Mobile station having plural antenna elements and interference suppression

• US 6,167,039 A
• Filed: 12/17/1997
• Issued: 12/26/2000
• Est. Priority Date: 12/17/1997
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Forssen, Ulf, Karlsson, Jonas, Gudmundson, Bjorn, Mazur, Sara
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): HOM, SHICK C
• Application Number:
  US08/992,174
• Time in Patent Office: 1,105 Days
• Field of Search: 370/310, 370/319, 370/320, 370/321, 370/342, 370/335, 370/336, 370/337, 370/343, 370/344, 370/347, 375/202, 375/203, 375/206, 375/340, 342/375, 455/562
• US Class Current: 370/342
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• CPC Class Codes: H04B 7/0897 using beamforming per multi-path, e.g. to cope with different directions of arrival [DOA] at different multi-paths
• CPC Class Codes: H04L 1/06 using space diversity

Abstract

Mobile stations using antenna diversity are described. Techniques for combining CDMA signals received over plural antennas at a mobile unit are provided which suppress interference from undesired base stations.

Claims

1. A mobile station for diversity combining different versions of a received signal and rejecting an interfering signal using interference suppression comprising:

at least two antenna elements for receiving first and second signals;

a plurality of receive signal processing branches for processing said first and second signals, each branch including a delay unit for generating a delayed version of a signal input thereto, a despreading unit for despreading said delayed version of said signal and a weighting unit for weighting an output of said despreading unit using a weighting factor based on a covariance of said interfering signal;

a plurality of first combiners for combining outputs from weighting units in processing branches having corresponding delays; and

a second combiner for combining outputs from said plurality of first combiners, said weighting factors being selected to reject said interfering signal.

2. The mobile station of claim 1, wherein said weighting factors are calculated using a combination of an interference rejection vector and a maximum ratio combining vector.

3. The mobile station of claim 1, wherein said weighting factors are calculated using a covariance of said unwanted signals.

4. The mobile station of claim 1, wherein said weighting factors are calculated using a covariance of all received signals.

5. The mobile station of claim 1, wherein said weighting factors are calculated separately for each delay.

6. The mobile station of claim 1, wherein said weighting factors are calculated simultaneously for all delays in a stacking operation.

7. A CDMA radiocommunication system having at least one base station for transmitting a desired CDMA signal to a mobile station and at least one base station for transmitting at least one interfering CDMA signal to said mobile station, said mobile station comprising:

antenna means for receiving at least two versions of said desired CDMA signal; and

receive signal processing means for detecting information intended for said mobile station using a combination of information contained in said at least two versions of said desired CDMA signal, said receive signal processing means including means for rejecting said at least one interfering CDMA signal, wherein said means for rejecting said at least one interfering CDMA signal uses weighting factors which are calculated using a combination of an interference rejection vector and a maximum ratio combining vector.

8. The mobile station of claim 7, wherein said means for rejecting said at least one interfering signal calculates said weighting factors using a covariance of said signals from said at least one base station transmitting said at least one interfering CDMA signal.

9. The mobile station of claim 7, wherein means for rejecting said at least one interfering signal calculates said weighting factors using a covariance of all received signals.

10. The mobile station of claim 7, wherein said weighting factors are calculated separately for each of a plurality of delays.

11. The mobile station of claim 7, wherein said weighting factors are calculated simultaneously for each of a plurality of delays using in a stacking operation.

12. A mobile station comprising:

at least two antenna elements, each for receiving a signal intended for said mobile station as well as at least one interfering signal; and

means for combining said signals received on each of said at least two antenna elements in a manner which suppresses said at least one interfering signal using an interference covariance matrix of said at least one interfering signal.

15. The mobile station of claim 12 further comprising:

means for calculating weights separately for each of a plurality of time delays using said covariance matrix.

16. The mobile station of claim 12, wherein said interference covariance matrix of said at least one interfering signal is estimated based on a covariance of a pre-correlation vector.

17. The mobile station of claim 12, wherein said interference covariance matrix of said at least one interfering signal is estimated based on a covariance of a post-correlation vector.

13. A radiocommunication system comprising:

a home base station for restricted access to equipment associated with a first user, which home base station transmits an interfering signal with respect to equipment associated with a second user;

a cellular base station for transmitting a desired signal to said second user;

a mobile station associated with said second user including;

two antenna elements for receiving a first and a second version of said desired signal, respectively, and for receiving said interfering signal transmitted by said home base station;

a signal processing unit for combining said first and second versions of said desired signal in a manner which suppresses said interfering signal using one of a covariance matrix associated with said interfering signals and a covariance matrix associated with both said desired signal and said interfering signal.

18. The radiocommunication system of claim 13, wherein said interference covariance matrix of said at least one interfering signal is estimated based on a covariance of a pre-correlation vector.

19. The radiocommunication system of claim 13, wherein said interference covariance matrix of said at least one interfering signal is estimated based on a covariance of a post-correlation vector.

14. A method for processing a composite CDMA signal received by a mobile station comprising the steps of:

assigning a plurality of spreading codes to said mobile station;

despreading said composite CDMA signal using each of said plurality of spreading codes to produce a plurality of despread signals;

calculating a covariance matrix for one of said plurality of despread signals to reject interference associated with undesired signals received in said composite CDMA signal; and

applying said covariance matrix to each of other of said plurality of despread signals to reject interference associated with undesired signals received in said composite CDMA signal.

20. The method of claim 14, wherein said interference covariance matrix of said at least one interfering signal is estimated based on a covariance of a pre-correlation vector.

21. The method of claim 14, wherein said interference covariance matrix of said at least one interfering signal is estimated based on a covariance of a post-correlation vector.