# US 2018/0324653 A1 · Ue selection of contention-free and contention-based random access for handover

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- Number: US 2018/0324653 A1
- Document ID: US20180324653A1
- Status: Published application
- Kind: A1
- Application number: 15/970,554
- Filed: 2018-05-03
- Published: 2018-11-08
- Earliest claimed: 2017-05-05
- Assignees: QUALCOMM Incorporated
- Applicants: QUALCOMM Incorporated
- Inventors: Sumeeth Nagaraja; Tao Luo; Makesh Pravin John Wilson; Sony Akkarakaran; Juan Montojo; Shengbo Chen; Wooseok Nam; Xiao Feng Wang; Kaushik Chakraborty
- Web page: https://patentgrep.com/patent/US20180324653A1

## CPC

- H04W 36/0044: {of quality context information}
- H04W 36/0077: {of access information of target access point}
- H04W 36/085: {involving beams of access points}
- H04W 36/302: {due to low signal strength}
- H04W 74/002: {Transmission of channel access control information}
- H04W 74/0833: Random access procedures, e.g. with 4-step access
- H04W 74/006: {in the downlink, i.e. towards the terminal}
- H04W 74/02: Hybrid access
- H04W 74/04: Scheduled access (hybrid access H04W74/02)
- H04W 74/0838: using contention-free random access [CFRA]
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

User equipment (UE) selection of contention-free random access (CFRA) and contention-based random access (CBRA) for handover processing is discussed. The aspects include receiving a random access configuration at the UE including configuration for CFRA and CBRA. The UE will determine a first random access resource, wherein the first random access resource maps to one or more beams from a target base station. The UE may initiate a random access request using the CFRA when the first random access resource is a contention-free resource, and initiate the random access request using the CBRA when the first random access resource is a contention-based resource.

## Claims

### Claim 1

A method of wireless communication, comprising:
receiving, at a user equipment (UE), a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
determining, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
determining, by the UE, a beam quality associated with the first random access resource; and
initiating, by the UE, a random access request using the CBRA when the first random access resource is a contention-free resource, and the beam quality of the first random access resource is below a threshold beam quality.

### Claim 2

A method of wireless communication, comprising:
receiving, at a user equipment (UE), a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
determining, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
initiating, by the UE, a random access request using the CFRA when the first random access resource is a contention-free resource;
failing, by the UE, to detect a random access response to the random access request using the CFRA prior to a predetermined period of time after the initiating the random access using the CFRA; and
initiating, by the UE, CBRA at a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station.

### Claim 3

A method of wireless communication, comprising:
receiving, at a user equipment (UE), a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
determining, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
initiating, by the UE, a random access request using the CFRA when the first random access resource is a contention-free resource; and
initiating, by the UE, the random access request using the CBRA when the first random access resource is a contention-based resource.

### Claim 4 (depends on 3)

The method of claim 3, further including:
determining, by the UE, a beam quality associated with the first random access resource; and
initiating, by the UE, the random access request using the CBRA when the first random access resource is the contention-free resource, and the beam quality of the first random access resource is below a threshold beam quality.

### Claim 5 (depends on 3)

The method of claim 3, further including:
receiving, at the UE, a random access response to the random access request using the CFRA, wherein the random access response identifies a next uplink transmission opportunity located after a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station; and
initiating, by the UE, CBRA at the next contention-based resource.

### Claim 6 (depends on 3)

The method of claim 3, further including:
failing, by the UE, to detect a random access response to the random access request using the CFRA prior to a predetermined period of time after the initiating the random access using the CFRA; and
initiating, by the UE, CBRA at a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station.

### Claim 7 (depends on 3)

The method of claim 3, further including one of:
initiating, by the UE, another random access request using the CBRA at contention-based random access resources in addition to the initiating the random access request using the CFRA; or
initiating, by the UE, the another random access request using the CFRA at contention-free random access resources in addition to the initiating the random access request using the CBRA.

