# US 2021/0243827 A1 · Method and apparatus for sidelink signaling radio bearer (srb) establishment in a wireless communication system

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- Number: US 2021/0243827 A1
- Document ID: US20210243827A1
- Status: Published application
- Kind: A1
- Application number: 17/233,509
- Filed: 2021-04-18
- Published: 2021-08-05
- Earliest claimed: 2019-11-26
- Assignees: ASUSTeK COMPUTER INC.
- Applicants: ASUSTek Computer Inc.
- Inventors: Li-Te Pan; Richard Lee-Chee Kuo
- Web page: https://patentgrep.com/patent/US20210243827A1

## CPC

- H04W 76/14: Direct-mode setup
- H04W 4/40: for vehicles, e.g. vehicle-to-pedestrians [V2P]
- H04W 76/27: Transitions between radio resource control [RRC] states
- H04W 80/02: Data link layer protocols
- H04W 12/037: of the control plane, e.g. signalling traffic
- H04W 92/18: between terminal devices
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

A method and apparatus are disclosed. A first sidelink Signaling Radio Bearer (SRB) for PC5-S message transmission is established. The first sidelink SRB is associated with a default Destination Layer-2 Identity (ID). A first PC5-S message is transmitted on the first sidelink SRB with a Source Layer-2 ID derived from a Layer-2 ID of the first UE and a Destination Layer-2 ID derived from the default Destination Layer-2 ID. A second PC5-S message is received from a second UE. The second PC5-S message is transmitted with a Source Layer-2 ID derived from a Layer-2 ID of the second UE and a Destination Layer-2 ID derived from the Layer-2 ID of the first UE. A second sidelink SRB for PC5-S message reception and/or transmission is established. The second sidelink SRB is associated with the Layer-2 ID of the second UE.

## Claims

### Claim 1

A method for unicast link establishment by a first User Equipment (UE), comprising:
establishing a first sidelink Signaling Radio Bearer (SRB) for PC5-S message transmission, wherein the first sidelink SRB is associated with a default Destination Layer-2 Identity (ID);
transmitting a first PC5-S message on the first sidelink SRB with a Source Layer-2 ID derived from a Layer-2 ID of the first UE and a Destination Layer-2 ID derived from the default Destination Layer-2 ID;
receiving a second PC5-S message from a second UE, wherein the second PC5-S message is transmitted with a Source Layer-2 ID derived from a Layer-2 ID of the second UE and a Destination Layer-2 ID derived from the Layer-2 ID of the first UE; and
establishing a second sidelink SRB for PC5-S message reception and/or transmission, wherein the second sidelink SRB is associated with the Layer-2 ID of the second UE.

### Claim 2 (depends on 1)

The method of claim 1, further comprising establishing a third sidelink SRB for PC5-Radio Resource Control (PC5-RRC) message transmission in response to a unicast link or the PC5-RRC connection establishment being successfully completed, wherein the third sidelink SRB is associated with the Layer-2 ID of the second UE.

### Claim 3 (depends on 2)

The method of claim 2, further comprising:
establishing a fourth sidelink SRB for protected PC5-S message transmission, wherein the fourth sidelink SRB is associated with the Layer-2 ID of the second UE.

### Claim 4 (depends on 2)

The method of claim 2, further comprising:
not establishing any sidelink SRB for PC5-RRC message transmission before the unicast link or the PC5-RRC connection establishment has been successfully completed.

### Claim 5 (depends on 2)

The method of claim 2, wherein a second Sidelink Control Channel (SCCH) configuration specified in a RRC specification is used for establishing the third sidelink SRB.

### Claim 6 (depends on 1)

The method of claim 1, wherein the second sidelink SRB is established in response to reception of the second PC5-S message by a physical layer of the first UE.

### Claim 7 (depends on 1)

The method of claim 1, wherein a first Sidelink Control Channel (SCCH) configuration specified in a Radio Resource Control (RRC) specification is used for establishing the first sidelink SRB and the second sidelink SRB.

### Claim 8 (depends on 1)

The method of claim 1, wherein the default Destination Layer-2 ID is associated with a sidelink service for which a unicast link or a PC5-Radio Resource Control (PC5-RRC) connection is established.

### Claim 9 (depends on 1)

The method of claim 1, wherein the first PC5-S message is a Direct Communication Request.

### Claim 10 (depends on 1)

The method of claim 1, wherein the second PC5-S message is a security related message.

### Claim 11 (depends on 1)

The method of claim 1, wherein each sidelink SRB corresponds to a Sidelink Control Channel (SCCH).

### Claim 12

A first UE (User Equipment) for establishing unicast link, comprising:
a processor; and
a memory operatively coupled to the processor, wherein the processor is configured to execute a program code to:
establish a first sidelink Signaling Radio Bearer (SRB) for PC5-S message transmission in response to a unicast link or a PCS-Radio Resource Control (PC5-RRC) connection establishment being initiated, wherein the first sidelink SRB is associated with a default Destination Layer-2 Identity (ID);
transmit a first PC5-S message for the unicast link or the PC5-RRC connection establishment on the first sidelink SRB with a Source Layer-2 ID derived from a Layer-2 ID of the first UE and a Destination Layer-2 ID derived from the default Destination Layer-2 ID;
receive a second PC5-S message from a second UE, wherein the second PC5-S message is transmitted with a Source Layer-2 ID derived from a Layer-2 ID of the second UE and a Destination Layer-2 ID derived from the Layer-2 ID of the first UE; and
establish a second sidelink SRB for PC5-S message reception and/or transmission, wherein the second sidelink SRB is associated with the Layer-2 ID of the second UE.

### Claim 13 (depends on 12)

The first UE of claim 12, wherein the processor is further configured to execute a program code to:
establish a third sidelink SRB for PC5-RRC message transmission in response to the unicast link or the PC5-RRC connection establishment being successfully completed, wherein the third sidelink SRB is associated with the Layer-2 ID of the second UE.

### Claim 14 (depends on 13)

The first UE of claim 13, wherein the processor is further configured to execute a program code to:
establish a fourth sidelink SRB for protected PC5-S message transmission, wherein the fourth sidelink SRB is associated with the Layer-2 ID of the second UE.

### Claim 15 (depends on 12)

The first UE of claim 12, wherein the processor is further configured to execute a program code to:
not establish any sidelink SRB for PC5-RRC message transmission before the unicast link or the PC5-RRC connection establishment has been successfully completed.

### Claim 16 (depends on 12)

The first UE of claim 12, wherein the second sidelink SRB is established in response to reception of the second PC5-S message by a physical layer of the first UE.

### Claim 17 (depends on 12)

The first UE of claim 12, wherein a first Sidelink Control Channel (SCCH) configuration specified in a RRC specification is used for establishing the first sidelink SRB and the second sidelink SRB.

### Claim 18 (depends on 13)

The first UE of claim 13, wherein a second Sidelink Control Channel (SCCH) configuration specified in a RRC specification is used for establishing the third sidelink SRB.

### Claim 19 (depends on 12)

The first UE of claim 12, wherein the first PC5-S message is a Direct Communication Request.

### Claim 20 (depends on 12)

The first UE of claim 12, wherein the second PC5-S message is a security related message.