13.2.1 PC5 unicast / link establishment / Reject / Conflict Layer 2 ID

38.523-13GPP5GSPart 1: ProtocolRelease 17TSUser Equipment (UE) conformance specification

13.2.1.1 Test Purpose (TP)

(1)

with { UE being out of coverage, Test loopback activated}

ensure that {

when { UE has a V2X packet to be transmitted over PC5 }

then { UE initiates PC5 unicast link establishment }

}

(2)

with { UE having transmitted PC5 unicast link establishment Request message }

ensure that {

when { The Layer 2 ID is conflicted }

then { the PC5 unicast link establishment procedure fails}

}

13.2.1.2 Conformance requirements

References: The conformance requirements covered in the present TC are specified in: TS 24.587 [FFS], subclause 6.1.2.2.2 and 6.1.2.2.5. Unless otherwise stated these are Rel-16 requirements.

[TS 24.587, subclause 6.1.2.2.2]

The initiating UE shall meet the following pre-conditions before initiating this procedure:

a) a request from upper layers to transmit the packet for V2X service over PC5;

b) the communication mode is unicast mode (e.g. pre-configured as specified in clause 5.2.3 or indicated by upper layers);

c) the link layer identifier for the initiating UE (i.e. layer-2 ID used for unicast communication) is available (e.g. pre-configured or self-assigned) and is not being used by other existing PC5 unicast links within the initiating UE;

d) the link layer identifier for the destination UE (i.e. the unicast layer-2 ID of the target UE or the broadcast layer-2 ID) is available to the initiating UE (e.g. pre-configured, obtained as specified in clause 5.2.3 or known via prior V2X communication);

NOTE 1: In the case where different V2X services are mapped to distinct default destination layer-2 IDs, when the initiating UE intends to establish a single unicast link that can be used for more than one V2X service identifiers, the UE can select any of the default destination layer-2 ID for unicast initial signalling.

[TS 24.587, subclause 6.1.2.2.5]

If the DIRECT LINK ESTABLISHMENT REQUEST message cannot be accepted, the target UE shall send a DIRECT LINK ESTABLISHMENT REJECT message. The DIRECT LINK ESTABLISHMENT REJECT message contains a PC5 signalling protocol cause IE set to one of the following cause values:

#1 direct communication to the target UE not allowed;

#3 conflict of layer-2 ID for unicast communication is detected;

#5 lack of resources for PC5 unicast link; or

#111 protocol error, unspecified.

…

For a received DIRECT LINK ESTABLISHMENT REQUEST message from a layer-2 ID (for unicast communication), if the target UE already has an existing link established to a UE using this layer-2 ID or is currently processing a DIRECT LINK ESTABLISHMENT REQUEST message from the same layer-2 ID, and with one of following parameters different from the existing link or the link for which the link establishment is in progress:

a) the source user info;

b) type of data (e.g. IP or non-IP); or

c) security policy,

the target UE shall send a DIRECT LINK ESTABLISHMENT REJECT message containing PC5 signalling protocol cause value #3 "conflict of layer-2 ID for unicast communication is detected".

NOTE: The type of data (e.g. IP or non-IP) is indicated by the optional IP address configuration IE included in the corresponding DIRECT LINK SECURITY MODE COMPLETE message, i.e. the type of data for the requested link is IP type if this IE is included, and the type of data for the requested link is non-IP if this IE is not included.

…

After sending the DIRECT LINK ESTABLISHMENT REJECT message, the target UE shall provide the following information along with the initiating UE’s layer-2 ID for unicast communication and the target UE’s layer-2 ID for unicast communication to the lower layer:

a) an indication of deactivation of the PC5 unicast security protection and deletion of security context for the PC5 unicast link, if applicable.

Upon receipt of the DIRECT LINK ESTABLISHMENT REJECT message, the initiating UE shall stop timer T5000 and abort the PC5 unicast link establishment procedure.

…

After receiving the DIRECT LINK ESTABLISHMENT REJECT message, the initiating UE shall provide the following information along with the initiating UE’s layer-2 ID for unicast communication and the target UE’s layer-2 ID for unicast communication to the lower layer:

a) an indication of deactivation of the PC5 unicast security protection and deletion of security context for the PC5 unicast link, if applicable.

