Partial decorrelation for a coherent multicode code division multiple access receiver

• US 6,201,799 B1
• Filed: 05/01/1997
• Issued: 03/13/2001
• Est. Priority Date: 05/01/1997
• Status: Expired due to Term

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: I, Chih-Lin, Huang, Howard C.
• Primary Examiner(s): Patel, Ajit
• Assistant Examiner(s): Nguyen, Brian
• Application Number:
  US08/846,454
• Time in Patent Office: 1,412 Days
• Field of Search: 370/342, 370/335, 370/328, 370/441, 370/320, 375/346, 375/343, 375/340, 375/341, 375/342, 375/347, 375/348, 375/349, 375/200, 375/208, 375/209, 375/210
• US Class Current: 370/342
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 1/71052 using decorrelation matrix
• CPC Class Codes: H04B 1/7107 Subtractive interference cancellation
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers

Abstract

A Multicode (MC) Code Division Multiple Access (CDMA) receiver receives J encoded multicode channels (where J>1) over L multiple air signal paths (where L>1) and forms a decorrelator output vector in which for each of the J multicode channels, the interference caused by the other J−1 multicode channels has been cancelled. When the MC CDMA receiver is a coherent receiver, a pilot interference canceller cancels a received pilot signal from the J channel code of each of the received J multicode channels prior to forming the decorrelator output vector.

Claims

1. A multiple-code (MC) code division multiple access (CDMA) receiver for simultaneously receiving and demodulating J data signals within a CDMA signal, where J is an integer, J>

1, and where the jth data signal, j=1 . . . J, is received over a plurality of L_j paths where L_j is an integer, L_j≧

1, the MC-CDMA receiver comprising

means for receiving the J data signals, and forming therefrom L_j multipath delay estimates and L_j channel estimates for the jth data signal,

means for demodulating L_j multipath components of the jth data signal and combining the results to form J decision statistics for the J data signals,

a decorrelator, responsive to the L, L=L₁+L₂+ . . . +L_J, channel estimates, the L multipath delays and the J data-signal codes, for suppressing, for a desired received data signal, interference caused by the other J−

1 data signals; and

a processor for producing therefrom the desired demodulated data signal.

2. The MC-CDMA receiver of claims 1 wherein

the interference suppression means includes means for forming a J-by-J inverse correlation matrix M^{− 1} from the J decision statistics.

3. The MC-CDMA receiver of claim 2 wherein

the M⁻

1 matrix forming means is approximated using a U₁ matrix.

4. The MC-CDMA receiver of claim 2 wherein

the M⁻

1 matrix forming means is approximated using a U₂ matrix.

5. The MC-CDMA receiver of claims 1 wherein

the received signal includes a separate pilot signal transmitted over the same channel as the desired data signal.

6. The MC-CDMA receiver of claim 5 wherein

the path demodulator means includes a pilot interference canceller for cancelling interference due to undesired pilot multipath components.

7. The pilot interference canceller of claims 5 including

a switch means in each path demodulator to switch on/off the pilot cancellation according to the path power of its designated multipath component.

8. The MC-CDMA receiver of claims 5 wherein

the received signal consisting of at least the J data signals and a pilot signal is transmitted from a common transmitter, so that L₁=L₂= . . . =L_J, and wherein

the receiving means is implemented using L₁ fat fingers, each fat finger having one pilot path demodulator and a plurality of J data-signal path demodulators.

9. The MC-CDMA receiver of claims 1 wherein

the received signal consisting of at least the J data signals is transmitted from a common transmitter.

10. The MC-CDMA receiver of claims 1 being part of a user station of a CDMA system including at least one base station and a plurality of user stations.

11.The MC-CDMA receiver of claims 1 being part of a base station of a CDMA system including at least one base station and a plurality of user stations.

11. The MC-CDMA receiver of claims 1 wherein

the processor means includes a Viterbi decoder to produce the desired demodulated data signal.

13. The method of claim 13 wherein the forming step uses a U₁ matrix to approximate the M⁻

1 matrix.

12. A method of operating a multiple-code (MC) code division multiple access (CDMA) receiver for simultaneously receiving and demodulating J data signals within a CDMA signal, where J is an integer, J>

1, and where the jth data signal, j=1 . . . J, is received over a plurality of L_j paths where L_j is an integer, L_j≧

1, the method comprising steps of

receiving the J data signals, and forming therefrom L_j multipath delay estimates and L_j channel estimates for the jth, j=1 to J, data signal,

demodulating L_j multipath components of the jth data signal and combining the results to form J decision statistics for the J data signals,

at a decorrelator, responsive to the L, L=L₁+L₂+ . . . +L_J, channel estimates, the L multipath delays and the J data-signal codes, suppressing, for a desired received data signal, interference caused by the other J−

1 data signals; and

at a processor, producing therefrom the desired demodulated data signal.

14.The method of claim 13 further including the step of;

forming a J-by-J inverse correlation matrix M<sup>−

1</sup> from the J decision statistics.

14. The method of claim 13 wherein the forming step uses a U₂ matrix to approximate the M⁻

1 matrix.

15. The method of claim 13 wherein the received signal includes a separate pilot signal transmitted over the same channel as the desired data signal.