Reduction of handover latencies in a wireless communication system

• US 7,962,139 B2
• Filed: 06/20/2007
• Issued: 06/14/2011
• Est. Priority Date: 06/20/2006
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Xhafa, Ariton E., Bertrand, Pierre, Kangude, Shantanu
• Primary Examiner(s): GELIN, JEAN ALLAND
• Application Number:
  US11/765,995
• Publication Number:
  US 20070293225A1
• Time in Patent Office: 1,455 Days
• Field of Search: 455/436, 455/432.1, 455/432.2, 455/434, 455/435.1, 455/435.2, 455/435.3, 455/437, 455/438, 455/439, 455/442, 370/329, 370/331
• US Class Current: 455/436
• CPC Class Codes: H04W 36/165 for reducing network power consumption H04W36/18 - H04W36/22 take precedence

Abstract

Systems and methods for reduction of handover latencies in wireless communication systems are described herein. Some illustrative embodiments include a wireless mobile communication device that includes a wireless transceiver including a transmitter configured to transmit a first signal synchronized for reception by a first cellular node, and processing logic that couples to the wireless transceiver. Before the wireless transceiver receives a handover command the processing logic causes the transmitter to transmit a second signal for reception by a second cellular node to request allocation of an upload resource for communication with the second cellular node as part of an impending handover.

Claims

1. A wireless mobile communication device, comprising:

a wireless transceiver comprising a transmitter configured to transmit a first signal synchronized for reception by a first cellular node; and

processing logic that couples to the wireless transceiver, wherein before the wireless transceiver receives a handover command, the processing logic causes the transmitter to transmit a second signal for reception by a second cellular node to request allocation of an upload resource for communication with the second cellular node as part of an impending handover;

wherein an allocated resource of a plurality of resources allocated to the wireless mobile communication device is associated with an earlier point in time and the handover command is received after the earlier point in time;

wherein another allocated resource of the plurality of resources is associated with a later point in time and the handover command is further received before the later point in time; and

wherein the wireless mobile communication device uses the allocated resource associated with the later point in time for data transmission.

2. The wireless mobile communication device of claim 1,

wherein the processing logic further configures the transmitter to use the upload resource if a message comprising synchronization and resource allocation information is received by the wireless mobile communication device;

and

wherein after the handover command is received by the wireless transceiver the processing logic causes the transmitter to terminate use of the first signal for data transmission, and further causes the transmitter to transmit the second signal for data transmission using the upload resource.

3. The wireless mobile communication device of claim 1, wherein the processing logic causes the transmitter to transmit the second signal based upon receipt by the wireless mobile communication device of a message indicating that a handover command is about to be received by the wireless mobile communication device.

4. The wireless mobile communication device of claim 1, wherein the processing logic causes the transmitter to transmit the second signal based on a prediction by the processing logic that a handover command is about to be received by the wireless mobile communication device.

5. The wireless mobile communication device of claim 4, wherein the prediction by the processing logic is based upon measurements determined by the processing logic that characterize incoming signals received by the wireless mobile communications device.

6. The wireless mobile communication device of claim 1,

wherein the request for allocation of the upload resource is transmitted using a random access channel;

and

wherein the request for allocation of the upload resource comprises a request for synchronization information.

7. The wireless mobile communication device of claim 1, wherein the processing logic detects a timeout if resource allocation information is not received within a maximum time limit after the transmission of the second signal to request allocation of the upload resource.

8. The wireless mobile communication device of claim 7, wherein the processing logic causes the transmitter to repeat sending the second signal to request the allocation of the upload resource if the timeout is detected.

9. The wireless mobile communication device of claim 1,

wherein the processing logic causes the transmitter to repeat sending the second signal to request the allocation of the upload resource if a prior request is unsuccessful;

and

wherein successive attempts to secure the allocation of the upload resource are separated by an inter-attempt time interval.

10. The wireless mobile communication device of claim 9, wherein the inter-attempt time interval is increased after each successive attempt to secure the allocation of the upload resource.

11. The wireless mobile communication device of claim 9, wherein the transmitter is concurrently configured to transmit either the first signal or the second signal.

