Out of channel cyclic redundancy code method for a discrete multitone spread spectrum communications system

• US 6,289,037 B1
• Filed: 02/24/1997
• Issued: 09/11/2001
• Est. Priority Date: 02/24/1997
• Status: Expired due to Term

• Current Assignee: Clearwire Ip Holdings LLC (Deutsche Telekom AG)
• Original Assignee: AT&T Wireless Services Incorporated (AT&T, Inc.)
• Inventors: Gibbons, David, Ryan, David James, Maxwell, Robert Lee
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): Tran, Khai
• Application Number:
  US08/803,831
• Time in Patent Office: 1,660 Days
• Field of Search: 375/200, 375/202, 375/147, 370/335, 370/320, 370/342, 371/43.4, 371/53
• US Class Current: 375/130
• CPC Class Codes: H04B 1/69 Spread spectrum techniques
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0045 Arrangements at the receiver end
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/16 in which the return channel carries supervisory signals, e.g. repetition request signals

Abstract

A new method makes the most efficient use of the scarce spectral bandwidth in a wireless discrete multitone spread spectrum communications system. Each remote station and each base station in the network prepares an error detection field, such as a cyclic code (CRC), on each block of data to be transmitted over the traffic channels. The sending station prepares an error detection message for transmission over the link control channel of the network. The sending station prepares the error detection message by forming a link control channel vector that will be spread using the discrete multitone spread spectrum (DMT-SS) protocol to distribute the data message over a plurality of discrete tone frequencies, forming a spread signal for the link control channel. A link control channel is associated with communications session using the traffic channels. The instant of transmission of the error detection message is allowed to be different from the instant of transmission of the data message. This permits the error detection messages to be transmitted when capacity is available on the link control channel. The receiving station buffers the error detection messages it receives from the link control channel, so that they are accessible by their block numbers. When the receiving station receives a data message on the traffic channel, it performs a CRC calculation on the data block in the message to obtain a resulting new CRC value. The new CRC value is also buffered at the receiving station with the block number so that it is accessible by its block number. Then, when both the received error message and the new CRC value are both available at the receiving station, they are matched by their common block number. The received CRC value in the error detection message is compared with the new CRC computed from the received data block. If the comparison determines that there is a difference in the values, then an error signal is generated.

Claims

1. A highly bandwidth-efficient communications method, comprising the steps of:

receiving at a base station a wireless spread signal comprising an incoming data message including a data block and a block number in a first channel at a first time spread over a plurality of discrete traffic frequencies;

adaptively despreading the data message received at the base station by using despreading weights;

receiving at said base station a wireless spread signal comprising an incoming error detection message including said block number and a first error detection code derived from said data block in a second channel at a second time spread over a plurality of wireless link control frequencies;

adaptively despreading the error detection message received at the base station by using said despreading weights;

computing a second error detection code for said received data block;

selecting said first error detection code using said block number received in said data message;

comparing the first error detection code with said second error detection code;

generating an error response signal at the base station in response to said first error detection code being different from said second error detection code.

2. The highly bandwidth-efficient communications method of claim 1, wherein said base station is part of a wireless discrete multitone spread spectrum communications system.

3. The highly bandwidth-efficient communications method of claim 1, wherein said second error detection code is a checksum resulting from the operation of a polynomial generator on said data block.

4. The highly bandwidth-efficient communications method of claim 1, wherein said second error detection code is a cyclic redundancy code.

5. The highly bandwidth-efficient communications method of claim 1, which further comprises:

prior to said comparing step, buffering said first error detection code.

6. The highly bandwidth-efficient communications method of claim 1, which further comprises:

initiating a negative acknowledgement signal to be sent from the base station to the sender requesting the sender to repeat the data block transmission, in response to said error response signal.

7. The highly bandwidth-efficient communications method of claim 1, which further comprises:

initiating an update in the spreading and despreading weights at the receiving station in an effort to improve the signal and interference to noise ratio of a traffic channel, in response to said error response signal.

8. The highly bandwidth-efficient communications method of claim 1, which further comprises:

initiating an alarm to be used for realtime control, in response to said error response signal.

9. The highly bandwidth-efficient communications method of claim 1, which further comprises:

logging the error signal for compilation of a longer term report of a traffic channel quality, in response to said error response signal.

