Transmit diversity processing for a multi-antenna communication system

• US 20060039275A1
• Filed: 10/13/2005
• Published: 02/23/2006
• Est. Priority Date: 10/25/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Howard, Steven J., Ketchum, John W., Walton, J. Rodney, Wallace, Mark S.
• Granted Patent: US 8,934,329 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• 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: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0017 where the mode-switching is based on Quality of Service requirement
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/0069 Puncturing patterns
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 1/16 in which the return channel carries supervisory signals, e.g. repetition request signals
• CPC Class Codes: H04L 2001/0093 Point-to-multipoint
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 25/0242 using matrix methods
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/261 : Details of reference signals
• CPC Class Codes: H04L 27/2647 : Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04W 28/20 : Negotiating bandwidth
• CPC Class Codes: H04W 52/50 : at the moment of starting communication in a multiple access environment

Abstract

For transmit diversity in a multi-antenna OFDM system, a transmitter encodes, interleaves, and symbol maps traffic data to obtain data symbols. The transmitter processes each pair of data symbols to obtain two pairs of transmit symbols for transmission from a pair of antennas either (1) in two OFDM symbol periods for space-time transmit diversity or (2) on two subbands for space-frequency transmit diversity. N_T·(N_T−1) 2 different antenna pairs are used for data transmission, with different antenna pairs being used for adjacent subbands, where NT is the number of antennas. The system may support multiple OFDM symbol sizes. The same coding, interleaving, and modulation schemes are used for different OFDM symbol sizes to simplify the transmitter and receiver processing. The transmitter performs OFDM modulation on the transmit symbol stream for each antenna in accordance with the selected OFDM symbol size. The receiver performs the complementary processing.

Claims

1. A method of processing data for transmission in a wireless multi-antenna orthogonal frequency division multiplexing (OFDM) communication system, the method comprising:

coding traffic data in accordance with a coding scheme to obtain coded data;

interleaving the coded data in accordance with an interleaving scheme to obtain interleaved data;

symbol mapping the interleaved data in accordance with a modulation scheme to obtain a stream of data symbols; and

processing each pair of data symbols in the stream to obtain two pairs of transmit symbols for transmission from a pair of antennas, wherein each transmit symbol is a version of a data symbol.

2. The method of claim 1, wherein the two pairs of transmit symbols for each pair of data symbols are transmitted from a pair of antennas on the same subband in two OFDM symbol periods.

3. The method of claim 1, wherein the two pairs of transmit symbols for each pair of data symbols are transmitted from a pair of antennas on two subbands in one OFDM symbol period.

4. The method of claim 1, wherein N antennas are available for data transmission and N_T·

(N_T−

1)/2 different pairs of antennas are used to transmit pairs of data symbols in the stream, where N>

2.

5. The method of claim 1, wherein a plurality of subbands are used for data transmission, and wherein different pairs of antennas are used for adjacent subbands used for data transmission.

6. The method of claim 1, wherein the system supports a first OFDM symbol size with S subbands and a second OFDM symbol size with L subbands, where S is an integer greater than one and L is an integer multiple of S.

7. The method of claim 6, further comprising:

forming a plurality of streams of transmit symbols for a plurality of antennas; and

transforming each stream of transmit symbols in accordance with the first or second OFDM symbol size to obtain a corresponding stream of OFDM symbols.

8. The method of claim 1, wherein the coding includes:

coding the traffic data in accordance with a base code to obtain code bits at a fixed code rate, and

puncturing the code bits at the fixed code rate to obtain the coded data comprised of code bits at one of a plurality of code rates supported by the system.

9. The method of claim 8, wherein the base code is a rate ½

convolutional code.

10. The method of claim 8, wherein the plurality of code rates are associated with a plurality of puncturing patterns.

11. The method of claim 1, wherein the coding includes:

coding the traffic data in accordance with a base code to obtain code bits at a fixed code rate, and

repeating the code bits at the fixed code rate to obtain the coded data comprised of code bits at a lower code rate than the fixed code rate.

12. The method of claim 1, wherein the interleaving includes:

forming sequences of code bits from the coded data, and

for each of the sequences, mapping each code bit in the sequence to one of a plurality of subbands based on the interleaving scheme.

13. The method of claim 12, wherein each sequence of code bits is designated for transmission on the plurality of subbands in one OFDM symbol period.

14. The method of claim 1, wherein the interleaving includes:

forming sequences of code bits from the coded data,

partitioning each of the sequences into M blocks of code bits for transmission on M disjoint groups of subbands, one block of code bits for each group of subbands, where M≧

2, and

for each of the M blocks for each sequence, mapping each code bit in the block to one of the subbands in the group for the block based on the interleaving scheme.

15. The method of claim 1, wherein the symbol mapping includes grouping sets of B bits in the interleaved data to form B-bit binary values, where B≧

1, and

mapping each of the B-bit binary values to a data symbol based on the modulation scheme, wherein the modulation scheme is defined with Gray mapping such that two adjacent data symbols in a signal constellation for the modulation scheme differ by at most one bit among B bits.

16. The method of claim 15, wherein the symbol mapping further includes

reordering the B bits for each of the sets, and wherein the sets of reordered B bits are used to form the B-bit binary values.

17. A transmitter in a wireless multi-antenna orthogonal frequency division multiplexing (OFDM) communication system, comprising:

an encoder operative to encode traffic data in accordance with a coding scheme to obtain coded data;

an interleaver operative to interleave the coded data in accordance with an interleaving scheme to obtain interleaved data;

a symbol mapping unit operative to symbol map the interleaved data in accordance with a modulation scheme to obtain a stream of data symbols; and

a transmit spatial processor operative to process each pair of data symbols in the stream to obtain two pairs of transmit symbols for transmission from a pair of antennas, wherein each transmit symbol is a version of a data symbol.

18. The transmitter of claim 17, wherein the transmit spatial processor is operative to implement space-time transmit diversity and provide the two pairs of transmit symbols for each pair of data symbols in two OFDM symbol periods.

19. The transmitter of claim 17, wherein the transmit spatial processor is operative to implement space-frequency transmit diversity and provide the two pairs of transmit symbols for each pair of data symbols on two subbands.

20. The transmitter of claim 17, wherein the system supports a first OFDM symbol size with S subbands and a second OFDM symbol size with L subbands, where S is an integer greater than one and L is an integer multiple of S.

21. The transmitter of claim 20, further comprising:

a plurality of modulators for a plurality of antennas, each modulator operative to transform a stream of transmit symbols for an associated antenna to obtain a corresponding stream of OFDM symbols for the antenna.

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

means for coding traffic data in accordance with a coding scheme to obtain coded data;

means for interleaving the coded data in accordance with an interleaving scheme to obtain interleaved data;

means for symbol mapping the interleaved data in accordance with a modulation scheme to obtain a stream of data symbols; and

means for processing each pair of data symbols in the stream to obtain two pairs of transmit symbols for transmission from a pair of antennas, wherein each transmit symbol is a version of a data symbol.

23. The apparatus of claim 22, wherein the two pairs of transmit symbols for each pair of data symbols are transmitted from a pair of antennas in two OFDM symbol periods.

24. The apparatus of claim 22, wherein the two pairs of transmit symbols for each pair of data symbols are transmitted from a pair of antennas on two subbands.