METHOD AND APPARATUS FOR SUPPORTING HANDOVER FROM LTE/EUTRAN TO GPRS/GERAN

• US 20080192697A1
• Filed: 02/12/2008
• Published: 08/14/2008
• Est. Priority Date: 02/12/2007
• Status: Active Grant

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Shaheen, Kamel M.
• Granted Patent: US 8,072,936 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04W 36/0011 for data sessions of end-to-end connection
• CPC Class Codes: H04W 36/0022 for transferring data sessions between adjacent core network technologies
• CPC Class Codes: H04W 36/0061 of neighbour cell information
• CPC Class Codes: H04W 36/125 involving different types of service backbones
• CPC Class Codes: H04W 36/14 Reselecting a network or an air interface
• CPC Class Codes: H04W 36/144 over a different radio air interface technology

Abstract

A method and apparatus for handover of a dual mode wireless transmit/receive unit (WTRU) from an LTE system to a GERAN system uses measurements of the LTE and GERAN frequencies and a decision by a source evolved Node B to perform the handover. A GERAN access procedure includes PS attach messages exchanged between the WTRU and the target base station controller and a target SGSN. Alternatively, the GERAN access procedure uses RAN mobility information messages exchanged by the WTRU and the target base station controller and a relocation detect message by the source evolved Node B.

Claims

1. A dual mode wireless transmit/receive unit (WTRU) comprising:

a receiver configured to receive global system for mobile (GSM)/enhanced data rates for GSM evolution (EDGE) radio access network (GERAN) cell information while receiving wireless communications in a long term evolution (LTE)/evolved universal terrestrial radio access network (EUTRAN) cell;

a processor configured to receive list of available cells and their technologies in order to perform measurements on LTE frequencies and GERAN frequencies to be used for a handover from a source LTE cell to other wireless coverage areas, including a target GERAN cell using the GERAN cell information; and

a transmitter configured to send a measurement report of the measurements on the GERAN frequencies to a source evolved Node B (eNB).

2. The WTRU as in claim 1, further comprising a second receiver configured to receive GERAN communications, where the receiver recognizes the target technology from among a plurality of radio access technologies that are supported, whereby the processor communicates the target channel ID to the second receiver.

3. The WTRU as in claim 1, further comprising a second transmitter configured to start GERAN access procedures by sending a packet switched (PS) attach request to a target base station controller (T-BSC), wherein the second receiver is configured to receive a PS attach accept signal from the T-BSC.

4. The WTRU as in claim 3 wherein the second transmitter is configured to send a PS attach accept ACK signal to the T-BSC.

5. The WTRU as in claim 1, further comprising:

a second receiver configured to receive GERAN communications and to receive a RAN mobility information signal from a target base station controller; and

a second transmitter configured to send GERAN communications and to send a RAN mobility information ACK signal to the target base station controller.

6. A source evolved Node B (eNB) comprising:

a transmitter configured to send a measurement list including different radio access technologies, including GERAN, to a wireless transmit/receive unit (WTRU);

a receiver configured to receive a measurement report from the WTRU having measurements of a target GERAN cell for a handover of the WTRU; and

a processor configured to make a decision for handover of the WTRU from a source LTE cell to the target GERAN cell based on the measurement report.

7. The eNB as in claim 6, wherein the transmitter is configured to send a relocation request to a source mobility management entity (MME) supporting the source eNB, the request having a target system ID and the source eNB ID.

8. The eNB as in claim 6, wherein the receiver is configured to receive a relocation command that includes a temporary mobile subscriber identity (TMSI) and a target base station controller (T-BSC) ID, whereby the processor is configured to establish a temporary tunnel to the T-BSC to forward data.

9. A source LTE mobility management entity (MME) comprising a processor configured to determine a handover target GERAN system for a handover of a wireless transmit/receive unit (WTRU) from a received relocation request from a serving eNB, the relocation request having a source cell ID and a target cell ID, the processor configured to identify a Serving GPRS Support Node (SGSN) that controls a target GERAN cell by mapping the target GERAN Cell ID to an SGSN IP address.

10. The MME as in claim 9, wherein the processor is configured to forward a request for resource allocation in the target system via a message that includes the target cell ID and the WTRU ID as an international mobile subscriber identity (IMSI).

11. The MME as in claim 9, wherein the processor is configured to release the resources allocated to the WTRU in LTE system after receiving handover complete message from a target SGSN.

12. A method for handover of a dual mode wireless transmit/receive unit (WTRU) from a long term evolution system cell to a global system for mobile (GSM)/enhanced data rates for GSM evolution (EDGE) radio access network (GERAN) cell, the method comprising:

receiving GERAN cell information while receiving wireless communications in a LTE cell;

receiving a list of available cells and their technologies from the LTE system in order to perform measurements on LTE frequencies and GERAN frequencies to be used for a handover from a source LTE cell to other wireless coverage areas, including a target GERAN cell using the GERAN cell information; and

sending a measurement report of the measurements on the GERAN frequencies to a source evolved Node B (eNB).

13. The method as in claim 12, further comprising a first receiver of the dual mode WTRU recognizing a target radio access technology from among a plurality of supported radio access technologies;

and communicating a target channel ID to a second receiver of the dual mode WTRU.

14. The method as in claim 12, further comprising starting GERAN access procedures by sending a packet switched (PS) attach request to a target base station controller (T-BSC), wherein the second receiver is configured to receive a PS attach accept signal from the T-BSC.

15. The method as in claim 14, further comprising sending a PS attach accept ACK signal to the T-BSC.

16. The method as in claim 12, further comprising:

receiving a RAN mobility information signal from a target base station controller; and

sending a RAN mobility information ACK signal to the target base station controller.

17. A method for an evolved Node B (eNB) performing handover of a wireless transmit/receive unit, comprising:

sending a measurement list including different radio access technologies, including GERAN, to the wireless transmit/receive unit (WTRU);

receiving a measurement report from the WTRU having measurements of a target GERAN cell for the handover; and

performing a decision for handover of the WTRU from a source LTE cell to the target GERAN cell based on the measurement report.

18. The method as in claim 17, wherein the transmitter is configured to send a relocation request to a source mobility management entity (MME) supporting the source eNB, the request having a target system ID and the source eNB ID.

19. The method as in claim 17, further comprising receiving a relocation command that includes a temporary mobile subscriber identity (TMSI) and a target base station controller (T-BSC) ID;

and establishing a temporary tunnel to the T-BSC to forward data in response to the relocation command.