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Content for  TS 38.351  Word version:  18.2.0

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1…   4…   5…   5.3a…   6… 
5.3a U2U SL Data transfer  5.3a.1 Transmitting operation of U2U Remote UE  5.3a.1.1 General  5.3a.1.2 Egress link, UE ID fields and BEARER ID field determination  5.3a.1.3 Egress RLC channel determination  5.3a.2 Receiving operation of U2U Relay UE  5.3a.3 Transmitting operation of U2U Relay UE  5.3a.3.1 General  5.3a.3.2 Egress link determination  5.3a.3.3 Egress RLC channel determination  5.3a.4 Receiving operation of U2U Remote UE  5.4 Handling of unknown, unforeseen, and erroneous protocol data 

 

5.3a  U2U SL Data transfer |R18|  p. 16

5.3a.1  Transmitting operation of U2U Remote UE  p. 16

5.3a.1.1  General  p. 16

The transmitting part of the SRAP entity on the PC5 interface of U2U Remote UE can receive SRAP SDU from upper layer and construct U2U SRAP Data PDU.
Upon receiving an SRAP SDU from upper layer, the transmitting part of the SRAP entity on the PC5 interface shall:
  • Determine the UE ID fields, egress link and BEARER ID field in accordance with clause 5.3a.1.2;
  • Construct a U2U SRAP Data PDU with SRAP header, where the UE ID fields and BEARER ID field are set to the determined values, in accordance with clause 6.2.2;
  • Determine the egress RLC channel in accordance with clause 5.3a.1.3;
  • Submit this U2U SRAP Data PDU to the determined egress PC5 Relay RLC channel of the determined egress link.
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5.3a.1.2  Egress link, UE ID fields and BEARER ID field determination  p. 16

For a U2U SRAP SDU received from upper layer, the SRAP entity shall:
  • Determine the egress link on PC5 interface towards the U2U relay UE based on the concerned sl-RemoteUE-L2Identity and sl-PeerRemoteUE-L2Identity as specified in TS 38.331;
  • Determine the UE ID (for SRC) field corresponding to sl-RemoteUE-LocalIdentity configured for the concerned sl-RemoteUE-L2Identity and UE ID (for DST) field corresponding to sl-PeerRemoteUE-LocalIdentity configured for the concerned sl-PeerRemoteUE-L2Identity as specified in TS 38.331;
  • Determine the BEARER ID field for SL-SRBs as the fixed value (i.e., set 0/1/2/3 for SL-SRB0/1/2/3 respectively) or for SL-DRBs as the 5 LSBs of slrb-PC5-ConfigIndex used in end-to-end SL DRB configuration procedure as specified in TS 38.331.
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5.3a.1.3  Egress RLC channel determination  p. 17

For a U2U SRAP Data PDU to be transmitted, the SRAP entity shall:
  • If the U2U SRAP Data PDU is for SL SRB (i.e., the BEARER ID field is 0/1/2/3):
    • Determine the egress PC5 Relay RLC channel in the determined egress link corresponding to logicalChannelIdentity for SL-U2U-RLC as specified in TS 38.331.
  • Else if the U2U SRAP Data PDU is for SL DRB:
    • Determine the egress PC5 Relay RLC channel in the determined egress link corresponding to SRAP configuration indicated by upper layer for the concerned bearer as specified in TS 38.331.
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5.3a.2  Receiving operation of U2U Relay UE  p. 17

Upon receiving a U2U SRAP Data PDU from lower layer, the receiving part of the SRAP entity on the PC5 interface between the U2U Relay UE and the U2U Remote UE shall:
  • Deliver the SRAP data packet to the transmitting part of the SRAP entity on the PC5 interface between the U2U Relay UE and the peer U2U Remote UE.

5.3a.3  Transmitting operation of U2U Relay UE  p. 17

5.3a.3.1  General  p. 17

The transmitting part of the SRAP entity of U2U Relay UE on the PC5 interface between the U2U Relay UE and the peer U2U Remote UE can receive SRAP data packets from the receiving part of the SRAP entity of the same U2U Relay UE on the PC5 interface between the U2U Relay UE and the U2U Remote UE, and construct U2U SRAP Data PDUs as needed (see clause 4.2.2).
When the transmitting part of the SRAP entity of the U2U Relay UE has a U2U SRAP Data PDU to transmit on the PC5 interface between U2U Relay UE and the peer U2U Remote UE, the transmitting part of the SRAP entity of U2U Relay UE shall:
  • Determine the egress link in accordance with clause 5.3a.3.2;
  • Determine the egress RLC channel in accordance with clause 5.3a.3.3;
  • Submit this U2U SRAP Data PDU to the determined egress RLC channel of the determined egress link.
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5.3a.3.2  Egress link determination  p. 17

