Methods for reliable user switchback on a PHS spatial division multiple access channel

• US 7,020,107 B2
• Filed: 01/21/2003
• Issued: 03/28/2006
• Est. Priority Date: 01/21/2003
• Status: Expired due to Fees

• Current Assignee: Intel Corporation
• Original Assignee: ArrayComm LLC (Ygomi LLC)
• Inventors: Kasapi, Athanasios A., Kerr, Adam B., Yu, Xiaoming, Persson, Lars Johan
• Primary Examiner(s): Sam, Phirin
• Assistant Examiner(s): TON, ANTHONY T
• Application Number:
  US10/348,923
• Publication Number:
  US 20040141478A1
• Time in Patent Office: 1,162 Days
• Field of Search: 370/319, 370/322, 370/324, 370/326, 370/329, 370339-341, 370/351, 370/395.21, 370/395.41, 370/397, 370/431, 370/433, 370/443, 370/503, 370/334, 370/323, 370/330, 370/336, 370/337, 370/241, 370/294, 370/400, 370343-347, 455/25, 455/67.1, 455/522, 455/562, 455/562.2, 342/457
• US Class Current: 370/329
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 56/001 Synchronization between nodes

Abstract

An embodiment of the invention provides a method for effecting switchback on a spatial division multiple access (SDMA) PHS channel. A communication signal is broadcast over each of one or more SDMA channels of a multi-access channel to one or more corresponding user terminals. A set of transmit spatial weights is determined for a synchronization burst to a user terminal attempting to reestablish communication over an SDMA channel of the multi-access channel. The set of transmit spatial weights is determined such that interference caused by one or more communication signals to the synchronization burst is reduced.

Claims

1. A method comprising:

transmitting a communication signal over each of one or more spatial division multiple access (SDMA) channels of a multi-access channel to one or more corresponding user terminals;

determining a set of transmit spatial weights for a synchronization burst corresponding to one of one or more user terminals attempting to reestablish communication over an SDMA channel of the multi-access channel, the set of transmit spatial weights determined such that interference caused by one or more communication signals to the synchronization burst is reduced;

broadcasting the synchronization burst to the corresponding user terminal; and

determining a set of transmit spatial weights for a synchronization burst corresponding to a next user terminal of the one or more user terminals attempting to reestablish, communication over an SDMA channel of the multi-access channel, the set of transmit spatial weights determined such that interference between the synchronization burst corresponding to the next user terminal and the one or more communication signals is reduced.

2. The method of claim 1 wherein the set of transmit spatial weights of the synchronization burst are orthogonal to a spatial signature of at least one of the one or more corresponding user terminals.

3. The method of claim 1 further comprising:

attenuating an amplitude of a set of transmit spatial weights of at least one of the one or more communication signals such that interference caused by one or more communication signals to the synchronization burst is reduced.

4. The method of claim 1 wherein the multi-access channel is a time division multiple access channel.

5. The method of claim 1 wherein the attenuated amplitude of the set of transmit spatial weights of the at least one communication signal is sufficient to maintain a communication link with the one or more corresponding user terminals.

6. The method of claim 2 wherein the transmit spatial weights of the synchronization burst are determined based upon a characteristic of the corresponding user terminal.

7. The method of claim 6 where in the characteristic is a spatial signature of the user terminal attempting to reestablish communication over an SDMA channel of the multi-access channel, the spatial signature determined when the user terminal was communicating over the SDMA channel of the multi-access channel.

8. The method of claim 1 in which communication is reestablished with the corresponding user terminal over the SDMA channel of the multi-access channel.

9. The method of claim 8 further comprising:

broadcasting the synchronization burst corresponding to the next user terminal; and

repeating the operations of determining a set of transmit spatial weights for a synchronization burst corresponding to a next user terminal, and broadcasting the synchronization burst to the corresponding user terminal until communication is reestablished with all of the one or more user terminals attempting to reestablish communication over an SDMA channel of the multi-access channel.

10. A method comprising:

alternately broadcasting each of a set of synchronization bursts, each synchronization burst corresponding to one of a plurality of user terminals attempting to reestablish communication over respective corresponding SDMA channels of a multi-access channel;

reestablishing communication with a first user terminal of the plurality of user terminals over the corresponding SDMA channel;

transmitting a communication signal to the first user terminal over the corresponding SDMA channel;

determining a set of transmit spatial weights for a synchronization burst corresponding to one of the one or more remaining user terminals attempting to reestablish communication over a corresponding SDMA channel of a multi-access channel, the set of transmit spatial weights determined such that interference between the synchronization burst and the communication signal to the first user terminal is reduced; and

broadcasting the corresponding synchronization burst to the corresponding user terminal such that communication with the corresponding user terminal over the corresponding SDMA channel is reestablished.

11. The method of claim 10 wherein a set of transmit spatial weights of each of the synchronization bursts is determined to approximate an omni-directional radiation pattern for the synchronization burst.

12. The method of claim 10 wherein the set of transmit spatial weights of the synchronization burst are orthogonal to a spatial signature of the first user terminal.

13. The method of claim 10 further comprising:

repeating the operations of determining a set of transmit spatial weights for a synchronization burst and broadcasting the synchronization burst to the corresponding user terminal until communication is reestablished with all of the one or more user terminals attempting to reestablish communication over an SDMA channel of the multi-access channel.

14. The method of claim 12 further comprising:

attenuating an amplitude of a set of transmit spatial weights of one or more of the communication signals such that interference between each synchronization burst and the one or more communication signals is reduced.

