Multi-user detection for antenna array receivers

• US 6,564,037 B1
• Filed: 12/02/1998
• Issued: 05/13/2003
• Est. Priority Date: 12/24/1997
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Sweatman, Catherine Zoe Wollaston Hassell, Thompson, John Scott, Mulgrew, Bernard
• Primary Examiner(s): VUONG, QUOCHIEN B
• Application Number:
  US09/203,852
• Time in Patent Office: 1,623 Days
• Field of Search: 455/427, 455/429, 455/12.1, 455/13.1, 455/13.3, 455/456, 455/63, 455/561, 455/562, 342/352, 342/354, 342/357.01, 342/373, 370/342, 370/329, 370/335, 375/324, 375/340, 375/341, 375/346
• US Class Current: 455/63.1
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• CPC Class Codes: H04W 16/28 using beam steering

Abstract

The present invention relates to radio communication antennas and in particular relates to multi-user detection for CDMA antenna array receivers. A reverse link (mobile to base) of a cellular direct sequence code division multiple access system is provided which increases system capacity whilst avoiding system complexity. The invention provides a method of signal detection which is based on the partitioning of users into equivalence classes by beam-forming with subsequent standard multi-user detection techniques applied within each class. Computation techniques are simplified and processing time can be considerably reduced. Furthermore, the capacity of a conventional receiver may be improved by employing multi-user detection techniques. These techniques are particularly useful for systems which involve large numbers of users. A method of operation is also disclosed.

Claims

1. A multi-user detection radio communications system wherein an equivalence relation is defined for a set of users based on a set of beam-forming terms to group the users according to their spatial signatures.

2. A system according to claim 1 wherein the beam-forming terms are a^H(θ

_i)a(θ

_j).

3. A system in accordance with claim 1 wherein the beam-forming terms are a^H(θ

_i)a(θ

_j) and wherein the user classes are determined so that, if user i and user j are not in equivalent classes, the absolute value of a^H(θ

_i)a(θ

_j) is small in some sense.

4. A system in accordance with claim 1 wherein the beam-forming terms are a^H(θ

_i)a(θ

_j) and wherein the absolute value of a^H(θ

_i)a(θ

_j) is then replaced by zero, which allows the multiple access interference to be ignored between equivalence classes.

5. A system in accordance with claim 1 wherein the beam-forming terms are a^H(θ

_i)a(θ

_j) and wherein the users are sorted into equivalence classes based on the beam patterns, where the beam pattern has a threshold Θ

which lies in the following range;

O≦

Θ

≦

1;

in accordance with the following relations;

a first relation ‘

≈

’

between users, which is symmetric, reflexive and non-transitive, and is defined by;

6. A system according to claim 1, wherein the modulation scheme is a code division multiple access scheme.

7. A system according to claim 1, wherein the beam-forming terms are (x^H_p,o/∥

x_p,o∥

)(x_i,o/∥

x_i,o∥

).

8. A system in accordance with claim 1, wherein the beam-forming terms are (x^H_p,o/∥

x_p,o∥

)(x_i,o/∥

x_i,o∥

) and wherein the user classes are determined so that, if user p and user i are not in equivalent classes, the absolute value of (x^H_p,o/∥

x_p,o∥

)(x_i,o/∥

x_i,o∥

) is small in some sense.

9. A system in accordance with claim 1, wherein the beam-forming terms are (x^H_p,o/∥

x_p,o∥

)(x_i,o/∥

x_i,o∥

) and wherein equivalence classes can be determined in this situation if it can be assumed that if the quantity (x^H_p,o/∥

x_p,o∥

)(x_i,o/∥

x_i,o∥

) is small, the quantities (x^H_p,j/∥

x_p,j∥

)(x_i,j′

/∥

x_i,j′

∥

), where 0≦

j, j′

≦

J, are also small. This permits all the multiple access interference between two users in different equivalence classes to be ignored.

10. A system in accordance with claim 1, wherein the beam-forming terms are (x^H_p,o/∥

x_p,o∥

)(x_i,o/∥

x_i,o∥

) and wherein user p and user i are sorted into equivalence classes based on the beam patterns according to a beam pattern threshold, Θ

, which lies in the following range;

O≦

Θ

≦

1; and

, wherein user p and user i are close in bearing if;

11. A system in accordance with claim 1, wherein the beam-forming terms are (x^H_p,o/∥

x_p,o∥

)(x_i,o/∥

x_i,o∥

) and wherein the users are sorted into equivalence classes based on the beam patterns, where the beam pattern has a threshold Θ

which lies in the following range;

O≦

Θ

≦

1;

in accordance with the following relations;

a first relation ‘

≈

’

between users is defined by;

12. A method of operating a multi-user detection radio communications system wherein an equivalence relation is defined for a set of users based on a set of beam-forming terms wherein the users are grouped according to their spatial signatures.

13. A method according to claim 12 wherein the beam-forming terms are a^H(θ

_i)a(θ

_j).

14. A method according to claim 12, wherein the beam-forming terms are (x^H_p,o/∥

x_p,o∥

)(x_i,o/∥

x_i,o∥

).

15. A method according to claim 12, wherein the modulation scheme is a code division multiple access scheme.

16. A multi-user detection radio receiver wherein an equivalence relation is defined for a set of users based on a set of beam-forming terms to group the users according to their spatial signatures.

17. A method of operating a multi-user detection radio receiver wherein an equivalence relation is defined for a set of users based on a set of beam-forming terms wherein the users are grouped according to their spatial signatures.