Method and apparatus for receiving diversity signals for use in OFDM radio communication system

• US 20030058786A1
• Filed: 10/17/2002
• Published: 03/27/2003
• Est. Priority Date: 01/08/1998
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Sato, Kazumi, Namekata, Minoru
• Granted Patent: US 7,266,108 B2
• Time in Patent Office: Days
• US Class Current: 370/203
• CPC Class Codes: H04B 7/082 selecting best antenna path
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: Y10S 370/913 Wireless or radio

Abstract

In a diversity receiving apparatus for use in an OFDM transmission radio communication/broadcasting system, OFDM signals are received by a plurality of antennas and are input into a plurality of receivers. The OFDM received signals are further input into a plurality of transformers and are transformed into frequency spectra. A plurality of channel frequency response calculating units calculate channel frequency responses by using the OFDM received signal frequency spectra and a reference frequency spectrum generated in a reference frequency spectrum generator. A plurality of distortion compensators then compensate for the distortions of the OFDM received signal frequency spectra by using the corresponding channel frequency responses. The OFDM received signal frequency spectra output from the first transformers are input into a selector unit as first input signals, while the distortion-compensated OFDM received signal frequency spectra are input into the selector unit as second input signals. The selector unit then selects the second input signal corresponding to the first input signal having the maximum amplitude or the maximum power. A demodulator then demodulates the output signal of the selector unit into a digital signal sequence.

Claims

1. A receiving apparatus comprising:

a plurality of diversity branches, each of said diversity branches including a receiver for receiving an orthogonal frequency division multiplexing signal and outputting an orthogonal frequency division multiplexing received signal, a transformer for transforming the orthogonal frequency division multiplexing received signal into a orthogonal frequency division multiplexing received signal frequency spectrum and outputting the orthogonal frequency division multiplexing received signal frequency spectrum, and a channel frequency response calculating unit for calculating a channel frequency response in accordance with the orthogonal frequency division multiplexing received signal frequency spectrum and a reference frequency spectrum; and

a selector unit for selecting the diversity branch that has generated the orthogonal frequency division multiplexing received signal frequency spectrum having a maximum amplitude or a maximum power.

2. A receiving apparatus comprising:

a plurality of diversity branches, each of said diversity branches including a receiver for receiving an orthogonal frequency division multiplexing signal and outputting an orthogonal frequency division multiplexing received signal, a transformer for transforming the orthogonal frequency division multiplexing received signal into a orthogonal frequency division multiplexing received signal frequency spectrum and outputting the orthogonal frequency division multiplexing received signal frequency spectrum, and a channel frequency response calculating unit for calculating a channel frequency response in accordance with the orthogonal frequency division multiplexing received signal frequency spectrum and a reference frequency spectrum; and

a selector unit for selecting the diversity branch that has generated the channel frequency response having a maximum amplitude or a maximum power.

13. A receiving apparatus according to claim 2, further comprising:

a re-modulator for re-modulating the digital signal sequence demodulated by said demodulator and for generating a re-modulated frequency spectrum; and

a frequency spectrum selector for selectively outputting the re-modulated frequency spectrum or the reference frequency spectrum to said channel frequency response calculating units.

19. A receiving apparatus according to claim 2, wherein said selector unit comprises a plurality of synthesizers for synthesizing the amplitudes or the power of line spectra forming the first input signal, and a comparator for comparing outputs of said synthesizers, thereby performing a selecting operation based on a comparison result of said comparator.

25. A receiving apparatus according to claim 2, wherein said selector unit comprises a comparator for comparing, among line spectra forming the first input signal, the amplitude or the power of the line spectra of the same frequency, thereby performing a selecting operation based on a comparison result of said comparator.

