Reception timing detection circuit of CDMA receiver and detection method

• US 5,982,763 A
• Filed: 07/14/1997
• Issued: 11/09/1999
• Est. Priority Date: 07/15/1996
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Sato, Toshifumi
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): Qureshi, Afsar M.
• Application Number:
  US08/892,497
• Time in Patent Office: 848 Days
• Field of Search: 370/335, 370/342, 370/490, 375/200, 375/207, 375/208, 375/210, 375/224, 455/67.1
• US Class Current: 370/342
• CPC Class Codes: H04B 1/70757 with increased resolution, i.e. higher than half a chip H04B1/70758 takes precedence
• CPC Class Codes: H04B 1/70775 Multi-dwell schemes, i.e. multiple accumulation times
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception

Abstract

A reception timing detection circuit of a CDMA receiver comprises an A/D converter 101 for obtaining a digital reception signal S, a correlator 102 for obtaining a cross-correlation between the digital reception signal S and a known signal series periodically within a predetermined lag, an interpolation filter 103 for re-sampling the signal R output from the correlator 102 at a frequency higher than a sampling frequency for the A/D converter 101, a power calculation section 104 for obtaining the re-sampled cross-correlation signal power P, an averaging section 105 for averaging the cross-correlation signal power P over a plurality of cycles, and a peak detection section 106 for obtaining a peak Popt of the averaged cross-correlation signal power P and determining an optimum reception timing τ opt.

Claims

1. A reception timing detection circuit of a CDMA receiver used for a mobile communication system using a direct spread code division multiple access method comprising:

correlation means for obtaining a cross-correlation between a reception signal and a known signal series periodically within a predetermined lag and outputting a cross-correlation signal indicating said obtained cross-correlation;

an interpolation filter for re-sampling said cross-correlation signal at a frequency higher than a sampling frequency for said cross-correlation signal and outputting said re-sampled cross-correlation signal;

power calculation means for calculating power of said re-sampled cross-correlation signal;

averaging means for averaging said calculated power of cross-correlation signal over a plurality of cycles; and

peak detection means for detecting a peak of said averaged power of cross-correlation signal and determining a timing at which said peak is detected as a reception timing.

2. The reception timing detection circuit of a CDMA receiver of claim 1, wherein said known signal series is obtained by spreading a known pilot symbol inserted to said reception signal at predetermined period with a spread code.

3. The reception timing detection circuit of a CDMA receiver of claim 1, wherein said known signal series is obtained by re-spreading a signal series produced by de-spreading said reception signal with a spread code.

4. The reception timing detection circuit of a CDMA receiver of claim 1, wherein said correlation means comprises a matched filter that matches a series produced by spreading a known signal series with a spread code and time window means that allows a signal output from said matched filter to pass through within a predetermined period only.

5. The reception timing detection circuit of a CDMA receiver of claim 1, wherein a cycle of a spread code is equivalent to that of a pilot symbol and said correlation means comprises:

a first memory of a serial input parallel output type for storing a reception signal for a period obtained by adding 1 symbol time length of said pilot symbol to a time length of a predetermined period;

demodulating means for demodulating a parallel output of said first memory based on a pilot symbol code;

coherent adder means for coherent adding said demodulated reception signals over a plurality of pilot symbols; and

a correlator for obtaining a cross-correlation between said coherent added reception signal and a spread code within a predetermined period.

6. The reception timing detection circuit of a CDMA receiver of claim 1, wherein said correlation means comprises:

a first memory for storing a reception signal for a period obtained by adding a time length of a pilot symbol series to a time length of a predetermined period;

a second memory for storing a spread code corresponding to a pilot symbol;

a correlator for obtaining a cross-correlation at each symbol by reading a reception signal and a spread code from said first memory and said second memory;

demodulating means for demodulating a correlation value output from said correlator based on a pilot symbol code;

coherent adder means for accumulation adding said demodulated correlation signals over a plurality of pilot symbols; and

timing control means for controlling a reception timing so that a pilot symbol is contained in a reception signal stored in said first memory and controlling a timing for reading said first memory and second memory until all cross-correlations are obtained within a predetermined period.

7. The reception timing detection circuit of a CDMA receiver of claim 1, wherein said correlation means comprises:

a first memory for storing a reception signal for a period obtained by adding a time length of a pilot symbol series to a time length of a predetermined period;

spreading means for spreading a pilot symbol with a spread code;

a second memory for storing said pilot symbol spread by said spread means;

a correlator for reading a reception signal and a spread pilot symbol from said first memory and said second memory, respectively and obtaining a cross-correlation; and

timing control means for controlling a reception timing so that a pilot symbol is contained in a reception signal stored in said first memory and controlling a timing for reading said first memory and said second memory until all cross-correlations are obtained within a predetermined period.

8. The reception timing detection circuit of a CDMA receiver of claim 1, wherein said correlation means further comprises means for obtaining a cross-correlation within a time corresponding to the time required for electric wave to propagate between a base station and a mobile station and outputting a cross-correlation signal indicating said obtained cross-correlation.

9. The reception timing detection circuit of a CDMA receiver of claim 1, wherein said interpolation filter operates in a segment where power of a cross-correlation value output from said correlation means exceeds a predetermined threshold value.

