Clear channel assessment in wireless communications

• US 7,876,770 B1
• Filed: 05/29/2008
• Issued: 01/25/2011
• Est. Priority Date: 10/09/2002
• Status: Expired due to Term

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Hsu, Yungping, Tang, Hsiao-Cheng, Hu, Guorong, Feng, Weishi
• Primary Examiner(s): Kumar; Pankaj
• Assistant Examiner(s): Sharma; Gautam
• Application Number:
  US12/156,080
• Time in Patent Office: 971 Days
• Field of Search: 370/338, 370/431, 370/441, 370/445, 370/447, 370/462, 455/234.1, 455/423
• US Class Current: 370/445
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 17/00 Monitoring; Testing of line transmission systems H04B3/46; arrangements for monitoring or testing transmission systems employing electromagnetic waves other than radio waves H04B10/07
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 74/08 Non-scheduled access, e.g. ALOHA hybrid access H04W74/02

Abstract

Techniques for and apparatus capable of implementing packet detection and signal recognition in wireless communications systems are disclosed. In particular, the disclosed techniques and apparatus incorporate at least one of relative energy detection operable on assessment of a relative energy threshold for an inbound signal borne across an RF channel, carrier sense operable upon on assessment of at least one of a peak-to-sidelobe ratio and peak-to-peak distance defined by the inbound signal, and comparison operable upon demodulated data corresponding to the inbound signal as compared to predetermined preamble data. Clear channel assessment is performed based on determinations undertaken by one or more of the aforementioned relative energy detection, carrier sense and comparison operations.

Claims

1. A packet detection unit comprising:

a relative energy detection unit configured to selectively issue an energy threshold validation signal based on a relative energy threshold for an inbound radio frequency (RF) signal;

a carrier sense unit configured to selectively issue a carrier sense validation signal based on the inbound RF signal,

wherein the carrier sense unit generates the carrier sense validation signal based on at least one of a peak-to-sidelobe average ratio or a consecutive peak-to-peak distance, the peak-to-sidelobe average ratio and the consecutive peak-to-peak distance being defined by the inbound RF signal; and

a clear channel assessment unit configured to selectively issue a channel busy signal based on (i) the carrier sense validation signal and (ii) the energy threshold validation signal, the channel busy signal indicating that the inbound RF signal is valid.

2. The packet detection unit of claim 1, further comprising a comparison unit configured to selectively issue a preamble validation signal based on a comparison between (i) demodulated data and (ii) predetermined preamble data,

wherein the demodulated data and the predetermined preamble data are generated based on the inbound RF signal.

3. The packet detection unit of claim 2, wherein the channel busy signal is further based on the preamble validation signal.

4. The packet detection unit of claim 1, wherein the carrier sense validation signal comprises a first carrier sense validation signal and a second carrier sense validation signal, and

wherein the carrier sense unit comprises:

a peak-to-sidelobe determination unit configured to calculate the peak-to-sidelobe average ratio for the inbound RF signal; and

a control unit configured to (i) issue the first carrier sense validation signal when the peak-to-sidelobe average ratio is greater than a first signal quality threshold and (ii) issue the second carrier sense validation signal when the peak-to-sidelobe average ratio is less than a second signal quality threshold.

5. The packet detection unit of claim 4, wherein the second signal quality threshold does not exceed the first signal quality threshold.

6. The packet detection unit of claim 4, wherein:

the carrier sense unit further comprises a consecutive peak-to-peak distance determination unit configured to calculate the consecutive peak-to-peak distance for the inbound RF signal; and

the control unit is configured to issue the first carrier sense validation signal when (i) the consecutive peak-to-peak distance is less than a predetermined distance and (ii) the peak-to-sidelobe average ratio is greater than the first signal quality threshold.

7. The packet detection unit of claim 4, wherein the energy threshold validation signal comprises first and second energy threshold validation signals, and

wherein the relative energy detection unit comprises:

a gain differential unit configured to determine a gain change over time for the inbound RF signal; and

a second control unit configured to (i) issue the first energy threshold validation signal when the gain change over time exceeds a first energy detection threshold and (ii) issue the second energy threshold validation signal when the gain change over time is less than a second energy detection threshold.

8. The packet detection unit of claim 7, wherein the clear channel assessment unit is configured to issue a channel idle signal based on at least one of the second energy threshold validation signal or the second carrier sense validation signal.

9. The packet detection unit of claim 8, wherein the clear channel assessment unit comprises:

a timer configured to issue a timeout signal after a predetermined time period; and

a control unit configured to selectively issue the channel idle signal based on (i) the timeout signal and (ii) at least one of the second energy threshold validation signal or the second carrier sense validation signal.

10. The packet detection unit of claim 1, wherein the carrier sense validation signal comprises first and second carrier sense validation signals, and

wherein the carrier sense unit comprises:

a consecutive peak-to-peak distance determination unit configured to calculate the consecutive peak-to-peak distance for the inbound RF signal; and

a control unit configured to (i) issue the first carrier sense validation signal when the consecutive peak-to-peak distance is less than a predetermined distance and (ii) issue the second carrier sense validation signal when the consecutive peak-to-peak distance is greater than the predetermined distance.

11. The packet detection unit of claim 10, wherein the energy threshold validation signal comprises first and second energy threshold validation signals, and

wherein the relative energy detection unit comprises:

a gain differential unit configured to determine a gain change over time for the inbound RF signal; and

a second control unit configured to (i) issue the first energy threshold validation signal when the gain change over time is greater than a first energy detection threshold and (ii) issue the second energy threshold validation signal when the gain change over time is less than a second energy detection threshold.