10. A highly bandwidth-efficient communications method, comprising the steps of:

receiving at a base station a first spread signal comprising an incoming data traffic signal in a first channel at a first time having a data block portion and a block number portion spread over a plurality of discrete traffic frequencies;

receiving at said base station a second spread signal comprising an incoming error detection signal in a second channel at a second time having an error detection portion and said block number portion spread over a plurality of link control frequencies, said error detection portion being derived from said data block portion;

adaptively despreading said first spread signal received at the base station by using despreading weights, recovering said data block portion and said block number portion;

computing an error detection value for said data block portion at said base station;

adaptively despreading said second spread signal received at the base station by using despreading weights, recovering said error detection portion and said block number portion;

selecting said error detection portion using said block number portion received in said data traffic signal;

comparing the error detection value with said error detection portion at said base station;

generating an error response signal at the base station in response to said error detection value not comparing with said error detection portion.

11. The highly bandwidth-efficient communications method of claim 10, wherein said base station is part of a wireless discrete multitone spread spectrum communications system.

12. The highly bandwidth-efficient communications method of claim 10, wherein said error detection signal is a checksum resulting from the operation of a polynomial generator on said data block.

13. The highly bandwidth-efficient communications method of claim 10, wherein said error detection signal is a cyclic redundancy code.

14. The highly bandwidth-efficient communications method of claim 10, which further comprises:

prior to said comparing step, buffering said error detection signal.

15. The highly bandwidth-efficient communications method of claim 10, which further comprises:

initiating a negative acknowledgement signal to be sent from the base station to the sender requesting the sender to repeat the data block transmission, in response to said error response signal.

16. The highly bandwidth-efficient communications method of claim 10, which further comprises:

initiating an update in the spreading and despreading weights at the receiving station in an effort to improve the signal and interference to noise ratio of a traffic channel, in response to said error response signal.

17. The highly bandwidth-efficient communications method of claim 10, which further comprises:

initiating an alarm to be used for realtime control, in response to said error response signal.

18. The highly bandwidth-efficient communications method of claim 10, which further comprises:

logging the error signal for compilation of a longer term report of a traffic channel quality, in response to said error response signal.

19. A highly bandwidth-efficient communications system, comprising:

means for receiving at a base station a wireless spread signal comprising an incoming data traffic signal including a data block and a block number in a first channel at a first time spread over a plurality of discrete traffic frequencies and an incoming error detection signal including said block number and a first error code derived from said data block in a second channel at a second time spread over a plurality of wireless link control frequencies;

means for adaptively despreading the data traffic and error detection signals received at the base station by using despreading weights;

means for computing an error detection value including a second error code for said data block;

means for selecting said first error code using said block number from said data traffic signal;

means for comparing the first error code with said second error code;

means for generating an error response signal at the base station in response to said first error code being different from said second error code.

20. The highly bandwidth-efficient communications system of claim 19, wherein said base station is part of a wireless discrete multitone spread spectrum communications system.

21. The highly bandwidth-efficient communications system of claim 19, wherein said error detection signal is a checksum resulting from the operation of a polynomial generator on a data block.

22. The highly bandwidth-efficient communications system of claim 19, wherein said error detection signal is a cyclic redundancy code.

23. The highly bandwidth-efficient communications system of claim 19, which further comprises:

means for buffering said error detection signal.

24. The highly bandwidth-efficient communications system of claim 19, which further comprises:

means for initiating a negative acknowledgement signal to be sent from the base station to the sender requesting the sender to repeat the data block transmission, in response to said error response signal.

25. The highly bandwidth-efficient communications system of claim 19, which further comprises:

means for initiating an update in the spreading and despreading weights at the receiving station in an effort to improve the signal ad interference to noise ratio of a traffic channel, in response to said error response signal.

26. The highly bandwidth-efficient communications system of claim 19, which further comprises:

means for initiating an alarm to be used for realtime control, in response to said error response signal.

27. The highly bandwidth-efficient communications system of claim 19, which further comprises:

means for logging the error signal for compilation of a longer term report of a traffic channel quality, in response to said error response signal.

