Spatio-temporal processing for communication

• US 6,144,711 A
• Filed: 08/27/1997
• Issued: 11/07/2000
• Est. Priority Date: 08/29/1996
• Status: Expired due to Term

• Current Assignee: Cisco Systems, Inc.
• Original Assignee: Cisco Systems, Inc.
• Inventors: Raleigh, Gregory G., Pollack, Michael A., Jones, Vincent K. IV
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Fan, Chieh M.
• Application Number:
  US08/921,633
• Time in Patent Office: 1,168 Days
• Field of Search: 375/219, 375/260, 375/316, 375/346, 375/347, 375/348, 375/285, 375/349, 375/350, 370/342, 370/203, 370/210, 455/63, 455/64, 455/65, 708/403, 708/404, 708/405
• US Class Current: 375/347
• CPC Class Codes: H04B 1/1081 Reduction of multipath noise by equalising H04B7/005
• CPC Class Codes: H04B 7/0443 utilizing "waterfilling" technique
• CPC Class Codes: H04B 7/0469 taking special antenna structures, e.g. cross polarized antennas into account
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/0619 using feedback from receiving side feedback signaling for adaptive modulation/coding H04L1/0001
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/0658 Feedback reduction
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/068 using space frequency diversity space-frequency coding H04L1/0606
• CPC Class Codes: H04B 7/0842 Weighted combining
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/006 Trellis-coded modulation
• CPC Class Codes: H04L 1/0065 Serial concatenated codes
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0606 Space-frequency coding
• CPC Class Codes: H04L 1/0618 : Space-time coding
• CPC Class Codes: H04L 1/18 : Automatic repetition systems, e.g. Van Duuren systems
• CPC Class Codes: H04L 1/1812 : Hybrid protocols; Hybrid automatic repeat request [HARQ]
• CPC Class Codes: H04L 2025/03414 : Multicarrier
• CPC Class Codes: H04L 2025/03426 : transmission using multiple-input and multiple-output channels
• CPC Class Codes: H04L 2025/03802 : Signalling on the reverse channel
• CPC Class Codes: H04L 25/0204 : of multiple channels
• CPC Class Codes: H04L 25/021 : Estimation of channel covariance
• CPC Class Codes: H04L 25/0212 : of impulse response
• CPC Class Codes: H04L 25/0242 : using matrix methods
• CPC Class Codes: H04L 25/03305 : Joint sequence estimation and interference removal joint detection of several desired signals H04L25/03331
• CPC Class Codes: H04L 25/03331 : Arrangements for the joint estimation of multiple sequences
• CPC Class Codes: H04L 25/03343 : Arrangements at the transmitter end
• CPC Class Codes: H04L 27/2601 : Multicarrier modulation systems
• CPC Class Codes: H04L 27/2626 : Arrangements specific to the transmitter only
• CPC Class Codes: H04L 27/2647 : Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 5/0007 : the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0023 : Time-frequency-space
• CPC Class Codes: H04L 5/0028 : Variable division signaling therefor H04L5/0092
• CPC Class Codes: H04L 5/0046 : Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04W 16/28 : using beam steering
• CPC Class Codes: H04W 72/00 : Local resource management
• CPC Class Codes: H04W 88/02 : Terminal devices
• CPC Class Codes: H04W 88/08 : Access point devices

Abstract

A space-time signal processing system with advantageously reduced complexity. The system may take advantage of multiple transmitter antenna elements and/or multiple receiver antenna elements, or multiple polarizations of a single transmitter antenna element and/or single receiver antenna element. The system is not restricted to wireless contexts and may exploit any channel having multiple inputs or multiple outputs and certain other characteristics. Multi-path effects in a transmission medium cause a multiplicative increase in capacity.