13.2.1.3 Test description

13.2.1.3.1 Pre-test conditions

System Simulator:

– NR-SS-UE

– NR-SS-UE1 operating as NR sidelink communication device on the resources (i.e. the frequency included in pre-configuration) that UE is expected to use for transmission and reception via PC5 interface.

– NR-SS-UE 1 is synchronised on GNSS.

– GNSS simulator

– The GNSS simulator is started and configured for Scenario #1.

UE:

– UE is authorised to perform NR sidelink communication.

– The UE is equipped with a USIM containing default values as per TS 38.508-1 [4] clause 4.8.3.3.3.

– UE is synchronised on GNSS.

Preamble:

– The UE is in state 4-A and Test Mode (On), Test Loop Function (Off) as defined in TS 38.508-1 [4], Table 4.5.7.2-1 using generic procedure parameter Sidelink (On),Cast Type (Unicast), UE initiating unicast mode NR sidelink communication, GNSS Sync (On).

13.2.1.3.2 Test procedure sequence

Table 13.2.1.3.2-1: Main behaviour

St

Procedure

Message Sequence

TP

Verdict

U – S

Message

1

The NR-SS-UE1 releases unicast mode sidelink connection by executing steps 1-2 of Table 4.9.30.2.2-1 in TS38.508-1 [4].

–

–

–

–

2

Trigger UE to close UE test loop mode E (transmission mode).

NOTE: The UE test loop mode E may be closed by MMI or AT command (+CCUTLE).

–

–

–

–

3

The UE transmits a DIRECT LINK ESTABLISHMENT REQUEST message.

–>

PC5-S: DIRECT LINK ESTABLISHMENT REQUEST

1

P

4

The NR-SS-UE1 transmits a DIRECT LINK ESTABLISHMENT REJECT message with the PC5 signalling protocol cause set to ‘conflict of layer-2 ID for unicast communication is detected’.

<–

PC5-S: DIRECT LINK ESTABLISHMENT REJECT

–

–

5

The NR-SS-UE1 transmits a DIRECT LINK SECURITY MODE COMMAND message

<–

PC5-S: DIRECT LINK SECURITY MODE COMMAND

–

–

–

EXCEPTION: Step 7 is optional and may occur during Step 6

–

–

–

–

6

Check: Does the UE transmit a DIRECT LINK SECURITY MODE COMPLETE message in the next 5 seconds?

–>

PC5-S: DIRECT LINK SECURITY MODE COMPLETE

2

F

7

The UE sends a DIRECT LINK ESTABLISHMENT REQUEST message.

–

PC5-S: DIRECT LINK ESTABLISHMENT REQUEST

–

–

–

EXCEPTION: steps 8-13 are executed if UE has sent DIRECT LINK ESTABLISHMENT REQUEST message in step7.

–

–

–

–

8-13

Steps 3-8 of the procedure defined in Table 4.5.2.2-2 in TS 38.508-1 [4] is performed.

–

–

–

–

14

The SS sends AT COMMAND +CCUTLE to open test loop function.

–

–

–

–

13.2.1.3.3 Specific message contents

Table 13.2.1.3.3-1: Message DIRECT LINK ESTABLISHMENT REQUEST (step 3, Table 13.2.1.3.2-1)

Derivation path: TS 38.508-1 [4], Table 4.7.4-7 with condition Tx

Table 13.2.1.3.3-2: Message DIRECT LINK ESTABLISHMENT REJECT (step 4, Table 13.2.1.3.2-1)

Derivation path: TS 38.508-1 [4], Table 4.7.4-28 with condition Rx

Information Element

Value/Remark

Comment

Condition

PC5 signalling protocol cause

‘0000 0011’B

Conflict of layer-2 ID for unicast communication is detected

Table 13.2.1.3.3-3: Message DIRECT LINK SECURITY MODE COMMAND (step 5, Table 13.2.1.3.2-1)

Derivation path: TS 38.508-1 [4], Table 4.7.4-18 with condition Rx

Table 13.2.1.3.3-4: Message DIRECT LINK SECURITY MODE COMPLETE (step 6, Table 13.2.1.3.2-1)

Derivation path: TS 38.508-1 [4], Table 4.7.4-19 with condition Tx