3. A receiving apparatus comprising:

a plurality of receivers, each of said receivers for receiving an orthogonal frequency division multiplexing signal and outputting an orthogonal frequency division multiplexing received signal;

a plurality of transformers, each of said transformers for transforming the orthogonal frequency division multiplexing received signal from a corresponding one of the plurality of receivers into a orthogonal frequency division multiplexing received signal frequency spectrum;

at least one reference frequency spectrum generator for generating a reference frequency spectrum relative to the orthogonal frequency division multiplexing received signal;

a plurality of channel frequency response calculating units, each of said channel frequency response calculating units for calculating a channel frequency response in accordance with the frequency spectrum output from a corresponding one of the plurality of transformers and the reference frequency spectrum;

a distortion compensator for compensating for a distortion of the frequency spectrum output from each of said transformers by using the corresponding channel frequency response;

a selector unit for selecting, from among the frequency spectra output from said transformer applied thereto as first input signals, the first input signals having a maximum amplitude or a maximum power, said outputting, from among the distortion compensated frequency spectra output from said distortion compensated applied thereto as second input signals, the second input signal corresponding to the selected first input signal; and

a demodulator for demodulating the output signal of said selector unit into a digital signal sequence.

8. A receiving apparatus according to claim 3, further comprising a filtering unit disposed between each of said channel frequency response calculating units and said distortion compensator, for filtering the channel frequency response calculated by each of said channel frequency response calculating units.

14. A receiving apparatus according to claim 3, further comprising:

a re-modulator for re-modulating the digital signal sequence demodulated by said demodulator and for generating a re-modulated frequency spectrum; and

a frequency spectrum selector for selectively outputting the re-modulated frequency spectrum or the reference frequency spectrum to said channel frequency response calculating units.

20. A receiving apparatus according to claim 3, wherein said selector unit comprises a plurality of synthesizers for synthesizing the amplitudes or the power of line spectra forming the first input signal, and a comparator for comparing outputs of said synthesizers, thereby performing a selecting operation based on a comparison result of said comparator.

26. A receiving apparatus according to claim 3, wherein said selector unit comprises a comparator for comparing, among line spectra forming the first input signal, the amplitude or the power of the line spectra of the same frequency, thereby performing a selecting operation based on a comparison result of said comparator.

4. A receiving apparatus comprising:

a plurality of receivers, each of said receivers for receiving an orthogonal frequency division multiplexing signal and outputting an orthogonal frequency division multiplexing received signal;

a plurality of transformers, each of said transformers for transforming the orthogonal frequency division multiplexing received signal from a corresponding one of the plurality of receivers into a orthogonal frequency division multiplexing received signal frequency spectrum;

at least one reference frequency spectrum generator for generating a reference frequency spectrum relative to the orthogonal frequency division multiplexing received signal;

a plurality of channel frequency response calculating units, each of said channel frequency response calculating units for calculating a channel frequency response in accordance with the frequency spectrum output from a corresponding one of the plurality of transformers and the reference frequency spectrum;

a distortion compensator for compensating for a distortion of the frequency spectrum output from each of said transformers by using the corresponding channel frequency response;

a selector unit for selecting, from among the channel frequency responses from said channel frequency response calculating units applied thereto as first input signals, the first input signals having a maximum amplitude or a maximum power, said outputting, from among the distortion compensated frequency spectra output from said distortion compensated applied thereto as second input signals, the second input signal corresponding to the selected first input signal; and

a demodulator for demodulating the output signal of said selector unit into a digital signal sequence.

9. A receiving apparatus according to claim 4, further comprising a filtering unit disposed between each of said channel frequency response calculating units and said distortion compensator, for filtering the channel frequency response calculated by each of said channel frequency response calculating units.

15. A receiving apparatus according to claim 4, further comprising:

a re-modulator for re-modulating the digital signal sequence demodulated by said demodulator and for generating a re-modulated frequency spectrum; and

a frequency spectrum selector for selectively outputting the re-modulated frequency spectrum or the reference frequency spectrum to said channel frequency response calculating units.

21. A receiving apparatus according to claim 4, wherein said selector unit comprises a plurality of synthesizers for synthesizing the amplitudes or the power of line spectra forming the first input signal, and a comparator for comparing outputs of said synthesizers, thereby performing a selecting operation based on a comparison result of said comparator.

27. A receiving apparatus according to claim 4, wherein said selector unit comprises a comparator for comparing, among line spectra forming the first input signal, the amplitude or the power of the line spectra of the same frequency, thereby performing a selecting operation based on a comparison result of said comparator.