Claims

1. In a digital communication system, a method for receiving via a plurality of outputs from a channel, said method comprising:

providing a time domain substantially orthogonalizing procedure to divide said channel into output bins;

providing one or more spatial directions for communication defined by corresponding weightings among said channel outputs wherein each output bin has at least one associated spatial direction, said weightings defining said one or more spatial directions so that each spatial direction corresponds to communication via more than one channel output; and

receiving information via subchannels of said channel by employing at least two independent parallel applications of said time domain substantially orthogonalizing procedure, each subchannel defined by a combination of output bin and spatial direction.

2. The method of claim 1 wherein receiving information comprises:

receiving input time domain symbols via said channel outputs;

applying said time domain substantially orthogonalizing procedure to said input time domain symbols independently for each of said channel outputs; and

applying ones of said weightings corresponding to each of said output bins to results of said time domain substantially orthogonalizing procedure to obtain symbols transmitted via each of said subchannels.

3. The method of claim 1 wherein receiving information comprises receiving information in subchannels defined by said output bins and at least two spatial directions associated with each of said output bins, said spatial directions being chosen independently for each of said output bins.

4. The method of claim 3 wherein said at least two spatial directions are mutually orthogonal for each of said output bins.

5. The method of claim 3 wherein receiving information comprises:

receiving time domain symbols via said channel outputs;

for each of said channel outputs, independently applying said time domain substantially orthogonalizing procedure to said received input time domain symbols; and

applying said weightings to results of said time domain substantially orthogonalizing procedure to obtain symbols transmitted via each of said subchannels.

6. The method of claim 5 wherein said weightings are selected according to singular value decompositions of matrices characterizing communication via each output bin of said channel.

7. The method of claim 5 further comprising applying a decoding procedure to said symbols transmitted via each of said subchannels.

8. The method of claim 3 wherein said at least two spatial directions are not mutually orthogonal for each of said output bins.

9. The method of claim 8 wherein receiving information comprises:

receiving time domain symbols via said channel outputs;

for each of said channel outputs, applying said weightings to said time domain symbols to obtain results corresponding to each of said spatial directions;

applying said time domain substantially orthogonalizing procedure to said results independently for each of said spatial directions to obtain symbols transmitted via each of said subchannels; and

decoding said symbols transmitted via each of said subchannels according to a coding scheme optimized to take advantage of multiple spatial directions.

10. The method of claim 1 wherein said time domain substantially orthogonalizing procedure belongs to one of a group consisting of a Fast Fourier Transform and an inverse Fast Fourier Transform.

11. The method of claim 10 wherein said Fast Fourier Transform or said inverse Fast Fourier Transform is preceded by removal of a cyclic prefix.

12. The method of claim 1 wherein said channel comprises a wireless channel and said plurality of channel outputs are associated with a corresponding plurality of receiver antenna elements.

13. The method of claim 12 wherein said plurality of receiver antenna elements are co-located.

14. The method of claim 12 wherein said plurality of receiver antenna elements are at disparate locations.

15. The method of claim 1 further comprising:

receiving via a particular one of said channel outputs, at least v frequency domain training symbols transmitted via a particular input to said channel in a single burst, v being an extent in symbol periods of a duration of significant terms of an impulse response of a channel component coupling said particular channel input and said particular channel output;

applying an inverse of said time domain substantially orthogonalizing procedure to said received at least v frequency domain training symbols to obtain a time domain response for said channel component; and

applying said time domain substantially orthogonalizing procedure to a zero-padded version of said time domain response to obtain a frequency response for said channel component.

16. A receiver system for receiving via a plurality of outputs from a channel, said receiver system comprising:

at least one processing element that applies a time domain substantially orthogonalizing procedure to divide said channel into output bins;

a spatial processor employing weightings among said channel outputs to define spatial directions wherein each output bin has at least one associated spatial direction, said weightings defining said one or more spatial directions so that each spatial direction corresponds to communication via more than one channel output; and

wherein said receiver system receives information via subchannels of said channel, by employing at least two independent parallel applications of said time domain substantially orthogonalizing procedure by said at least one processing element, each of said subchannels being defined by a combination of output bin and spatial direction.

