Method and apparatus for determining the rate of received data in a variable rate communication system

• US 5,751,725 A
• Filed: 10/18/1996
• Issued: 05/12/1998
• Est. Priority Date: 10/18/1996
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Chen, Tao
• Primary Examiner(s): Canney, Vincent P.
• Application Number:
  US08/730,863
• Time in Patent Office: 571 Days
• Field of Search: 371/5.5, 371/27, 371/37.7, 371/38.1, 371/39.1, 371/44, 371/50.1, 375/225, 375/222, 375/200, 455/422
• US Class Current: 714/708
• CPC Class Codes: H04L 1/0046 Code rate detection or code type detection H04L1/0038 takes precedence; detection of the data rate H04L25/0262; for packet format H04L1/0091
• CPC Class Codes: H04L 25/0262 Arrangements for detecting the data rate of an incoming signal

Abstract

The apparatus and method are employed in a communications system has a transmitter and a receiver, where the receiver determines at which of several rates individual frames in a signal have been transmitted by the transmitter. For example, if the transmitter employs four transmission rates, the receiver decodes each frame of the received signal based on the four rates to produce four cyclic redundancy check (CRC) bits, four symbol error rate (SER) values and one or more Yamamoto check values. If only two of the CRC bits check, then the receiver compares to each other the SER values for those two rates to determine at which of the two rates a current frame was transmitted. If only one of the CRC bits check for a given rate, then the SER value for that rate is compared with a maximum SER threshold for that rate. Additionally, SER values for the other rates can be compared to minimum SER thresholds. Furthermore, the Yamamoto check values can be analyzed to determined whether looser or tighter minimum and maximum SER thresholds should be employed if the Yamamoto values check for the current rate, or do not check, respectively.

Claims

1. In a communication system having a transmitter that transmits to a receiver, said transmitter transmitting each of a plurality of frames at a current rate, wherein said current rate corresponds to one of a plurality of rates, a method at said receiver for determining said current rate of a current frame comprising the steps of:

generating a plurality of error check values each based on whether said current frame has one of said plurality of rates, wherein only a first check value of a selected rate favorably checks, and wherein said selected rate is one of said plurality of rates;

generating a plurality of error rate codes each based on whether said current frame has one of said plurality of rates, wherein a selected error rate code corresponds to said selected rate;

generating a plurality of decoding codes each based on whether said current frame has one of said plurality of rates, wherein a selected decoding code corresponds to said selected rate;

determining if said selected rate of said selected error rate code corresponds to a predetermined rate;

if said selected rate corresponds to said predetermined rate, comparing said selected decoding code to a selected value;

if said selected rate does not correspond to said predetermined rate, comparing said selected error rate code to a first value based on a predetermined operational relationship;

if said selected decoding code corresponds to said selected value, comparing said selected error rate code to a second value based on said predetermined operational relationship;

if said selected decoding code does not correspond to said selected value, comparing said selected error rate code to a third value based on said predetermined operational relationship; and

determining that said current rate of said current frame is said selected rate if said selected error rate code has said predetermined operational relationship to said first, second or third value.

2. The method of claim 1 wherein the step of generating a plurality of error check values generates a plurality of cyclic redundancy check values, wherein the step of generating a plurality of error rate codes generates a plurality of symbol error rates, and wherein the step of generating a plurality of decoding codes generates a plurality of Yamamoto check codes.

3. The method of claim 1 wherein said plurality of rates include full, half, quarter and eighth rates, and wherein the step of determining if said selected rate of said selected error rate code corresponds to a predetermined rate determines if said selected rate corresponds to said eighth rate.

4. The method of claim 1 wherein the step of generating a plurality of decoding codes generates a plurality of Yamamoto check codes, and wherein the step of comparing said selected decoding code to a selected value includes the step of determining if said selected Yamamoto code checks acceptably.

5. The method of claim 1 wherein said first, second and third values are error rate code threshold values, wherein the steps of comparing said selected error rate code to said first, second and third values determines whether said selected error rate code is less than said first, second and third threshold values, respectively, and wherein said second threshold value is greater than said third threshold value.

6. The method of claim 1 wherein the step of determining that said current rate of said current frame is said selected rate includes the step of determining that said current frame is erased if said selected error rate code does not have said predetermined operational relationship to said first, second or third value.

