Random access procedures under coverage limitations

Patent metadata

Field	Value
Publication number	US-2016295609-A1
Application number	US-201615089528-A
Country	US
Kind code	A1
Filing date	Apr 2, 2016
Priority date	Apr 3, 2015
Publication date	Oct 6, 2016
Grant date	—

Abstract

Methods, systems, and devices for wireless communication are described. A user equipment (UE) may select a coverage enhancement (CE) level based on a coverage limitation. The UE may then receive system information from a base station indicating an index of CE levels and corresponding physical random access channel (PRACH) configurations, and the UE may transmit a random access preamble using the PRACH configuration for the selected CE level. For example, the UE may transmit the preamble based on a frequency offset that corresponds to the selected CE level. In some cases, the UE and base station may also associate groups of preambles with downlink (DL) CE levels. The UE may select a preamble from a group corresponding to a desired DL CE level for a random access response message. The base station may determine the DL CE level based on the group the preamble was selected from and respond accordingly.

First claim

What is claimed is:

1 . A method of wireless communication, comprising:
receiving signaling indicative of a set of physical random access channel (PRACH) configurations, wherein each PRACH configuration of the set corresponds to a coverage enhancement (CE) level supported by a base station; selecting one of the CE levels based at least in part on a coverage limitation; and transmitting a random access message according to a PRACH configuration corresponding to the selected CE level.

2 . The method of claim 1 , further comprising:
receiving signaling indicative of one or more coverage limitation thresholds from the base station; and determining the coverage limitation based at least in part on the received coverage limitation thresholds.

3 . The method of claim 2 , wherein the coverage limitation comprises at least one of a link budget, a path loss threshold, a reference signal received power (RSRP) threshold, or an initial PRACH target power, or any combination thereof.

4 . The method of claim 1 , further comprising:
selecting a preamble format for the random access message based at least in part on the coverage limitation.

5 . The method of claim 4 , further comprising:
estimating a downlink (DL) CE level based at least in part on explicit signaling from the base station, a comparison between a downlink signal measurement and a DL signal threshold, or the selected coverage enhancement level, or any combination thereof, wherein the selected preamble format is indicative of the estimated DL CE level.

6 . The method of claim 5 , wherein the DL signal threshold is determined based at least in part on a reference DL transmission format.

7 . The method of claim 1 , further comprising:
determining one or more resources for receiving a random access response based at least in part on an estimated downlink (DL) CE level; and monitoring the one or more resources for the random access response.

8 . The method of claim 1 , further comprising:
selecting a subsequent CE level based at least in part on an unsuccessful random access transmission; and reestimating an estimated downlink (DL) CE level based at least in part on selecting the subsequent CE level.

9 . The method of claim 1 further comprising:
receiving a random access response; and
decoding the random access response based at least in part on an estimated downlink (DL) CE level.

10 . The method of claim 9 , wherein decoding the random access response comprises:
decoding a control portion of the random access response based at least in part on the estimated DL CE level; identifying an indicated CE level based at least in part on the control portion of the random access response; and decoding a data portion of the random access response based at least in part on the indicated CE level.

11 . The method of claim 1 , further comprising:
selecting resources for transmitting the random access message based at least in part on the PRACH configuration; and monitoring one or more pre-defined time intervals for receiving a random access response based at least in part on the selected resources.

12 . The method of claim 11 , wherein the one or more pre-defined time intervals for monitoring is based at least in part on the selected preamble format of the random access message.

13 . The method of claim 11 , further comprising:
receiving an indication in a random access response to continue monitoring for one or more further response messages.

14 . The method of claim 1 , further comprising:
selecting resources for transmitting the random access message based at least in part on the PRACH configuration; monitoring one or more pre-defined time intervals for receiving a random access response control message based at least in part on the selected resources; and receiving a random access response based at least in part on the random access response control message.

15 . The method of claim 14 , wherein the one or more pre-defined time intervals for monitoring is based at least in part on the selected preamble format of the random access message.

16 . The method of claim 14 , wherein the one or more pre-defined time intervals for monitoring is based at least in part on a CE level of the selected preamble format of the random access message.

17 . The method of claim 1 , further comprising:
determining a target transmit power for the random access message based at least in part on the PRACH configuration, a selected preamble format, a prior transmission count, or any combination thereof.

18 . The method of claim 1 , wherein the selecting one of the CE levels is based at least in part on a counter of prior PRACH transmissions.

19 . The method of claim 1 , further comprising:
selecting a candidate CE level of the one or more CE levels supported by the base station; determining a candidate transmit power for the random access message; determining that the candidate transmit power exceeds a transmit power threshold; and wherein the selection of one of the CE levels is based at least in part on determining that the candidate transmit power exceeds the transmit power threshold, wherein the selected CE level is higher than the candidate CE level.

20 . The method of claim 1 , further comprising:
receiving signaling indicative of a CE level from the base station, wherein the selected CE level corresponds to the CE level indicated by the base station.

21 . The method of claim 20 , wherein the signaling from the base station comprises a PRACH mask index or a frequency offset, or both.

22 . The method of claim 1 , wherein the set of PRACH configurations comprises a set of PRACH configurations for frequency division duplex (FDD) operation or a set of PRACH configurations for time division duplex (TDD) operation, or both.

23 . The method of claim 1 , wherein the set of PRACH configurations comprises a set of deterministic values for each supported CE level.

24 . The method of claim 1 , wherein the set of PRACH configurations comprises a PRACH frequency offset corresponding to each supported CE level.

25 . The method of claim 1 , further comprising:
identifying a default PRACH configuration based at least in part on a user equipment (UE) type, wherein the random access message is transmitted according to the default PRACH configuration.

26 . The method of claim 25 , wherein the UE type comprises at least one of a UE category or a previously configured UE, or both.

27 . The method of claim 1 , wherein the set of PRACH configurations comprise designated resources that are frequency division multiplexing (FDM) or time division multiplexing (TDM), or both, over a plurality of resource blocks.

28 . The method of claim 27 , wherein the received signaling comprises at least one of a starting subframe index, a PRACH periodicity, a PRACH offset, a time duration, or a frequency offset, or any combination thereof.

29 . The method of claim 1 , further comprising:
initiating a random access transmission counter upon transmitting the random access message; selecting a subsequent CE level based at least in part on an unsuccessful random access transmission; and resetting the random access transmission counter based at least in part on selecting the subsequent CE level.

30 . The method of claim 1 , furth

Assignees

• Qualcomm Inc

Inventors

• Vajapeyam Madhavan Srinivasan
• Xu Hao
• Chen Wanshi

Classifications

• H04W72/542

  using measured or perceived quality · CPC title

• H04W72/23

  in the downlink direction of a wireless link, i.e. towards a terminal · CPC title

• H04W74/006 Primary

  in the downlink, i.e. towards the terminal · CPC title

• H04W24/08

  Testing, {supervising or monitoring} using real traffic · CPC title

• H04L5/14

  Two-way operation using the same type of signal, i.e. duplex · CPC title