28. A highly bandwidth-efficient communications system, comprising:

means for receiving at a base station a first spread signal comprising an incoming data traffic signal in a first channel at a first time having a data block portion and a block number portion spread over a plurality of discrete traffic frequencies;

means for receiving at said base station a second spread signal comprising an incoming error detection signal in a second channel at a second time having an error detection portion and said block number portion spread over a plurality of link control frequencies;

means for adaptively despreading said first spread signal received at the base station by using despreading weights, recovering said data block portion and a block number portion;

means for computing an error detection value for said data block portion at said base station;

means for adaptively despreading said second spread signal received at the base station by using despreading weights, recovering said error detection portion and said block number portion;

means for selecting said error detection portion using said block number portion from said data traffic signal;

means for comparing the error detection value with said error detection portion at said base station; and

means for generating an error response signal at the base station in response to said error detection value not comparing with said error detection portion.

29. The highly bandwidth-efficient communications system of claim 28, wherein said base station is part of a wireless discrete multitone spread spectrum communications system.

30. The highly bandwidth-efficient communications system of claim 28, wherein said error detection signal is a checksum resulting from the operation of a polynomial generator on said data block.

31. The highly bandwidth-efficient communications system of claim 28, wherein said error detection signal is a cyclic redundancy code.

32. The highly bandwidth-efficient communications system of claim 28, which further comprises:

means for buffering said error detection signal.

33. The highly bandwidth-efficient communications system of claim 28, which further comprises:

means for initiating a negative acknowledgement signal to be sent from the base station to the sender requesting the sender to repeat the data block transmission, in response to said error response signal.

34. The highly bandwidth-efficient communications system of claim 28, which further comprises:

means for initiating an update in the spreading and despreading weights at the receiving station in an effort to improve the signal and interference to noise ratio of a traffic channel, in response to said error response signal.

35. The highly bandwidth-efficient communications system of claim 28, which further comprises:

means for initiating an alarm to be used for realtime control, in response to said error response signal.

36. The highly bandwidth-efficient communications system of claim 28, which further comprises:

means for logging the error signal for compilation of a longer term report of a traffic channel quality, in response to said error response signal.

37. A highly bandwidth-efficient communications method, comprising the steps of:

receiving at a base station a wireless spread signal comprising an incoming data traffic signal including a data block and a block number in a first channel at a first time spread over a plurality of discrete traffic frequencies and an incoming error detection signal in a second channel at a different time when capacity is available on the second channel, spread over a plurality of wireless link control frequencies;

said error detection signal including said block number and a first code value derived from said data block;

adaptively despreading the data traffic and error detection signals received at the base station by using despreading weights;

computing an error detection value for said data block in said data traffic signal;

said error detection value being a second code value;

selecting said first code value using said block number from said data traffic signal;

comparing the first code value with said second code value;

generating an error response signal at the base station in response to said first code value being different from said second code value.

38. A highly bandwidth-efficient communications method, comprising the steps of:

receiving at a base station a first spread signal comprising an incoming data traffic signal in a first channel at a first time having a data block portion and a block number portion spread over a plurality of discrete traffic frequencies;

receiving at said base station a second spread signal comprising an incoming error detection signal in a second, different channel at a different time when capacity is available on the second channel, having an error detection portion and said block number portion spread over a plurality of link control frequencies;

adaptively despreading said first spread signal received at the base station by using despreading weights, recovering said data block portion and a block number portion;

buffering said data block portion and a block number portion;

computing an error detection value for said data block portion at said base station;

adaptively despreading said second spread signal received at the base station by using despreading weights, recovering said error detection portion and said block number portion;

buffering said error detection portion and said block number portion;

comparing the error detection value with said error detection portion when both are available at said base station;

generating an error response signal at the base station in response to said error detection value not comparing with said error detection portion.

39. A highly bandwidth-efficient communications system, comprising:

means for receiving at a base station a wireless spread signal comprising an incoming data traffic signal including a data block and a block number in a first channel at a first time spread over a plurality of discrete traffic frequencies and an incoming error detection signal in a second channel at a different time when capacity is available on the second channel, spread over a plurality of wireless link control frequencies;

said error detection signal including said block number and a first code value derived from said data block;

means for adaptively despreading the data traffic and error detection signals received at the base station by using despreading weights;

means for computing an error detection value for said data block in said data traffic signal;

said error detective value being a second code value;

means for selecting said first code value using said block number from said data traffic signal;

means for comparing the first code value with said second code value;

means for generating an error response signal at the base station in response to said first code value being different from said second code value.