### Claim 8 (depends on 3)

The method of claim 3, wherein the random access configuration further includes identification for the UE to perform one of:
the initiating the random access request using the CFRA;
the initiating the random access request using the CBRA; or
initiating the random access request using both the CFRA and the CBRA.

### Claim 9 (depends on 3)

The method of claim 3, wherein the random access configuration further includes identification for the UE to perform, according to a predetermined priority, one of:
the initiating the random access request using the CFRA;
the initiating the random access request using the CBRA; or
initiating the random access request using both the CFRA and the CBRA.

### Claim 10

A method of wireless communication, comprising:
receiving, at a target base station, a random access request from a user equipment (UE) using a contention-free random access (CFRA) procedure at one or more beams scheduled for CFRA;
transmitting, by the target base station, a random access response to the UE identifying a delay until an uplink transmission opportunity;
detecting, by the target base station, a contention-based random access (CBRA) request from the UE prior to the uplink transmission opportunity; and
reducing, by the target base station, the delay for a next uplink transmission opportunity using CFRA.

### Claim 11

A method of wireless communication, comprising:
receiving, at a target base station, a handover request associated with a user equipment (UE);
generating, by the target base station, a handover command including a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
scheduling, by the target base station, one or more beams for CFRA and one or more additional beams for CBRA;
detecting, by the target base station, handover initiation by the UE using the one or more additional beams for CBRA; and
releasing, by the target base station, schedule of the one or more beams for CFRA.

### Claim 12

An apparatus configured for wireless communication, comprising:
means for receiving, at a user equipment (UE), a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
means for determining, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
means for determining, by the UE, a beam quality associated with the first random access resource; and
means for initiating, by the UE, a random access request using the CBRA when the first random access resource is a contention-free resource, and the beam quality of the first random access resource is below a threshold beam quality.

### Claim 13

An apparatus configured for wireless communication, comprising:
means for receiving, at a user equipment (UE), a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
means for determining, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
means for initiating, by the UE, a random access request using the CFRA when the first random access resource is a contention-free resource;
means for failing, by the UE, to detect a random access response to the random access request using the CFRA prior to a predetermined period of time after the means for initiating the random access using the CFRA; and
means for initiating, by the UE, CBRA at a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station.

### Claim 14

An apparatus configured for wireless communication, comprising:
means for receiving, at a user equipment (UE), a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
means for determining, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
means for initiating, by the UE, a random access request using the CFRA when the first random access resource is a contention-free resource; and
means for initiating, by the UE, the random access request using the CBRA when the first random access resource is a contention-based resource.

### Claim 15 (depends on 14)

The apparatus of claim 14, further including:
means for determining, by the UE,_a beam quality associated with the first random access resource; and
means for initiating, by the UE, the random access request using the CBRA when the first random access resource is the contention-free resource, and the beam quality of the first random access resource is below a threshold beam quality.

### Claim 16 (depends on 14)

The apparatus of claim 14, further including:
means for receiving, at the UE, a random access response to the random access request using the CFRA, wherein the random access response identifies a next uplink transmission opportunity located after a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station; and
means for initiating, by the UE, CBRA at the next contention-based resource.

### Claim 17 (depends on 14)

The apparatus of claim 14, further including:
means for failing, by the UE, to detect a random access response to the random access request using the CFRA prior to a predetermined period of time after the means for initiating the random access using the CFRA; and
means for initiating, by the UE, CBRA at a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station.

### Claim 18 (depends on 14)

The apparatus of claim 14, further including one of:
means for initiating, by the UE, another random access request using the CBRA at contention-based random access resources in addition to the means for initiating the random access request using the CFRA; or
means for initiating, by the UE, the another random access request using the CFRA at contention-free random access resources in addition to the means for initiating the random access request using the CBRA.

### Claim 19 (depends on 14)

The apparatus of claim 14, wherein the random access configuration further includes identification for the UE to perform one of:
the means for initiating the random access request using the CFRA;
the means for initiating the random access request using the CBRA; or
means for initiating the random access request using both the CFRA and the CBRA.