5. A receiving apparatus comprising:

a plurality of receivers, each of said receivers for receiving an orthogonal frequency division multiplexing signal and outputting an orthogonal frequency division multiplexing received signal;

a plurality of transformers, each of said transformers for transforming the orthogonal frequency division multiplexing received signal from a corresponding one of the plurality of receivers into a orthogonal frequency division multiplexing received signal frequency spectrum;

at least one reference frequency spectrum generator for generating a reference frequency spectrum relative to the orthogonal frequency division multiplexing received signal;

a plurality of channel frequency response calculating units, each of said channel frequency response calculating units for calculating a channel frequency response in accordance with the frequency spectrum output from each of said transformers and the reference frequency spectrum;

a distortion compensator for compensating for a distortion of the frequency spectrum output from each of said transformers by using the corresponding channel frequency response;

a selector unit for selecting and outputting, from among the distortion-compensated frequency spectra output from said distortion compensator, the distortion-compensated frequency spectrum having a maximum amplitude or a maximum power; and

a demodulator for demodulating the output signal of said selector unit into a digital signal sequence.

10. A receiving apparatus according to claim 5, further comprising a filtering unit disposed between each of said channel frequency response calculating units and said distortion compensator, for filtering the channel frequency response calculated by each of said channel frequency response calculating units.

16. A receiving apparatus according to claim 5, further comprising:

a re-modulator for re-modulating the digital signal sequence demodulated by said demodulator and for generating a re-modulated frequency spectrum; and

a frequency spectrum selector for selectively outputting the re-modulated frequency spectrum or the reference frequency spectrum to said channel frequency response calculating units.

22. A receiving apparatus according to claim 5, wherein said selector unit comprises a plurality of synthesizers for synthesizing the amplitudes or the power of line spectra forming the first input signal, and a comparator for comparing outputs of said synthesizers, thereby performing a selecting operation based on a comparison result of said comparator.

28. A receiving apparatus according to claim 5, wherein said selector unit comprises a comparator for comparing, among line spectra forming the first input signal, the amplitude or the power of the line spectra of the same frequency, thereby performing a selecting operation based on a comparison result of said comparator.

6. A receiving apparatus comprising:

a plurality of receivers, each of said receivers for receiving an orthogonal frequency division multiplexing signal and outputting an orthogonal frequency division multiplexing received signal;

a plurality of transformers, each of said transformers for transforming the orthogonal frequency division multiplexing received signal from a corresponding one of the plurality of receivers into a orthogonal frequency division multiplexing received signal frequency spectrum;

at least one reference frequency spectrum generator for generating a reference frequency spectrum relative to the orthogonal frequency division multiplexing received signal;

a plurality of channel frequency response calculating units, each of said channel frequency response calculating units for calculating a channel frequency response in accordance with the frequency spectrum output from each of said transformers and the reference frequency spectrum;

a selector unit for selecting, in a case where the frequency spectra output from said transformers are determined as first input signals and where the channel frequency responses calculated by said channel frequency response calculating units are determined as second input signals, the first input signal having a maximum amplitude or a maximum power and the second input signal corresponding to the selected first input signal, said selector unit for outputting the selected first input signal and the selected second input signal as a first output signal and a second output signal, respectively;

a distortion compensator for compensating for a distortion of the first output signal of said selector unit by using the second output signal of said selector unit; and

a demodulator for demodulating the output signal of said distortion compensator into a digital signal sequence.

11. A receiving apparatus according to claim 6, further comprising a filtering unit disposed between each of said channel frequency response calculating units and said selector unit, for filtering the channel frequency response calculated by each of said channel frequency response calculating units.

17. A receiving apparatus according to claim 6, further comprising:

a re-modulator for re-modulating the digital signal sequence demodulated by said demodulator and for generating a re-modulated frequency spectrum; and

a frequency spectrum selector for selectively outputting the re-modulated frequency spectrum or the reference frequency spectrum to said channel frequency response calculating units.

23. A receiving apparatus according to claim 6, wherein said selector unit comprises a plurality of synthesizers for synthesizing the amplitudes or the power of line spectra forming the first input signal, and a comparator for comparing outputs of said synthesizers, thereby performing a selecting operation based on a comparison result of said comparator.

29. A receiving apparatus according to claim 6, wherein said selector unit comprises a comparator for comparing, among line spectra forming the first input signal, the amplitude or the power of the line spectra of the same frequency, thereby performing a selecting operation based on a comparison result of said comparator.

