Method and apparatus for orthogonal code management in CDMA systems using smart antenna technology

• US 20030114162A1
• Filed: 05/31/2001
• Published: 06/19/2003
• Est. Priority Date: 05/31/2001
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Wang, Yiping, Yavuz, Mehmet, Chheda, Ashvin H.
• Granted Patent: US 6,996,056 B2
• Time in Patent Office: Days
• US Class Current: 455/447
• CPC Class Codes: H04W 16/02 Resource partitioning among network components, e.g. reuse partitioning
• CPC Class Codes: H04W 16/12 Fixed resource partitioning
• CPC Class Codes: H04W 16/24 Cell structures

Abstract

A method and apparatus for enabling Orthogonal codes to be reused within the same cell of a code division multiple access telecommunication network includes an base station transceiver system that comprises logic circuitry for enabling the base station transceiver system to reuse Orthogonal codes in a manner that reduces the likelihood of collision between two mobile stations having the same Orthogonal code and corresponding communication channels. The method of the present invention specifically includes analyzing user characteristics including factors such as his physical movement, location and mobile station communication type, as well as angular placement

Claims

1. A method for assigning Orthogonal codes in a code division multiple access network, comprising:

determining that there is a need to reuse a code within a defined cell area; and

determining an optimal mobile station whose Orthogonal code is to be reused.

2. The method of claim 1 further comprising defining a plurality of zones.

3. The method of claim 2 further comprising statically building a ranked list of zones according to interference there between.

4. The method of claim 2 further comprising statically building a ranked list of zones according to angular separation.

5. The method of claim 2 further comprising defining a ranked list of zones according to interference between zones and according to angular separation between zones.

6. The method of claim 5 wherein zones in which side lobes are present for a primary lobe in a zone in which the reused code is to be assigned are eliminated from the ranked list.

7. The method of claim 6 wherein the mobile station is selected by considering, at least in part, whether the mobile station is a fixed wireless access user.

8. The method of claim 6 wherein the mobile station is selected by considering, at least in part, its speed.

9. The method of claim 6 wherein the mobile station is selected by considering, at least in part, its direction of travel.

10. The method of claim 6 wherein the mobile station is selected by considering, at least in part, its location.

11. The method of claim 6 wherein the mobile station is selected by considering, at least in part, its call duration length.

12. The method of claim 6 wherein the mobile station is selected by considering, at least in part, its frame error rate.

13. The method of claim 6 wherein the mobile station is selected by considering, at least in part, its power consumption level.

14. The method of claim 6 wherein the mobile station is selected by considering, at least in part, a known interference between the mobile station and the mobile station to whom the code is to be reassigned.

15. The method of claim 6 wherein the mobile station is selected by considering, at least in part, a correlation of its time and speed.

16. The method of claim 6 wherein the mobile station is selected by considering, at least in part, whether a hysterisis is in effect for the user.

17. The method of claim 6 wherein the mobile station is selected by considering, at least in part, according to whether the call is a data or voice call.

18. The method of claim 6 wherein the mobile station is selected by considering, at least in part, whether, if the call is a data call, whether it is bursty or continuous.

19. The method of claim 1 wherein the need to reuse an Orthogonal code occurs because of a determination that a collision is eminent between the two mobile stations using the same Orthogonal code.

20. The method of claim 19 wherein the need is determined prior to the occurrence of an actual collision.

21. The method of claim 19 wherein the determination is made by considering whether the frame error rate is increasing.

22. The method of claim 19 wherein the determination is made by considering whether the power usage is increasing.

23. The method of claim 19 wherein the determination is made by considering whether there is a significant change in speed.

24. The method of claim 19 wherein the determination is made by considering whether there is a significant change in direction.

25. The method of claim 19 wherein the determination is made by considering whether a handoff is occurring to a non-compatible zone.

26. The method of claim 19 wherein the determination is made by considering whether the mobile station is moving towards the cell center.

27. The method of claim 19 wherein the determination is made by considering whether the mobile station is too close to the cell center.

28. The method of claim 19 wherein the determination is made by considering whether the signal quality falls below a specified threshold.

31. The method of claim 28, wherein selecting a donor mobile station includes selecting an Orthogonal code for a mobile station whose location is in a zone that has significant angular separation from the zone in which a requesting mobile station is located when the requesting mobile station is the one needing to reuse an Orthogonal code.

32. The method of claim 28, further comprising monitoring the Orthogonal code mobile station characteristics for the two mobile stations using the same Orthogonal code to determine whether a likelihood of a collision is increasing beyond a specified threshold.

29. A method for assigning an Orthogonal code in a code division multiple access network, comprising:

determining that a need exists to reuse an Orthogonal code that is already assigned to a mobile station for creating a communication channel;

evaluating at least one of zone interference, zone separation and mobile station characteristics for those mobile stations that already have been assigned Orthogonal code and selecting an Orthogonal code to be reused and assigning the selected Orthogonal code to a mobile station that is requiring an Orthogonal code.

30. The method of claim 29, wherein the candidate donor mobile station'"'"'s characteristics that are evaluated include at least one of whether the candidate donor mobile station is a fixed wireless access user, its speed, its direction, the candidate donor location, the candidate donor'"'"'s call duration, the candidate donor'"'"'s frame error rate, the candidate donor'"'"'s power consumption, whether the candidate donor is transmitting data or voice, if the candidate donor is transmitting data, whether it is bursty or continuous data.

33. A base station transceiver system for assigning Orthogonal codes to create communication channels in a code division multiple access network, comprising circuitry for performing routine base station transceiver system operations;

and

logic circuitry for selecting an Orthogonal code for reuse from a mobile station located in a cell portion according to the location of the mobile station and specified mobile station characteristics.

34. The base station transceiver system of claim 34, wherein the cell portion that is selected for initially evaluating mobile stations for donating their Orthogonal code for reuse includes evaluating the angular separation between the cell portion and a cell portion in which the code is to be reused.