METHOD AND APPARATUS FOR PERFORMING CONTENTION BASED RANDOM ACCESS PROCEDURE OVER CONTENTION FREE RANDOM ACCESS PROCEDURE IN WIRELESS COMMUNICATION SYSTEM

• US 20180124825A1
• Filed: 04/11/2016
• Published: 05/03/2018
• Est. Priority Date: 04/10/2015
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: LEE, Youngdae, YI, Seungjune, KIM, Sangwon, LEE, Sunyoung
• Granted Patent: US 10,477,574 B2
• Time in Patent Office: Days
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 74/006 in the downlink, i.e. towards the terminal
• CPC Class Codes: H04W 74/04 Scheduled access hybrid access H04W74/02
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]
• CPC Class Codes: H04W 74/085 collision avoidance

Abstract

A method and apparatus for performing a random access procedure in a wireless communication system is provided. A user equipment (UE) performs a contention free random access procedure on a first frequency, detects a failure of the contention free random access procedure, and performs a contention based random access procedure. When the first frequency is occupied by other media as a result of listen-before-talk (LBT) operation, the contention based random access procedure may be performed on a second frequency.

Claims

1. A method for performing, by a user equipment (UE), a random access procedure in a wireless communication system, the method comprising:

performing a contention free random access procedure on a first frequency;

detecting a failure of the contention free random access procedure; and

performing a contention based random access procedure.

2. The method of claim 1, wherein performing the contention free random access procedure on the first frequency comprising:

receiving a physical downlink control channel (PDCCH) order indicating a dedicated random access preamble from a network on a downlink component carrier (DL CC) of the first frequency; and

transmitting the dedicated random access preamble to the network on a uplink component carrier (UL CC) of the first frequency.

3. The method of claim 2, wherein the DL CC of the first frequency is associated with the UL CC of the first frequency via a system information block 2 (SIB 2).

4. The method of claim 2, wherein the UL CC of the first frequency is one of unoccupied UL cells in a timing advance group (TAG).

5. The method of claim 1, wherein the failure of the contention free random access procedure on the first frequency is detected as a result of a listen-before-talk (LBT) operation.

6. The method of claim 5, wherein the failure of the contention free random access procedure on the first frequency corresponds to that the first frequency is occupied by other media as a result of the LBT operation.

7. The method of claim 1, wherein the contention based random access procedure is performed on a second frequency, which is not occupied by other media.

8. The method of claim 7, wherein performing the contention based random access procedure on the second frequency comprising:

randomly selecting a random access preamble; and

transmitting the randomly selected random access preamble to the network on a UL CC of the second frequency.

9. The method of claim 1, wherein the contention based random access procedure is performed on the first frequency.

10. The method of claim 1, wherein a timer is configured for validity of the dedicated random access preamble.

11. The method of claim 10, wherein performing the contention free random access procedure on a first frequency continues until the timer expires.

12. The method of claim 10, wherein the timer is configured per unlicensed cell or per UL CC.

13. The method of claim 1, wherein the UE is configured with at least one TAG to which at least two UL cells belong.

14. The method of claim 1, wherein the first frequency corresponds to an unlicensed carrier.

15. A user equipment (UE) in a wireless communication system, the UE comprising:

a memory;

a transceiver; and

a processor coupled to the memory and the transceiver,

wherein the processor is configured to;

perform a contention free random access procedure on a first frequency;

detect a failure of the contention free random access procedure; and

perform a contention based random access procedure.