the detection of the Barker sequence of the received transmission from the user;
e) means for measuring received signal level via bit error rate estimation or relative received power level for closed loop power control of the user transmitter.
8. The RF communication system defined in claim 2, said user station including:
a) means for routing in-band signaling ATM cells to and from the ATM switching or segmentation and reassembly device to the user equipment central processing unit;
b) adjusting transmitter power based on received power level and power control commands via in-band signaling ATM cells from the base station;
c) means for slaving the transmit symbol clock reference to the received symbol clock reference;
d) means for adjusting the transmit symbol clock timing to minimize interface to other users.
a) means for routing in-band signaling ATM cells to and from the ATM switching or segmentation and reassembly device to the user equipment central processing unit;
b) adjusting transmitter power based on received power level and power control commands via in-band signaling ATM cells from the base station;
c) means for slaving the transmit symbol clock reference to the received symbol clock reference;
d) means for adjusting the transmit symbol clock timing to minimize interface to other users.
9. A time-division wireless two-way point to multi-point communication system including base and user stations, the base station using one frequency band and the user stations another, wherein the modulation of transmission from the base station comprises sequentially transmitted groups of digital data cells, and each such cell contains both message data and digital information directing that message data to a particular user station or stations, each data frame transmitted from a user station to the base station comprises zero or more cells of similar structure to those in base station transmissions, transmitted discontinuously and such that in regular operation, cells transmitted by a user station do not occupy the same time interval as those from other user stations, frames of cells transmitted by user stations are synchronized to the frames transmitted by the base station, so that a user to base station frame follows each base station to user frame and each base station transmitted frame begins with a unique frame start cell.
10. A communication system as described in Claim 9 characterized by said frame for base station to user station and user station to base station transmissions being approximately six milliseconds in duration.
11. A communication system as described in Claim g wherein transmissions from base to user stations employ a continuous carrier signal modulated with .alpha. = 0.23 root-raised cosine filtered digital signals, the structure of each data cell is that described in the Asynchronous Transmission Method (ATM) standard, modulation is a combination of 4-phase modulation and multilevel amplitude modulation and error correction is accomplished . through concatenated forward error correction coding using a Reed-Solomon code applied to each set of four adjacent data cells.
12. A communication system as described in Claim 9 wherein cell transmissions from user stations to base station employ bursts of carrier modulated with .alpha. = 0.23 root-raised cosine filtered digital signals, tile structure of each data cell is that described in the Asynchronous Transmission Method (ATM) standard, modulation is quadrature-phase-shift-keyed, and error correction is accomplished through forward error correction coding using a Reed-Solomon code applied to each data cell transmitted.
13. A communication system as described in Claim 9 wherein medium access control is carried out by:
transmission of access control-related information within ATM standard data cells having unique identifiers that identify the data they contain, thus enabling any cell to contain either message data or control data, access control means associated with the base station that, on the basis of requests made by user stations, dynamically assigns cells (time slots) in the user to base station transmission frames to accommodate the transmission demands of the user stations, where the cell or cells assigned to each user station are transmitted in the frame start cell of the base station's frame.
time periods at the beginning of the base to user frame sequence set aside for transmissions by user stations entering the network until they can be detected, recognized and assigned cell slots in a subsequent user to base station frame, ATM-cell time periods set aside, in user to base station frames, for use by user stations that have previously joined the network but have not recently requested to transmit data cells, where acknowledgment of service requests by user stations is made by the access control means through data within the frame start ATM cell.
transmission of access control-related information within ATM standard data cells having unique identifiers that identify the data they contain, thus enabling any cell to contain either message data or control data, access control means associated with the base station that, on the basis of requests made by user stations, dynamically assigns cells (time slots) in the user to base station transmission frames to accommodate the transmission demands of the user stations, where the cell or cells assigned to each user station are transmitted in the frame start cell of the base station's frame.
time periods at the beginning of the base to user frame sequence set aside for transmissions by user stations entering the network until they can be detected, recognized and assigned cell slots in a subsequent user to base station frame, ATM-cell time periods set aside, in user to base station frames, for use by user stations that have previously joined the network but have not recently requested to transmit data cells, where acknowledgment of service requests by user stations is made by the access control means through data within the frame start ATM cell.
14. A communication system as described in Claim 9 wherein system management synchronization and transmit power control functions are carried out by transmission of system management commands or requests in base station frame start cells, each user station slaving its transmit clock to timing derived from the received, where the cell or cells assigned to each user station are transmitted in the frame start cell of the base station's frame.
time periods at the beginning of the base to user frame sequence set aside for transmissions by user stations entering the network until they can be detected, recognized and assigned cell slots in a subsequent user to base station frame, ATM-cell time periods set aside, in user to base station frames, for use by user stations that have previously joined the network but have not recently requested to transmit data cells, where acknowledgment of service requests by user stations is made by the access control means through data within the frame start ATM cell.
time periods at the beginning of the base to user frame sequence set aside for transmissions by user stations entering the network until they can be detected, recognized and assigned cell slots in a subsequent user to base station frame, ATM-cell time periods set aside, in user to base station frames, for use by user stations that have previously joined the network but have not recently requested to transmit data cells, where acknowledgment of service requests by user stations is made by the access control means through data within the frame start ATM cell.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/568,600 US5751702A (en) | 1995-12-05 | 1995-12-05 | Network protocol for wireless broadband ISDN using ATM |
| US08/568,600 | 1995-12-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2237464A1 true CA2237464A1 (en) | 1997-06-12 |
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ID=24271950
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002237464A Abandoned CA2237464A1 (en) | 1995-12-05 | 1996-12-05 | Network protocol for wireless broadband isdn using atm |
Country Status (9)
| Country | Link |
|---|---|
| US (2) | US5751702A (en) |
| EP (1) | EP0872045A4 (en) |
| JP (1) | JP2000508129A (en) |
| KR (1) | KR19990071919A (en) |
| CN (1) | CN1203712A (en) |
| AU (1) | AU709237B2 (en) |
| BR (1) | BR9612116A (en) |
| CA (1) | CA2237464A1 (en) |
| WO (1) | WO1997021285A1 (en) |
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-
1995
- 1995-12-05 US US08/568,600 patent/US5751702A/en not_active Expired - Fee Related
-
1996
- 1996-06-10 US US08/662,772 patent/US5886989A/en not_active Expired - Fee Related
- 1996-12-05 EP EP96944753A patent/EP0872045A4/en not_active Withdrawn
- 1996-12-05 JP JP9521409A patent/JP2000508129A/en active Pending
- 1996-12-05 CN CN96198805A patent/CN1203712A/en active Pending
- 1996-12-05 WO PCT/US1996/019341 patent/WO1997021285A1/en not_active Application Discontinuation
- 1996-12-05 BR BR9612116A patent/BR9612116A/en not_active Application Discontinuation
- 1996-12-05 AU AU13290/97A patent/AU709237B2/en not_active Ceased
- 1996-12-05 CA CA002237464A patent/CA2237464A1/en not_active Abandoned
- 1996-12-05 KR KR1019980704206A patent/KR19990071919A/en not_active Application Discontinuation
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| WO1997021285A1 (en) | 1997-06-12 |
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| AU1329097A (en) | 1997-06-27 |
| US5751702A (en) | 1998-05-12 |
| KR19990071919A (en) | 1999-09-27 |
| EP0872045A1 (en) | 1998-10-21 |
| AU709237B2 (en) | 1999-08-26 |
| BR9612116A (en) | 1999-02-17 |
| JP2000508129A (en) | 2000-06-27 |
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