Random access procedures in wireless system

Patent metadata

Field	Value
Publication number	US-9980295-B2
Application number	US-201715410979-A
Country	US
Kind code	B2
Filing date	Jan 20, 2017
Priority date	Mar 16, 2012
Publication date	May 22, 2018
Grant date	May 22, 2018

Abstract

A wireless transmit/receive unit (WTRU) may detect cell congestion by selecting a preamble type as a function of priority level, transmitting the preamble to a serving cell, receiving a random access response (RAR) from the serving cell, determining a congestion state of the serving cell as a function of the received RAR, and/or responding to the congestion state of the serving cell. RACH functionality may be improved by allocating one or more sets of Physical RACH (PRACH) resources to a WTRU. The WTRU may configure the additional PRACH resources based on the allocation. A WTRU may determine a second set of PRACH resources based at least in part on a first set of PRACH resources. A WTRU may determine additional sets of PRACH preambles and may utilize modified PRACH preambles and/or modified PRACH preamble formats. The WTRU may signal additional PRACH resources.

First claim

What is claimed:

1. A method implemented by a wireless transmit receive unit (WTRU), the method comprising:
the WTRU determining a Radio Network Temporary Identifier (RNTI);
the WTRU attempting to decode a downlink control channel using the RNTI, wherein a downlink control information (DCI) that is successfully decoded using the RNTI comprises one or more of a resource block assignment and timing information granting physical resources to be used for a physical random access channel (PRACH) preamble transmission; and
the WTRU sending a preamble transmission using the physical resources granted via the DCI.

2. The method of claim 1 , further comprising receiving a PRACH configuration, wherein the PRACH configuration comprises the RNTI.

3. The method of claim 2 , wherein the DCI is received on the downlink control channel in a subframe as indicated in the PRACH configuration.

4. The method of claim 2 , wherein the DCI includes one or more of a carrier indicator, an index to the PRACH configuration, a frequency offset for PRACH, a preamble format, or a system frame number (SFN).

5. The method of claim 1 , wherein the RNTI is common for a plurality of WTRUs, and wherein the decoding is performed in a common downlink control channel search space.

6. The method of claim 1 , wherein the RNTI is associated with a dedicated WTRU, and wherein the decoding is performed in a dedicated PDCCH search space.

7. The method of claim 1 , wherein the preamble transmission is transmitted in a second subframe that is after a first subframe in which the DCI is decoded, wherein the delay between the first subframe and the second subframe is derived from timing information.

8. The method of claim 1 , wherein the RNTI is associated with one of a high priority traffic, a low priority traffic, or an application with intermittent data.

9. The method of claim 1 , wherein a PRACH configuration is received via broadcast system information or dedicated signaling.

10. The method of claim 1 , further comprising sending a PRACH re-transmission, wherein the PRACH re-transmission is sent using the RNTI on a scheduled PRACH resource.

11. A wireless transmit receive unit (WTRU) comprising:
a processor configured to at least:
determine a Radio Network Temporary Identifier (RNTI);
attempt to decode a downlink control channel using the RNTI, wherein a downlink control information (DCI) that is successfully decoded using the RNTI comprises one or more of a resource block assignment and timing information granting physical resources to be used for a physical random access channel (PRACH) preamble transmission; and

a transmitter configured to at least send a preamble transmission using the physical resources granted via the DCI.

12. The WTRU of claim 11 , further comprising a receiver configured to at least receive a PRACH configuration, wherein the PRACH configuration comprises the RNTI.

13. The WTRU of claim 12 , wherein the DCI is received on the downlink control channel in a subframe as indicated in the PRACH configuration.

14. The WTRU of claim 12 , wherein the DCI includes one or more of a carrier indicator, an index to the PRACH configuration, a frequency offset for PRACH, a preamble format, or a system frame number (SFN), or timing.

15. The WTRU of claim 11 , wherein the RNTI is common for a plurality of WTRUs, and wherein the decoding is performed in a common downlink control channel search space.

16. The WTRU of claim 11 , wherein the RNTI is associated with a dedicated WTRU, and wherein the decoding is performed in a dedicated PDCCH search space.

17. The WTRU of claim 11 , wherein the preamble transmission is transmitted in a second subframe that is after a first subframe in which the DCI is decoded, wherein the delay between the first subframe and the second subframe is derived from timing information.

18. The WTRU of claim 11 , wherein the RNTI is associated with one of a high priority traffic, a low priority traffic, or an application with intermittent data.

19. The WTRU of claim 11 , wherein a PRACH configuration is received via broadcast system information or dedicated signaling.

20. The WTRU of claim 11 , further comprising sending a PRACH re-transmission, wherein the PRACH re-transmission is sent using the RNTI on a scheduled PRACH resource.

Assignees

• Interdigital Patent Holdings Inc

Inventors

• Pelletier Ghyslain
• Ahmad Saad

Classifications

• H04W74/0833 Primary

  Random access procedures, e.g. with 4-step access · CPC title

• H04L5/005

  of common pilots, i.e. pilots destined for multiple users or terminals · CPC title

• H04W74/0838

  using contention-free random access [CFRA] · CPC title

• H04W28/0284

  detecting congestion or overload during communication (monitoring arrangements H04L43/00) · CPC title

• H04L5/0053

  Allocation of signalling, i.e. of overhead other than pilot signals · CPC title