4.7.5 Radio protocol aspects

36.3003GPPEvolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN)Overall descriptionRelease 17Stage 2TS

The RN connects to the DeNB via the Un interface using the same radio protocols and procedures as a UE connecting to an eNB. The control plane protocol stack is shown in Figure 4.7.5-1 and the user plane protocol stack is shown in Figure 4.7.5-2.

The following relay-specific functionalities are supported:

– the RRC layer of the Un interface has functionality to configure and reconfigure an RN subframe configuration through the RN reconfiguration procedure (e.g. DL subframe configuration and an RN-specific control channel) for transmissions between an RN and a DeNB. The RN may request such a configuration from the DeNB during the RRC connection establishment, and the DeNB may initiate the RRC signalling for such configuration. The RN applies the configuration immediately upon reception;

NOTE: The RN subframe configuration on the Un interface can be temporarily misaligned with the MBSFN subframes configured in the RN cell due to the RN subframe configuration; i.e. a new subframe configuration can be applied earlier by the RN on Un than in the RN cell.

– the RRC layer of the Un interface has functionality to send updated system information in a dedicated message to an RN with an RN subframe configuration. The RN applies the received system information immediately;

– the PDCP layer of the Un interface has functionality to provide integrity protection for the user plane. The integrity protection is configured per DRB.

To support PWS towards UEs, the RN receives the relevant information over S1. The RN should hence ignore DeNB system information relating to PWS.

Figure 4.7.5-1: Radio control plane protocol stack for supporting RNs

Figure 4.7.5-2: Radio user plane protocol stack for supporting RNs