7. The method of claim 1, further comprising the steps of:

comparing at least another of said error rate codes to a minimum threshold error rate code based on a selected operational relationship; and

determining that said current frame is erased if said another of said error rate codes has said selected operational relationship to said minimum threshold.

8. In a communication system having a transmitter and a receiver, said transmitter transmitting a signal at a current rate, wherein said current rate corresponds to one of a plurality of rates, and wherein said receiver generates a plurality of error check values and error rate codes and at least one decoding code each based on whether said signal has one of said plurality of rates, a method for determining said current rate of said signal comprising the steps of:

determining if only a first check value of a selected rate favorably checks, wherein said selected rate is one of said plurality of rates;

determining if said selected rate corresponds to a predetermined rate;

if said selected rate corresponds to said predetermined rate, comparing a selected decoding code to a selected value;

if said selected rate does not correspond to said predetermined rate, comparing a selected error rate code to a first value based on a predetermined operational relationship, wherein said selected rate code corresponds to said selected rate;

if said selected decoding code corresponds to said selected value, comparing said selected error rate code to a second value based on said predetermined operational relationship;

if said selected decoding code does not correspond to said selected value, comparing said selected error rate code to a third value based on said predetermined operational relationship; and

determining that said current rate of said signal is said selected rate if said selected error rate code has said predetermined operational relationship to said first, second or third value.

9. The method of claim 8 wherein said plurality of rates include full, half, quarter and eighth rates, and wherein the step of determining if said selected rate corresponds to a predetermined rate determines if said selected rate corresponds to said eighth rate.

10. The method of claim 8 wherein said selected decoding code is a Yamamoto check code, and wherein the step of comparing a selected decoding code to a selected value includes the step of determining if said selected Yamamoto code checks acceptably.

11. The method of claim 8 wherein said first, second and third values are error rate code threshold values, wherein the steps of comparing said selected error rate code to said first, second and third values determines whether said selected error rate code is less than said first, second and third threshold values, respectively, and wherein said second threshold value is greater than said third threshold value.

12. The method of claim 8 wherein said signal includes a plurality of frames including a current frame, and wherein the step of determining that said current rate of said signal is said selected rate includes the step of determining that said current frame is erased if said selected error rate code does not have said predetermined operational relationship to said first, second or third value.

13. The method of claim 8, further comprising the steps of:

comparing at least another of said error rate codes to a minimum threshold error rate code based on a selected operational relationship; and

determining that said signal is erroneous if said another of said error rate codes has said selected operational relationship to said minimum threshold.

14. The method of claim 8 wherein the steps of comparing include the step of comparing said selected error rate code to first, second and third weighting values plus said first, second and third values, respectively.

15. The method of claim 8 wherein the steps of comparing include the step of comparing said selected error rate code to first, second and third multiplicative factor times said first, second and third values, respectively.

16. The method of claim 8 wherein said first value is an error rate code threshold value, and wherein the method further includes the steps of:

comparing said selected rate to a previous rate;

decreasing said first threshold value if said selected rate and said previous rate are approximately equal; and

increasing said first threshold rate if said selected rate and said previous rate are not equal.

17. In a communication system having means for transmitting that transmits to a receiver each of a plurality of frames at a current rate, wherein said current rate corresponds to one of a plurality of rates, said receiver comprising:

means for generating a plurality of error check values each based on whether said current frame has one of said plurality of rates, wherein only a first check value of a selected rate favorably checks, and wherein said selected rate is one of said plurality of rates;

means for generating a plurality of error rate codes each based on whether said current frame has one of said plurality of rates, wherein a selected error rate code corresponds to said selected rate;

means for generating at least one decoding code, each decoding code being based on whether said current frame has one of said plurality of rates, wherein a selected decoding code corresponds to said selected rate;

means, coupled to said means for generating a plurality of error rate codes, for determining if said selected rate of said selected error rate code corresponds to a predetermined rate;

means, coupled to said means for generating a plurality of decoding codes, for comparing said selected decoding code to a selected value if said selected rate corresponds to said predetermined rate;

means, coupled to said means for generating a plurality of error rate codes, for comparing said selected error rate code to a first value based on a predetermined operational relationship if said selected rate does not correspond to said predetermined rate for comparing said selected error rate code to a second value based on said predetermined operational relationship if said selected decoding code corresponds to said selected value, and for comparing said selected error rate code to a third value based on said predetermined operational relationship if said selected decoding code does not correspond to said selected value; and

means, coupled to said means for comparing said first, second and third values, for determining that said current rate of said current frame is said selected rate if said selected error rate code has said predetermined operational relationship to said first, second or third value.

