Transmit diversity and spatial spreading for an OFDM-based multi-antenna communication system

• US 8,520,498 B2
• Filed: 05/01/2012
• Issued: 08/27/2013
• Est. Priority Date: 02/18/2004
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Walton, Jay Rodney, Wallace, Mark S., Howard, Steven J., Nanda, Sanjiv, Ketchum, John Wendell
• Primary Examiner(s): Thier, Michael
• Assistant Examiner(s): Alia, Curtis A
• Application Number:
  US13/461,707
• Publication Number:
  US 20120213181A1
• Time in Patent Office: 483 Days
• Field of Search: 370/203, 370/208, 370/209, 370/295, 370/307, 370/310, 370/329, 370/335, 370/342, 370/343, 370/431, 370/464, 370478-480, 370/491, 370536-537
• US Class Current: 370/208
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/2626 Arrangements specific to the transmitter only
• CPC Class Codes: H04W 12/02 Protecting privacy or anonymity, e.g. protecting personally identifiable information [PII]

Abstract

A multi-antenna transmitting entity transmits data to a single- or multi-antenna receiving entity using (1) a steered mode to direct the data transmission toward the receiving entity or (2) a pseudo-random transmit steering (PRTS) mode to randomize the effective channels observed by the data transmission across the subbands. For transmit diversity, the transmitting entity uses different pseudo-random steering vectors across the subbands but the same steering vector across a packet for each subband. The receiving entity does not need to have knowledge of the pseudo-random steering vectors or perform any special processing. For spatial spreading, the transmitting entity uses different pseudo-random steering vectors across the subbands and different steering vectors across the packet for each subband. Only the transmitting and receiving entities know the steering vectors used for data transmission. Other aspects, embodiments, and features are also claimed and disclosed.

Claims

1. A method of transmitting data from a transmitting entity to a receiving entity in a wireless multi-antenna communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

processing a data packet to obtain a block of data symbols;

demultiplexing pilot symbols and the block of data symbols using OFDM onto a plurality of subbands to obtain, for the data packet, a plurality of sequences of pilot and data symbols for the plurality of subbands; and

performing spatial processing on the sequence of pilot and data symbols for each subband with at least one steering vector selected for the subband, the spatial processing randomizing a plurality of channels observed by the plurality of sequences of pilot and data symbols sent on the plurality of subbands.

2. The method of claim 1, wherein the sequence of pilot and data symbols for each subband is spatially processed with one steering vector selected for the subband.

3. The method of claim 2, wherein a plurality of different steering vectors are used for the plurality of subbands.

4. The method of claim 2, wherein the one steering vector used for spatial processing for each subband is unknown to the receiving entity.

5. The method of claim 1, wherein the sequence of pilot and data symbols for each subband is spatially processed with at least two steering vectors selected for the subband.

6. The method of claim 1, wherein one pilot or data symbol is sent on each subband in each symbol period, and wherein the sequence of pilot and data symbols for each subband is spatially processed with a different steering vector for each symbol period.

7. The method of claim 1, wherein the at least one steering vector used for spatial processing for each subband is known only to the transmitting entity and the receiving entity.

8. The method of claim 1, wherein the spatial processing with the at least one steering vector for each subband is performed only on the data symbols.

9. The method of claim 1, wherein the processing a data packet includes encoding the data packet in accordance with a coding scheme to obtain coded data,

interleaving the coded data to obtain interleaved data, and

symbol mapping the interleaved data in accordance with a modulation scheme to obtain the block of data symbols.

10. The method of claim 1, further comprising:

selecting the at least one steering vector for each subband from among a set of L steering vectors, where L is an integer greater than one.

11. The method of claim 10, wherein the L steering vectors are such that any pair of steering vectors among the L steering vectors have low correlation.

12. The method of claim 6, further comprising:

selecting a steering vector for each subband in each symbol period from among a set of L steering vectors, where L is an integer greater than one.

13. The method of claim 1, wherein each steering vector includes T elements having the same magnitude but different phases, where T is the number of transmit antennas at the transmitting entity and is an integer greater than one.

