Communications system and method for measuring short-term and long-term channel characteristics

• US 20020172166A1
• Filed: 03/22/2001
• Published: 11/21/2002
• Est. Priority Date: 03/22/2001
• Status: Abandoned Application

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Khayrallah, Ali S., Bottomley, Gregory E., Arslan, Huseyin, Molnar, Karl J.
• Application Number:
  US09/814,889
• Publication Number:
  US 20020172166A1
• Time in Patent Office: Days
• US Class Current: 370/317
• CPC Class Codes: H04L 1/20 using signal quality detector

Abstract

A communications system and method for compensating for an interferer signal in a received signal comprising a radio processor for filtering the received signal, and a demodulator coupled to the radio processor for demodulating the filtered received signal. A channel quality estimator coupled to the demodulator determines a channel characteristic based on instantaneous noise values of the received signal, for controlling the demodulation of the received signal to compensate for the interferer signal responsive to the channel characteristic. Further, where the channel characteristic is a first channel characteristic, the channel quality estimator determines a second channel characteristic based on instantaneous noise values of the received signal and controls demodulation of the received signal to compensate for the interferer signal responsive to the first and the second channel characteristics.

Claims

1. A method for compensating for an interferer signal in a received signal for a communications system comprising:

measuring a channel characteristic based on instantaneous noise values of the received signal; and

compensating for the interferer signal in the received signal by processing the received signal responsive to the channel characteristic.

2. The method of claim 1 wherein the channel characteristic is a long-term channel characteristic measured from a plurality of time slots of the received signal for detecting presence of an interferer in the received signal.

3. The method of claim 2 wherein the long-term channel characteristic measured from a plurality of time slots of the received signal comprises a long-term noise value estimate calculated by adding a previous time slot long term noise estimate using a smoothing factor.

4. The method of claim 3 further comprising adaptively changing the smoothing factor.

5. The method of claim 2 wherein the long-term channel characteristic measured from a plurality of time slots of the received signal comprises averaging instantaneous noise values over the plurality of time slots by summing corresponding instantaneous noise value samples from each of the plurality of time slots.

6. The method of claim 1 wherein the channel characteristic is a short-term channel characteristic measured from a time slot of the received signal for indicating a location of the interferer signal in the time slot of the received signal.

7. The method of claim 6 wherein the short-term channel characteristic measured from a time slot of the received signal is calculated by adding an average of the instantaneous noise value for a previous sample of the time slot multiplied by a smoothing factor with an instantaneous error value from a current sample of the time slot multiplied by one less the smoothing factor.

8. The method of claim 7 further comprising adaptively changing the smoothing factor.

9. The method of claim 1 wherein the channel characteristic is a first channel characteristic, and further comprising measuring a second channel characteristic based on instantaneous noise values of the received signal;

and

compensating for the interferer signal in the received signal comprises processing the received signal responsive to the first and second channel characteristics.

10. The method of claim 9 wherein the first channel characteristic based on instantaneous noise values of the received signal is a long-term channel characteristic measured from a plurality of time slots of the received signal for detecting the presence of an interferer in the received signal, and the second channel characteristic based on instantaneous noise values is a short-term channel characteristic measured from at least one time slot of the received signal for indicating a location of the interferer signal in the received signal.

11. The method of claim 1 wherein compensating for interference in the received signal by processing the received signal responsive to the channel characteristic comprises selecting a demodulator for processing the received signal responsive to the channel characteristic.

12. The method of claim 1 wherein compensating for interference in the received signal by processing the received signal responsive to the channel characteristic comprises changing adaptation parameters of a demodulator responsive to the channel characteristic.

13. The method of claim 1 wherein compensating for interference in the received signal by processing the received signal responsive to the channel characteristic comprises changing soft information values of a demodulator responsive to the channel characteristic.

14. The method of claim 13 wherein changing of soft information values of a demodulator responsive to the channel characteristic comprises normalizing the soft information values of the demodulator.