7. A receiving apparatus comprising:

a plurality of receivers, each of said receivers for receiving an orthogonal frequency division multiplexing signal and outputting an orthogonal frequency division multiplexing received signal;

a plurality of transformers, each of said transformers for transforming the orthogonal frequency division multiplexing received signal from a corresponding one of the plurality of receivers into a orthogonal frequency division multiplexing received signal frequency spectrum;

at least one reference frequency spectrum generator for generating a reference frequency spectrum relative to the orthogonal frequency division multiplexing received signal;

a plurality of channel frequency response calculating units, each of said channel frequency response calculating units for calculating a channel frequency response in accordance with the frequency spectrum output from each of said transformers and the reference frequency spectrum;

a selector unit for selecting, in a case where the channel frequency responses calculated by said channel frequency response calculating units are determined as first input signals and where the frequency spectra output from said transformers are determined as second input signals, the first input signal having a maximum amplitude or a maximum power and the second input signal corresponding to the selected first input signal, said selector unit for outputting the selected first input signal and the selected second input signal as a first output signal and a second output signal, respectively;

a distortion compensator for compensating for a distortion of the second output signal of said selector unit by using the first output signal of said selector unit; and

a demodulator for demodulating the output signal of said distortion compensator into a digital signal sequence.

12. A receiving apparatus according to claim 7, further comprising a filtering unit disposed between each of said channel frequency response calculating units and said selector unit, for filtering the channel frequency response calculated by each of said channel frequency response calculating units.

18. A receiving apparatus according to claim 7, further comprising:

a re-modulator for re-modulating the digital signal sequence demodulated by said demodulator and for generating a re-modulated frequency spectrum; and

a frequency spectrum selector for selectively outputting the re-modulated frequency spectrum or the reference frequency spectrum to said channel frequency response calculating units.

24. A receiving apparatus according to claim 7, wherein said selector unit comprises a plurality of synthesizers for synthesizing the amplitudes or the power of line spectra forming the first input signal, and a comparator for comparing outputs of said synthesizers, thereby performing a selecting operation based on a comparison result of said comparator.

30. A receiving apparatus according to claim 7, wherein said selector unit comprises a comparator for comparing, among line spectra forming the first input signal, the amplitude or the power of the line spectra of the same frequency, thereby performing a selecting operation based on a comparison result of said comparator.

31. A method for receiving a diversity signal for use in a radio communication system that uses an orthogonal frequency division multiplexing technique, said method comprising the steps of:

providing a plurality of diversity branches, each of said diversity branches including a receiver for receiving an orthogonal frequency division multiplexing signal via an antenna and outputting the orthogonal frequency division multiplexing received signal, a transformer for transforming the orthogonal frequency division multiplexing received signal into a frequency spectrum and outputting the orthogonal frequency division multiplexing received signal frequency spectrum, and a channel frequency response calculating unit for calculating a channel frequency response in accordance with the orthogonal frequency division multiplexing received signal frequency spectrum and a reference frequency spectrum; and

selecting the diversity branch that has generated the orthogonal frequency division multiplexing received signal frequency spectrum having a maximum amplitude or a maximum power.

32. A method for receiving a diversity signal for use in a radio communication system that uses an orthogonal frequency division multiplexing technique, said method comprising the steps of:

providing a plurality of diversity branches, each of said diversity branches including a receiver for receiving an orthogonal frequency division multiplexing signal via an antenna and outputting the orthogonal frequency division multiplexing received signal, a transformer for transforming the orthogonal frequency division multiplexing received signal into a frequency spectrum and outputting the orthogonal frequency division multiplexing received signal frequency spectrum, and a channel frequency response calculating unit for calculating a channel frequency response in accordance with the orthogonal frequency division multiplexing received signal frequency spectrum and a reference frequency spectrum; and

selecting the diversity branch that has generated the channel frequency response having a maximum amplitude or a maximum power.

