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

• US 7,266,108 B2
• Filed: 10/17/2002
• Issued: 09/04/2007
• Est. Priority Date: 01/08/1998
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Sato, Kazumi, Namekata, Minoru
• Primary Examiner(s): Jung; Min
• Application Number:
  US10/271,546
• Publication Number:
  US 20030058786A1
• Time in Patent Office: 1,783 Days
• Field of Search: 370/343, 370/480, 370/492, 370/310, 370/315, 370/203, 379/347, 375/347
• US Class Current: 370/343
• 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

A diversity receiving apparatus for use in an OFDM transmission radio communication/broadcasting system where OFDM signals are received by a plurality of antennas and input into a plurality of receivers. The OFDM received signals are further transformed into frequency spectra. Channel frequency responses are calculated by using OFDM received signal frequency spectra and a reference frequency spectrum generated in a reference spectrum generator. OFDM received signal frequency spectra distortions are compensated by using corresponding channel frequency responses. The transformed OFDM received signal frequency spectra 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 a second input signal corresponding to a first input signal having maximum amplitude or 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 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 plurality of distortion compensators 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 frequency spectra output from said transformer applied thereto as first input signals, the first input signals having a maximum amplitude or a maximum power, and from among distortion compensated frequency spectra output from said distortion compensators applied thereto as second input signals, the second input signals correspond to selected first input signals; and

a demodulator for demodulating an output signal of said selector unit into a digital frequency response having a maximum amplitude or a maximum power.

3. A receiving apparatus according to claim 2, further comprising a filtering unit disposed between each of said channel frequency response calculating units and said distortion compensators, for filtering the channel frequency responses calculated by each of said channel frequency response calculating units.

4. 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.

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

6. A receiving apparatus according to claim 2, wherein said selector unit comprises a comparator for comparing, among line spectra forming the first input signals, amplitude or power of 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 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 plurality of distortion compensators 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 distortion-compensated frequency spectra outputs from said distortion compensators, the distortion-compensated frequency spectrum having a maximum amplitude or a maximum power; and

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

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

9. 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.

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

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

12. A receiving apparatus comprising:

a plurality of receivers, each of said receivers for receiving an orthogonal frequency division multiplexing signal 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 frequency spectra output from said transformed are determined as first input signals and where channel frequency responses calculated by said channel frequency response calculating units are determined as second input signals, the first input signals having a maximum amplitude or a maximum power and the second input signals correspond to a selected first input signal, said selector unit for outputting the selected first input signal and a selected second input signal as a first output signal and a second output signal, respectively;

distortion compensators 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 an output signal of said distortion compensators into a digital sequence.

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

14. A receiving apparatus according to claim 12, 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.

15. A receiving apparatus according to claim 12, wherein said selector unit comprises a plurality of synthesizers for synthesizing amplitudes or power of line spectra forming the first input signals, and a comparator for comparing outputs of said synthesizers, thereby performing a selecting operation based on a comparison result of said comparator.

16. A receiving apparatus according to claim 12, wherein said selector unit comprises a comparator for comparing, among line spectra forming the first input signals, amplitude or power of line spectra of the same frequency, thereby performing a selecting operation based on a comparison result of said comparator.

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

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

a demodulator for demodulating an output signal of said distortion compensators into a digital signal sequence.

18. A receiving apparatus according to claim 17, further comprising a filtering unit disposed between each of said channel frequency response calculating units and said selector unit, for filtering the channel frequency responses calculated by each of said channel frequency response calculating units.

19. A receiving apparatus according to claim 17, 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 17, wherein said selector unit comprises a plurality of synthesizers for synthesizing amplitudes or power of line spectra forming the first input signals, and a comparator for comparing outputs of said synthesizers, thereby performing a selecting operation based on a comparison result of said comparator.

21. A receiving apparatus according to claim 17, wherein said selector unit comprises a comparator for comparing, among line spectra forming the first input signals, amplitude or power of line spectra of the same frequency, thereby performing a selecting operation based on a comparison result of said comparator.

22. 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.

23. 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 step 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 channel frequency responses in accordance with the frequency spectrum and the reference frequency spectrum;

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

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

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

24. 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 channel frequency responses in accordance with the frequency spectrum and the reference frequency spectrum;

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

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

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

25. 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 receiving 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 receiving signal;

calculating channel frequency responses in accordance with the frequency spectrum and the reference frequency spectrum;

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

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

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

26. 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 receiving signal into a frequency spectrum;

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

calculating channel frequency responses 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 frequency spectra are determined as second input signals, wherein the first input signals having a maximum amplitude or a maximum power and the second input signals correspond to a selected first input signal and a selected second input signal as a first output signal and a second output signal, respectively;

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

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