12. The packet detection unit of claim 11, wherein the clear channel assessment unit is configured to issue a channel idle signal based on at least one of the second energy threshold validation signal or the second carrier sense validation signal.

13. The packet detection unit of claim 12, wherein the clear channel assessment unit comprises:

a timer configured to issue a timeout signal after a predetermined time period; and

a control unit configured to selectively issue the channel idle signal based on (i) the timeout signal and (ii) at least one of the second energy threshold validation signal or the second carrier sense validation signal.

14. A packet detection unit comprising:

a comparison unit configured to

receive demodulated data corresponding to an inbound radio frequency (RF) signal, and

selectively issue a preamble validation signal based on a comparison between (i) the demodulated data and (ii) predetermined preamble data;

a carrier sense unit configured to selectively issue a carrier sense validation signal based on the inbound RF signal,

wherein the carrier sense validation signal is generated based on at least one of a peak-to-sidelobe average ratio or a consecutive peak-to-peak distance, the peak-to-sidelobe average ratio and the consecutive peak-to-peak distance being defined by the inbound RF signal; and

a clear channel assessment unit configured to selectively issue a channel busy signal based on (i) the carrier sense validation signal and (ii) the preamble validation signal, the channel busy signal indicating that the inbound RF signal is valid.

15. The packet detection unit of claim 14, further comprising a relative energy detection unit configured to selectively issue an energy threshold validation signal based on a relative energy threshold for the inbound RF signal.

16. The packet detection unit of claim 15, wherein the clear channel assessment unit is configured to selectively issue the channel busy signal further based on the energy threshold validation signal.

17. The packet detection unit of claim 14, wherein the carrier sense validation signal comprises a first carrier sense validation signal and a second carrier sense validation signal, and

wherein the carrier sense unit comprises:

a peak-to-sidelobe determination unit configured to calculate the peak-to-sidelobe average ratio for the inbound RF signal; and

a control unit configured to (i) issue the first carrier sense validation signal when the peak-to-sidelobe average ratio is greater than a first signal quality threshold and (ii) issue the second carrier sense validation signal when the peak-to-sidelobe average ratio is less than a second signal quality threshold.

18. The packet detection unit of claim 17, wherein:

the carrier sense unit further comprises a consecutive peak-to-peak distance determination unit configured to calculate the consecutive peak-to-peak distance for the inbound RF signal; and

the control unit is configured to issue the first carrier sense validation signal when (i) the consecutive peak-to-peak distance is less than a predetermined distance and (ii) the peak-to-sidelobe average ratio is greater than the first signal quality threshold.

19. The packet detection unit of claim 17, wherein the energy threshold validation signal comprises a first energy threshold validation signal and a second energy threshold validation signal, and

wherein the relative energy detection unit comprises:

a gain differential unit configured to determine a gain change over time for the inbound RF signal; and

a second control unit configured to (i) issue the first energy threshold validation signal when the gain change over time exceeds a first energy detection threshold and (ii) issue the second energy threshold validation signal when the gain change over time is less than a second energy detection threshold.

20. The packet detection unit of claim 19, wherein the clear channel assessment unit is configured to issue a channel idle signal based on at least one of the second energy threshold validation signal or the second carrier sense validation signal.

21. The packet detection unit of claim 20, wherein the clear channel assessment unit comprises:

a timer configured to issue a timeout signal after a predetermined time period; and

a control unit configured to selectively issue the channel idle signal based on (i) the timeout signal and (ii) at least one of the second energy threshold validation signal or the second carrier sense validation signal.

22. The packet detection unit of claim 15, wherein the carrier sense validation signal comprises first and second carrier sense validation signals, and

wherein the carrier sense unit comprises:

a consecutive peak-to-peak distance determination unit configured to calculate the consecutive peak-to-peak distance for the inbound RF signal; and

a control unit configured to (i) issue the first carrier sense validation signal when the consecutive peak-to-peak distance is less than a predetermined distance and (ii) issue the second carrier sense validation signal when the consecutive peak-to-peak distance is greater than the predetermined distance.

23. The packet detection unit of claim 22, wherein the energy threshold validation signal comprises a first energy threshold validation signal and a second energy threshold validation signal, and

wherein the relative energy detection unit comprises:

a gain differential unit configured to determine a gain change over time for the inbound RF signal; and

a second control unit configured to (i) issue the first energy threshold validation signal when the gain change over time is greater than a first energy detection threshold and (ii) issue the second energy threshold validation signal when the gain change over time is less than a second energy detection threshold.

24. A packet detection unit comprising:

a relative energy detection unit configured to selectively issue an energy threshold validation signal based on a relative energy threshold for an inbound radio frequency (RF) signal;

a carrier sense unit configured to selectively issue a carrier sense validation signal based on the inbound RF signal;

wherein the carrier sense unit generates the carrier sense validation signal based on at least one ala peak-to-sidelobe average ratio or a consecutive peak-to-peak distance, the peak-to-sidelobe average ratio and the consecutive peak-to-peak distance being defined by the inbound RF signal;

and a clear channel assessment unit configured to selectively issue a channel busy signal based on the earner sense validation signal or the energy threshold validation signal, the channel busy signal indicating that the inbound RE signal is valid,

wherein said carrier sense unit issues the carrier sense validation signal based on whether the inbound RF signal includes at least one of a valid direct sequence spread spectrum (DSSS) signal or a valid Barker modulated header.

25. The packet detection unit of claim 24, wherein said carrier sense unit is configured to issue the carrier sense validation signal based on whether the inbound RF signal includes the valid DSSS signal and the valid Barker modulated header.