14. An apparatus in a wireless multi-antenna communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

a data processor operative to process a data packet to obtain a block of data symbols;

a demultiplexer operative to demultiplex pilot symbols and the block of data symbols onto a plurality of subbands to obtain, for the data packet, a plurality of sequences of pilot and data symbols for the plurality of subbands; and

a spatial processor operative to perform spatial processing on the sequence of pilot and data symbols for each subband with at least one steering vector selected for the subband, the spatial processing randomizing a plurality of effective single-input single-output (SISO) channels observed by the plurality of sequences of pilot and data symbols sent on the plurality of subbands.

15. The apparatus of claim 14, wherein the spatial processor is operative to spatially process the sequence of pilot and data symbols for each subband with one steering vector selected for the subband.

16. The apparatus of claim 14, wherein the spatial processor is operative to spatially process the sequence of pilot and data symbols for each subband with at least two steering vectors selected for the subband.

17. The apparatus of claim 16, wherein the at least two steering vectors for each subband are known only to a transmitting entity and a receiving entity for the data packet.

18. The apparatus of claim 14, wherein each steering vector includes T elements having the same magnitude but different phases, where T is the number of antennas used to transmit the data packet and is an integer greater than one.

19. A method of transmitting data from a transmitting entity to a receiving entity in a wireless multiple-input multiple-output (MIMO) communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

processing a data packet to obtain a block of data symbols;

demultiplexing pilot symbols and the block of data symbols using OFDM onto a plurality of subbands; and

performing spatial processing on the pilot and data symbols for each subband with at least one steering matrix selected for the subband, the spatial processing randomizing a plurality of channels for the plurality of subbands observed by the pilot and data symbols sent on the plurality of subbands.

20. The method of claim 19, wherein the pilot and data symbols for each subband are spatially processed with one steering matrix selected for the subband.

21. The method of claim 19, wherein the one steering matrix used for spatial processing for each subband is unknown to the receiving entity.

22. The method of claim 19, wherein the pilot and data symbols for each subband are spatially processed with a different steering matrix for each symbol period.

23. The method of claim 19, wherein the at least one steering matrix used for spatial processing for each subband is known only to the transmitting entity and the receiving entity.

24. The method of claim 19, wherein the spatial processing with the at least one steering matrix for each subband is performed only on the data symbols.

25. The method of claim 24, further comprising:

multiplying spread symbols for each subband, obtained from the spatial processing with the at least one steering matrix, to transmit the spread symbols on eigenmodes of the channel for the subband.

26. An apparatus in a wireless multiple-input multiple-output (MIMO) communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

a data processor operative to process a data packet to obtain a block of data symbols;

a demultiplexer operative to demultiplex pilot symbols and the block of data symbols onto a plurality of subbands; and

a spatial processor operative to perform spatial processing on the pilot and data symbols for each subband with at least one steering matrix selected for the subband, the spatial processing randomizing a plurality of effective MIMO channels for the plurality of subbands observed by the pilot and data symbols sent on the plurality of subbands.

27. An apparatus in a wireless multi-antenna communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

a controller operative to select a first mode for data transmission to a receiving entity if channel response estimates for the receiving entity are unavailable and select a second mode for data transmission to the receiving entity if the channel response estimates are available, wherein data symbols are spatially processed with pseudo-random steering vectors in the first mode and with steering vectors derived from the channel response estimates in the second mode; and

a spatial processor operative to perform spatial processing for each block of data symbols in accordance with the mode selected for the block.

28. A receiver apparatus in a wireless multiple-antenna communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

a demodulator operative to provide S sequences of received symbols, obtained via a single received antenna, for S sequences of pilot and data symbols transmitted via S subbands by a transmitting entity, where S is an integer greater than one, and wherein the S sequences of pilot and data symbols are spatially processed with a plurality of steering vectors at the transmitting entity to randomize S effective single-input single-output (SISO) channels observed by the S sequences of pilot and data symbols;

a channel estimator operative to derive channel response estimates for the S effective SISO channels based on received pilot symbols in the S sequences of received symbols; and

a detector operative to perform detection on received data symbols in the S sequences of received symbols based on the channel response estimates for the S effective SISO channels to obtain detected symbols.