METHOD AND APPARATUS FOR ACCESSING A RANDOM ACCESS CHANNEL BY SELECTIVELY USING DEDICATED OR CONTENTION-BASED PREAMBLES DURING HANDOVER

• US 20090285180A1
• Filed: 02/25/2009
• Published: 11/19/2009
• Est. Priority Date: 03/04/2008
• Status: Active Grant

• Current Assignee: InterDigital Patent Holdings, Inc. (InterDigital, Inc.)
• Original Assignee: InterDigital Patent Holdings, Inc. (InterDigital, Inc.)
• Inventors: Wang, Jin, Zhang, Guodong
• Granted Patent: US 8,649,353 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04W 36/0005 Control or signalling for completing the hand-off
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 74/004 in the uplink, i.e. towards network
• CPC Class Codes: H04W 74/0833 Random access procedures, e.g. with 4-step access
• CPC Class Codes: H04W 74/0866 using a dedicated channel for access
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A method and apparatus for accessing a random access channel (RACH) during handover are disclosed. A handover procedure is initiated and a maximum handover interruption timer is activated. A dedicated preamble is transmitted in an attempt to access the RACH on a condition that the dedicated preamble is reserved in a current random access opportunity and the maximum handover interruption timer has not expired. A contention-based preamble is transmitted in an attempt to access the RACH on a condition that a dedicated preamble is not reserved in a current random access opportunity. If the maximum handover interruption timer has expired, a contention-based preamble is transmitted in an attempt to access the RACH.

Claims

1. A method for a wireless transmit/receive unit (WTRU) to access a random access channel (RACH) during handover, the method comprising:

the WTRU initiating a handover procedure;

activating a maximum handover interruption timer in the WTRU;

the WTRU transmitting a dedicated preamble in an attempt to access the RACH on a condition that the dedicated preamble is reserved in a current random access opportunity and the maximum handover interruption timer has not expired; and

the WTRU transmitting a contention-based preamble in an attempt to access the RACH on a condition that a dedicated preamble is not reserved in a current random access opportunity.

2. The method of claim 1 further comprising:

determining that the maximum handover interruption timer has expired; and

the WTRU transmitting a contention-based preamble in an attempt to access the RACH.

3. The method of claim 2 further comprising:

failing to access a RACH; and

the WTRU transmitting a contention-based preamble in subsequent random access opportunities until a successful RACH access attempt occurs, or a random access opportunity occurs in which there is a reserved dedicated preamble.

4. The method of claim 1 wherein a non-contention based procedure is used on a condition that the dedicated preamble is reserved in a current random access opportunity and the maximum handover interruption timer has not expired.

5. The method of claim 1 wherein a contention-based random access procedure is used on a condition that the dedicated preamble is not reserved in a current random access opportunity and the maximum handover interruption timer has expired.

6. A wireless transmit/receive unit (WTRU) configured to access a random access channel (RACH) during handover, the WTRU comprising:

a maximum handover interruption timer;

a processor configured to initiate handover and activate the maximum handover interruption timer; and

a transmitter configured to transmit a dedicated preamble in an attempt to access the RACH on a condition that the dedicated preamble is reserved in a current random access opportunity and the maximum handover interruption timer has not expired, and transmit a contention-based preamble in an attempt to access the RACH on a condition that a dedicated preamble is not reserved in a current random access opportunity.

7. The WTRU of claim 6 wherein the transmitter is configured to transmit a contention-based preamble in an attempt to access the RACH on a condition that the maximum handover interruption timer has expired.

8. The WTRU of claim 7 wherein the transmitter is configured to transmit, on a condition that a failure to access a RACH has failed, a contention-based preamble in subsequent random access opportunities until a successful RACH access attempt occurs, or a random access opportunity occurs in which there is a reserved dedicated preamble.

9. The WTRU of claim 6 wherein a non-contention based procedure is used on a condition that the dedicated preamble is reserved in a current random access opportunity and the maximum handover interruption timer has not expired.

10. The WTRU of claim 6 wherein a contention-based random access procedure is used on a condition that the dedicated preamble is not reserved in a current random access opportunity and the maximum handover interruption timer has expired.