Signal processing for multiple chains including barker code correlation and auto-correlation

• US 8,068,562 B1
• Filed: 10/29/2007
• Issued: 11/29/2011
• Est. Priority Date: 10/29/2007
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm Atheros Incorporated (Qualcomm, Inc.)
• Inventors: Chen, Bianca, Jauh, Alan, Zhang, Ning
• Primary Examiner(s): Tran; Khanh C
• Assistant Examiner(s): Ghulamali; Qutbuddin
• Application Number:
  US11/927,574
• Time in Patent Office: 1,492 Days
• Field of Search: 375/316, 375/150, 375/130
• US Class Current: 375/324
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers

Abstract

A method of processing a signal in a wireless network including multiple chains is provided. This method can include receiving the signal in a receiver and, for each chain, performing a Barker correlation on the signal to generate a Barker correlated signal. At this point, an autocorrelation can be performed on the Barker correlated signal to generate an autocorrelated signal. The autocorrelated signals from the multiple chains can be summed to generate a summed output. Additional processing, e.g. at least one of CCK weak signal detection, peak selection in a rake receiver, frequency estimation, and differential decoding, can then be performed based on the summed output.

Claims

1. A method of processing a signal in a wireless network including multiple chains, the method comprising:

receiving the signal in a receiver;

for each chain, performing a Barker correlation on the signal to generate a Barker correlated signal;

for each chain, performing an autocorrelation on the Barker correlated signal to generate an autocorrelated signal;

summing autocorrelated signals from the multiple chains to generate a summed output; and

performing additional processing based on the summed output,

wherein the additional processing includes CCK weak signal detection, the method further comprising;

applying a window sum with a predetermined length to the summed output to derive a window value;

generating decision flags based on the window value;

generating accumulated values based on the decision flags; and

generating a decision index based on the accumulated values, wherein the decision index indicates whether a CCK weak signal is detected.

2. The method of claim 1, further including for each chain, performing a maximal ratio combining (MRC) buffering to generate a buffered signal, wherein the Barker correlation is performed on the buffered signal.

3. The method of claim 2, wherein a gain of each channel in the MRC buffering is made proportional to a root-mean-square (RMS) signal level and inversely proportional to a mean square noise level in that channel, thereby providing a different proportionality constant for each chain.

4. The method of claim 1, wherein the additional processing further includes at least one of peak selection in a rake receiver, frequency estimation, and differential decoding.

5. The method of claim 4, wherein for peak selection in a rake receiver, the method further includes:

determining a power of the summed output;

summing the power and a time-delayed version of the power to generate a power sum;

summing two adjacent power sum signals over time to determine peak index selection;

performing a window sum with a predetermined length using the power sum and the peak index selection to generate a center index signal.

6. The method of claim 5, wherein the center index signal is used for channel estimation.

7. The method of claim 4, wherein for frequency estimation, the method further includes:

squaring the summed output collected from peaks of the multiple chains to generate a squared output signal;

summing two adjacent T/2 spaced squared output signals to generate a signal-to-noise-ratio (SNR) improved signal;

summing SNR improved signals over symbols and chains to generate a modified signal; and

using the modified signal for frequency offset correction.

8. The method of claim 4, wherein for differential decoding, the method further includes:

summing two adjacent T/2 spaced summed output signals to generate a signal-to-noise-ratio (SNR) improved signal;

summing SNR improved signals over chains to generate a modified signal; and

using the modified signal for differential decoding.

9. A receiver in a wireless network including multiple chains, the receiver comprising:

a Barker correlation block that performs a Barker correlation on a received signal for each chain;

an autocorrelation block that performs an autocorrelation on an output of the Barker correlation block for each chain;

an adder that sums outputs of the autocorrelation block from the multiple chains; and

at least one processing block that uses an output of the adder to perform signal processing,

wherein the at least one processing block includes a CCK weak signal detection block, which includes;

a window sum block that applies a window sum with a predetermined length to the output of the adder;

a decision flag block that generates decision flags based on an output of the window sum block;

an accumulated value block that generates accumulated values based on an output of the decision flag block; and

a decision index block that generates a decision index based on an output of the accumulated value block, wherein an output of the decision index block indicates whether a CCK weak signal is detected.

10. The receiver of claim 9, further including a maximal ratio combining (MRC) buffer for each chain, wherein an output of the MRC buffer is provided to the Barker correlation block.

11. The receiver of claim 10, wherein a gain of each channel in the MRC buffer is made proportional to a root-mean-square (RMS) signal level and inversely proportional to a mean square noise level in that channel, thereby providing a different proportionality constant for each chain.

12. The receiver of claim 9, wherein the at least one processing block further includes at least one of a peak selection block in a rake receiver, a frequency estimation block, and a differential decoding block.

13. The receiver of claim 12, wherein the peak selection block in the rake receiver includes:

a power determination block that determines a power of the output of the adder;

a second adder that sums the power and a time-delayed version of the power;

a summing block that sums two adjacent signals over time to determine peak index selection;

a window sum block that performs a window sum with a predetermined length using an output of the second adder and the peak index selection.

14. The receiver of claim 13, wherein an output of the window sum block is provided to a channel estimation block.

15. The receiver of claim 12, wherein the frequency estimation block includes:

a square computation block that squares the output of the adder collected from peaks of the multiple chains;

an SNR block that sums two adjacent T/2 spaced signals output by the square computation block;

a sum block that sums signals output by the SNR block over symbols and chains; and

a frequency offset block that uses an output of the sum block.

16. The receiver of claim 12, wherein the differential decoding block includes:

an SNR block that sums two adjacent T/2 spaced signals output by the adder;

a sum block that sums signals output by the SNR block over chains; and

a differential decoding block that uses signals output by the sum block.