13.2.4 PC5 unicast / link Release / Reestablish PC5 unicast link to same UE

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

13.2.4.1 Test Purpose (TP)

(1)

with { UE having established a V2X DIRECT LINK with a K_NRP ID to a SS-UE, and released the DIRECT LINK after receiving a DIRECT LINK RELEASE REQUEST message }

ensure that {

when { UE has a V2X packet to be transmitted over PC5 to the same SS-UE }

then { UE transmits DIRECT LINK ESTABLISHMENT REQUEST }

}

13.2.4.2 Conformance requirements

References: The conformance requirements covered in the present TC are specified in: TS 24.587 , subclause 6.1.2.4.2, 6.1.2.4.4, 6.1.2.2.2. Unless otherwise stated these are Rel-16 requirements.

[TS 24.587, subclause 6.1.2.4.2]

The initiating UE shall initiate the procedure if a request from upper layers to release a PC5 unicast link with the target UE which uses a known layer-2 ID (for unicast communication) is received and there is an existing PC5 unicast link between these two UEs.

The initiating UE may initiate the procedure if the target UE has been non-responsive, e.g. no response in the PC5 unicast link modification procedure, PC5 unicast link identifier update procedure, PC5 unicast link re-keying procedure or PC5 unicast link keep-alive procedure.

The initiating UE may initiate the procedure to release an established PC5 unicast link if the UE has reached the maximum number of established PC5 unicast links and there is a need to establish a new PC5 unicast link. In this case, which PC5 unicast link is to be released is up to UE implementation.

The initiating UE may initiate the procedure to release an established PC5 unicast link upon expiry of the timer T5005.

In order to initiate the PC5 unicast link release procedure, the initiating UE shall create a DIRECT LINK RELEASE REQUEST message with a PC5 signalling protocol cause IE indicating one of the following cause values:

#1 direct communication with the target UE not allowed;

#2 direct communication to the target UE no longer needed;

#4 direct connection is not available anymore;

#5 lack of resources for PC5 unicast link; or

#111 protocol error, unspecified.

The initiating UE shall include the new MSB of KNRP ID in the DIRECT LINK RELEASE REQUEST message.

After the DIRECT LINK RELEASE REQUEST message is generated, the initiating UE shall pass this message to the lower layers for transmission along with the initiating UE’s layer-2 ID for unicast communication and the target UE’s layer-2 ID for unicast communication, and shall stop T5011 if running. The initiating UE shall start timer T5002.

Figure 6.1.2.4.2.1: PC5 unicast link release procedure

[TS 24.587, subclause 6.1.2.4.4]

Upon receipt of the DIRECT LINK RELEASE ACCEPT message, the initiating UE shall stop timer T5002 and shall release the PC5 unicast link by performing the following behaviors:

a) inform the lower layer along with the PC5 link identifier that the PC5 unicast link has been released; and

b) delete the PC5 unicast link context of the PC5 unicast link after an implementation specific time.

The initiating UE shall form the new KNRP ID from the MSB of KNRP ID included in the DIRECT LINK RELEASE REQUEST message and the LSB of KNRP ID received in the DIRECT LINK RELEASE ACCEPT message. The initiating UE shall replace the existing KNRP ID with the new KNRP ID. The initiating UE may include the new KNRP ID in DIRECT LINK ESTABLISHMENT REQUEST message with the target UE as specified in clause 6.1.2.2.2.

[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.

e) the initiating UE is either authorised for V2X communication over PC5 in NR-PC5 in the serving PLMN, or has a valid authorization for V2X communication over PC5 in NR-PC5 when not served by E-UTRA and not served by NR. The UE considers that it is not served by E-UTRA and not served by NR if the following conditions are met:

1) not served by NR and not served by E-UTRA for V2X communication over PC5;

2) in limited service state as specified in 3GPP TS 23.122 [2], if the reason for the UE being in limited service state is one of the following;

i) the UE is unable to find a suitable cell in the selected PLMN as specified in 3GPP TS 38.304 [9];

ii) the UE received a REGISTRATION REJECT message or a SERVICE REJECT message with the 5GMM cause #11 "PLMN not allowed" as specified in 3GPP TS 24.501 [6]; or

iii) the UE received a REGISTRATION REJECT message or a SERVICE REJECT message with the 5GMM cause #7 "5GS services not allowed" as specified in 3GPP TS 24.501 [6]; or

3) in limited service state as specified in 3GPP TS 23.122 [2] for reasons other than i), ii) or iii) above, and located in a geographical area for which the UE is provisioned with "non-operator managed" radio parameters as specified in clause 5.2.3;

f) there is no existing PC5 unicast link for the pair of peer application layer IDs, or there is an existing PC5 unicast link for the pair of peer application layer IDs and:

1) the network layer protocol of the existing PC5 unicast link is not identical to the network layer protocol required by the upper layer in the initiating UE for this V2X service; or

2) the security policy (either signalling security policy or user plane security policy) corresponding to the V2X service identifier is not compatible with the security policy of the existing PC5 unicast link; and

g) the number of established PC5 unicast links is less than the implementation-specific maximum number of established NR PC5 unicast links allowed in the UE at a time.

After receiving the service data or request from the upper layers, the initiating UE shall derive the PC5 QoS parameters and assign the PQFI(s) for the PC5 QoS flows(s) to be established as specified in clause 6.1.2.12.