40. A highly bandwidth-efficient communications system, comprising:

means for receiving at a base station a first spread signal comprising an incoming data traffic signal in a first channel at a first time having a data block portion and a block number portion spread over a plurality of discrete traffic frequencies;

means for receiving at said base station a second spread signal comprising an incoming error detection signal in a second, different channel at a different time when capacity is available on the second channel, having an error detection portion and said block number portion spread over a plurality of link control frequencies;

means for adaptively despreading said first spread signal received at the base station by using despreading weights, recovering said data block portion and a block number portion;

means for buffering said data block portion and a block number portion;

means for computing an error detection value for said data block portion at said base station;

means for adaptively despreading said second spread signal received at the base station by using despreading weights, recovering said error detection portion and said block number portion;

means for buffering said error detection portion and said block number portion;

means for comparing the error detection value with said error detection portion when both are available at said base station; and

means for generating an error response signal at the base station in response to said error detection value not comparing with said error detection portion.

41. A communications method, comprising the steps of:

receiving at a station a wireless signal comprising an incoming data message including a data block and a block number in a first discrete traffic frequency channel;

receiving at said station a wireless signal comprising an incoming error detection message including said block number and a first error detection code derived from said data block in a second wireless link control frequency channel;

computing a second error detection code for said received data block;

selecting said first error detection code using said block number received in said data message;

comparing the first error detection code with said second error detection code; and

generating an error response signal at the station in response to said first error detection code being different from said second error detection code.

42. The communications method of claim 41, wherein said second error detection code is a checksum resulting from the operation of a polynomial generator on said data block.

43. The communications method of claim 41, wherein said second error detection code is a cyclic redundancy code.

44. The communications method of claim 41, which further comprises:

prior to said comparing step, buffering said first error detection code.

45. A communications method, comprising the steps of:

receiving at a station a first spread signal comprising an incoming data traffic signal in a first channel having a data block portion and a block number portion spread over a plurality of discrete traffic frequencies;

receiving at said station a second spread signal comprising an incoming error detection signal in a second channel having an error detection portion and said block number portion spread over a plurality of link control frequencies, said error detection portion being derived from said data block portion;

adaptively despreading said first spread signal received at the station by using despreading weights, recovering said data block portion and said block number portion;

computing an error detection value for said data block portion at said station;

adaptively despreading said second spread signal received at the station by using despreading weights, recovering said error detection portion and said block number portion;

selecting said error detection portion using said block number portion received in said data traffic signal;

comparing the error detection value with said error detection portion at said station;

generating an error response signal at the station in response to said error detection value not comparing with said error detection portion.

46. The communications method of claim 45, which further comprises:

prior to said comparing step, buffering said error detection signal.

47. A communications system, comprising:

means for receiving at a station a wireless signal comprising an incoming data traffic signal including a data block and a block number in a first discrete traffic frequency channel and an incoming error detection signal including said block number and a first error code derived from said data block in a second wireless link control frequency channel;

means for computing an error detection value including a second error code for said data block;

means for selecting said first error code using said block number from said data traffic signal;

means for comparing the first error code with said second error code;

means for generating an error response signal at the station in response to said first error code being different from said second error code.

48. The communications system of claim 47, which further comprises:

means for buffering said error detection signal.

49. A communications system, comprising:

means for receiving at a station a first spread signal comprising an incoming data traffic signal in a first channel having a data block portion and a block number portion spread over a plurality of discrete traffic frequencies;

means for receiving at said station a second spread signal comprising an incoming error detection signal in a second channel having an error detection portion and said block number portion spread over a plurality of link control frequencies;

means for adaptively despreading said first spread signal received at the station by using despreading weights, recovering said data block portion and a block number portion;

means for computing an error detection value for said data block portion at said station;

means for adaptively despreading said second spread signal received at the station by using despreading weights, recovering said error detection portion and said block number portion;

means for selecting said error detection portion using said block number portion from said data traffic signal;

means for comparing the error detection value with said error detection portion at said station; and

means for generating an error response signal at the station in response to said error detection value not comparing with said error detection portion.

50. The communications system of claim 49, which further comprises:

means for buffering said error detection signal.