TDD system based cell handoff method and user equipment

• US 7,978,634 B2
• Filed: 04/20/2006
• Issued: 07/12/2011
• Est. Priority Date: 06/06/2005
• Status: Active Grant

• Current Assignee: Shanghai Ultimate Power Communications Technology Co., Ltd.
• Original Assignee: Shanghai Ultimate Power Communications Technology Co., Ltd.
• Inventors: Yang, Guiliang, Wu, Na, Li, Feng, Qiao, Yuanxin
• Primary Examiner(s): Ngo; Ricky
• Assistant Examiner(s): Zaidi; Iqbal
• Application Number:
  US11/916,502
• Publication Number:
  US 20090122730A1
• Time in Patent Office: 1,909 Days
• Field of Search: 370200-253, 370/312, 370280-281, 370331-335, 370491-497, 370/74, 370/98, 370500-545, 370/395.41, 455/442
• US Class Current: 370/280
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data
• CPC Class Codes: H04W 36/304 due to measured or perceived resources with higher communication quality
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

The present invention discloses a cell handoff method and a UE based on a TDD system. A UE measures received pilot channels of a source cell and a neighboring cell according to a measurement control message and reports measurement result to a RNC. The RNC, determines whether a target cell to be subject to a cell handoff process has available resources at a time slot different from that of the source cell and if yes, transmits a cell handoff command to the UE, allocates available resources for the UE in the target cell and transmits traffic carrier data of the UE to the source cell and the target cell respectively. After receiving the cell handoff command, the UE communicates with the source cell and the target cell at a same frame and at same time according to the allocated available resources.

Claims

1. A cell handoff method based on a TDD system, comprising:

step A. measuring, by a UE, received pilot channels of a source cell and a neighboring cell according to a measurement control message and reporting measurement result to a RNC;

step B. determining, by the RNC, whether to perform the cell handoff process according to the reported measurement result and if yes, entering step C, otherwise maintaining former radio link;

Step C. when the RNC determines according to the reported measurement result that a cell handoff process is to be performed, determining, by the RNC, whether a target cell to be subject to a cell handoff process has available resources at a time slot different from that of the source cell and if yes, transmitting a cell handoff command to the UE, allocating available resources for the UE in the target cell and transmitting traffic carrier data of the UE to the source cell and the target cell respectively;

Step D. after receiving the cell handoff command, communicating, by the UE, with the source cell and the target cell at a same frame and at same time according to the allocated available resources; and

step E. when the UE performs a reliable communication at the uplink and downlink of the target cell, reporting, by the UE, a handoff successful message to the RNC from the target cell, and continuing, by the RNC, to determine on the reported measurement result and controlling the UE to delete a communication link with the source cell.

2. The method according to claim 1, wherein in step B, the measurement result is a pilot channel power measurement result and when at least one neighboring cell has a pilot channel power measurement result equal to or larger than the preset handoff threshold, the RNC determines that the cell handoff process should be performed.

3. The method according to claim 1, wherein in step B, the measurement result is a pilot channel signal/interference ratio measurement result and when at least one neighboring cell has a pilot channel signal/interference ratio measurement result equal to or larger than a preset handoff threshold, the RNC determines that the cell handoff process should be performed.

4. The method according to claim 1, wherein in step C, when available resources of the target cell and the source cell are at different carrier frequencies, the RNC determines there are available resources at different time slots.

5. The method according to claim 1, wherein in step C, when the RNC determines the target cell to be subject to the cell handoff process has no available resources at a time slot different from that of the source cell, it controls the UE to perform the cell handoff process by a traditional cell handoff method.

6. The method according to claim 1, wherein

in implementation procedure of step D, the UE transmits uplink signals to the source cell and the target cell respectively at different time slots in a same frame according to the allocated resources and receives downlink signals at different time slots from the source cell and the target cell.

7. The method according to claim 1, wherein the UE determines whether it successfully communicates with the target cell according to a cyclic redundancy code of a demodulated data block of the downlink signal of the target cell.

8. The method according to claim 7, wherein when at least one of the cyclic redundancy codes of continuous multiple data blocks is correct, it is determined that the UE successfully communicates with the target cell.

9. The method according to claim 1, wherein the available resources comprise available code channel resources and/or time slot resources and/or frequency resources.

10. A system, comprising:

a user equipment (UE), for measuring, received pilot channels of a source cell and a neighboring cell according to a measurement control message and reporting measurement result to a RNC;

after receiving the cell handoff command, communicating with the source cell and the target cell at a same frame and at same time according to the allocated available resources;

when performing a reliable communication at the uplink and downlink of the target cell, reporting a handoff successful message to the RNC from the target cell; and

an RNC, for determining whether to perform the cell handoff process according to the reported measurement result;

determining whether a target cell to be subject to a cell handoff process has available resources at a time slot different from that of the source cell and if yes, transmitting a cell handoff command to the UE, allocating available resources for the UE in the target cell and transmitting traffic carrier data of the UE to the source cell and the target cell respectively;

determining on the reported measurement result and controlling the UE to delete a communication link with the source cell,

wherein the RNC maintains former radio link while determining not to perform the cell handoff process according to the reported measurement result.

11. The system according to claim 10, wherein the available resources comprise available code channel resources and/or time slot resources and/or frequency resources.