10. A reception timing detection circuit of a CDMA receiver used for a mobile communication system using a direct spread code division multiple access method comprising:

an A/D converter for converting a reception signal into a digital reception signal;

a matched filter for matching a signal series produced by spreading a pilot symbol with a spread code, obtaining a cross-correlation between said signal series and said digital reception signal and outputting a cross-correlation signal;

time window means for allowing said cross-correlation signal output from said matched filter to pass through within a delay range only;

an interpolation filter for re-sampling said cross-correlation signal at a frequency higher than a sampling frequency for a cross-correlation signal that has passed through said time window means and outputting said re-sampled cross-correlation signal;

power calculation means for calculating power of said re-sampled cross-correlation signal;

averaging means for averaging said calculated power of cross-correlation signal over a plurality of cycles; and

peak detection means for detecting a peak of said averaged power of cross-correlation signal and determining a timing when said peak is detected as a reception timing.

11. A reception timing detection circuit of a CDMA receiver used for a mobile communication system using a direct spread code division multiple access method comprising:

an A/D converter for converting a reception signal into a digital reception signal;

a first memory of a serial input parallel output type for storing said digital reception signal for a period obtained by adding 1 symbol time length of a pilot symbol to a time length of a predetermined period;

demodulating means for demodulating a parallel output of said first memory based on a pilot symbol code;

coherent adder means for coherent adding said demodulated reception signal over a plurality of pilot symbols;

a correlator for obtaining a cross-correlation between said coherent added reception signal and a spread code and outputting a cross-correlation signal;

an interpolation filter for re-sampling said cross-correlation signal at a frequency higher than a sampling frequency for said cross-correlation signal and outputting said re-sampled cross-correlation signal;

power calculation means for calculating said power of re-sampled cross-correlation signal,

averaging means for averaging said calculated power of cross-correlation over a plurality of cycles; and

peak detection means for detecting a peak of said averaged power of cross-correlation signal and determining a timing when said peak is detected as a reception timing.

12. A reception timing detection circuit of a CDMA receiver for a mobile communication system using a direct spread code division multiple access method comprising:

an A/D converter for converting a reception signal into a digital reception signal;

a first memory for storing said digital reception signal for a period obtained by adding a time length of a pilot symbol series to a time length of a predetermined period;

a second memory for storing a spread code corresponding to a pilot symbol;

a correlator for obtaining a cross-correlation at each symbol by reading a reception signal and a spread code from said first memory and said second memory, respectively;

demodulating means for demodulating a correlation value output from said correlator conforming to a pilot symbol code;

coherent adder means for accumulation adding said demodulated correlation values over a plurality of pilot symbols and outputting a cross-correlation signal;

timing control means for controlling a reception timing so that a pilot symbol is contained in said reception signal stored in said first memory and controlling a timing for reading said first memory and said second memory;

an interpolation filter for re-sampling said cross-correlation signal at a frequency higher than a sampling frequency for said cross-correlation signal and outputting said re-sampled signal;

power calculation means for calculating power of said re-sampled cross-correlation;

averaging means for averaging said calculated power of cross-correlation signal over a plurality of cycles; and

peak detection means for detecting a peak of said averaged power of cross-correlation signal and determining a timing when said peak is detected as a reception timing.

13. A reception timing detection circuit of a CDMA receiver used for a mobile communication system using a direct spread code division multiple access method comprising:

an A/D converter for converting a reception signal into a digital reception signal;

a first memory for storing said digital reception signal for a period obtained by adding a time length of a pilot symbol series to a time length of a predetermined period;

spread means for spreading a pilot symbol with said spread means;

a second memory for storing a pilot symbol spread with said spread means;

a correlator for obtaining a cross-correlation by reading a reception signal and a spread pilot symbol from said first memory and said second memory, respectively and outputting a cross-correlation signal;

timing control means for controlling a reception timing so that a pilot symbol is contained in said reception signal stored in said first memory and controlling a timing for reading said first memory and said second memory;

an interpolation filter for re-sampling said cross-correlation signal at a frequency higher than a sampling frequency for said cross-correlation signal and outputting said re-sampled signal;

power calculation means for calculating power of said re-sampled cross-correlation signal;

averaging means for averaging said calculated power of cross-correlation signal over a plurality of cycles; and

peak detection means for detecting a peak of said averaged power of cross-correlation signal and determining a timing when said peak is detected as a reception timing.

14. A method of detecting a reception timing of a CDMA receiver for a mobile communication system using a direct spread code division multiple access method comprising the steps of:

obtaining a cross-correlation value between a reception signal and a known signal series periodically within a predetermined lag;

re-sampling said cross-correlation value at a frequency higher than a sampling frequency for said obtained cross-correlation value;

calculating power of said re-sampled cross-correlation value;

averaging said calculated power of cross-correlation value over a plurality of cycles; and

detecting a peak of said averaged power of cross-correlation value and determining a timing when said peak is detected as a reception timing.

15. The method of detecting a reception timing of a CDMA receiver of claim 14, wherein said known signal series is obtained by spreading a known pilot symbol inserted to said reception signal at a predetermined period with a spread code.

16. The method of detecting a reception timing of a CDMA receiver of claim 14, wherein said known signal series is obtained by re-spreading said signal series resulted from de-spreading said reception signal with a spread code.