Code division multiple access communication with enhanced multipath diversity

• US 6,373,832 B1
• Filed: 07/02/1998
• Issued: 04/16/2002
• Est. Priority Date: 07/02/1998
• Status: Expired due to Term

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Vannucci, Giovanni, Mailaender, Laurence Eugene, Huang, Howard C.
• Primary Examiner(s): Marcelo, Melvin
• Assistant Examiner(s): Kwoh, Jasper
• Application Number:
  US09/108,775
• Time in Patent Office: 1,384 Days
• Field of Search: 370/334, 370/335, 370/342, 370/414, 370/479, 375/221, 375/267, 375/299, 375/349, 455/88, 455/68, 455/69-500, 455/504, 455/506, 455/65, 455/70, 455/78, 455/562, 455/101
• US Class Current: 370/342
• CPC Class Codes: H04B 7/0671 using different delays between antennas

Abstract

A system, a transceiver, and methods for code division multiple access (CDMA) communication. The system includes first and second code division multiple access transceivers. The first code division multiple access transceiver has a plurality antennas disposed to provide transmission via a plurality of paths and the second code division multiple access transceiver has a rake arrangement for processing a plurality of signals received at the rake arrangement with differing delays or other characteristics. A driving arrangement is provided for causing the first code division multiple access transceiver to use a relative few, e.g., one, of the plurality of antennas. When, however, an indication is obtained that an adequate number of resolvable signals are likely not received at the rake arrangement of the second transceiver, a circuit switches the driving arrangement to cause the first transceiver to use more of the plurality of antennas. In one implementation, the second transceiver sends a feedback signal indicating the number of useful signals being received and the first transceiver responds to the feedback signal by selecting and using a desirable number of transmit antennas. In an implementation suitable for a time-division duplexing (TDD) communication system, the first transceiver obtains the indication by inference from the fact that it is not receiving an adequate plurality of resolvable signals from the second transceiver. When the first transceiver obtains the indication, it drives the increased number of antennas either with respective delays or with different codes of the CDMA type.

Claims

1. A code division multiple access communication system, comprising:

first and second code division multiple access transceivers employing multipath diversity, the first code division multiple access transceiver having a plurality of antennas disposed to provide transmission via a plurality of paths, the second code division multiple access transceiver having a rake arrangement for processing a plurality of versions of a signal received at the rake arrangement with differing delays or differing other characteristics;

means for operating said first code division multiple access transceiver to use a subset of the plurality of antennas in the absence of an indication that an adequate plurality of resolvable multipath versions of the signal are not received at the rake arrangement of the second code division multiple access transceiver; and

means for switching said first code division multiple access transceiver to use more of the plurality of antennas when an indication is obtained that an adequate plurality of resolvable multipath versions of the signal are not received at the rake arrangement of the second code division multiple access transceiver, said switching means comprising means for providing a feedback signal from the second code division multiple access transceiver to the first code division multiple access transceiver to provide the indication that the adequate plurality of resolvable multipath versions of the signal are not received at the rake arrangement of the second code division multiple access transceiver.

2. The code division multiple access communication system according to claim 1, wherein the first code division multiple access transceiver is a base station transceiver and the second code division multiple access transceiver is a mobile transceiver.

3. The code division multiple access communication system according to claim 2, further including means for driving the plurality of antennas of the base station transceiver with respective delays.

4. The code division multiple access communication system according to claim 2, further including means for driving the plurality of antennas of the base station transceiver with respective spreading codes.

5. A transceiver for code division multiple access communication, comprising:

on the transmitter side of the transceiver, a plurality of antennas disposed to provide transmission using a plurality of paths to provide multipath diversity;

on the receiver side of the transceiver, a demodulator and demultiplexer for signals received from a remote transceiver;

means for operating the transmitter side of the transceiver to use a subset of the plurality of antennas in the absence of an indication that an adequate plurality of resolvable multipath signal versions are not received at the remote transceiver; and

means for switching the transceiver to use at least one more antenna of the plurality of antennas than is used in said subset when an indication is obtained that an adequate plurality of resolvable multipath signal versions are not received at the remote transceiver, comprising means for responding to a feedback signal from the remote transceiver providing the indication that an adequate plurality of resolvable multipath signal versions are not received at the remote transceiver.

6. The transceiver according to claim 5 that is a base station transceiver.

7. The transceiver according to claim 6, wherein the means for responding to the feedback signal from the remote transceiver comprises an adaptive splitter and normalizer connected from the demodulator and demultiplexer to the plurality of antennas.

8. The transceiver according to claim 6, further including, on its receiver side, a plurality of antennas, and wherein the demodulator is a rake demodulator-combiner connecting the plurality of antennas on its receiver side to the demultiplexer for diversity reception.

9. The transceiver according to claim 8, wherein the means for switching the transceiver comprises, on the transmitter side, an adaptive splitter and normalizer connected to the plurality of antennas.

10. The transceiver according to claim 5, further including means for driving the plurality of antennas with respective delays.

11. The transceiver according to claim 5, further including means for driving the plurality of antennas with respective spreading codes.

