Mobile Communication System, Mobile Station Device, Base Station Device and Handover Method

• US 20110034172A1
• Filed: 04/14/2009
• Published: 02/10/2011
• Est. Priority Date: 04/18/2008
• Status: Active Grant

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Corporation
• Inventors: Sahara, Toru
• Granted Patent: US 8,599,882 B2
• Time in Patent Office: Days
• US Class Current: 455/436
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 56/002 Mutual synchronization

Abstract

A mobile station which performs a soft handover from a serving base station to a base station in which frame synchronization is established in the uplink direction with the base station calculates the time difference between the receive timing of a downlink signal sent from the base station and the receive timing of a broadcast control channel sent from the base station at S100 to use as a timing correct amount, and corrects the transmission timing of an uplink ANCH to the base station, based on the transmission timing of an uplink signal to the base station and the time difference calculated at S126, to thereby establish frame synchronization in the uplink direction with the base station.

Claims

1. A mobile communication system including a first base station device, a second base station device, and a mobile station device which performs a soft handover from the first base station device to the second base station device, in which frame synchronization is established in an uplink direction with the first base station device, wherein

the mobile station device comprises

receive timing difference calculation means for calculating a time difference between a receive timing of a downlink signal sent from the first base station device and a receive timing of a broadcast signal sent from the second base station device, and

uplink frame synchronizing means for correcting a transmission timing of an uplink signal to the second base station device, based on a transmission timing of an uplink signal to the first base station device and the time difference calculated by the receive timing difference calculation means, to thereby establish frame synchronization in the uplink direction with the second base station device.

2. The mobile communication system according to claim 1, wherein

the second base station device comprises

communication channel determination means for determining a communication channel to be allocated to the mobile station device in response to a switching request received via the first base station device from the mobile station device, and

communication channel notifying means for notifying the mobile station device of the communication channel determined by the communication channel determination means via a switching response sent from the first base station device to the mobile station device, and

the mobile station device sends the uplink signal to the second base station device, using the communication channel notified via the switching response.

3. The mobile communication system according to claim 1, wherein the first base station device and the second base station device communicate with the mobile station device, using an orthogonal frequency division multiple access system.

4. A mobile station device for performing a soft handover from a first base station device to a second base station device, in which frame synchronization is established in an uplink direction with the first base station, comprising:

receive timing difference calculation means for calculating a time difference between a receive timing of a downlink signal sent from the first base station device and a receive timing of a broadcast signal sent from the second base station device, and uplink frame synchronizing means for correcting a transmission timing of an

uplink signal to the second base station device, based on a transmission timing of an uplink signal to the first base station device and the time difference calculated by the receive timing difference calculation means, to thereby establish frame synchronization in the uplink direction with the second base station device.

5. The second base station device according to claim 4, comprising:

communication channel determination means for determining a communication channel to be allocated to the mobile station device in response to a switching request received via the first base station device from the mobile station device, and

communication channel notifying means for notifying the mobile station device of the communication channel determined by the communication channel determination means via a switching response sent from the first base station device to the mobile station device.

6. A handover method for carrying out a soft handover from a first base station device to a second base station device, in which frame synchronization is established in an uplink direction with the first base station, comprising:

a step of calculating a time difference between a receive timing of a downlink signal sent from the first base station device and a receive timing of a broadcast signal sent from the second base station device, and

a step of correcting a transmission timing of an uplink signal to the second base station device, based on a transmission timing of an uplink signal to the first base station device and the time difference calculated to thereby establish frame synchronization in the uplink direction with the second base station device.