16. The receiver of claim 15 wherein the channel characteristic is a long-term channel characteristic measured from a plurality of time slots of the received signal for detecting the presence of an interferer in the received signal.

17. The receiver of claim 16 wherein the long-term channel characteristic measured from a plurality of time slots of the received signal comprises a long-term noise value estimate, and the channel quality estimator calculates the long term noise value estimate by adding a previous time slot long term noise estimate using by a smoothing factor.

18. The receiver of claim 17 wherein the channel quality estimator adaptively changes the smoothing factor.

19. The receiver of claim 16 wherein the long-term channel characteristic measured from a plurality of time slots of the received signal comprises averaging instantaneous noise values over the plurality of time slots calculated by the channel quality estimator by summing corresponding instantaneous noise value samples from each of the plurality of time slots.

20. The receiver of claim 15 wherein the channel characteristic is a short-term channel characteristic measured from a time slot of the received signal for indicating a location of the interferer signal in the time slot of the received signal.

21. The receiver of claim 20 wherein the short-term channel characteristic measured from a time slot of the received signal is calculated by the channel quality estimator by adding an average of the instantaneous noise value for a previous sample of the time slot using a smoothing factor.

22. The receiver of claim 21 wherein the channel quality estimator adaptively changes the smoothing factor.

23. The receiver of claim 15 wherein the channel characteristic is a first channel characteristic, and further comprising the channel quality estimator determining a second channel characteristic based on instantaneous noise values of the received signal and controlling demodulation of the received signal to compensate for the interferer signal responsive to the first and second channel characteristics.

24. The receiver of claim 23 wherein the first channel characteristic based on instantaneous noise values of the received signal is a long-term channel characteristic measured from a plurality of time slots of the received signal for detecting the presence of an interferer in the received signal, and the second channel characteristic based on instantaneous noise values is a short-term channel characteristic measured from at least one time slot of the received signal for indicating a location of the interferer signal in the received signal.

25. The receiver of claim 15 wherein the demodulator is a first demodulator and further comprising a second demodulator coupled to the radio processor and the channel quality processor for demodulating the filtered received signal, wherein the channel quality estimator selects one of the first demodulator and the second demodulator for demodulating the filtered received signal responsive to the channel characteristic.

26. The receiver of claim 15 wherein the demodulator is a first demodulator and further comprising a second demodulator coupled to the radio processor and the channel quality processor for parallel demodulation of the filtered received signal, and further comprising a combiner coupled to the channel quality processor, and to the first and second demodulators, wherein the channel quality estimator causes the combiner to select one of the demodulated signal from the first demodulator and the second demodulator responsive to the channel characteristic.

27. The receiver of claim 15 wherein the channel quality estimator controls the demodulation responsive to the channel characteristic by changing adaptation parameters of a demodulator responsive to the channel characteristic.

28. The receiver of claim 15 wherein the channel quality estimator controls the demodulation responsive to the channel characteristic by changing soft information of a demodulator responsive to the channel characteristic.

29. The receiver of claim 28 wherein the channel quality estimator changes the soft information values of the demodulation responsive to the channel characteristic by normalizing the soft information values of the demodulator.

15. A receiver for compensating for an interferer signal in a received signal comprising:

a radio processor for filtering the received signal;

a demodulator coupled to the radio processor for demodulating the filtered received signal; and

a channel quality estimator coupled to the demodulator for determining a channel characteristic based on instantaneous noise values of the received signal for controlling the demodulation of the received signal to compensate for the interferer signal responsive to the channel characteristic.

30. A mobile terminal for use in a mobile communications system comprising:

a receiver for receiving a signal comprising a desired signal and an interferer signal;

a radio processor for filtering the signal;

a demodulator coupled to the radio processor for demodulating the filtered signal; and

a channel quality estimator coupled to the demodulator for determining a channel characteristic based on instantaneous noise values of the signal for controlling the demodulation of the signal such that the desired signal is extracted by compensating for the interferer signal responsive to the channel characteristic.

31. The mobile terminal of claim 30 wherein the channel characteristic is a long-term channel characteristic measured from a plurality of time slots of the received signal for detecting the presence of an interferer in the received signal.

