System for detecting collisions in a shared communications medium

• US 7,626,996 B2
• Filed: 07/20/2006
• Issued: 12/01/2009
• Est. Priority Date: 06/08/2001
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Min, Jonathan S., Currivan, Bruce J., Lu, Fang
• Primary Examiner(s): Vu; Thong H
• Application Number:
  US11/489,525
• Publication Number:
  US 20060274778A1
• Time in Patent Office: 1,230 Days
• Field of Search: 370/474, 370/347, 370/342, 370/441, 370/204, 370/445, 370/335
• US Class Current: 370/445
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 12/44 Star or tree networks

Abstract

A system for detecting collisions in a shared communications medium, such as a TDMA medium, includes a receive path adapted to generate a first intermediate signal, a second intermediate signal, and a data symbol sequence from an input signal. A preamble detection module generates a correlation metric from the first intermediate signal. A power measurement module generates a power indication signal from the second intermediate signal. A noise measurement module generates a noise indication signal from the second intermediate signal and the data symbol sequence. A processing module is adapted to characterize the input signal as a collision for certain values of correlation metric, power indication signal, and noise indication signal.

Claims

1. A system for detecting collisions in a shared communications medium, comprising:

first means for generating a first intermediate signal, a second intermediate signal, and a data symbol sequence from an input signal;

second means for generating a correlation metric from the first intermediate signal and a predetermined preamble sequence;

third means for generating a power indication signal from the second intermediate signal;

fourth means for generating a SNR indication signal from the second intermediate signal and the data symbol sequence; and

fifth means for characterizing the input signal as a collision or a non-collision based on two or more of the correlation metric, the power indication signal, and the SNR indication signal.

2. The system of claim 1, wherein the fifth means is configured to characterize the input signal as a collision when the correlation metric is greater than a first threshold and the SNR indication signal is less than a second threshold.

3. The system of claim 1, wherein the fifth means is configured to characterize the input signal as a collision when the correlation metric is less than or equal to a first threshold and the power indication signal is greater than a second threshold.

4. The system of claim 1, wherein the first intermediate signal is a baseband signal generated by filtering a baseband pulse sequence.

5. The system of claim 1, wherein the second intermediate signal is a soft decision signal generated by demodulating a baseband signal.

6. The system of claim 1, wherein the input signal comprises one or more transmissions received from a time division multiple access (TDMA) medium.

7. A system for detecting collisions in a shared communications medium, comprising:

means for correlating a received signal with a second signal to obtain a correlation metric;

means for measuring a signal to noise ratio (SNR) of the received signal when the correlation metric is greater than a first threshold; and

means for classifying the received signal as an in-phase collision when the measured SNR is less than a second threshold.

8. The system of claim 7, further comprising means for measuring a power of the received signal when the correlation metric is less than or equal to the first threshold.

9. The system of claim 8, further comprising means for classifying the received signal as an empty slot when the measured received signal power is less than or equal to a third threshold.

10. The system of claim 9, further comprising means for classifying the received signal as an out-of-phase collision when the measured received signal power is greater than the third threshold and a fourth threshold.

11. The system of claim 10, further comprising means for classifying the received signal as a bad packet when the measured received signal power is greater than the third threshold and less than or equal to the fourth threshold.

12. The system of claim 11, further comprising means for classifying the received signal as a good packet when the measured SNR is greater than the second threshold.

13. The system of claim 7, wherein second signal corresponds to a predetermined preamble sequence.

14. The system of claim 7, wherein said means for measuring SNR measures a SNR of a data portion of the received signal.

15. The system of claim 7, wherein said means for measuring power measures a power of a data portion of the received signal.

16. The system of claim 7, wherein said received signal is from a time division multiple access (TDMA) medium.

17. A system for detecting collisions in a shared communications medium, comprising:

a receive path configured to generate a first intermediate signal, a second intermediate signal, and a data symbol sequence from an input signal;

a preamble detection module configured to generate a correlation metric from the first intermediate signal and a predetermined preamble sequence;

a power measurement module configured to generate a power indication signal from the second intermediate signal;

a signal to noise ratio (SNR) measurement module configured to generate a SNR indication signal from the second intermediate signal and the data symbol sequence; and

a processing module configured to characterize the input signal as a collision or a non-collision based on a logical combination of the correlation metric, the measured signal power, and the SNR.

18. The system of claim 17, wherein the processing module is configured to classify the received signal as an in-phase collision when the correlation metric is greater than a first threshold and the SNR is less than or equal to a second threshold, and the measured signal power is greater than a third threshold.

19. The system of claim 17, wherein the processing module is configured to classify the received signal as a collision when the correlation metric is greater than a first threshold, the SNR is less than or equal to a second threshold, and the measured signal power is greater than a third threshold and less than or equal to a fourth threshold.

20. The system of claim 17, wherein the processing module is configured to classify the received signal as a collision when the correlation metric is less than or equal to a first threshold, and the measured signal power is greater than a second threshold.