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

• US 6,628,638 B1
• Filed: 01/07/1999
• Issued: 09/30/2003
• Est. Priority Date: 01/08/1998
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Sato, Kazumi, Namekata, Minoru
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): LOGSDON, JOSEPH B
• Application Number:
  US09/226,721
• Time in Patent Office: 1,727 Days
• Field of Search: 370/310, 370/315, 370/343, 370/480, 370/492, 370/913, 379/338, 379/339, 379/398
• 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 channel frequency response having a maximum amplitude or a maximum power.

2. A receiving apparatus according to claim 1, 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.

3. A receiving apparatus according to claim 1, wherein said selector unit comprises a plurality of synthesizers for synthesizing amplitudes or power of line spectra forming 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.

4. A receiving apparatus according to claim 1, wherein said selector unit comprises a comparator for comparing, among line spectra forming 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.

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 a corresponding one of the plurality of transformers and the reference 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 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, and from among distortion compensated frequency spectra output from said distortion compensators applied thereto as second input signals, the second input signals correspond to the selected first input signals; and

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

6. 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 compensators, for filtering the channel frequency responses calculated by each of said channel frequency response calculating units.

7. 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.

8. A receiving apparatus according to claim 5, 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.

9. A receiving apparatus according to claim 5, 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.

10. 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.

11. 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 suing the corresponding channel frequency response;

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

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