Data detection and demodulation for wireless communication systems

• US 20040137863A1
• Filed: 10/23/2003
• Published: 07/15/2004
• Est. Priority Date: 10/25/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Walton, J. Rodney, Wallace, Mark S.
• Granted Patent: US 8,170,513 B2
• Time in Patent Office: Days
• US Class Current: 455/130
• 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 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• 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 1/0068 by puncturing
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/06 using space diversity
• 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 27/0012 : arrangements for identifying the type of modulation
• 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

Techniques for detecting and demodulating data transmissions in wireless communication systems. In one aspect, a decision-directed detector detects for data transmissions in a received signal by utilizing received data symbols as well as received pilot symbols. The decision-directed detector may be designed to perform differential detection in the frequency domain or coherent detection in the time domain, and may be used with multi-carrier modulation (e.g., OFDM). In another aspect, an adaptive threshold is used to perform detection of received data transmissions. A threshold may be determined for each data transmission hypothesized to have been received. The threshold may be computed, for example, based on the signal plus noise energy of the hypothesized data transmission.

Claims

1. A receiver unit in a wireless communication system, comprising:

a demodulator operative to process received data symbols to provide recovered symbols;

a first data processor operative to process the recovered symbols to provide decoded data;

a second data processor operative to process the decoded data to provide remodulated symbols; and

a detector operative to process the received data symbols and the remodulated symbols to provide a detector output.

2. The receiver unit of claim 1, wherein the received data symbols are for a data transmission hypothesized to have been received, and wherein the detector output indicates whether or not the data transmission is deemed to have been received.

3. The receiver unit of claim 2, further comprising:

a threshold computation unit operative to determine a threshold to use for the data transmission, and

wherein the detector is operative to provide a metric based on the received data symbols and the remodulated symbols, and wherein the detector output is determined based on the metric and the threshold.

4. The receiver unit of claim 3, wherein the threshold computation unit is operative to determine the threshold based on a plurality of received signals for a plurality of antennas, and wherein the detector is operative to determine the metric based on the plurality of received signals.

5. The receiver unit of claim 1, wherein the detector is further operative to process received pilot symbols to provide the detector output.

6. The receiver unit of claim 5, wherein data symbols are transmitted on data subbands and pilot symbols are transmitted on pilot subbands, and wherein the data subbands are multiplexed with the pilot subbands.

7. The receiver unit of claim 6, wherein the data subbands are interlaced with the pilot subbands such that each of the data subbands is flanked on both sides by pilot subbands.

8. The receiver unit of claim 1, wherein the detector is operative to perform coherent detection in time domain.

9. The receiver unit of claim 8, wherein the received data symbols are obtained based on input samples for a data transmission hypothesized to have been received, and wherein the detector is operative to perform correlation between the input samples and reconstructed samples obtained based on the remodulated symbols.

10. The receiver unit of claim 8, wherein the received data symbols are obtained based on input samples for a data transmission hypothesized to have been received, and wherein the detector is operative to perform correlation between the input samples and reconstructed samples obtained based on the remodulated symbols and pilot symbols for the data transmission.

11. The receiver unit of claim 1, wherein the detector is operative to perform differential detection in the frequency domain.

12. The receiver unit of claim 5, wherein the detector is operative to

multiply each of the received data symbols with a corresponding one of the remodulated symbols to provide a demodulated data symbol,

multiply each of the received pilot symbols with a corresponding one of known pilot symbols to provide a demodulated pilot symbol,

perform dot products between demodulated data symbols and demodulated pilot symbols, and

accumulate results of the dot products.

13. The receiver unit of claim 2, wherein the data transmission is for a random access channel in the wireless communication system.

14. The receiver unit of claim 1, wherein the wireless communication system uses multi-carrier modulation.

15. The receiver unit of claim 1, wherein the wireless communication system uses orthogonal frequency division multiplexing (OFDM).

16. A receiver unit in a wireless communication system, comprising:

a processor operative to process received data symbols for a data transmission hypothesized to have been received and provide remodulated symbols that are estimates of transmitted data symbols; and

a detector operative to process the received data symbols and the remodulated symbols to provide a detector output that indicates whether or not the data transmission is deemed to have been received.

17. The receiver unit of claim 16, wherein the processor is operative to demodulate the received data symbols to provide recovered symbols, decode the recovered symbols to provide decoded data, and re-encode the decoded data to provide the remodulated symbols.

18. The receiver unit of claim 16, wherein the processor is further operative to process received pilot symbols for the data transmission and corresponding known pilot symbols to provide the detector output.

19. A receiver unit in a wireless communication system, comprising:

a signal detector operative to determine a metric for a data transmission hypothesized to have been received;

a threshold computation unit operative to determine a threshold for the hypothesized data transmission; and

a comparator operative to receive the metric and the threshold and provide an output indicating whether or not the data transmission is deemed to have been received.

20. The receiver unit of claim 19, wherein the threshold is determined based on received pilot symbols for the hypothesized data transmission.

21. The receiver unit of claim 20, wherein the threshold is further determined based on received data symbols for the hypothesized data transmission.

22. The receiver unit of claim 19, wherein the metric relates to signal energy of the hypothesized data transmission.

23. The receiver unit of claim 19, wherein the signal detector is operative to determine the metric based on a plurality of received signals for a plurality of antennas, and wherein the threshold computation unit is operative to determine the threshold based on the plurality of received signals.

24. A method of detecting data transmissions in a wireless multiple-access communication system, comprising:

first processing received data symbols for a data transmission hypothesized to have been received to provide remodulated symbols that are estimates of transmitted data symbols; and

second processing the received data symbols and the remodulated symbols to provide a detector output that indicates whether or not the data transmission is deemed to have been received.

25. The method of claim 24, wherein the first processing includes

demodulating the received data symbols to provide recovered symbols,

decoding the recovered symbols to provide decoded data, and

re-encoding the decoded data to provide the remodulated symbols.

26. The method of claim 24, further comprising:

determining a threshold to use for the hypothesized data transmission, and wherein the detector output is further determined based on the threshold.

27. The method of claim 26, wherein the second processing includes

determining a metric based on the received data symbols and the remodulated symbols, and

comparing the metric against the threshold, and wherein the detector output is based on the comparing.

28. A method of detecting data transmissions in a wireless multiple-access communication system, comprising:

determining a metric for a data transmission hypothesized to have been received;

determining a threshold for the hypothesized data transmission based on samples received for the hypothesized data transmission; and

comparing the metric against the threshold to provide an output indicating whether or not the data transmission is deemed to have been received.

29. An apparatus in a wireless multiple-access communication system, comprising:

means for processing received data symbols for a data transmission hypothesized to have been received to provide remodulated symbols that are estimates of transmitted data symbols; and

means for processing the received data symbols and the remodulated symbols to provide a detector output that indicates whether or not the data transmission is deemed to have been received.

30. The apparatus of claim 29, further comprising:

means for demodulating the received data symbols to provide recovered symbols;

means for decoding the recovered symbols to provide decoded data; and

means for re-encoding the decoded data to provide the remodulated symbols.

31. An apparatus in a wireless multiple-access communication system, comprising:

means for determining a metric for a data transmission hypothesized to have been received;

means for determining a threshold for the hypothesized data transmission based on samples received for the hypothesized data transmission; and

means for comparing the metric against the threshold to provide an output indicating whether or not the data transmission is deemed to have been received.