Regarding MBS data processing, carrier aggregation and discontinuous reception in 5G(NR) networks, 3GPP defines the following in TS38.300;
1. DATA RECEIVING In 5G(NR) the network for multicast service base station side of the gNB can transmit MBS multicast packets using the following methods:
* PTP transmission:The gNB transmits a copy of the MBS packet to each terminal (UE) individually, i.e., the gNB uses the UE-specific PDCCH (CRC is scrambled by the UE-specific RNTI (e.g., C-RNTI)) to schedule the UE-specific PDSCH that is scrambled using the same UE-specific RNTI.
* PTM Transmission:The gNB transmits a single copy of the MBS packet to a group of terminals (UEs), e.g., the gNB uses a group common PDCCH (CRC is scrambled by a group common RNTI) to schedule a group common PDSCH that uses the same group common RNTI scrambling.
2.Terminal (UE) Processing If the UE is configured for both PTM and PTP transmission, the gNB dynamically decides whether or not to transmit multicast data over the PTM line and/or the PTP line for a given UE, based on the defined protocol stack in accordance with the information on the MBS session QoS requirements, the number of UEs joining, the UEs individual feedback on the quality of reception and other criteria. The same QoS requirements apply regardless of the decision made. Among other things:
* UE in RRC_INACTIVE state, MBS multicast session data reception does not support PTP transmission.
* UE in RRC_INACTIVE state, MBS multicast session data reception does not support SPS.
3.Carrier Aggregation (CA) supports 5G terminals (UEs) that can be configured to receive MBS multicast data from a PCell or a single SCell at a time.
4.Discontinuous Reception (DRX) The 5G terminal (UE) performing MBS service can use the following DRX configuration when performing PTM/PTP transmission in RRC_CONNECTED state:
* For PTM transmissions, the multicast DRX is configured according to G-RNTI/G-CS-RNTI, independent of the 5G terminal (UE)-specific DRX;
* For PTP transmissions, the UE-specific DRX will be reused, i.e., the 5G terminal (UE)-specific DRX can be used for both unicast transmissions for MBS multicast and PTP transmissions. For PTM retransmission via PTP, the UE monitors the PDCCH that is scrambled by C-RNTI/CS-RNTI during the specific DRX activity time.
The 5G terminal (UE) of RRC_INACTIVE can use the following DRX configurations when performing PTM transmission:
* For PTM transmissions, multicast DRX is configured per G-RNTI.
---PTM (Point to Multipoint): Point to Multipoint (Transport)
---PTP(Point to Point):Point to Point (transmission)