18. The receiver of claim 17 wherein said means for generating a plurality of error check values generates a plurality of cyclic redundancy check values, wherein said means for generating a plurality of error rate codes generates a plurality of symbol error rates, and wherein said means for generating a plurality of decoding codes generates a plurality of Yamamoto check codes.

19. The receiver of claim 17 wherein said plurality of rates include full, half, quarter and eighth rates, and wherein said means for determining if said selected rate of said selected error rate code corresponds to a predetermined rate includes means for determining if said selected rate corresponds to said eighth rate.

20. The receiver of claim 17 wherein said means for generating a plurality of decoding codes generates a plurality of Yamamoto check codes, and wherein said means for comparing said selected decoding code to a selected value includes means for determining if said selected Yamamoto code checks acceptably.

21. The receiver of claim 17 wherein said first, second and third values are error rate code threshold values, wherein said means for comparing said selected error rate code to said first, second and third values includes means for determining whether said selected error rate code is less than said first, second and third threshold values, respectively, and wherein said second threshold value is greater than said third threshold value.

22. The receiver of claim 17 wherein said means for determining that said current rate of said current frame is said selected rate includes means for determining that said current frame is erased if said selected error rate code does not have said predetermined operational relationship to said first, second or third value.

23. The receiver of claim 17, further comprising:

means for comparing at least another of said error rate codes to a minimum threshold error rate code based on a selected operational relationship; and

means for determining that said current frame is erased if said another of said error rate codes has said selected operational relationship to said minimum threshold.

24. In a communication system having a transmitter that transmits a signal at a current rate, and wherein said current rate corresponds to one of a plurality of rates, a receiver comprising:

an error check value generator configured to generate a plurality of error check values each based on whether said signal has one of said plurality of rates, wherein only a first check value of a selected rate favorably checks, and wherein said selected rate is one of said plurality of rates;

an error rate code generator configured to generate a plurality of error rate codes each based on whether said signal has one of said plurality of rates, wherein a selected error rate code corresponds to said selected rate;

a decoding code generator configured to generate at least a selected decoding code, based on whether said signal has said selected rate; and

a decoder coupled to said error check value generator, error rate code generator and decoding code generator and configured to (a) determine if said selected rate of said selected error rate code corresponds to a predetermined rate, (b) compare said selected decoding code to a selected value if said selected rate corresponds to said predetermined rate, (c) compare said selected error rate code to a first value based on a predetermined operational relationship if said selected rate does not correspond to said predetermined rate, (d) compare said selected error rate code to a second value based on said predetermined operational relationship if said selected decoding code corresponds to said selected value, (e) compare said selected error rate code to a third value based on said predetermined operational relationship if said selected decoding code does not correspond to said selected value, (f) determine that said current rate of said signal is said selected rate if said selected error rate code has said predetermined operational relationship to said first, second or third value, and (g) decode said signal based on said selected rate.

25. The receiver of claim 24 wherein said error check value generator generates a plurality of cyclic redundancy check values, wherein said error rate code generator generates a plurality of symbol error rates, and wherein said decoding code generator generates a plurality of Yamamoto check codes.

26. The receiver of claim 24 wherein said plurality of rates include full, half, quarter and eighth rates, and wherein said decoder determines if said selected rate corresponds to said eighth rate.

27. The receiver of claim 24 wherein said decoding code generator generates a plurality of Yamamoto check codes, and wherein said decoder determines if said selected Yamamoto code checks acceptably.

28. The receiver of claim 24 wherein said first, second and third values are error rate code threshold values, wherein said decoder determines whether said selected error rate code is less than said first, second and third values, respectively, and wherein said second threshold value is greater than said third threshold value.

29. The receiver of claim 24 wherein said signal includes a plurality of frames, including a current frame, and wherein said decoder determines that said current frame is erased if said selected error rate code does not have said predetermined operational relationship to said first, second or third value.

30. The receiver of claim 24 wherein said decoder compares at least another of said error rate co des to a minimum threshold based on a selected operational relationship, and determines that said signal is erroneous if said another of said error rate codes has said selected operational relationship to said minimum threshold.

