Method and apparatus for the detection and classification of collisions on a shared RF network

• US 7,420,986 B1
• Filed: 11/02/2000
• Issued: 09/02/2008
• Est. Priority Date: 11/02/1999
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Sala, Dolors, Howard, Daniel H.
• Primary Examiner(s): Orgad; Edan
• Assistant Examiner(s): Lee; Andrew C.
• Application Number:
  US09/704,809
• Time in Patent Office: 2,861 Days
• Field of Search: 370/348, 370/445, 370/447, 370/448, 370/328, 370/329, 370/337, 370/341, 370/347, 370/431, 370/442, 370/443, 370/252, 370/446, 370/222
• US Class Current: 370/445
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 69/323 in the physical layer [OSI layer 1]
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements

Abstract

The present invention is directed toward a method and apparatus for detecting collisions on a shared access network. In accordance with the present invention, two or more RF modulated signals having a plurality of different phase states are transmitted to a central controller, wherein two or more of the transmitted signals collide at the central controller. The collision detection system then determines a characteristic of the collision signal, such as the absolute value of the peak amplitude of the collision signal. The collision detection system then compares the characteristic with a plurality of thresholds and determines the number of RF modulated signals that collided as a function of the comparison.

The method for detecting collisions may further include monitoring a plurality of collision events to determine a characteristic, such as the absolute value of the peak amplitude of the collision signal, of each of the collision events. The collision detection system then determines the thresholds in accordance with the characteristics of the monitored collision events. The monitored collision events may be simulated or the result of actual laboratory experimentation.

Claims

1. A method for detecting collisions on a shared access network, comprising:

modulating a preamble of each of a plurality of RF modulated signals with a plurality of different phase states;

transmitting two or more of the RF modulated signals, wherein two or more of the transmitted signals collide at a central controller resulting in a collision signal having an amplitude determined by the combination of the corresponding different phases in the two or more transmitted signals;

correlating the collision signal with a plurality of stored parameters; and

determining the number of transmitted signals that collided as a function of said correlation.

2. The method of claim 1 further comprising modulating a payload of the transmitted signals to increase the number of different phase states in the payload.

3. The method of claim 1 further comprising generating a random binary sequence in a preamble of the transmitted signals to increase the number of different phase states in the preamble.

4. The method of claim 1 further comprising generating a random binary sequence in a payload of the transmitted signals to increase the number of different phase states in the payload.

5. A method for detecting collisions on a shared access network, comprising:

modulating a preamble of each of a plurality of RF modulated signals with a plurality of different phase states;

transmitting two or more of the RF modulated signals, wherein two or more preambles of the transmitted signals collide at a central controller to create a collision signal based on the different phase states of each preamble;

determining a characteristic of the collision signal;

comparing the characteristic with a plurality of predetermined thresholds; and

determining the number of the transmitted signals that collided as a function of the comparison.

6. The method of claim 5 further comprising:

monitoring a plurality of collision events;

determining the characteristic of each of the plurality of collision events; and

determining the predetermined thresholds in accordance with the characteristics of the collision events.

7. The method of claim 6 wherein determining a characteristic of each of the plurality of collision events comprises determining a peak power of each of the plurality of collision events, wherein the predetermined thresholds are determined in accordance with the peak power of each of the plurality of collision events.

8. The method of claim 7 wherein determining the predetermined thresholds in accordance with the peak power of each of the collision events comprises statistically analyzing the peak power of each of the plurality of collision events to establish minimum thresholds for estimating a minimum number of signals that collided.

9. The method of claim 8 wherein determining the number of transmitted signals that collided as a function of the comparison of the characteristic of the collided signals and a plurality of predetermined thresholds comprises comparing peak power of the collided signal to the minimum thresholds.

10. The method of claim 7 wherein determining the predetermined thresholds in accordance with the peak power of each of the collision events comprises statistically analyzing the peak power of each of the plurality of collision events to establish maximum thresholds for estimating a maximum number of signals that collided.

11. The method of claim 9 wherein determining the number of transmitted signals that collided as a function of the comparison of the characteristic of the collided signal and a plurality of predetermined thresholds comprises comparing peak power of the collided signal to the maximum thresholds.

12. The method of claim 6 wherein determining a characteristic of each of the plurality of collision events comprises locating a peak symbol of each of the plurality of collision events, wherein the predetermined thresholds are determined in accordance with the peak symbol of each of the plurality of collision events.

13. The method of claim 12 wherein determining the predetermined thresholds in accordance with the peak symbol of each of the collision events comprises cross correlating the peak symbol of each of the plurality of collision events with an uncollided symbol and statistically analyzing the cross correlations to establish minimum thresholds for estimating a minimum number of signals that collided.

14. The method of claim 13 wherein determining the number of transmitted signals that collided as a function of the comparison of the characteristic of the collided signal and a plurality of predetermined thresholds comprises comparing a cross correlation of the peak symbol of the collided signal with an uncollided signal and comparing the cross correlation to the minimum thresholds.

15. The method of claim 5 further comprising modulating a preamble of the transmitted signals to increase the number of different phase states in the preamble.

16. The method of claim 5 further comprising modulating a payload of the transmitted signals to increase the number of different phase states in the payload.

17. The method of claim 5 further comprising generating a random binary sequence in a preamble of the transmitted signals to increase the number of different phase states in the preamble.

18. The method of claim 5 further comprising generating a random binary sequence in a payload of the transmitted signals to increase the number of different phase states in the payload.