32. The mobile terminal of claim 30 wherein the channel characteristic is a short-term channel characteristic measured from at least one time slot of the received signal for indicating a location of the interferer signal in the time slot of the received signal.

33. The mobile terminal of claim 30 wherein the channel characteristic is a first channel characteristic, and further comprising the channel quality estimator determining a second channel characteristic based on instantaneous noise values of the received signal and controlling demodulation of the received signal to compensate for the interferer signal responsive to the first and second channel characteristics.

34. The mobile terminal of claim 30 wherein the demodulator is a first demodulator and further comprising a second demodulator coupled to the radio processor and the channel quality processor for demodulating the filtered received signal, wherein the channel quality estimator selects one of the first demodulator and the second demodulator for demodulating the filtered received signal responsive to the channel characteristic.

35. The mobile terminal of claim 30 wherein the channel characteristic is calculated utilizing an adaptively changeable smoothing factor.

37. The base station of claim 36 wherein the channel characteristic is a long-term channel characteristic measured from a plurality of time slots of the received signals for detecting the presence of an interferer in the received signals.

38. The base station of claim 36 wherein the channel characteristic is a short-term channel characteristic measured from at least one time slot of the received signals for indicating a location of the interferer signal in the time slot of the received signals.

39. The base station of claim 36 wherein the channel characteristic is a first channel characteristic, and further comprising the channel quality estimator determining a second channel characteristic based on instantaneous noise values of the received signals and controlling demodulation of the received signals to compensate for the interferer signal responsive to the first and second channel characteristics.

40. The base station of claim 36 wherein the demodulator is a first demodulator and further comprising a second demodulator coupled to the radio processor and the channel quality processor for demodulating the filtered received signals, wherein the channel quality estimator selects one of the first demodulator and the second demodulator for demodulating the filtered received signals responsive to the channel characteristic.

41. The base station of claim 36 wherein the channel characteristic is calculated utilizing an adaptively changeable smoothing factor.

36. A base station for use in a mobile communications system comprising:

a base station receiver for receiving signals comprising a desired signal and an interferer signal;

a radio processor for filtering the received signals;

a demodulator coupled to the radio processor for demodulating the filtered signals; and

a channel quality estimator coupled to the demodulator for determining a channel characteristic based on instantaneous noise values of the signals for controlling the demodulation of the signals such that the desired signal is extracted by compensating for the interferer signal responsive to the channel characteristic.

42. A mobile communications system for compensating for interferer signals comprising:

a plurality of transmitters each transmitting a corresponding signal, one of the signals being a desired signal and the other signals being interfering signals; and

a receiver for receiving a signal comprising the desired signal and the interferer signal and including a radio processor for filtering the signal, a demodulator coupled to the radio processor for demodulating the filtered signal, and a channel quality estimator coupled to the demodulator for determining a channel characteristic based on instantaneous noise values of the signal for controlling the demodulation of the signal such that the desired signal is extracted by compensating for the interferer signal responsive to the channel characteristic.

43. The mobile communications system of claim 42 wherein the channel characteristic is a long-term channel characteristic measured from a plurality of time slots of the received signal for detecting the presence of an interferer in the received signal.

44. The mobile communications system of claim 42 wherein the channel characteristic is a short-term channel characteristic measured from at least one time slot of the received signal for indicating a location of the interferer signal in the time slot of the received signal.

45. The mobile communications system of claim 42 wherein the channel characteristic is a first channel characteristic, and further comprising the channel quality estimator determining a second channel characteristic based on instantaneous noise values of the received signal and controlling demodulation of the received signal to compensate for the interferer signal responsive to the first and second channel characteristics.

46. The mobile communications system of claim 42 wherein the demodulator is a first demodulator and further comprising a second demodulator coupled to the radio processor and the channel quality processor for demodulating the filtered received signal, wherein the channel quality estimator selects one of the first demodulator and the second demodulator for demodulating the filtered received signal responsive to the channel characteristic.