### Claim 20 (depends on 14)

The apparatus of claim 14, wherein the random access configuration further includes identification for the UE to perform, according to a predetermined priority, one of:
the means for initiating the random access request using the CFRA;
the means for initiating the random access request using the CBRA; or
means for initiating the random access request using both the CFRA and the CBRA.

### Claim 21

An apparatus configured for wireless communication, comprising:
means for receiving, at a target base station, a random access request from a user equipment (UE) using a contention-free random access (CFRA) procedure at one or more beams scheduled for CFRA;
means for transmitting, by the target base station, a random access response to the UE identifying a delay until an uplink transmission opportunity;
means for detecting, by the target base station, a contention-based random access (CBRA) request from the UE prior to the uplink transmission opportunity; and
means for reducing, by the target base station, the delay for a next uplink transmission opportunity using CFRA.

### Claim 22

An apparatus configured for wireless communication, comprising:
means for receiving, at a target base station, a handover request associated with a user equipment (UE);
means for generating, by the target base station, a handover command including a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
means for scheduling, by the target base station, one or more beams for CFRA and one or more additional beams for CBRA;
means for detecting, by the target base station, handover initiation by the UE using the one or more additional beams for CBRA; and
means for releasing, by the target base station, schedule of the one or more beams for CFRA.

### Claim 23

A non-transitory computer-readable medium having program code recorded thereon, the program code comprising:
program code executable by a computer for causing the computer to receive, at a user equipment (UE), a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
program code executable by the computer for causing the computer to determine, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
program code executable by the computer for causing the computer to determine, by the UE, a beam quality associated with the first random access resource; and
program code executable by the computer for causing the computer to initiate, by the UE, a random access request using the CBRA when the first random access resource is a contention-free resource, and the beam quality of the first random access resource is below a threshold beam quality.

### Claim 24

A non-transitory computer-readable medium having program code recorded thereon, the program code comprising:
program code executable by a computer for causing the computer to receive, at a user equipment (UE), a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
program code executable by the computer for causing the computer to determine, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
program code executable by the computer for causing the computer to initiate, by the UE, a random access request using the CFRA when the first random access resource is a contention-free resource;
program code executable by the computer for causing the computer to fail, by the UE, to detect a random access response to the random access request using the CFRA prior to a predetermined period of time after execution of the program code executable by the computer for causing the computer to initiate the random access using the CFRA; and
program code executable by the computer for causing the computer to initiate, by the UE, CBRA at a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station.

### Claim 25

A non-transitory computer-readable medium having program code recorded thereon, the program code comprising:
program code executable by a computer for causing the computer to receive, at a user equipment (UE), a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
program code executable by the computer for causing the computer to determine, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
program code executable by the computer for causing the computer to initiate, by the UE, a random access request using the CFRA when the first random access resource is a contention-free resource; and
program code executable by the computer for causing the computer to initiate, by the UE, the random access request using the CBRA when the first random access resource is a contention-based resource.

### Claim 26 (depends on 25)

The non-transitory computer-readable medium of claim 25, further including:
program code executable by the computer for causing the computer to determine, by the UE, a beam quality associated with the first random access resource; and
program code executable by the computer for causing the computer to initiate, by the UE, the random access request using the CBRA when the first random access resource is the contention-free resource, and the beam quality of the first random access resource is below a threshold beam quality.

### Claim 27 (depends on 25)

The non-transitory computer-readable medium of claim 25, further including:
program code executable by the computer for causing the computer to receive, at the UE, a random access response to the random access request using the CFRA, wherein the random access response identifies a next uplink transmission opportunity located after a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station; and
program code executable by the computer for causing the computer to initiate, by the UE, CBRA at the next contention-based resource.