19. The method of claim 5 further comprising adjusting a number of time slots available in a request contention area in accordance with a number of RF modulated signals that collided.

20. A method for detecting collisions on a shared access RF network, comprising:

formatting transmit data packets to include a plurality of different phase states;

modulating a preamble of each of the transmit data packets to include a number of different phase states in the preamble;

determining a characteristic of a collision signal caused by a collision between two or more of the transmit data packets;

correlating the characteristic of the collision signal with a plurality of stored parameters; and

determining the number of transmitted signals data packets that collided as a function of the correlation.

21. The method of claim 20 wherein formatting transmit data packets to include the plurality of different phase states comprises generating a random binary sequence in the preamble of the transmit data packet to increase the number of different phase states in the preamble.

22. The method of claim 20 wherein formatting transmit data packets to include the plurality of different phase states comprises generating a random binary sequence in a payload of the transmit data packet to increase the number of different phase states in the payload.

23. The method of claim 20 further comprising adjusting the number of time slots available in a request contention area in accordance with the number of RF modulated signals that collided.

24. A method for detecting collisions on a shared access RF network, comprising:

detecting an occurrence of a collision event;

determining an absolute value of peak amplitude of a collision signal;

comparing the absolute value of the peak amplitude with a predetermined threshold; and

determining the number of transmitted signals that collided as a function of the comparison by assuming two or more signals collided when the absolute value of the peak amplitude of the collision signal is less than twice the amplitude of the uncollided signal.

25. A method for detecting collisions on a shared access RF network, comprising:

simulating a plurality of collisions;

determining a peak amplitude of each of the simulated collisions;

establishing maximum thresholds as a function of the peak amplitudes of the simulated collisions;

establishing minimum thresholds as a function of the peak amplitudes of the simulated collisions;

storing the minimum and maximum thresholds;

detecting an occurrence of a collision event;

determining a peak amplitude of a collided signal;

comparing the peak amplitude of collided signal to the minimum and maximum thresholds; and

determining the number of transmitted signals that collided as a function of the comparison.

26. A method for detecting collisions on a shared access RF network, comprising:

simulating a plurality of collisions;

locating a peak symbol of each of the simulated collisions;

cross correlating the peak symbol with uncollided symbol waveforms;

establishing maximum thresholds as a function of the cross correlation of the peak symbol with the uncollided symbol waveforms;

establishing minimum thresholds as a function of the cross correlation of the peak symbol with the uncollided symbol waveforms;

storing the minimum and maximum thresholds;

detecting an occurrence of a collision event;

locating a peak symbol of a collided signal;

correlating the peak symbol with the uncollided symbol waveforms; and

determining the number of transmitted signals that collided as a function of the correlation.

27. A collision detection system for shared access RF networks, comprising:

a correlation processor for correlating a characteristic of a collided RF waveform with a plurality of stored characteristics, wherein a number of received signals involved in a collision event is determined in accordance with the correlation; and

a peak detector coupled to the correlation processor for determining an absolute value of a peak amplitude of the collided RF waveform, wherein the correlation processor cross correlates the absolute value of the peak amplitude with a predetermined threshold, wherein the correlation processor determines the number of transmitted signals that collided as a function of the correlation.

28. A data communication system, comprising:

two or more subscriber RF transceivers, each subscriber RF transceiver being configured to transmit one or more RF modulated signals having a preamble being modulated to have a plurality of different phase states;

a collision detection system that includes a correlation processor for correlating a characteristic of a collided RF waveform with a plurality of stored characteristics, wherein the number of transmitted RF modulated signals involved in a collision event is determined in accordance with the correlation.

29. The data communication system of claim 28 further comprising:

a peak detector coupled to the correlation processor for detecting a peak amplitude of the collided RF waveform, wherein the correlation processor correlates the peak amplitude of the collided RF waveform with a plurality of stored values to determine the number of received signals involved in the collision event.

30. The data communication system of claim 28 further comprising;

a peak detector coupled to the correlation processor for detecting a peak symbol of said collided RF waveform, wherein the correlation processor cross correlates the peak symbol with a predetermined uncollided symbol; and

a comparator coupled to said correlation processor to compare the cross correlation with a plurality of stored values to determine the number of received signals involved in the collision event.

31. The data communication system of claim 28 wherein each of the subscriber RF transceivers comprises an upstream modulator for transmitting an RF modulated signal having a plurality of different phase states.

32. The data communication system of claim 28 wherein each of the subscriber RF transceivers comprises an upstream modulator for modulating a preamble of the transmitted signals to increase the number of different phase states in the preamble.

33. The data communication system of claim 28 wherein each of the subscriber RF transceivers comprises an upstream modulator for modulating a payload of the transmitted signals to increase the number of different phase states in the payload.

34. The data communication system of claim 28 wherein each of the subscriber RF transceivers comprises an upstream modulator for generating a random binary sequence in a preamble of the transmitted signals to increase the number of different phase states in the preamble.

35. The data communication system of claim 28 wherein each of the subscriber RF transceivers comprises an upstream modulator for generating a random binary sequence in a payload of the transmitted signals to increase the number of different phase states in the payload.

36. A method for detecting collisions on a shared access RF network, comprising:

detecting the occurrence of a collision event;

determining absolute value of peak amplitude of collision signal;

comparing the absolute value of the peak amplitude with a predetermined threshold; and

determining the number of transmitted signals that collided as a function of the comparison by assuming the number of signals that collided is greater than or equal to a ceiling of the absolute value of the peak amplitude of the collision signal divided by a nominal value of the peak amplitude in an uncollided signal.