12. A plurality of cellular nodes, each comprising:

a wireless transceiver comprising a transmitter and a receiver, and configured to transmit signals to, and receive signals from, a wireless mobile communication device; and

processing logic that couples to the wireless transceiver;

wherein before the processing logic of a first cellular node of the plurality of cellular nodes causes its transmitter to transmit a handover command, the receiver of a second cellular node of the plurality of cellular nodes receives a request to allocate an upload resource as part of an impending handover;

wherein an allocated upload resource of a plurality of resources allocated to the wireless mobile communication device is associated with an earlier point in time and the handover command is transmitted after the earlier point in time;

wherein another allocated upload resource of the plurality of resources is associated with a later point in time and the handover command is further transmitted before the later point in time; and

wherein the wireless transceiver is configured to use the allocated upload resource associated with the later point in time for data transmission.

13. The plurality of cellular nodes of claim 12, wherein the processing logic of the first cellular node causes its transmitter to transmit a handover decision notification message before the first cellular node sends the handover command, and before the second cellular node receives the request to allocate the upload resource.

14. The plurality of cellular nodes of claim 12,

wherein the request to allocate the upload resource is received on a random access channel;

and

wherein the request for allocation of the upload resource comprises a request for synchronization information.

15. The plurality of cellular nodes of claim 12, wherein the processing logic of the second cellular node causes its transmitter to transmit a message comprising synchronization and allocation information before the handover command is transmitted by the first cellular node.

16. The plurality of cellular nodes of claim 12, wherein the processing logic of the second cellular node causes its transmitter to transmit a message comprising synchronization and allocation information after the handover command is transmitted by the first cellular node.

17. A method, comprising:

receiving, by a target cellular node within a wireless communication system, a request to allocate an upload resource as part of an impending handover;

transmitting, by the target cellular node in response to the request to allocate the upload resource, a message comprising synchronization and resource allocation information;

transmitting, by a source cellular node, a handover command after the receiving by the target cellular node the request to allocate the upload resource;

transmitting, by the source cellular node, the handover command after an earlier point in time, an allocated resource of a plurality of resources allocated to the wireless mobile device being associated with the earlier point in time;

transmitting, by the source cellular node, the handover command before a later point in time, another allocated resource of the plurality of resources being associated with the later point in time; and

using, by the wireless mobile device, the allocated resource associated with the later point in time to communicate with the target cellular node.

18. The method of claim 17, further comprising:

transmitting, by a wireless mobile device to the target cellular node, the request to allocate the upload resource before the transmitting of the handover command; and

receiving, by the wireless mobile device, the message comprising the synchronization and resource allocation information after transmitting the request to allocate the upload resource.

19. The method of claim 18, further comprising:

receiving, by the wireless mobile device, the handover command after transmitting the request to allocate the upload resource; and

ending, by the wireless mobile device, communications with the source cellular node and continuing to communicate with a target cellular node in response to receiving the handover command.

20. The method of claim 18, further comprising:

transmitting, by the source cellular node to the wireless mobile device, a handover decision message notifying the wireless mobile device that a handover command will be transmitted by the source cellular node to the wireless mobile device; and

transmitting, by the wireless mobile device to the target cellular node, the request to allocate the upload resource in response to receiving the handover decision message.

21. The method of claim 18, further comprising:

predicting, by the wireless mobile device, that the handover command will be transmitted by the source cellular node; and

transmitting, by the wireless mobile device to the target cellular node, the request to allocate the upload resource in response to the predicting that the handover command will be transmitted.

22. The method of claim 18, further comprising:

repeating the request to allocate the upload resource if the message comprising the synchronization and resource allocation information is not received within a maximum time interval after the transmitting to the target cellular node of the request to allocate the upload resource.

23. The method of claim 18, further comprising:

retransmitting the request to allocate the upload resource if a prior request is unsuccessful; and

separating successive retransmitting attempts by a time interval that increases with each successive attempt.

24. The method of claim 18, wherein the transmitting to the target cellular node of the request to allocate the upload resource comprises using a random access channel and further comprises transmitting a request for synchronization information as part of the request to allocate the upload request.