31. The receiver of claim 24 wherein said decoder compares said selected error rate code to first, second and third weighting values plus said first, second and third values, respectively.

32. The receiver of claim 24 wherein said decoder compares said selected error rate code to first, second and third multiplicative factors times said first, second and third values, respectively.

33. The receiver of claim 24 wherein said decoder compares said selected rate to a previous rate and decreases said first value if said selected rate and said previous rate are approximately equal.

34. A communication system comprising:

a transmitter configured to transmit a signal at a current rate, wherein said current rate corresponds to one of a plurality of rates; and

a receiver configured to receive said signal, said receiver including;

an error check value generator configured to generate a plurality of error check values each based on whether said signal has one of said plurality of rates, wherein only a first check value of a selected rate favorably checks, and wherein said selected rate is one of said plurality of rates;

an error rate code generator configured to generate a plurality of error rate codes each based on whether said signal has one of said plurality of rates, wherein a selected error rate code corresponds to said selected rate;

a decoding code generator configured to generate a plurality of decoding codes each based on whether said signal has one of said plurality of rates, wherein a selected decoding code corresponds to said selected rate; and

a decoder coupled to said error check value generator, error rate code generator and decoding code generator and configured to (a) determine if said s elected rate of said selected error rate code corresponds to a predetermined rate, (b) compare said selected decoding code to a selected value if said selected rate corresponds to said predetermined rate, (c) compare said selected error rate code to a first value based on a predetermined operational relationship if said selected rate does not correspond to said predetermined rate, (d) compare said selected error rate code to a second value based on said predetermined operational relationship if said selected decoding code corresponds to said selected value, (e) compare said selected error rate code to a third value based on said predetermined operational relationship if said selected decoding code does not correspond to said selected value, (f) determine that said current rate of said signal is said selected rate if said selected error rate code has said predetermined operational relationship to said first, second or third value, and (g) decode said signal based on said selected rate.

35. In a communication system having a transmitter that transmits to a receiver, said transmitter transmitting each of a plurality of frames at a current rate, wherein said current rate corresponds t o one of a plurality of rates, a method at said receiver for determining said current rate of a current frame comprising the steps of:

generating a plurality of error check values each based on whether said current frame has one of said plurality of rates, wherein only first and second error check values of first and second rates favorably check, and wherein said first and second rates are from said plurality of rates;

generating a plurality of error rate codes each based on whether said current frame has one of said plurality of rates, wherein first and second error rate codes correspond to said first and second rates;

comparing said first error rate code to said second error rate code plus a first value based on a predetermined operational relationship; and

determining that said current rate of said current frame is said second rate if said first error rate code has said predetermined operational relationship to said second error rate code plus a first value, and otherwise deter mining that said current rate is said first rate.

36. The method of claim 35 wherein the step of generating a plurality of error check values generates a plurality of cyclic redundancy check values, and wherein the step of generating a plurality of error rate codes generates a plurality of symbol error rates.

37. The method of claim 35, further comprising the steps of:

comparing said first error rate code to a threshold value based on a selected operational relationship if said first error rate code does not have said predetermined operational relationship to said second error rate code plus a first value; and

determining that said current frame is erased if said first error rate code has said selected operational relationship to said threshold value.

38. The method of claim 35 where in the step of comparing compares said first error rate code to s aid second error rate codes times a multiplicative factor.

39. In a communication system having a transmitter and a receiver, said transmitter transmitting a signal at a current rate, wherein said current rate corresponds to one of a plurality of rates, and wherein said receiver generates a plurality of error check values and error rate codes each based on whether said signal has one of said plurality of rates, a method for determining said current rate of said signal comprising the steps of:

determining that only first and second error check values of first and second rates favorably check, wherein said first and second rates are from said plurality of rates;

comparing a first error rate code to a second error rate code plus a first value based on a predetermined operational relationship, wherein said first and second error rate codes correspond to said first and second rates; and

determining that said current rate of said signal is said first rate if said second error rate code has said predetermined operational relationship to said second error rate code plus a first value, and otherwise determining that said current rate is said first rate.

40. The method of claim 39 wherein said first and second error check values are first and second cyclic redundancy check values, and wherein said first and second error rate codes are first and second symbol error rates.

