TDD system based cell handoff method and user equipment

• US 20090122730A1
• Filed: 04/20/2006
• Published: 05/14/2009
• 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
• Granted Patent: US 7,978,634 B2
• Time in Patent Office: Days
• 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 user equipment based on a TDD system. The method includes: step A. 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; step B. 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; and step C. 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. According to the handoff method of the present invention, UE can more reliably receive the handoff control command transmitted by the RNC and during the handoff process, the transmission power and interference are reduced so that the reliable handoff of a UE is guaranteed and the system performance is improved.

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 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; and

step C. 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.

2. The method according to claim 1, wherein between step A and step B further comprising:

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

3. The method according to claim 2, wherein in step D, 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.

4. The method according to claim 2, wherein in step D, 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.

5. The method according to claim 1, wherein in step B, 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.

6. The method according to claim 1, wherein in step B, 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.

7. The method according to claim 1, wherein

in implementation procedure of step C, 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.

8. The method according to claim 1, wherein further comprises:

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.

9. The method according to claim 8, 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.

10. The method according to claim 9, 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.

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

12. A user equipment, comprising:

a measurement unit, for performing a channel measurement on a neighboring cell according to a measurement control message allocated to a user by a RNC and reporting a measurement result to the RNC; and

a handoff unit, for receiving a handoff command transmitted from the RNC and for communicating with a source cell and a target cell at a same time in a same frame according to available resources in the target cell allocated by the RNC during a cell handoff process.

13. The user equipment according to claim 12, wherein the available resources comprise available code channel resources and/or time slot resources and/or frequency resources.