Receiving method and receiver

• US 6,011,812 A
• Filed: 04/24/1996
• Issued: 01/04/2000
• Est. Priority Date: 08/25/1994
• Status: Expired due to Term

• Current Assignee: RPX Corporation
• Original Assignee: Nokia Telecommunications Oy (Nokia Corporation)
• Inventors: Laakso, Timo, Hottinen, Ari
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): Tran, Khai
• Application Number:
  US08/632,416
• Time in Patent Office: 1,350 Days
• Field of Search: 375/208, 375/205, 375/206, 375/200, 375/207, 370/342, 370/335, 370/320, 370/441, 370/213, 370/239, 455/504
• US Class Current: 375/152
• CPC Class Codes: H04B 1/71052 using decorrelation matrix

Abstract

A receiving method and a receiver in a data transmission system in which CDMA multiple access is applied, the receiver having a decorrelating detector. In order that the receiver can function effectively both in the event of multiuser interference and on a multipath channel, the decorrelating detector of the receiver has separate equalizers for equalizing the effect of the multipath channel in the received signal, and filters matched with the codes contained in the received signal, and multipliers for multiplying the received signal by the inverse matrix of the cross-correlation matrix of the codes contained in the received signal.

Claims

1. A method for receiving in a data transmission system in which code division multiple access involving multipath propagation of signals each as respective signal components which are mutually out of phase by temporally varying amounts, and multiuser interference among respective signals, each signal communicating a succession of symbols translated into bits and transmitted at a rate of a plurality of chips per bit, spread by a respective spreading code is applied for detecting a particular received signal, from among a plurality of received signals, said code division multiple access using long codes, comprising:

equalizing effects of multipath signal component propagation on the received signal using an equalizer provided as a distinct functional element in a decorrelating detector to obtain an equalized signal which remains affected by multiuser interference and providing first samples thereof at a rate of at least one sample per chip;

detecting from said first samples said equalized signal in said decorrelating detector and providing second samples thereof at a symbol rate; and

decorrelating said equalized signal from said second samples, using a cross-correlation matrix.

2. The receiving method according to claim 1, further comprising:

implementing said equalizer by using adaptive filters, said adaptive filters including;

filter equalizing multipath channel effects, providing output samples at said rate of at least one sample per chip; and

code matched filtering filter output and said spreading codes, and correlating said code matched filtered output using said cross-correlation matrix of said despread symbols.

3. The receiving method according to claim 1, further comprising:

subjecting the equalized signal to interference cancellation after performing said decorrelating.

4. The receiving method according to claim 1, wherein:

said equalizing includes equalizing said effects in said particular received signal using as said equalizer a different equalizer than respective equalizers used for providing equalizing in regard to others of said plurality of received signals.

5. The receiving method according to claim 1, wherein:

said plurality of received signals comprises transmissions from a plurality of asynchronous users, further comprising;

updating said cross-correlation matrix based on mutual delays of the respective ones of said transmissions as received, wherein said cross-correlation matrix is a correlation matrix of said transmitted signals.

6. The receiving method according to claim 1, comprising:

practicing said decorrelating in a receiver which has multiple stages such that said decorrelating detector is followed in said receiver by other detector stages, wherein said decorrelating detector functions at said symbol rate.

7. A receiving method in a cellular radio system for signals for data transmission in which code division multiple access using long codes is used, comprising:

multiplying cellular radio system data transmission signals of each of a plurality of users, by a respective, different spreading code;

equalizing the effect of multipath signal component propagation in the respective multiplied signals as received in a receiver to obtain respective equalized signals;

supplying the equalized signals to filters matched with the spreading codes which were used for multiplying the respective signals, to obtain respective output signals;

forwarding the output signals of said filters to multipliers, and therein multiplying the respective output signals by an inverse matrix of said spreading codes used to obtain respective multiplied signals; and

subjecting the multiplied signals to multi-user interference cancellation and estimation of received bits.

8. A receiver in a data transmission system in which code division multiple access involving multipath propagation of signals each as respective signal components which are mutually out of phase by temporally varying amounts, and multiuser interference among respective signals, each signal communicating a succession of symbols translated into bits and transmitted at a rate of a plurality of chips per bit, spread by a respective spreading code is applied for detecting a particular received signal, from among a plurality of received signals spread according to respective spreading codes having a cross-correlation matrix, said code division multiple access using long codes, comprising:

a decorrelating detector including an equalizer which equalizes effects of multipath signal component propagation in said signals received by said receiver, to provide for each of said received signals a respective equalized signal which remains affected by multiuser interference and first samples of each respective equalized signal at a rate of at least one sample per chip;

filters matched with codes contained in the respective equalized signals;

a multiplier which multiplies the respective equalized signals by an inverse matrix of the cross-correlation matrix of the codes contained in the respective received signals, to obtain respective decorrelated equalized signals; and

said detector including another detector which detects said particular received signal from symbol rate samples of said decorrelated equalized signals.

9. The receiver according to claim 8, wherein:

said equalizer is a plurality of adaptive filters.

10. The receiver according the claim 8, wherein:

said multiplier is arranged to be implemented on a one-shot principle.

11. The receiver according to claim 8, further comprising:

a signal processor, located after said multiplier, which processes said signals, said signal processor being arranged to subject said decorrelated equalized signals to multi-user interference cancellation and detection.

12. The receiver according to claim 8, wherein:

said receiver has multiple stages of which said decorrelating detector is a first stage.

13. The receiver according to claim 8, wherein:

said decorrelating detector comprises a bank of matched filters providing an output signal for each said equalized signal;

each said filter bank comprises a respective correlator for each said signal component; and

said decorrelating detector comprises another multiplier which multiplies said output signals of the matched filters by the inverse matrix of the cross-correlation matrix of the codes contained in the received signal components, a signal comb which combs the signal components, and a detector which detects the signal components.