Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
2002-09-03
2004-05-25
Vo, Don Nguyen (Department: 2631)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S148000, C375S267000, C375S347000
Reexamination Certificate
active
06741635
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to wireless systems and, more particularly, to systems having more than one antenna at the receiver and at the transmitter.
Physical constraints as well as narrow bandwidth, co-channel interference, adjacent channel interference, propagation loss and multi-path fading limit the capacity of cellular systems. These are severe impairments, which liken the wireless channel to a narrow pipe that impedes the flow of data. Nevertheless, interest in providing high speed wireless data services is rapidly increasing. Current cellular standards such as IS-136 can only provide data rates up to 9.6 kbps, using 30 kHz narrowband channels. In order to provide wideband services, such as multimedia, video conferencing, simultaneous voice and data, etc., it is desirable to have data rates in the range of 64-144 kbps.
Transmission schemes for multiple antenna systems may be part of a solution to the problem of the currently available low data rates. Such schemes were first proposed in papers by Wittneben, and by Seshadri and Winters, where the problem was addressed in the context of signal processing.
One prior art arrangement having a single transmitter antenna and multiple receiver antennas is shown in FIG.
1
. Each of the receiver antennas receives the transmitted signal via a slightly different channel, where each channel i is characterized by transfer function &agr;
i
. Using an approach known as “Maximum Ratio Combining”, the prior art approach to detection contemplates multiplying each received signal that had been influenced by &agr;
i
by the complex conjugate signal, &agr;
i
*, summed, and then processed.
In a co-pending application titled “Method and Apparatus for Data Transmission Using Space-Time Codes and Multiple Transmit Antennas”, filed on May 6, 1997, bearing the Serial No. 08/847,635, and assigned to the assignee of this invention, a coding perspective was adopted to propose space-time coding using multiple transmit and receive antennas. Space-time coding integrates channel coding, modulation, and multiple transmit antennas to achieve higher data rates, while simultaneously providing diversity that combats fading. It may be demonstrated that adding channel coding provides significant gains over the schemes of Wittneben and Seshadri and Winters. In said co-pending application, space-time codes were designed for transmission using 2-4 transmit antennas. These codes perform extremely well in slowly varying fading environments (such as indoor transmission media). The codes have user bandwidth efficiencies of up to 4 bits/sec/Hz which are about 3-4 times the efficiency of current systems. Indeed, it can be shown that the designed codes are optimal in terms of the trade-off between diversity advantage, transmission rate, decoding complexity and constellation size.
It can also be shown that as the number of antennas is increased, the gain increases in a manner that is not unlike a multi-element antenna that is tuned to, say, a particular direction. Unfortunately, however, when maximum likelihood detection is employed at the receiver, the decoding complexity increases when the number of transmit and receive antennas is increased. It would be obviously advantageous to allow a slightly sub-optimal detection approach that substantially reduces the receiver's computation burden.
SUMMARY
Such an approach is achieved with a receiver arrangement where signals received at a plurality of antennas are each multiplied by a respective constant and then summed prior to being applied to a maximum likelihood detector. The respective constants, &lgr;
j
, where j is an index designating a particular receiver antenna, are derived from a processor that determines the largest eigenvector of the matrix A, where &Lgr; is a vector containing the values &lgr;
j
, and A is a matrix containing elements &agr;
ij
, which is the transfer function between the i
th
transmitter antenna to the j
th
receiver antenna. The &agr;
ij
terms are determined in the receiver in conventional ways.
REFERENCES:
patent: 3633107 (1972-01-01), Brady
patent: 3978408 (1976-08-01), Gupta et al.
patent: 4001692 (1977-01-01), Fenwick et al.
patent: 4099121 (1978-07-01), Fang
patent: 4369516 (1983-01-01), Byrns
patent: 4567464 (1986-01-01), Siegel et al.
patent: 4577332 (1986-03-01), Brenig
patent: 4675880 (1987-06-01), Davarian
patent: 4733402 (1988-03-01), Monsen
patent: 4763331 (1988-08-01), Matsumoto
patent: 4953183 (1990-08-01), Bergmans et al.
patent: 5022053 (1991-06-01), Chung et al.
patent: 5029185 (1991-07-01), Wei
patent: 5088113 (1992-02-01), Wei
patent: 5101501 (1992-03-01), Gilhousen et al.
patent: 5109390 (1992-04-01), Gilhousen et al.
patent: 5202903 (1993-04-01), Okanoue
patent: 5283780 (1994-02-01), Schuchman et al.