In order to initiate the PC5 unicast link establishment procedure, the initiating UE shall create a DIRECT LINK ESTABLISHMENT REQUEST message. The initiating UE:

a) shall include the source user info set to the initiating UE’s application layer ID received from upper layers;

b) shall include the V2X service identifier(s) received from upper layer;

c) shall include the target user info set to the target UE’s application layer ID if received from upper layers or if the destination layer-2 ID is the unicast layer-2 ID of target UE;

d) shall include the Key establishment information container if the UE PC5 unicast signalling integrity protection policy is set to "signalling integrity protection required" or "signalling integrity protection preferred", and may include the Key establishment information container if the UE PC5 unicast signalling integrity protection policy is set to "signalling integrity protection not needed";

NOTE 2: The Key establishment information container is provided by upper layers.

e) shall include a Nonce_1 set to the 128-bit nonce value generated by the initiating UE for the purpose of session key establishment over this PC5 unicast link if the UE PC5 unicast signalling integrity protection policy is set to "signalling integrity protection required" or "signalling integrity protection preferred";

f) shall include its UE security capabilities indicating the list of algorithms that the initiating UE supports for the security establishment of this PC5 unicast link;

g) shall include the 8 MSBs of KNRP-sess ID chosen by the initiating UE as specified in 3GPP TS 33.536 [20] if the UE PC5 unicast signalling integrity protection policy is set to "signalling integrity protection required" or "signalling integrity protection preferred";

h) may include a KNRP ID if the initiating UE has an existing KNRP for the target UE; and

i) shall include its UE PC5 unicast signalling security policy. In the case where the different V2X services are mapped to the different PC5 unicast signalling security policies, when the initiating UE intends to establish a single unicast link that can be used for more than one V2X service, each of the signalling security polices of those V2X services shall be compatible, e.g. "signalling integrity protection not needed" and "signalling integrity protection required" are not compatible.

After the DIRECT LINK ESTABLISHMENT REQUEST message is generated, the initiating UE shall pass this message to the lower layers for transmission along with the initiating UE’s layer-2 ID for unicast communication and the destination layer-2 ID, and start timer T5000. The UE shall not send a new DIRECT LINK ESTABLISHMENT REQUEST message to the same target UE identified by the same application layer ID while timer T5000 is running. If the target user info IE is not included in the DIRECT LINK ESTABLISHMENT REQUEST message (i.e. V2X service oriented PC5 unicast link establishment procedure), the initiating UE shall handle multiple DIRECT LINK ESTABLISHMENT ACCEPT messages, if any, received from different target UEs for the establishment of multiple PC5 unicast links before the expiry of timer T5000.

NOTE 3: In order to ensure successful PC5 unicast link establishment, T5000 should be set to a value larger than the sum of T5006 and T5007.

Figure 6.1.2.2.2: UE oriented PC5 unicast link establishment procedure

Initiating UE

Target UEs

Start T5000

DIRECT LINK ESTABLISHMENT REQUEST

DIRECT LINK ESTABLISHMENT ACCEPT

T5000 expires

DIRECT LINK ESTABLISHMENT ACCEPT

Figure 6.1.2.2.3: V2X service oriented PC5 unicast link establishment procedure

13.2.4.3 Test description

13.2.4.3.1 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 with 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), NR-SS-UE initiating unicast mode NR sidelink communication, Cast Type (Unicast), GNSS Sync (On).

13.2.4.3.2 Test procedure sequence

Table 13.2.4.3.2-1: Main behaviour

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 TS 38.508-1 [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

Check: Does 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 SECURITY MODE COMMAND message.

<–

PC5-S: DIRECT LINK SECURITY MODE COMMAND

5

Check: Does the UE transmit a DIRECT LINK SECURITY MODE COMPLETE message.

–>

PC5-S: DIRECT LINK SECURITY MODE COMPLETE

–

–

6

The NR-SS-UE1 transmits a DIRECT LINK ESTABLISHMENT ACCEPT message.

<–

PC5-S: DIRECT LINK ESTABLISHMENT ACCEPT

–

–

7

Check: Does the UE send an RRCReconfigurationSidelink message to establish a unicast mode SL-DRB?

–>

PC5-RRC: RRCReconfigurationSidelink

–

–

8

The NR-SS-UE sends an RRCReconfigurationCompleteSidelink message.

<–

PC5-RRC: RRCReconfigurationCompleteSidelink

–

–

9

UE continuously sends SDAP SDUs on SL-DRB

–

–

–

–

10

Trigger UE to deactivate UE test loop mode.

NOTE: The deactivation of UE test loop mode may be performed by MMI or AT command (+CATM).

–

–

–

–

13.2.4.3.3 Specific message contents

Table 13.2.4.3.3-1: 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 13.2.4.3.3-2: Message DIRECT LINK SECURITY MODE COMMAND (step 4, Table 13.2.4.3.2-1)

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

Table 13.2.4.3.3-3: Message DIRECT LINK SECURITY MODE COMPLETE (step 5, Table 13.2.4.3.2-1)

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

Table 13.2.4.3.3-4: Message DIRECT LINK ESTABLISHMENT ACCEPT (step 6, Table 13.2.4.3.2-1)

Derivation path: TS 38.508-1 [4], Table 4.7.4-8 with condition Rx

Table 13.2.4.3.3-5: RRCReconfigurationSidelink (step 7, Table 13.2.4.3.2-1)

Derivation path: TS 38.508-1 [4], Table 4.6.1A-3 with condition TX

Table 13.2.4.3.3-6: RRCReconfigurationCompleteSidelink (steps 8, Table 13.2.4.3.2-1)

Derivation path: TS 38.508-1 [4], Table 4.6.1A-4 with condition RX