41. The method of claim 39, further comprising the steps of:

comparing said first error rate code to a n error rate code threshold value based on a selected operational relationship if said first error rate code does not have said predetermined operational relationship to said second error rate code plus a first value; and

determining that said signal is erroneous if said first error rate code has said selected operational relationship to said threshold value.

42. The method of claim 39 wherein the step of comparing compares said first error rate code to said second error rate codes times a multiplicative factor .

43. The method of claim 39, further comprising the steps of:

generating at least a selected decoding code based on said first rate;

determining if said first rate corresponds to a predetermined rate;

if said first rate corresponds to said predetermined rate, comparing said selected decoding code to a selected value; and

if said selected decoding code corresponds to said selected value, altering said first value.

44. In a communication system having means for transmitting that transmits each of a plurality of frames at a current rate, wherein said current rate corresponds to one of a plurality of rates, a receiver comprising:

means for generating a plurality of error check values each based on whether said current frame has one of said plurality of rates, wherein only first and second check values of first and second rates favorably check, and wherein said plurality of rates includes said first and second rates;

means for generating a plurality of error rate codes each based on whether said current frame has one of said plurality of rates, wherein first and second error rate codes correspond to said first and second rates;

means, coupled to said means for generating a plurality of error check values and said means for generating a plurality of error rate codes, for comparing said first error rate code to said second error rate code plus a first value based on a predetermined operational relationship; and

means, coupled to said means for comparing, for determining that said current rate of said current frame is said second rate if said first error rate code has said predetermined operational relationship to said second error rate code plus a first value, and otherwise determining that said current rate is said first rate.

45. The receiver of claim 44 wherein said means for generating a plurality of error check values generates a plurality of cyclic redundancy check values, and wherein said means for generating a plurality of error rate codes generates a plurality of symbol error rates.

46. The receiver of claim 44, further comprising:

means for comparing said first error rate code to a threshold value based on a selected operational relationship if said first error rate code does not have said predetermined operational relationship to said second error rate code plus a first value; and

means for determining that said current frame is erased if said first error rate code has said selected operational relationship to said threshold value.

47. The receiver of claim 44 wherein said means for comparing compares said first error rate code to said second error rate code times a multiplicative factor.

48. In a communication system having a transmitter that transmits each of a signal at a current rate, wherein said current rate corresponds to one of a plurality of rates, a receiver comprising:

an error check value generator configured to generate a plurality of error check values each based on whether said current frame has one of said plurality of rates, wherein only first and second check values of first and second rates favorably check, and wherein said first and second rates are from said plurality of rates;

an error rate code generator configured to generate a plurality of error rate codes each based on whether said current frame has one of said plurality of rates, wherein first and second error rate codes correspond to said first and second rates; and

a decoder coupled to said error check value generator and error rate code generator and configured to compare said first error rate code to said second error rate code plus a first value based on a predetermined operational relationship, determine that said current rate of said current frame is said second rate if said first error rate code has said predetermined operational relationship to said second error rate code plus a first value, and otherwise determine that said current rate is said first rate.

49. The receiver of claim 48 wherein said error check value generator generates a plurality of cyclic redundancy check values, and wherein said error rate code generator generates a plurality of symbol error rates.

50. The receiver of claim 48 wherein said decoder compares said first error rate code to a threshold value based on a selected operational relationship if said first error rate code has said predetermined operational relationship to said second error rate code plus a first value determines that said current frame is erased if said first error rate code has said selected operational relationship to said threshold value.

51. The receiver of claim 48 wherein said decoder compares said first error rate code to a multiplicative factor times said second error rate code.

52. A communication system comprising:

a transmitter configured to transmit a signal at a current rate, wherein said current rate corresponds to one of a plurality of rates; and

a receiver configured to receive said signal, said receiver including;

an error check value generator configured to generate a plurality of error check values each based on whether said current frame has one of said plurality of rates, wherein only first and second check values of first and second rates favorably check, and wherein said first and second rates are from said plurality of rates;

an error rate code generator configured to generate a plurality of error rate codes each based on whether said current frame has one of said plurality of rates, wherein first and second error rate codes correspond to said first and second rates; and

a decoder coupled to said error check value generator and error rate code generator and configured to compare said first error rate code to said second error rate code plus a first value based on a predetermined operational relationship, determine that said current rate of said current frame is said second rate if said first error rate code has said predetermined operational relationship to said second error rate code plus a first value, and otherwise determine that said current rate is said first rate.