For a U2U SRAP Data PDU to be transmitted, the SRAP entity shall:
  • If there is an entry in sl-LocalID-PairToAddModList, in which the sl-RemoteUE-LocalIdentity and sl-PeerRemoteUE-LocalIdentity match the UE ID fields in the U2U SRAP Data PDU:
    • Determine the egress link on PC5 interface towards the peer U2U remote UE identified by sl-PeerRemoteUE-L2Identity configured for the concerned sl-PeerRemoteUE-LocalIdentity as specified in TS 38.331.
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5.3a.3.3  Egress RLC channel determination  p. 18

For a U2U SRAP Data PDU to be transmitted, the SRAP entity shall:
  • If the U2U SRAP Data PDU is for SRB (i.e., the BEARER ID field is 0/1/2/3):
    • Determine the egress PC5 Relay RLC channel in the determined egress link corresponding to logicalChannelIdentity for SL-U2U-RLC as specified in TS 38.331.
  • Else if the U2U SRAP Data PDU is for DRB:
    • Determine the egress PC5 Relay RLC channel in the determined egress link corresponding to SRAP configuration indicated by upper layer for the concerned bearer as specified in TS 38.331.
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5.3a.4  Receiving operation of U2U Remote UE  p. 18

Upon receiving a U2U SRAP Data PDU from lower layer, the receiving part of the SRAP entity shall:
  • Remove the SRAP header of this U2U SRAP Data PDU and deliver the U2U SRAP SDU to upper layer entity corresponding to the BEARER ID and UE ID fields of this U2U SRAP Data PDU.

5.4  Handling of unknown, unforeseen, and erroneous protocol data  p. 18

For U2N Remote UE, if sl-LocalIdentity and sl-RemoteUE-RB-Identity are both configured, when a SRAP Data PDU with SRAP header that contains a UE ID field or BEARER ID field which does not match sl-LocalIdentity or sl-RemoteUE-RB-Identity included in sl-SRAP-ConfigRemote is received, the SRAP entity shall:
  • Discard the received SRAP Data PDU.
For U2N Relay UE, when a SRAP Data PDU with SRAP header that contains a UE ID field or BEARER ID field which does not match sl-LocalIdentity or sl-RemoteUE-RB-Identity included in sl-SRAP-ConfigRelay is received except in the case where the SRAP Data PDU from SL-RLC1 as specified in TS 38.331 is the first SRAP Data PDU received from a U2N Remote UE, or when a SRAP Data PDU that contains a UE ID which does not match the concerned sl-LocalIdentity corresponding to sl-L2IdentityRemote of the ingress link is received by U2N Relay UE, the SRAP entity shall:
  • Discard the received SRAP Data PDU.
For U2U Remote UE, if sl-RemoteUE-LocalIdentity and sl-PeerRemoteUE-LocalIdentity are both configured, when an SRAP Data PDU with SRAP header that contains UE ID fields which does not match sl-PeerRemoteUE-LocalIdentity and sl-RemoteUE-LocalIdentity included in any one of the entries in sl-LocalID-PairToAddModList or an SRAP Data PDU with SRAP header that contains BEARER ID field which does not match 0/1/2/3 or the 5 bits LSBs of slrb-PC5-ConfigIndex used in end-to-end SL DRB configuration procedure is received, the SRAP entity shall:
  • Discard the received SRAP Data PDU.
For U2U Relay UE, when an SRAP Data PDU with SRAP header that contains a UE ID (for DST) field which does not match sl-PeerRemoteUE-LocalIdentity included in any one of the entries in sl-LocalID-PairToAddModList or an SRAP Data PDU with SRAP header contains BEARER ID field which does not match 0/1/2/3 or the 5 bits LSBs of slrb-PC5-ConfigIndex used in end-to-end SL DRB configuration procedure is received, or when an SRAP Data PDU that contains a UE ID (for SRC) field which does not match the concerned sl-RemoteUE-LocalIdentity corresponding to sl-RemoteUE-L2Identity of the ingress link is received by U2U Relay UE, the SRAP entity shall:
  • Discard the received SRAP Data PDU.
When any of the U2N Remote UE, the U2N Relay UE, the U2U Remote UE or the U2U Relay UE receives an SRAP Data PDU with invalid or reserved values, the SRAP entity shall:
  • Discard the received SRAP Data PDU.
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