15. A wireless communication system comprising:

a mobile switching center; and

a plurality of base stations coupled to the mobile switching center, each base station servicing a plurality of user terminals wherein a base station alternately broadcasts each of a set of synchronization bursts, each synchronization burst corresponding to one of a plurality of user terminals attempting to reestablish communication over respective corresponding SDMA channels of a multi-access channel, and reestablishes communication with a first user terminal of the plurality of user terminals over the corresponding SDMA channel wherein the base station subsequently transmits a communication signal to the first user terminal over the corresponding SDMA channel, determines a set of transmit spatial weights for a synchronization burst corresponding to one of the one or more remaining user terminals attempting to reestablish communication over a corresponding SDMA channel of a multi-access channel, the set of transmit spatial weights determined such that interference between the synchronization burst and the communication signal to the first user terminal is reduced, and broadcasts the corresponding synchronization burst to the corresponding user terminal such that communication with the corresponding user terminal over the corresponding SDMA channel is reestablished.

16. The wireless communication system of claim 15 wherein a set of transmit spatial weights of each of the synchronization bursts are determined to approximate an omni-directional radiation pattern for the synchronization burst.

17. The wireless communication system of claim 15 wherein the set of transmit spatial weights of the synchronization burst are orthogonal to a spatial signature of the first user terminal.

18. The wireless communication system of claim 15 wherein the base station repeats the operations of determining a set of transmit spatial weights for a synchronization burst and broadcasting the synchronization burst to the corresponding user terminal are repeated until communication is reestablished with all of the one or more user terminals attempting to reestablish communication over an SDMA channel of the multi-access channel.

19. The wireless communication system of claim 17 wherein the base station attenuates an amplitude of a set of transmit spatial weights of one or more of the communication signals such that interference between each synchronization burst and the one or more communication signals is reduced.

20. A machine-readable medium having one or more executable instructions stored thereon, which when executed by a digital processing system cause the digital processing system to perform a method, the method comprising:

transmitting a communication signal over each of one or more SDMA channels of a multi-access channel to one or more corresponding user terminals;

determining a set of transmit spatial weights for a synchronization burst corresponding to one of one or more user terminals attempting to reestablish communication over an SDMA channel of the multi-access channel, the set of transmit spatial weights determined such that interference caused by one or more communication signals to the synchronization burst is reduced;

broadcasting the synchronization burst to the corresponding user terminal; and

determining a set of transmit spatial weights for a synchronization burst corresponding to a next user terminal of the one or more user terminals attempting to reestablish communication over an SDMA channel of the multi-access channel, the set of transmit spatial weights determined such that interference between the synchronization burst corresponding to the next user terminal and the one or more communication signals is reduced.

21. The machine-readable medium of claim 20 wherein the set of transmit spatial weights of the synchronization burst are orthogonal to a spatial signature of at least one of the one or more corresponding user terminals.

22. The machine-readable medium of claim 20 further comprising:

attenuating an amplitude of a set of transmit spatial weights of at least one of the one or more communication signals such that interference caused by one or more communication signals to the synchronization burst is reduced.

23. The machine-readable medium of claim 20 wherein the multi-access channel is a time division multiple access channel.

24. The machine-readable medium of claim 20 wherein the attenuated amplitude of the set of transmit spatial weights of the at least one communication signal is sufficient to maintain a communication link with the one or more corresponding user terminals.

25. The machine-readable medium of claim 20 wherein the transmit spatial weights of the synchronization burst are determined based upon a characteristic of the corresponding user terminal.

26. The machine-readable medium of claim 25 wherein the characteristic is a spatial signature of the user terminal attempting to reestablish communication ever an SDMA channel of the multi-access channel, the spatial signature determined when the user terminal was communicating over the SDMA channel of the multi-access channel.

27. The machine-readable medium of claim 20 in which communication is reestablished with the corresponding user terminal over the SDMA channel of the multi-access channel.

28. The machine-readable medium of claim 27 wherein the method further comprises:

repeating the operations of determining a set of transmit spatial weights for a synchronization burst, and broadcasting the synchronization burst to the corresponding user terminal until communication is reestablished with all of the one or more user terminals attempting to reestablish communication over an SDMA channel of the multi-access channel.

29. A machine-readable medium having one or more executable instructions stored thereon, which when executed by a digital processing system cause the digital processing system to perform a method, the method comprising:

alternately broadcasting each of a set of synchronization bursts, each synchronization burst corresponding to one of a plurality of user terminals attempting to reestablish communication over respective corresponding SDMA channels of a multi-access channel;

reestablishing communication with a first user terminal of the plurality of user terminals over the corresponding SDMA channel;

transmitting a communication signal to the first user terminal over the corresponding SDMA channel;

determining a set of transmit spatial weights for a synchronization burst corresponding to one of the one or more remaining user terminals attempting to reestablish communication over a corresponding SDMA channel of a multi-access channel, the set of transmit spatial weights determined such that interference between the synchronization burst and the communication signal to the first user terminal is reduced; and

broadcasting the corresponding synchronization burst to the corresponding user terminal such that communication with the corresponding user terminal over the corresponding SDMA channel is reestablished.

30. The machine-readable medium of claim 29 wherein a set of transmit spatial weights of each of the synchronization bursts is determined to approximate an omni-directional radiation pattern for the synchronization burst.

31. The machine-readable medium of claim 29 wherein the set of transmit spatial weights of the synchronization burst are orthogonal to a spatial signature of the first user terminal.

32. The machine-readable medium of claim 29 further comprising:

repeating the operations of determining a set of transmit spatial weights for a synchronization burst and broadcasting the synchronization burst to the corresponding user terminal are repeated until communication is reestablished with all of the one or more user terminals attempting to reestablish communication over an SDMA channel of the multi-access channel.

33. The machine-readable medium of claim 31 wherein the method further comprises:

attenuating an amplitude of a set of transmit spatial weights of one or more of the communication signals such that interference between each synchronization burst and the one or more communication signals is reduced.