33. A method for receiving a diversity signal for use in a radio communication system that uses an orthogonal frequency division multiplexing technique, said method comprising the steps of:

receiving an orthogonal frequency division multiplexing signal via an antenna and outputting the orthogonal frequency division multiplexing received signal;

transforming the orthogonal frequency division multiplexing received signal into a frequency spectrum;

generating a reference frequency spectrum relative to the orthogonal frequency division multiplexing received signal;

calculating a channel frequency response in accordance with the frequency spectrum and the reference frequency spectrum;

compensating for a distortion of the frequency spectrum by using the corresponding channel frequency response;

selecting and outputting, in a case where the frequency spectra are determined as first input signals and where the distortion-compensated frequency spectra are determined as second input signals, the second input signal corresponding to the first input signal having a maximum amplitude or a maximum power; and

demodulating the output signal of said selecting step into a digital signal sequence.

34. A method for receiving a diversity signal for use in a radio communication system that uses an orthogonal frequency division multiplexing technique, said method comprising the steps of:

receiving an orthogonal frequency division multiplexing signal via an antenna and outputting the orthogonal frequency division multiplexing received signal;

transforming the orthogonal frequency division multiplexing received signal into a frequency spectrum;

generating a reference frequency spectrum relative to the orthogonal frequency division multiplexing received signal;

calculating a channel frequency response in accordance with the frequency spectrum and the reference frequency spectrum;

compensating for a distortion of the frequency spectrum by using the corresponding channel frequency response;

selecting and outputting, in a case where the channel frequency responses are determined as first input signals and where the distortion-compensated frequency spectra are determined as second input signals, the second input signal corresponding to the first input signal having a maximum amplitude and/or a maximum power; and

demodulating the output signal of said selecting step into a digital signal sequence.

35. A method for receiving a diversity signal for use in a radio communication system that uses an orthogonal frequency division multiplexing technique, said method comprising the steps of:

receiving an orthogonal frequency division multiplexing signal via an antenna and outputting the orthogonal frequency division multiplexing received signal;

transforming the orthogonal frequency division multiplexing received signal into a frequency spectrum;

generating a reference frequency spectrum relative to the orthogonal frequency division multiplexing received signal;

calculating a channel frequency response in accordance with the frequency spectrum and the reference frequency spectrum;

compensating for a distortion of the frequency spectrum by using the corresponding channel frequency response;

selecting and outputting, among the distortion-compensated frequency spectra, the distortion-compensated frequency spectrum having a maximum amplitude or a maximum power; and

demodulating the output signal of said selecting step into a digital signal sequence.

36. A method for receiving a diversity signal for use in a radio communication system that uses an orthogonal frequency division multiplexing technique, said method comprising the steps of:

receiving an orthogonal frequency division multiplexing signal via an antenna and outputting the orthogonal frequency division multiplexing received signal;

transforming the orthogonal frequency division multiplexing received signal into a frequency spectrum;

generating a reference frequency spectrum relative to the orthogonal frequency division multiplexing received signal;

calculating a channel frequency response in accordance with the frequency spectrum and the reference frequency spectrum;

selecting, in a case where the frequency spectra are determined as first input signals and where the channel frequency responses are determined as second input signals, the first input signal having a maximum amplitude or a maximum power and the second input signal corresponding to the selected first input signal, and outputting the selected first input signal and the selected second input signal as a first output signal and a second output signal, respectively;

compensating for a distortion of the first output signal by using the second output signal; and

demodulating the output signal of said compensating step into a digital signal sequence.

37. A method for receiving a diversity signal for use in a radio communication system that uses an orthogonal frequency division multiplexing technique, said method comprising the steps of:

receiving an orthogonal frequency division multiplexing signal via an antenna and outputting the orthogonal frequency division multiplexing received signal;

transforming the orthogonal frequency division multiplexing received signal into a frequency spectrum;

generating a reference frequency spectrum relative to the orthogonal frequency division multiplexing received signal;

calculating a channel frequency response in accordance with the frequency spectrum and the reference frequency spectrum;

selecting, in a case where the channel frequency responses are determined as first input signals and where the frequency spectra are determined as second input signals, the first input signal having a maximum amplitude or a maximum power and the second input signal corresponding to the selected first input signal, and outputting the selected first input signal and the selected second input signal as a first output signal and a second output signal, respectively;

compensating for a distortion of the second output signal by using the first output signal; and

demodulating the output signal of said compensating step into a digital signal sequence.