patent: 5305353 (1994-04-01), Weerackody
patent: 5319677 (1994-06-01), Kim
patent: 5396518 (1995-03-01), How
patent: 5416797 (1995-05-01), Gilhousen et al.
patent: 5418798 (1995-05-01), Wei
patent: 5442627 (1995-08-01), Viterbi et al.
patent: 5457712 (1995-10-01), Weerackody
patent: 5461646 (1995-10-01), Anvari
patent: 5461696 (1995-10-01), Frank et al.
patent: 5479448 (1995-12-01), Seshadri
patent: 5481572 (1996-01-01), Skold et al.
patent: 5499272 (1996-03-01), Bottomley
patent: 5553102 (1996-09-01), Jasper et al.
patent: 5675590 (1997-10-01), Alamouti
patent: 5790570 (1998-08-01), Heegard et al.
patent: 5848103 (1998-12-01), Weerackody
patent: 5943372 (1999-08-01), Gans et al.
patent: 5949833 (1999-09-01), Weerackody
patent: 5960039 (1999-09-01), Martin et al.
patent: 5991331 (1999-11-01), Chennakeshu et al.
patent: 6034987 (2000-03-01), Chennakeshu et al.
patent: 6094465 (2000-07-01), Stein et al.
patent: 6115427 (2000-09-01), Calderbank et al.
patent: 6144711 (2000-11-01), Raleigh et al.
patent: 6185258 (2001-02-01), Alamouti et al.
patent: 6188736 (2001-02-01), Lo et al.
patent: 6393074 (2002-05-01), Mandyam et al.
patent: 6470043 (2002-10-01), Lo et al.
patent: 6501803 (2002-12-01), Alamouti et al.
patent: 6549585 (2003-04-01), Naguib et al.
patent: 2252664 (1997-11-01), None
patent: 2302289 (1998-03-01), None
patent: 2276207 (2003-02-01), None
patent: 298 24 760 (2002-06-01), None
patent: 298 24 761 (2002-06-01), None
patent: 298 24 762 (2002-06-01), None
patent: 298 24 763 (2002-06-01), None
patent: 298 24 765 (2002-06-01), None
patent: 0 767 546 (1997-04-01), None
patent: 1 016 228 (2003-06-01), None
patent: 2 280 575 (1995-02-01), None
patent: 2 290 010 (1995-12-01), None
patent: 2 311 445 (1997-09-01), None
patent: WO 91/20142 (1991-12-01), None
patent: WO 95/22214 (1995-08-01), None
patent: WO 97/24849 (1997-07-01), None
patent: WO 97/41670 (1997-11-01), None
patent: WO 98/09385 (1998-03-01), None
patent: WO 99/14871 (1999-03-01), None
Alamouti, Siavash M.,“A Simple Transmit Diversity Technique for Wireless Communications,”IEEE Journal on Select Areas in Communications, Oct. 1998, pp. 1451-1458, vol. 16, No. 8, The Institute of Electrical and Electronics Engineers, Inc., New York, NY.
Cavers, James K., “An Analysis of Pilot Symbol Assisted Modulation for Rayleigh Fading Channels,”IEEE Transactions on Vehicular Technology, Nov. 1991, pp. 686-693, vol. 40, No. 4, The Institute of Electrical and Electronics Engineers, Inc., New York, NY.
Naguib, Ayman et al., “A Space-Time Coding Modem for High-Data-Rate Wireless Communications,”IEEE Journal On Selected Areas in Communications, Oct. 1998, pp. 1459-1478, The Institute of Electrical and Electronics Engineers, Inc. New York, NY.
Sampei, Seiichi et al., “Rayleigh Fading Compensation Method for 16QAM in Digital Land Mobile Radio Channels,”Proceedings of the 1989 IEEE Vehicular Technology Conference, May 1989, pp. 640-646, The Institute of Electrical and Electronics Engineers, Inc., New York, NY.
Seshadri, N. et al., “Advanced Techniques for Modulation, Error Correction, Channel Equalization and Diversity,”AT&T Tech. Journal 47(4): 48-63, Jul. 1993.
Seshadri, N. et al., “Space-Time Codes for Wireless Communication: Code Construction,” IEEE 47thVehicular Technology Cont., Phoenix, pp. 637-641,
Lo Titus
Tarokh Vahid
AT&T Wireless Services Inc.
Perkins Coie LLP
Vo Don Nguyen
LandOfFree
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