Radio receiver

• US 20030081703A1
• Filed: 04/01/2002
• Published: 05/01/2003
• Est. Priority Date: 10/30/2001
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Kimura, Dai, Kawaguchi, Noriyuki, Minowa, Morihiko
• Granted Patent: US 7,133,475 B2
• Time in Patent Office: Days
• US Class Current: 375/343
• CPC Class Codes: H04L 7/042 Detectors therefor, e.g. correlators, state machines digital correlators in general G06F17/15

Abstract

The invention relates to a radio receiver which receives reception waves modulated with a frame being a sequence of slots and reproduces transmission information that is distributed to the slots. An object of the invention is to increase the reliability of channel inference and improve the transmission quality without substantially altering a basic configuration. A radio receiver of the invention performs quasi-synchronous detection on reception waves modulated with a frame; determines an error in a sequence of first vectors and a sequence of second vectors as an average of deviations of particular symbol positions to be indicated by the sequence of first vectors indicating a sequence of words included in each slot in a signal space, and the sequence of second vectors indicating known information included in the slots; and compensates for the error in the signal space.

Claims

1. A radio receiver comprising:

a detecting section for performing quasi-synchronous detection on a signal that is modulated with a frame, and for outputting a baseband signal, the frame being a sequence of slots each of which includes known information and possibly includes words having a steep autocorrelation characteristic and a small and gentle cross-correlation characteristic;

a synchronizing section for performing frame synchronization with a frame indicated by said baseband signal;

a vector extracting section for extracting a sequence of first vectors and a sequence of second vectors by analyzing said baseband signal based on a formation of said frame, the sequence of first vectors indicating a sequence of words individually included in said slots, the sequence of second vectors indicating said known information included in said slots;

a channel inferring section for obtaining an error in said first vectors and said second vectors from deviations of particular symbol positions to be indicated in a signal space by said sequence of first vectors and said sequence of second vectors; and

a transmission-characteristic compensating section for compensating for an error in a vector indicating said baseband signal in said signal space, the error being obtained by said channel inferring section.

2. The radio receiver according to claim 1, wherein:

said transmission-characteristic compensating section is structured of a plurality of sections corresponding to respective fingers to be RAKE combined, for compensating in parallel for errors obtained by said channel inferring section for every finger; and

said synchronizing section obtains a delay profile as a distribution, on the time axis, of correlations between said formation of said frame and components indicating said extracted sequences of first vectors and second vectors among components of baseband signals, and performs frame synchronization with said baseband signals based on the delay profile, the baseband signals being received parallel via a radio transmission channel formed as a multipath and through which said signal propagates.

3. The radio receiver according to claim 1, wherein said vector extracting section provides a compensation for an error previously obtained by said channel inferring section to said extracted sequence of second vectors.

4. The radio receiver according to claim 1, wherein said channel inferring section provides a compensation for the previously obtained error to an error obtained by said channel inferring section.

6. The radio receiver according to claim 1, wherein:

said vector extracting section determines a sequence of words by analyzing said baseband signal based on said autocorrelation characteristic; and

said channel inferring section calculates, in said signal space, an average of deviations of said particular symbol positions to be indicated by said first and second vectors, according to an operation procedure that conforms to the determined sequence of words.

8. The radio receiver according to claim 1, wherein said vector extracting section extracts, from said words included in said slots, a sequence of first vectors as a sequence of vectors indicating a word which directly corresponds to a symbol position in said signal space and conforms to said formation of said frame and to a modulation scheme used for generating said signal.

10. The radio receiver according to claim 1, wherein said synchronizing section performs frame synchronization based on a correlation between said baseband signal and said words having a steep autocorrelation characteristic.

12. The radio receiver according to claim 1, wherein said synchronizing section performs frame synchronization based on correlations between said baseband signal and said words having a steep autocorrelation characteristic, and between said baseband signal and a sync word included in said frame.

14. The radio receiver according to claim 1, wherein said synchronizing section performs frame synchronization based on a correlation between said baseband signal and a sync word included in said frame, and on a correlation between said baseband signal and said words indicated by said sequence of first vectors.

16. The radio receiver according to claim 1, further comprising a frequency deviation suppressing section for maintaining a frequency of said local frequency signal used for said quasi-synchronous detection at such a value that a variation rate of a phase of said obtained error is suppressed, or for correcting said frequency of said local frequency signal to the value in the baseband domain.

18. The radio receiver according to claim 1, further comprising a speed detecting section for determining a speed of a transmitting end of said signal modulated with said frame according to a frequency at which a cross-correlation between said extracted sequences of first and second vectors and symbol positions varies, the symbol positions signifying a word and known information to be indicated by said first and second vectors, respectively.

20. The radio receiver according to claim 1, wherein said particular symbol positions are given according to one or both of a channel control procedure and a call setting procedure.

22. The radio receiver according to claim 1, wherein said particular symbol positions are known and known to be included in both of said sequence of first vectors and said sequence of second vectors.

24. The radio receiver according to claim 1, wherein the number of said particular symbol positions is set to a larger value as said signal modulated with said frame has a lower quality.

26. The radio receiver according to claim 1, wherein said vector extracting section determines said sequence of first vectors in order for each sequence of a minimum number of symbols whose autocorrelation characteristic is likely to be considered steep.

