Correlation detection improvement by averaging spread spectrum signals

• US 20040165656A1
• Filed: 02/24/2003
• Published: 08/26/2004
• Est. Priority Date: 02/24/2003
• Status: Active Grant

• Current Assignee: InterDigital Patent Holdings, Inc. (InterDigital, Inc.)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Virag, David Emery, Shiue, Dong-Chang
• Granted Patent: US 7,042,925 B2
• Time in Patent Office: Days
• US Class Current: 375/150
• CPC Class Codes: H03G 3/3052 in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver H03G3/32, H03G3/34 take precedence
• CPC Class Codes: H04B 1/708 Parallel implementation
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04L 1/0045 Arrangements at the receiver end

Abstract

There is provided a correlation method for spread spectrum signals. Correlation peaks in packet headers included in the spread spectrum signals are detected by averaging known signals that repeat in the packet headers. Data corresponding to the spread spectrum signals is recovered based on the correlation peaks.

Claims

1. A correlation method for spread spectrum signals, comprising the steps of:

detecting correlation peaks in packet headers included in the spread spectrum signals by averaging known signals that repeat in the packet headers; and

recovering the spread spectrum signals based on the correlation peaks.

2. The method of claim 1, wherein said detecting step comprises the step of detecting averaged correlation peaks, and said method further comprises the step of estimating timing errors from the averaged correlation peaks.

3. The method of claim 1, wherein said detecting step employs sample-based averaging.

4. The method of claim 1, wherein said detecting step is performed over a number of fields, each of the fields comprising at least one packet.

5. The method of claim 1, wherein the number of fields is dynamically adjustable.

6. The method of claim 1, wherein the known signals correspond to an origin of a given packet and a status of the given packet.

7. The method of claim 6, wherein the status of the given packet corresponds to an FEC status of the given packet.

8. The method of claim 1, wherein said detecting step comprises the step of artificially injecting a timing error into the spread spectrum signals to aid in the detection of the correlation peaks.

9. A correlation method for spread spectrum signals, comprising the step of:

correlating the spread spectrum signals to obtain correlation values therefore;

assigning the correlation values to a plurality of bins;

averaging the correlation values in the plurality of bins to obtain averaged correlation values for the plurality of bins;

detecting peaks in the averaged correlation values; and

generating a bit stream corresponding to the spread spectrum signals, based on the peaks and an average of known signals that repeat in packets headers included in the spread spectrum signals.

10. The method of claim 9, wherein the known signals correspond to a Forward Error Correcting (FEC) mode of the spread spectrum signals.

11. The method of claim 9, wherein said generating step comprises the step of selecting between two decoded bit streams respectively corresponding to a strong mode FEC and a weak mode FEC, based on lowest error rate.

12. The method of claim 9, wherein said detecting step comprises the step of deciding whether a packet was transmitted with a strong FEC mode or a weak FEC mode, using a majority vote scheme on un-encoded symbols in the packet header.

13. An apparatus for correlating spread spectrum signals, comprising:

an integrator for detecting correlation peaks in packet headers included in the spread spectrum signals by averaging known signals that repeat in the packet headers; and

a recovery circuit for recovering data corresponding to the spread spectrum signals based on the correlation peaks.

14. The apparatus of claim 13, wherein said integrator detects averaged correlation peaks, and said apparatus further comprises an estimator for estimating timing errors from the averaged correlation peaks.

15. The apparatus of claim 13, wherein said integrator employs sample-based averaging.

16. The apparatus of claim 13, wherein said integrator averages the known signals over a number of fields, each of the fields comprising at least one packet.

17. The apparatus of claim 13, wherein the number of fields is dynamically adjustable.

18. The apparatus of claim 13, wherein the known signals correspond to an origin of a given packet and a status of the given packet.

19. The apparatus of claim 18, wherein the status of the given packet corresponds to an FEC status of the given packet.

20. An apparatus for correlating spread spectrum signals, comprising:

a correlator for correlating the spread spectrum signals to obtain correlation values therefor and for assigning the correlation values to a plurality of bins;

an integrator for averaging the correlation values in the plurality of bins to obtain averaged correlation values for the plurality of bins;

a detector for detecting peaks in the averaged correlation values; and

a decoder for generating a bit stream corresponding to the spread spectrum signals, based on the peaks and an average of known signals that repeat in packets headers included in the spread spectrum signals.

21. The apparatus of claim 20, wherein the known signals correspond to a Forward Error Correcting (FEC) mode of the spread spectrum signals.

22. The apparatus of claim 20, further comprising a selector for selecting between two decoded bit streams respectively corresponding to a strong mode FEC and a weak mode FEC, based on lowest error rate.

23. The apparatus of claim 20, further comprising an FEC mode detector for deciding whether a packet was transmitted with a strong FEC mode or a weak FEC mode, using a majority vote scheme on un-encoded symbols in the packet header.