17. The receiver system of claim 16 further comprising:

a system input that receives time domain input symbols via said channel outputs; and

wherein

said at least one processing element applies said time domain substantially orthogonalizing procedure to said time domain input symbols independently for each of said channel outputs; and

wherein

said spatial processor applies ones of said weightings corresponding to each of said output bins to results of said time domain substantially orthogonalizing procedure to obtain symbols transmitted via each of said subchannels.

18. The receiver system of claim 16 wherein said receiver system receives information in subchannels defined by said output bins and at least two spatial directions associated with each of said output bins, each of said output bins having identical associated spatial directions.

19. The receiver system of claim 16 wherein said receiver system receives information in subchannels defined by said output bins and at least two spatial directions associated with each of said output bins, said spatial directions being chosen independently for each of said output bins.

20. The receiver system of claim 19 wherein said at least two spatial directions are mutually orthogonal for each of said output bins.

21. The receiver system of claim 19 further comprising:

a system input that receives time domain symbols via said channel outputs; and

wherein

said at least one processing element, for each of said channel outputs, independently applies said time domain substantially orthogonalizing procedure to said received time domain symbols; and

wherein

said spatial processor applies said weightings to results of said time domain substantially orthogonalizing procedure to obtain symbols transmitted via each of said subchannels.

22. The receiver system of claim 21 wherein said weightings are selected according to singular value decompositions of matrices characterizing communication via each output bin of said channel.

23. The receiver system of claim 21 further comprising a decoding system that applies a decoding procedure to said symbols transmitted via each of said subchannels.

24. The receiver system of claim 19 wherein said at least two spatial directions are rot mutually orthogonal for each of said output bins.

25. The receiver system of claim 24 further comprising:

a system input that receives time domain symbols via said channel outputs; and

wherein

said spatial processor, for each of said channel outputs, applies said weightings to said time domain symbols to obtain result symbols corresponding to each of said spatial directions; and

wherein

said at least one processing element applies said time domain substantially orthogonalizing procedure to said result symbols independently for each of said spatial directions to obtain symbols transmitted via each of said subchannels; and

wherein said receiver system further comprises;

a decoding system that decodes symbols transmitted via each of said subchannels according to a coding scheme optimized to take advantage of multiple spatial directions.

26. The receiver system of claim 16 wherein said time domain substantially orthogonalizing procedure belongs to one of a group consisting of a Fast Fourier Transform and an inverse Fast Fourier Transform.

27. The receiver system of claim 26 wherein said Fast Fourier Transform or said inverse Fast Fourier Transform is preceded by removal of a cyclic prefix.

28. The receiver system of claim 16 wherein said channel comprises a wireless channel and said plurality of channel outputs are associated with a corresponding plurality of receiver antenna elements.

29. The receiver system of claim 28 wherein said plurality of receiver antenna elements are co-located.

30. The receiver system of claim 28 wherein said plurality of receiver antenna elements are at disparate locations.

31. The receiver system of claim 16 further comprising:

a channel estimation processor that receives via a particular one of said channel outputs, at least v frequency domain training symbols transmitted via a particular input to said channel, v being an extent in symbol periods of a duration of significant items of an impulse response of channel component coupling said particular channel input and said particular channel, applies an inverse of said time domain substantially orthogonalizing procedure to said received at least v frequency domain training symbols to obtain a time domain response for said channel component, and that applies said time domain substantially orthogonalizing procedure to a zero-padded version of said time domain response to obtain a frequency response for said channel component.

32. A receiver system that receives a burst of time domain symbols via an output of a channel, said receiver system comprising:

at least one processing element that performs a time domain substantially orthogonalizing procedure on said burst of time domain symbols to recover a bust of frequency domain symbols; and

a channel estimation processor that receives at least v training symbols belonging to said burst of frequency domain symbols, v being an extent in symbol periods of a duration of significant terms of an impulse response of said channel, applies an inverse of said time domain substantially orthogonalizing procedure to said received at least v training symbols to obtain a time domain response for said channel, and that applies said time domain substantially orthogonalizing procedure to a zero-padded version of said time domain response to obtain a frequency response for said channel.