Method for accessing a cellular communications network in unlicensed spectrum

Patent metadata

Field	Value
Publication number	US-2022225411-A1
Application number	US-202017608641-A
Country	US
Kind code	A1
Filing date	Apr 30, 2020
Priority date	May 3, 2019
Publication date	Jul 14, 2022
Grant date	—

Abstract

A method for accessing a cellular communications network in unlicensed spectrum is provided. More specifically, the method is related to performing a Listen-Before-Talk (LBT) procedure prior to transmitting a Physical Random Access Channel (PRACH) preamble for accessing a New Radio-Unlicensed (NR-U) network. A User Equipment (UE) first performs the LBT procedure. If the LBT procedure is successful, the UE then generates a punctured PRACH preamble and transmits the punctured PRACH preamble. By puncturing the PRACH preamble, it is possible to create a gap(s) for performing the LBT procedure in a way that is backward compatible with existing NR-U specification and does not reduce a number of random access occasions in a slot or a mini-slot. As a result, it is possible to transmit PRACH preambles in consecutive random access occasions, thus helping to increase spectrum utilization and reduce latency in the cellular communications network.

First claim

1 . A method performed by a wireless device for accessing a cellular communications network in unlicensed spectrum, the method comprising:
performing a Listen-Before-Talk, LBT, procedure during any of two or more back-to-back random access occasions; and responsive to a success of the LBT procedure:
generating a punctured random access preamble responsive to a success of the LBT procedure; and
transmitting the punctured random access preamble if the LBT procedure is successful.

2 . The method of claim 1 , wherein:
performing the LBT procedure comprises performing the LBT procedure during a first of the two or more back-to-back random access occasions; and transmitting the punctured random access preamble comprises transmitting the punctured random access preamble in a second of the two or more back-to-back random access occasions succeeding the first of the two or more back-to-back random access occasions, responsive to the success of the LBT procedure.

3 . The method of claim 1 , wherein:
performing the LBT procedure comprises:
performing the LBT procedure during a first random access occasion of the two or more back-to-back random access occasions, wherein the LBT procedure fails during the first random access occasion; and
performing the LBT procedure at a beginning portion of a second random access occasion of the two or more back-to-back random access occasions that succeeds the first random access occasion, wherein the LBT procedure succeeds during the beginning portion of the second random access occasion; and
generating the punctured random access preamble comprises generating the punctured random access preamble responsive to the success of the LBT procedure during the beginning portion of the second random access occasion; and transmitting the punctured random access preamble comprises transmitting the punctured random access preamble in the second random access occasion starting after the beginning portion of the second random access occasion in which the LBT procedure was performed.

4 . The method of claim 1 , wherein:
performing the LBT procedure comprises performing the LBT procedure during any one of the two or more back-to-back random access occasions; and transmitting the punctured random access preamble comprises transmitting the punctured random access preamble in the any one of the two or more back-to-back random access occasions.

5 . (canceled)

6 . The method of claim 1 wherein transmitting the punctured random access preamble comprises transmitting the punctured random access preamble in one of the two or more back-to-back random access occasions such that the punctured random access preamble creates a gap between the one of the two or more back-to-back random access occasions and at least one other of the two or more back-to-back random access occasions.

7 . (canceled)

8 . The method of claim 1 wherein the punctured random access preamble is punctured at a beginning or an end of the corresponding random access preamble based on estimated tendency of a propagation delay.

9 - 12 . (canceled)

13 . The method of claim 1 wherein the punctured random access preamble is adapted to create a puncturing gap at a beginning and/or an end of a respective one of the two or more back-to-back random access occasions.

14 - 19 . (canceled)

20 . The method of claim 13 wherein a duration of the puncturing gap is adapted based on an outcome of the LBT procedure.

21 . (canceled)

22 . The method of claim 13 wherein the duration of the puncturing gap is less than or equal to a predefined or configured maximum gap size.

23 . The method of claim 13 wherein the duration of the puncturing gap is one of a number of predefined or configured possible gap sizes.

24 . The method of claim 1 wherein generating the punctured random access preamble comprises determining whether to puncture a corresponding random access preamble at the beginning of the corresponding random access preamble or at the end of the corresponding random access preamble, to provide the punctured random access preamble, based on one or more parameters related to propagation delay.

25 . The method of claim 1 wherein transmitting the punctured random access preamble comprises transmitting the punctured random access preamble at a transmit power that compensates for a shortened duration of the punctured random access preamble as compared to a corresponding non-punctured random access preamble.

26 . The method of claim 1 wherein transmitting the punctured random access preamble comprises transmitting the punctured random access preamble over a bandwidth that is wider than that used for transmitting a corresponding non-punctured random access preamble.

27 . (canceled)

28 . The method of claim 1 further comprising:
performing a second LBT procedure during a first random access occasion of a second set of two or more back-to-back random access occasions;
generating a random access preamble without puncturing responsive to a success of the second LBT procedure prior to a start of a second random access occasion of the second set of two or more back-to-back random access occasions; and
transmitting the random access preamble in the second random access occasion of the second set of two or more back-to-back random access occasions.

29 . The method of claim 1 , wherein the two-or-more back-to-back random access occasions are separated by a gap substantially less than a symbol duration.

30 . (canceled)

31 . A wireless device comprising:
a radio unit configured to perform a Listen-Before-Talk, LBT, procedure during any of two or more back-to-back random access occasions; and a control system configured to:
generate a punctured random access preamble responsive to a success of the LBT procedure; and
transmit the punctured random access preamble if the LBT procedure is successful.

32 . (canceled)

33 . A method performed by a base station, the method comprising:
detecting a punctured random access preamble transmitted by a wireless device in unlicensed spectrum; and in response, transmitting a random access response to the wireless device.

34 . The method of claim 33 wherein detecting the punctured random access preamble comprises detecting the punctured random access preamble in one of two or more back-to-back random access occasions.

35 . (canceled)

36 . (canceled)

37 . The method of any one of claim 33 wherein the punctured random access preamble is a version of a corresponding random access preamble that is punctured at a beginning of the corresponding random access preamble.

38 - 40 . (canceled)

41 . The method of claim 33 wherein the punctured random access preamble is adapted to create a puncturing gap at a beginning and/or an end of a respective one of the two or more back-to-back random access occasions.

42 . The method of claim 41 wherein a duration of the puncturing gap is predefined.

43 . The method of claim 42 further comprising sending, to the wireless device, a configuration of a duration of the puncturing gap.

44 - 47 . (canceled)

48 . The method of claim 33 wherein detecting the punctured random access preamble comprises detecting the punctured random access preambl

Assignees

• Ericsson Telefon Ab L M

Inventors

• Axnäs Johan
• Grant Stephen
• Cheng Jung-Fu
• Sugirtharaj David
• Rune Johan

Classifications

• H04W74/0838

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

• H04W74/0833 Primary

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

• H04W74/0816 Primary

  with collision avoidance · CPC title

• H04W16/14

  Spectrum sharing arrangements {between different networks} · CPC title

• H04W74/0808 Primary

  using carrier sensing, e.g. carrier sense multiple access [CSMA] · CPC title