### Claim 28 (depends on 25)

The non-transitory computer-readable medium of claim 25, further including:
program code executable by the computer for causing the computer to fail, by the UE, to detect a random access response to the random access request using the CFRA prior to a predetermined period of time after the program code executable by the computer for causing the computer to initiate the random access using the CFRA; and
program code executable by the computer for causing the computer to initiate, by the UE, CBRA at a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station.

### Claim 29 (depends on 25)

The non-transitory computer-readable medium of claim 25, further including one of:
program code executable by the computer for causing the computer to initiate, by the UE, another random access request using the CBRA at contention-based random access resources in addition to the program code executable by the computer for causing the computer to initiate the random access request using the CFRA; or
program code executable by the computer for causing the computer to initiate, by the UE, the another random access request using the CFRA at contention-free random access resources in addition to the program code executable by the computer for causing the computer to initiate the random access request using the CBRA.

### Claim 30 (depends on 25)

The non-transitory computer-readable medium of claim 25, wherein the random access configuration further includes identification for the UE to perform one of:
the program code executable by the computer for causing the computer to initiate the random access request using the CFRA;
the program code executable by the computer for causing the computer to initiate the random access request using the CBRA; or
program code executable by the computer for causing the computer to initiate the random access request using both the CFRA and the CBRA.

### Claim 31 (depends on 25)

The non-transitory computer-readable medium of claim 25, wherein the random access configuration further includes identification for the UE to perform, according to a predetermined priority, one of:
the program code executable by the computer for causing the computer to initiate the random access request using the CFRA;
the program code executable by the computer for causing the computer to initiate the random access request using the CBRA; or
program code executable by the computer for causing the computer to initiate the random access request using both the CFRA and the CBRA.

### Claim 32

A non-transitory computer-readable medium having program code recorded thereon, the program code comprising:
program code executable by a computer for causing the computer to receive, at a target base station, a random access request from a user equipment (UE) using a contention- free random access (CFRA) procedure at one or more beams scheduled for CFRA;
program code executable by the computer for causing the computer to transmit, by the target base station, a random access response to the UE identifying a delay until an uplink transmission opportunity;
program code executable by the computer for causing the computer to detect, by the target base station, a contention-based random access (CBRA) request from the UE prior to the uplink transmission opportunity; and
program code executable by the computer for causing the computer to reduce, by the target base station, the delay for a next uplink transmission opportunity using CFRA.

### Claim 33

A non-transitory computer-readable medium having program code recorded thereon, the program code comprising:
program code executable by a computer for causing the computer to receive, at a target base station, a handover request associated with a user equipment (UE);
program code executable by the computer for causing the computer to generate, by the target base station, a handover command including a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
program code executable by the computer for causing the computer to schedule, by the target base station, one or more beams for CFRA and one or more additional beams for CBRA;
program code executable by the computer for causing the computer to detect, by the target base station, handover initiation by the UE using the one or more additional beams for CBRA; and
program code executable by the computer for causing the computer to release, by the target base station, schedule of the one or more beams for CFRA.

### Claim 34

An apparatus configured for wireless communication, the apparatus comprising:
at least one processor; and
a memory coupled to the at least one processor,
wherein the at least one processor is configured:
to receive, at a user equipment (UE), a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
to determine, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
to determine, by the UE, a beam quality associated with the first random access resource; and
to initiate, by the UE, a random access request using the CBRA when the first random access resource is a contention-free resource, and the beam quality of the first random access resource is below a threshold beam quality.

### Claim 35

An apparatus configured for wireless communication, the apparatus comprising:
at least one processor; and
a memory coupled to the at least one processor,
wherein the at least one processor is configured:
to receive, at a user equipment (UE), a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
to determine, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
to initiate, by the UE, a random access request using the CFRA when the first random access resource is a contention-free resource;
to fail, by the UE, to detect a random access response to the random access request using the CFRA prior to a predetermined period of time after execution of the configuration of the at least one processor to initiate the random access using the CFRA; and
to initiate, by the UE, CBRA at a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station.