28. The radio receiver according to claim 26, wherein said vector extracting section determines said sequence of first vectors in order for each sequence of a number of symbols that conforms to one or both of a channel control procedure and a call setting procedure.

30. The radio receiver according to claim 28, further comprising a particular-slot identifying section for identifying a sequence of particular slots that conform to one or both of said channel control procedure and said call setting procedure and in which said words are to be uniform, and wherein

said transmission-characteristic compensating section compensates all or part of symbols indicating said sequence of particular slots for an error obtained first by said channel inferring section for the identified sequence of particular slots.

32. The radio receiver according to claim 30, wherein said channel inferring section omits to repeat processing of obtaining an error for said identified sequence of particular slots.

34. The radio receiver according to claim 30, wherein said vector extracting section omits to repeat processing of extracting a sequence of first vectors for said identified sequence of particular slots.

36. The radio receiver according to claim 32, wherein said vector extracting section omits to repeat processing of extracting a sequence of first vectors for said identified sequence of particular slots.

5. A radio receiver comprising:

a detecting section for performing synchronous detection on a signal that is modulated with a frame, and for outputting a baseband signal, the frame being a sequence of slots each of which includes known information and possibly includes words having a steep autocorrelation characteristic and a small and gentle cross-correlation characteristic;

a synchronizing section for performing frame synchronization with a frame indicated by said baseband signal;

a vector extracting section for extracting a sequence of first vectors and a sequence of second vectors by analyzing said baseband signal based on a formation of said frame, the sequence of first vectors indicating a sequence of words individually included in said slots, the sequence of second vectors indicating said known information included in said slots;

a channel inferring section for obtaining an error in said first vectors and said second vectors from deviations of particular symbol positions to be indicated in a signal space by said sequence of first vectors and said sequence of second vectors; and

a transmission-characteristic compensating section for maintaining one or both of a phase and an amplitude of a local frequency signal used for said synchronous detection at such a value that said obtained error is suppressed, or for correcting one or both of the phase and the amplitude of the local frequency signal to the value in the baseband domain.

7. The radio receiver according to claim 5, wherein:

said vector extracting section determines a sequence of words by analyzing said baseband signal based on said autocorrelation characteristic; and

said channel inferring section calculates, in said signal space, an average of deviations of said particular symbol positions to be indicated by said first and second vectors, according to an operation procedure that conforms to the determined sequence of words.

9. The radio receiver according to claim 5, wherein said vector extracting section extracts, from said words included in said slots, a sequence of first vectors as a sequence of vectors indicating a word which directly corresponds to a symbol position in said signal space and conforms to said formation of said frame and to a modulation scheme used for generating said signal.

11. The radio receiver according to claim 5, wherein said synchronizing section performs frame synchronization based on a correlation between said baseband signal and said words having a steep autocorrelation characteristic.

13. The radio receiver according to claim 5, wherein said synchronizing section performs frame synchronization based on correlations between said baseband signal and said words having a steep autocorrelation characteristic, and between said baseband signal and a sync word included in said frame.

15. The radio receiver according to claim 5, wherein said synchronizing section performs frame synchronization based on a correlation between said baseband signal and a sync word included in said frame, and on a correlation between said baseband signal and said words indicated by said sequence of first vectors.

17. The radio receiver according to claim 5, further comprising a frequency deviation suppressing section for maintaining a frequency of said local frequency signal used for said synchronous detection at such a value that a variation rate of a phase of said obtained error is suppressed, or for correcting said frequency of said local frequency signal to the value in the baseband domain.

19. The radio receiver according to claim 5, further comprising a speed detecting section for determining a speed of a transmitting end of said signal modulated with said frame according to a frequency at which a cross-correlation between said extracted sequences of first and second vectors and symbol positions varies, the symbol positions signifying a word and known information to be indicated by said first and second vectors, respectively.

21. The radio receiver according to claim 5, wherein said particular symbol positions are given according to one or both of a channel control procedure and a call setting procedure.

23. The radio receiver according to claim 5, wherein said particular symbol positions are known and known to be included in both of said sequence of first vectors and said sequence of second vectors.

25. The radio receiver according to claim 5, wherein the number of said particular symbol positions is set to a larger value as said signal modulated with said frame has a lower quality.

27. The radio receiver according to claim 5, wherein said vector extracting section determines said sequence of first vectors in order for each sequence of a minimum number of symbols whose autocorrelation characteristic is likely to be considered steep.

29. The radio receiver according to claim 27, wherein said vector extracting section determines said sequence of first vectors in order for each sequence of a number of symbols that conforms to one or both of a channel control procedure and a call setting procedure.

31. The radio receiver according to claim 29, further comprising a particular-slot identifying section for identifying a sequence of particular slots that conform to one or both of said channel control procedure and said call setting procedure and in which said words are to be uniform, and wherein

said transmission-characteristic compensating section compensates all or part of symbols indicating said sequence of particular slots for an error obtained first by said channel inferring section for the identified sequence of particular slots.

33. The radio receiver according to claim 31, wherein said channel inferring section omits to repeat processing of obtaining an error for said identified sequence of particular slots.

35. The radio receiver according to claim 31, wherein said vector extracting section omits to repeat processing of extracting a sequence of first vectors for said identified sequence of particular slots.

37. The radio receiver according to claim 33, wherein said vector extracting section omits to repeat processing of extracting a sequence of first vectors for said identified sequence of particular slots.