47. The mobile communications system of claim 42 wherein the channel characteristic is calculated utilizing an adaptively changeable smoothing factor.

49. The receiver of claim 48 wherein the channel characteristic is a long-term channel characteristic measured from a plurality of time slots of the received signal for detecting the presence of an interferer in the received signal.

50. The receiver of claim 48 wherein the channel characteristic is a short-term channel characteristic measured from at least one time slot of the received signal for indicating a location of the interferer signal in the time slot of the received signal.

51. The receiver of claim 48 wherein the channel characteristic is a first channel characteristic, and further comprising the channel quality estimator determining a second channel characteristic based on instantaneous noise values of the received signal and controlling the selector responsive to the first and second channel characteristics.

52. The receiver of claim 48 wherein the channel characteristic is calculated utilizing an adaptively changeable smoothing factor.

48. A receiver for compensating for an interferer signal in a received signal comprising:

a radio processor for filtering the received signal;

a selector coupled to the radio processor;

a single user demodulator coupled to the selector and adapted for demodulating the received signal comprising little or no interferer signal, for demodulating the filtered received signal;

a multiuser demodulator coupled to the selector and adapted for demodulating the received signal comprising the interferer signal, for demodulating the filtered received signal; and

a channel quality estimator coupled to the radio processor, the selector and the single user demodulator, for determining a channel characteristic based on instantaneous noise values of the received signal as demodulated by the single user demodulator, and for controlling the selector to select one of the single user demodulator and the multiuser demodulator for demodulating the received signal to compensate for the interferer signal responsive to the channel characteristic.

53. A receiver for compensating for an interferer signal in a received signal comprising:

a radio processor for filtering the received signal;

a single user demodulator coupled to the radio processor and adapted for demodulating the received signal comprising little or no interferer signal, for demodulating the filtered received signal;

a multiuser demodulator coupled to the radio processor and adapted for demodulating the received signal comprising the interferer signal, for parallel demodulation of the filtered received signal;

a combiner coupled to the single user demodulator and to the multiuser demodulator, having a combiner output node; and

a channel quality estimator coupled to the single user demodulator and to the combiner, for determining a channel characteristic based on instantaneous noise values of the received signal as demodulated by the single user demodulator, and for controlling the combiner to select one of the signals provided by the single user demodulator and the multiuser demodulator to be provided at the combiner output node responsive to the channel characteristic to compensate for the interferer signal.

54. The receiver of claim 53 wherein the channel characteristic is a long-term channel characteristic measured from a plurality of time slots of the received signal for detecting the presence of an interferer in the received signal.

55. The receiver of claim 53 wherein the channel characteristic is a short-term channel characteristic measured from at least one time slot of the received signal for indicating a location of the interferer signal in the time slot of the received signal.

56. The receiver of claim 53 wherein the channel characteristic is a first channel characteristic, and further comprising the channel quality estimator determining a second channel characteristic based on instantaneous noise values of the received signal and controlling the combiner responsive to the first and second channel characteristics.

57. The receiver of claim 53 wherein the channel characteristic is calculated utilizing an adaptively changeable smoothing factor.

59. The receiver of claim 58 wherein the switching time estimator utilizes edge detection of averaged short-term channel characteristics from the single user demodulator to detect the presence of the interferer signal.

58. A receiver for compensating for an interferer signal in a received signal comprising:

a radio processor for filtering the received signal;

a selector coupled to the radio processor;

a single user demodulator coupled to the selector and adapted for demodulating the received signal comprising little or no interferer signal, for demodulating the filtered received signal;

a multiuser demodulator coupled to the selector and adapted for demodulating the received signal comprising the interferer signal, for demodulating the filtered received signal; and

a switched time estimator coupled to the radio processor and the selector for determining which portion of the received signal contains a dominant interferer signal and which portion of the received signal does not contain a dominant interferer signal, and for controlling the selector to select one of the single user demodulator and the multiuser demodulator for demodulating the received signal to compensate for the interferer signal responsive to a portion of the received signal, if any, containing a dominant interferer signal.