12. A method for operating first and second transceivers for code division multiple access communication, the first transceiver having on the transmitter side of the transceiver a plurality of antennas disposed to provide transmission employing multipath diversity using a plurality of paths and, on the receiver side of the transceiver, a demodulator and demultiplexer for signals received from the second transceiver, comprising the steps of:

operating the transmitter side of the first transceiver to use a subset of the plurality of antennas in the absence of an indication that a signal transmitted from the transmitter side does not provide an adequate plurality of resolvable multipath signal versions at the second transceiver; and

switching the transmitter side of the first transceiver to use more of the plurality of antennas when an indication is obtained that the signal transmitted from the transmitter side does not provide an adequate plurality of resolvable multipath signal versions at the second transceiver, comprising the step of responding to a feedback signal from the second transceiver providing the indication that the second transceiver is not receiving the adequate plurality of resolvable multipath signal versions.

13. The method of operating first and second transceivers according to claim 12, wherein the first transceiver is operated as a base station transceiver, the second transceiver being operated as a mobile transceiver.

14. The method of operating first and second transceivers according to claim 13, wherein the step of responding to a signal from the second transceiver comprises adaptively splitting and normalizing a modulated data signal for transmission from the plurality of antennas.

15. The method of operating first and second transceivers according to claim 13, further including the step of providing diversity reception for signals from the second transceiver.

16. The method of operating a transceiver according to claim 12, further including the step of driving the plurality of antennas with respective delays.

17. The method of operating first and second transceivers according to claim 12, further including the step of driving the plurality of antennas with respective spreading codes.

18. A method for operating a code division multiple access communication system including first and second code division multiple access transceivers, the first code division multiple access transceiver having a transmitter side having a plurality antennas disposed to provide transmission employing multipath diversity via a plurality of paths, the second code division multiple access transceiver having a receiver side having a rake arrangement for processing a plurality of multipath versions of a signal received at the rake arrangement with differing delays or differing other characteristics, the method comprising the steps of:

operating the transmitter side of the first code division multiple access transceiver to use a subset of the plurality of antennas in the absence of an indication that resolvable multipath is not obtained at the rake arrangement of the second code division multiple access transceiver; and

switching the transmitter side of the first code division multiple access transceiver to use at least one more antenna of the plurality of antennas than is used in said subset when an indication is obtained that resolvable multipath is not obtained at the rake arrangement of the second code division multiple access transmitter, comprising the step of providing a feedback signal from the second code division multiple access transceiver to the first code division multiple access transceiver to provide the indication that resolvable multipath is not obtained at the rake arrangement of the second code division multiple access transmitter.

19. The method of operating a code division multiple access communication system according to claim 18, wherein the step of operating the first code division multiple access transceiver comprises operating it as a base station transceiver, the method further including the step of operating the second code division multiple access transceiver as a mobile transceiver.

20. The method of operating a code division multiple access communication system according to claim 18, further including the step of driving the increased number of antennas with respective delays.

21. The method for operating a code division multiple access communication system according to claim 18, further including the step of driving the increased number of antennas with respective spreading codes.

22. A mobile transceiver for code division multiple access communication employing multipath diversity, comprising:

on the transmitter side of the mobile transceiver, a multiplexer and modulator for data signals;

on the receiver side of the mobile transceiver, a rake arrangement for separating a plurality of multipath versions of a signal received from a remote base station transceiver; and

a searcher connected from the rake arrangement to the multiplexer to provide a feedback signal for multiplexing for transmission to the remote base station transceiver whenever the searcher does not find resolvable multipath at the rake arrangement, the feedback signal indicating absence of resolvable multipath.

23. A method for operating a mobile transceiver for code division multiple access communication employing multipath diversity, comprising the steps of:

multiplexing and modulating data signals for transmission to a remote base station transceiver;

demultiplexing and demodulating signals from the remote base station transceiver; and

searching for a plurality of resolvable multipath signal versions from the remote base station transceiver and providing a feedback signal for the multiplexing and modulating step indicating the absence of resolvable multipath whenever a plurality of resolvable multipath signal versions are not found.

24. A method for operating a system for code division multiple access communication employing multipath diversity, comprising the steps of:

determining the presence or absence of resolvable multipath at a receiver of a first tranceiver of two communicating transceivers;

feeding back from a transmitter of the first transceiver to a receiver of a second transceiver of the two communicating transceivers a feedback signal indicating the lack of resolvable multipath at the first transceiver; and

transmitting additional multipath signals from the second transceiver toward the first transceiver to enhance the existence of resolvable multipath at the first transceiver.

25. The method according to claim 24, wherein the step of feeding back a feedback signal comprises multiplexing said feedback signal with other signals for transmission from the transmitter of the first transceiver to the receiver of the second transceiver.

26. A system for code division multiple access communication employing multipath diversity between first and second communicating transceivers, comprising:

the first and second communicating transceivers;

means for determining that a lack of resolvable multipath exists at a receiver of the first tranceiver;

means for feeding back from a transmitter of the first transceiver to a receiver of a second transceiver of the two communicating transceivers a feedback signal indicating the lack of resolvable multipath at the first transceiver; and

means for transmitting additional multipath signals from the second transceiver toward the first transceiver to enhance the existence of resolvable multipath at the first transceiver.

27. The system according to claim 26, wherein the means for feeding back a feedback signal comprises means for multiplexing said feedback signal with other signals for transmission from the transmitter of the first transceiver to the receiver of the second transceiver.