### Claim 36

An apparatus configured for wireless communication, the apparatus comprising:
at least one processor; and
a memory coupled to the at least one processor,
wherein the at least one processor is configured:
to receive, at a user equipment (UE), a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
to determine, at the UE, a first random access resource, wherein the first random access resource maps to one or more beams from a target base station;
to initiate, by the UE, a random access request using the CFRA when the first random access resource is a contention-free resource; and
to initiate, by the UE, the random access request using the CBRA when the first random access resource is a contention-based resource.

### Claim 37 (depends on 36)

The apparatus of claim 36, further including configuration of the at least one processor:
to determine, by the UE, a beam quality associated with the first random access resource; and
to initiate, by the UE, the random access request using the CBRA when the first random access resource is the contention-free resource, and the beam quality of the first random access resource is below a threshold beam quality.

### Claim 38 (depends on 36)

The apparatus of claim 36, further including configuration of the at least one processor:
to receive, at the UE, a random access response to the random access request using the CFRA, wherein the random access response identifies a next uplink transmission opportunity located after a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station; and
to initiate, by the UE, CBRA at the next contention-based resource.

### Claim 39 (depends on 36)

The apparatus of claim 36, further including configuration of the at least one processor:
to fail, by the UE, to detect a random access response to the random access request using the CFRA prior to a predetermined period of time after the configuration of the at least one processor to initiate the random access using the CFRA; and
to initiate, by the UE, CBRA at a next contention-based resource, wherein the next contention-based resource maps to one or more additional beams of the target base station.

### Claim 40 (depends on 36)

The apparatus of claim 36, further including configuration of the at least one processor to one of:
initiate, by the UE, another random access request using the CBRA at contention- based random access resources in addition to the configuration of the at least one processor to initiate the random access request using the CFRA; or
initiate, by the UE, the another random access request using the CFRA at contention- free random access resources in addition to the configuration of the at least one processor to initiate the random access request using the CBRA.

### Claim 41 (depends on 36)

The apparatus of claim 36, wherein the random access configuration further includes identification for the UE to perform one of:
the configuration of the at least one processor to initiate the random access request using the CFRA;
the configuration of the at least one processor to initiate the random access request using the CBRA; or
configuration of the at least one processor to initiate the random access request using both the CFRA and the CBRA.

### Claim 42 (depends on 36)

The apparatus of claim 36, wherein the random access configuration further includes identification for the UE to perform, according to a predetermined priority, one of:
the configuration of the at least one processor to initiate the random access request using the CFRA;
the configuration of the at least one processor to initiate the random access request using the CBRA; or
configuration of the at least one processor to initiate the random access request using both the CFRA and the CBRA.

### Claim 43

An apparatus configured for wireless communication, the apparatus comprising:
at least one processor; and
a memory coupled to the at least one processor,
wherein the at least one processor is configured:
to receive, at a target base station, a random access request from a user equipment (UE) using a contention-free random access (CFRA) procedure at one or more beams scheduled for CFRA;
to transmit, by the target base station, a random access response to the UE identifying a delay until an uplink transmission opportunity;
to detect, by the target base station, a contention-based random access (CBRA) request from the UE prior to the uplink transmission opportunity; and
to reduce, by the target base station, the delay for a next uplink transmission opportunity using CFRA.

### Claim 44

An apparatus configured for wireless communication, the apparatus comprising:
at least one processor; and
a memory coupled to the at least one processor,
wherein the at least one processor is configured:
to receive, at a target base station, a handover request associated with a user equipment (UE);
to generate, by the target base station, a handover command including a random access configuration, wherein the random access configuration includes configuration for contention-free random access (CFRA) and contention-based random access (CBRA);
to schedule, by the target base station, one or more beams for CFRA and one or more additional beams for CBRA;
to detect, by the target base station, handover initiation by the UE using the one or more additional beams for CBRA; and
to release, by the target base station, schedule of the one or more beams for CFRA. NRF NO. QLXX.P1188US