Reverse link correlation filter in wireless communication systems

• US 20080075150A1
• Filed: 09/17/2007
• Published: 03/27/2008
• Est. Priority Date: 02/23/2000
• Status: Active Grant

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Patel, Samir, Proctor, James, Riley, Daniel, Rouphael, Antoine, Nelson, George, Hoffmann, John
• Granted Patent: US 7,613,227 B2
• Time in Patent Office: Days
• US Class Current: 375/150
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7105 Joint detection techniques, e.g. linear detectors
• CPC Class Codes: H04B 1/712 Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop
• CPC Class Codes: H04B 2201/70703 using multiple or variable rates
• CPC Class Codes: H04B 2201/70705 Rate detection
• CPC Class Codes: H04B 2201/7071 with dynamic control of receiver resources

Abstract

A single, common correlation filter (CF) core is provided in a receiver for recovery of data from received code division multiple access (CDMA) signals. Signals are received over CDMA channels with different data rates, where the received signals include user information such as pilot and data symbols that have been spread according to different despreading rates including tier 1, tier 2 and tier 3 rates, where tier 1 is the smallest despreading rate. The received signal is correlated at the smallest despreading rate in the correlation filter (CF) by time multiplexing delayed versions of the pseudorandom noise (PN) code. The correlated information is then demultiplexed and pilot-aided QPSK demodulated. The demodulated information is summed at the proper integer multiple of the tier 1 rate to achieve tier 2 and tier 3 despreading rates. According to an embodiment, the three strongest multipaths components in terms of the received power are selected in a window or time period for optimal information recovery.

Claims

1. A method for receiving signals over a code division multiple access (CDMA) channel, each received signal having a user-unique code and an associated despreading rate, the method comprising:

correlating a received signal with the user-unique code at a basic despreading rate using time multiplexing in a single correlation filter to produce one or more sets of correlated outputs;

demultiplexing and demodulating the sets of correlated outputs; and

when the associated despreading rate is a multiple of the basic despreading rate, summing the demultiplexed and demodulated sets of correlated outputs at the multiple of the basic despreading rate to recover user information from the received signal at the associated despreading rate.

2. The method of claim 1, wherein the demodulating is according to quadrature phase shift keying (QPSK) demodulation.

3. The method of claim 2, wherein the demodulating is according to pilot-aided QPSK demodulation.

4. The method of claim 1, wherein the user-unique code is a pseudorandom noise (PN) code.

5. The method of claim 1, wherein the recovered user information includes pilot symbols and data symbols interleaved in a specified and known order.

6. The method of claim 5, further comprising:

determining a channel estimate from the pilots symbols; and

after the summing, selecting three strongest peaks in terms of received power in the recovered user information based on the determined channel estimate.

7. The method of claim 6, wherein the selected three strongest peaks are combined into one output for each data symbol.

8. The method of claim 7, wherein the selected three strongest peaks are combined into one output using maximum ratio combining (MRC).

9. The method of claim 1, wherein the CDMA channel is one of an access channel, a maintenance channel, or a traffic channel.

10. The method of claim 1, wherein the basic despreading rate is 8 chips per symbol and the multiple of the basic despreading rate is one of 4 or 16.

11. The method of claim 1, wherein the basic despreading rate is 8 chips per symbol and the associated despreading rates is one of 8, 32 or 128 chips per symbol.

12. The method of claim 1, wherein the correlating, demodulating and summing are programmable by a digital signal processor (DSP).

23. The receiver of claim 1, wherein the basic despreading rate is 8 chips per symbol and the associated despreading rates is one of 8, 32 or 128 chips per symbol.

24. The receiver of claim 1 further comprising a digital signal processor configured to provide instructions to the correlation filter and the data post processor.

13. A receiver configured to receive signals over a code division multiple access (CDMA) channel, each received signal having a user-unique code and an associated despreading rate, comprising:

a correlation filter configured to correlate a received signal with the user-unique code at a basic despreading rate using time multiplexing to produce one or more sets of correlated outputs;

a demultiplexer configured to demultiplex the sets of correlated outputs;

a data post processor configured to demodulate the sets of demultiplexed outputs; and

when the associated despreading rate is a multiple of the basic despreading rate, said data post processor configured to sum the demultiplexed and demodulated sets of correlated outputs at the multiple of the basic despreading rate to recover user information from the received signal at the associated despreading rate.

14. The receiver of claim 13, wherein the data post processor is configured to demodulate according to quadrature phase shift keying (QPSK) demodulation.

15. The receiver of claim 14, wherein the data post processor is configured to demodulate according to pilot-aided QPSK demodulation.

16. The receiver of claim 13, wherein the user-unique code is a pseudorandom noise (PN) code.

17. The receiver of claim 13, wherein the recovered user information includes pilot symbols and data symbols interleaved in a specified and known order.

18. The receiver of claim 17, further comprising:

a pilot post processor configured to determine a channel estimate from the pilots symbols, wherein the data post processor is further configured to select three strongest peaks in terms of received power in the recovered user information based on the determined channel estimate.

19. The receiver of claim 18, wherein the data post processor is further configured to combine the selected three strongest peaks into one output for each data symbol.

20. The receiver of claim 19, wherein the data post processor is further configured to combine the selected three strongest peaks into one output using maximum ratio combining (MRC).

21. The receiver of claim 13, wherein the CDMA channel is one of an access channel, a maintenance channel, or a traffic channel.

22. The receiver of claim 13, wherein the basic despreading rate is 8 chips per symbol and the multiple of the basic despreading rate is one of 1, 4 or 16.

25. A base station comprising the receiver of claim 13.

26. A mobile station comprising the receiver of claim 13.