Method and apparatus for accessing a random access channel by selectively using dedicated or contention-based preambles during handover

• US 10,368,270 B2
• Filed: 05/11/2018
• Issued: 07/30/2019
• 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: Zhang, Guodong, Wang, Jin
• Primary Examiner(s): Wong, Warner
• Application Number:
  US15/977,706
• Publication Number:
  US 20180262956A1
• Time in Patent Office: 445 Days
• Field of Search: 455436
• 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 wireless transmit/receive unit (WTRU) comprising:

a transmitter; and

a processor configured to;

activate a timer;

transmit, via the transmitter, a dedicated non-contention based random access channel (RACH) preamble to attempt RACH access prior to an expiration of the timer; and

transmit, via the transmitter, a contention-based RACH preamble after the RACH access attempt fails using the dedicated non-contention based RACH preamble and after the expiration of the timer.

2. The WTRU of claim 1, wherein the processor is further configured to transmit, via the transmitter, a contention-based RACH preamble for the RACH access prior to the expiration of the timer.

3. The WTRU of claim 1, wherein the processor is further configured to reserve the dedicated non-contention based RACH preamble a subset N out of a possible M random access opportunities.

4. The WTRU of claim 3, wherein N is 1, and wherein M is 4.

5. The WTRU of claim 1, wherein portions of the dedicated non-contention based RACH preamble are shared with other WTRUs in a time domain.

6. The WTRU of claim 1, wherein the processor is configured to receive a configuration for the dedicated non-contention based RACH preamble from an evolved Node-B (eNB).

7. The WTRU of claim 6, wherein the configuration indicates a subset of random access opportunities reserved for the WTRU to attempt the RACH access using the dedicated non-contention based RACH preamble.

8. The WTRU of claim 1, wherein the processor is configured to receive a configuration for the dedicated non-contention based RACH preamble in a handover command.

9. The WTRU of claim 1, wherein the processor is configured to receive a configuration for the dedicated non-contention based RACH preamble during a handover procedure.

10. A method comprising:

activating a timer;

transmitting, via a wireless transmit/receive unit (WTRU), a dedicated non-contention based random access channel (RACH) preamble to attempt RACH access prior to an expiration of the timer; and

transmitting, via the WTRU, a contention-based RACH preamble after the RACH access attempt fails using the dedicated non-contention based RACH preamble and after the expiration of the timer.

11. The method of claim 10, further comprising transmitting, via the WTRU, a contention-based RACH preamble for the RACH access prior to the expiration of the timer.

12. The method of claim 10, further comprising reserving the dedicated non-contention based RACH preamble a subset N out of a possible M random access opportunities.

13. The method of claim 12, wherein N is 1, and wherein M is 4.

14. The method of claim 10, wherein portions of the dedicated non-contention based RACH preamble are shared with other WTRUs in a time domain.

15. The method of claim 10, further comprising receiving a configuration for the dedicated non-contention based RACH preamble from an evolved Node-B (eNB).

16. The method of claim 15, wherein the configuration indicates a subset of random access opportunities reserved for the WTRU to attempt the RACH access using the dedicated non-contention based RACH preamble.

17. The method of claim 10, further comprising receiving a configuration for the dedicated non-contention based RACH preamble in a handover command.

18. The method of claim 10, further comprising receiving a configuration for the dedicated non-contention based RACH preamble during a handover procedure.