Methods and apparatus for selecting and signaling a preferred link among a plurality of maintained wireless communications links

• US 20070104128A1
• Filed: 11/04/2005
• Published: 05/10/2007
• Est. Priority Date: 11/04/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Das, Arnab, Laroia, Rajiv, Anigstein, Pablo, Parizhsky, Vladimir, Srinivasan, Murari
• Granted Patent: US 7,953,417 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data

Abstract

Methods and apparatus for maintaining, selecting and indicating a preferred communications link with an access node, e.g., base station, are described.

Claims

1. A method of operating a wireless terminal comprising:

maintaining a communications link with a plurality of different attachment points at the same time;

selecting a preferred downlink wireless communications link from the maintained communications links; and

signaling the preferred communications link to at least one of the attachment points.

2. The method of claim 1, wherein selecting a preferred downlink is performed as a function of downlink signals received from at least two attachment points included in said plurality of attachment points.

3. The method of claim 2, further comprising:

repeating said selecting and signaling steps.

4. The method of claim 3, wherein the selection of a preferred downlink is based on at least one of:

a determined signal to noise ratio, a determined signal to interference ratio, a received signal strength measurement, traffic loading conditions at one of said attachment points, and a type of traffic to the wireless terminal.

5. The method of claim 3, wherein the selection of a preferred downlink is performed based on measurements of pilot signals received from at least two of said base stations.

6. The method of claim 3, wherein said signaling includes communicating the preferred downlink to each of the attachments points with which a communications link is maintained.

7. The method of claim 6 further comprising:

maintaining a dedicated uplink communications channel with each of said attachment points with which the wireless terminal maintains a communications link, and

wherein said signaling indicating the preferred downlink is transmitted using the dedicated uplink communications channels.

8. The method of claim 7, further comprising:

jointly coding said preferred link information with channel coding report information; and

transmitting said coded signal conveying both the preferred link information and channel condition report information over the dedicated control channel.

9. The method of claim 8, further comprising:

receiving downlink user data over at least one of said downlink channels, said downlink channel having been determined by at least one of said base stations.

10. The method of claim 9, wherein the selected downlink channel is the indicated preferred channel.

11. The method of claim 9, wherein the selected downlink channel is different from the indicated preferred downlink channel.

12. The method of claim 3, wherein said selecting of a preferred downlink communications link results in selection of a different downlink from a current preferred downlink, a delay period is required before a change in the new current preferred downlink is allowed.

13. The method of claim 12, wherein the length of said delay is a predetermined period corresponding to a predetermined number of downlink transmission time slots.

14. The method of claim 12, wherein the delay is determined by the time required to signal the preferred link to one of said plurality of base stations a predetermined number of times, the time between signaling varying depending on which one of a plurality of modes of operation the wireless terminal is operating in.

15. The method of claim 1, wherein said selecting of the preferred link includes:

processing signals from different downlinks to generate a signal quality indicator on a per link basis;

comparing generated signal quality indicators to the signal quality indicator of the current preferred link; and

selecting a new current preferred link when said comparison indicating a difference between the signal quality indication of the current preferred link and a signal quality indicator of another link which exceeds a threshold.

16. The method of claim 15, further comprising:

changing said threshold as a function of the amount of time said current preferred link remains unchanged.

17. The method of claim 15, further comprising:

changing the processing used to generate signals from different downlinks to generate a signal quality indicator on a per link basis as a function of the amount of time said current preferred link remains unchanged.

18. The method of claim 1, wherein the attachment points correspond to different base stations located in adjacent cells of a communications system.

19. The method of claim 1, wherein the attachment points correspond to different sectors of the same cell.

20. The method of claim 1, wherein the attachment points correspond to different tone blocks of a sector.

21. A wireless terminal comprising:

a link module for maintaining a communications link with a plurality of different attachment points at the same time;

a link selection module for selecting a preferred downlink wireless communications link from the maintained communications links; and

a preferred link reporting module for signaling the preferred communications link to at least one of the attachment points.

22. The wireless terminal claim 21, further comprising:

a receiver for receiving signals from at least two attachment points; and

a signal measurement module for measuring signals received from said at least two attachment points, said signal measurement being coupled to said link selection module for providing signal measurement information used in selecting a preferred downlink as a function of downlink signals received from at least two attachment points included in said plurality of attachment points.

23. The wireless terminal of claim 22, further comprising:

a signal to noise ratio measurement module for measuring a signal to noise ratio of signals received on different links.

24. The wireless terminal of claim 22, wherein said selection module selects a preferred downlink based on at least one of:

a determined signal to noise ratio, a determined signal to interference ratio, a received signal strength measurement, traffic loading conditions at one of said attachment points, and a type of traffic to the wireless terminal.

25. The wireless terminal of claim 22, wherein said signal measurement module is a pilot signal measurement module and wherein the selection of a preferred downlink is performed based on measurements of pilot signals received from at least two of said base stations.

26. The wireless terminal of claim 23, wherein said preferred link reporting module includes an OFDM transmitter for transmitting at least one signal to each of the attachments points with which a communications link is maintained to indicate to the attachment point the preferred downlink selected by the wireless terminal.