School of Specs 38.300v19.3.0

3GPP 38.300 v19.3.0 — the document's own text

4.7.5.1 General

Taught in 4. What NR actually is, in the shape its own document gives it (TSG RAN — the group that specifies the radio, overview).

Mobile IAB introduces the mobile IAB-node, which is a RAN node that provides NR access links to UEs and an NR backhaul link to a parent node, and that can conduct physical mobility across the RAN area. The mobile IAB-node includes a mobile IAB-MT and a mobile IAB-DU. Mobile IAB supports the same functionality as IAB unless explicitly specified. The following enhancements/restrictions only apply to mobile IAB:

  • The mobile IAB-node uses the mobile IAB-node authorization procedure defined in TS 38.401 [4] and the MBSR authorization procedure defined in TS 23.501 [3].
  • A RAN node operating as a mobile IAB-node shall not concurrently operate as an IAB-node. During network integration, the RAN node shall indicate whether it intends to operate as a mobile IAB-node or as an IAB-node via an indicator in the RRCSetupComplete message.
  • The parent node indicates support for mobile IAB-nodes by broadcasting a mobile-IAB-specific indicator in SIB1.
  • The mobile IAB-node shall not have descendent nodes. A mobile-IAB cell shall therefore not broadcast any indication that it is a suitable parent node for IAB-nodes or mobile IAB-nodes.
  • The cell of a mobile IAB-DU may indicate to UEs via a SIB1 indicator that it is a mobile-IAB cell.
  • The mobile IAB-node uses the mobile IAB-node network integration procedure as defined in TS 38.401 [4].
  • The mobile IAB-MT can perform the mobile IAB-MT migration procedures via Xn handover and/or via NG handover as defined in TS 38.401 [4]. The mobile IAB-MT can also perform the mobile IAB-node recovery procedure as defined in TS 38.401 [4].
  • The mobile IAB-node can perform the mobile IAB-DU migration procedure, where a new logical mobile IAB-DU is established on the mobile IAB-node and the initial logical mobile IAB-DU is released some time later. The UE identifies the cells of the two logical mobile IAB-DUs as different physical cells. During this procedure, the UEs connected via the mobile IAB-node are handed over from the initial logical mobile IAB-DU, referred to as the source logical mobile IAB-DU, to the new logical mobile IAB-DU, referred to as the target logical mobile IAB-DU. The details of this procedure are defined in TS 38.401 [4]. Enhancements related to BAP for mobile IAB-DU migration are defined in TS 38.340 [31].
  • When a RAN node is operating as a mobile IAB node, dual connectivity for this node is not supported.

RACH-less handover as specified in 9.2.3.6, in TS 38.321 [6] and in TS 38.331 [12] is supported in mobile IAB. RACH-less handover can be used during the mobile IAB-DU migration procedure for a UE that is migrated from the source logical mobile IAB-DU to the target logical mobile IAB-DU.