PTM retransmission reception by UES in RRC_INACTIVE/idle with DRX
Described herein is a User Equipment, UE, comprising: at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the UE at least to, during or before a Multicast/Broadcast Service, MBS, session; receive, from a network node, a configuration message configuring at least one Retransmission Timer; receive, while the UE is in an inactive state or an idle state, a Physical Downlink Control Channel, PDCCH, transmission that is associated with the MBS session and that schedules a Transport Block, TB, of the MBS session with a group identifier identifying a group of UEs comprising the UE in the inactive or idle state and one or more UEs in a connected state; receive the scheduled TB in the inactive or idle state, via Point-To-Multipoint, PTM, Physical Downlink Shared Channel, PDSCH transmission associated with the MBS session; and in case of determining a failure in decoding the received TB; start the at least one Retransmission Timer based on the configuration message; and monitor, before the at least one Retransmission Timer expires, a PDCCH for at least one PTM retransmission for the failed TB requested by the one or more UEs in the connected state via at least one Hybrid Automatic Repeat Request, HARQ, feedback to the network node.
1. A User Equipment, UE, comprising:
at least one processor, and
at least one memory storing instructions that, when executed by the at least one processor, cause the UE at least to, during or before a Multicast/Broadcast Service, MBS, session:
receive, from a network node, a configuration message configuring at least one Retransmission Timer;
receive, while the UE is in an inactive state or an idle state, a Physical Downlink Control Channel, PDCCH, transmission that is associated with the MBS session and that schedules a Transport Block, TB, of the MBS session with a group identifier identifying a group of UEs comprising the UE in the inactive or idle state and one or more UEs in a connected state;
receive the scheduled TB in the inactive or idle state, via Point-To-Multipoint, PTM, Physical Downlink Shared Channel, PDSCH transmission associated with the MBS session; and
in case of determining a failure in decoding the received TB:
start the at least one Retransmission Timer based on the configuration message; and
monitor, before the at least one Retransmission Timer expires, a PDCCH for at least one PTM retransmission for the failed TB requested by the one or more UEs in the connected state via at least one Hybrid Automatic Repeat Request, HARQ, feedback to the network node.
2. The UE according to claim 1 , wherein the at least one Retransmission Timer comprises a HARQ Round-Trip-Time, RTT, Timer and a Discontinuous Reception, DRX, Retransmission Timer,
wherein the UE, in the inactive or idle state, is configured to:
receive, via the PDCCH transmission, Downlink Control Information, DCI, comprising a timing indicator for indicating a time slot for the at least one HARQ feedback,
start the HARQ RTT Timer after a predetermined symbol in the indicated time slot; and
start the DRX Retransmission Timer after the HARQ RTT Timer expires.
3. The UE according to claim 2 , wherein:
the indicated time slot comprises a plurality of symbols,
the UE is pre-configured with a fixed number indicating a corresponding symbol comprised in the indicated time slot as the predetermined symbol that is default for all MBS sessions.
4. The UE according to claim 2 , wherein:
the indicated time slot comprises a plurality of symbols,
the configuration message further configures the UE with a specific number indicating a corresponding symbol of the indicated time slot as the predetermined symbol for a specific MBS session or default for all MBS sessions.
5. The UE according to claim 2 , wherein the UE is configured to:
extend the configured DRX Retransmission Timer with at least one additional time slot, when the predetermined symbol is the first symbol in the indicated time slot.
6. The UE according to claim 2 , wherein the configuration message comprises information for further configuring the UE with a list of values for interpreting the timing indicator by reference to a value comprised in the list, and wherein the UE is configured to determine the time slot on the basis of the received timing indicator indicating one of the values of the list.
7. The UE according to claim 6 , wherein the timing indicator is a PDSCH-to-HARQ_feedback timing indicator, wherein the list is provided via dl-DataToUL-ACK parameter or dl-DataToUL-ACK-MulticastDCI-Format4-1 parameter or the list comprises values {1, 2, 3, 4, 5, 6, 7, 8}.
8. The UE according to claim 2 , wherein:
the configuration message comprises a full PUCCH configuration for the UE, and
the DCI comprises, in addition to the timing indicator, a PUCCH resource indicator, PRI, indicating the predetermined symbol comprised in the time slot indicated by the timing indicator for sending the at least one HARQ feedback.
9. The UE according to claim 1 , wherein the configuration message is per Temporary Mobile Group Identity, TMGI, or a corresponding identifier identifying a specific multicast service or all multicast services of the group of UEs.
10. The UE according to claim 1 , wherein the UE is configured to, in the inactive or idle state, receive the same PDCCH transmission associated with the MBS session as the one or more UEs in connected state.
11. The UE according to claim 1 , wherein:
the PTM PDSCH transmission for the failed TB comprises a plurality of symbols,
wherein the UE is further caused to, in the inactive or idle state:
start the at least one Retransmission Timer after the last symbol comprised in the PTM PDSCH transmission for the failed TB.
12. The UE according to claim 1 , wherein:
the UE, in the inactive or idle state, is configured to receive, via the PDCCH transmission, Downlink Control Information, DCI, scheduling the failed TB transmission, wherein the DCI comprises information for indicating a time slot in which the HARQ feedback in response to the failed TB is sent by the one or more UEs in the connected state,
wherein the UE is further caused to, in the inactive or idle state:
determine to start the at least one Retransmission Timer in the indicated time slot.
13. The UE according to claim 1 , wherein the configuration message is a Radio Resource Control, RRC, release message or an MBS Control Channel, MCCH message.
14. A network node of a radio access network, configured to establish communication to a group of UEs, the group being identified by a group identifier, the network node comprising:
at least one processor, and
at least one memory storing instructions that, when executed by the at least one processor, cause the network node at least to, during or before a Multicast/Broadcast Service, MBS, session:
transmit a configuration message to at least one of said plurality of UEs for configuring the at least one UE with at least one Retransmission Timer, wherein the at least one UE is in an inactive state or an idle state and at least one UE is in connected state;
schedule, via one or more Physical Downlink Control Channel, PDCCH, transmissions associated with the MBS session, a Transport Block, TB, towards the group of UEs identified by the group identifier;
transmit the scheduled TB, via Point-To-Multipoint, PTM, Physical Downlink Shared Channel, PDSCH associated with the MBS session, to the group of UEs identified by the group identifier;
determine resources for retransmissions for the transmitted TB in response to receiving at least one Hybrid Automatic Repeat Request, HARQ, feedback from the at least one UE in connected state indicating a failure in decoding the TB; and
initiate retransmissions for the failed TB at the determined resources and based on the at least one Retransmission Timer configured for the at least one UE in inactive or idle state,
wherein the configuration message comprises information for the at least one UE in inactive or idle state to determine when to start the at least one Retransmission Timer based on the configuration message.
15. A method of a User Equipment, UE, during or before a Multicast/Broadcast Service, MBS, session:
receiving, from a network node, a configuration message configuring at least one Retransmission Timer;
receiving, while the UE is in an inactive state or an idle state, a Physical Downlink Control Channel, PDCCH, transmission that is associated with the MBS session and that schedules a Transport Block, TB, of the MBS session with a group identifier identifying a group of UEs comprising the UE in the inactive or idle state and one or more UEs in a connected state;
receiving the scheduled TB in the inactive or idle state, via Point-To-Multipoint, PTM, Physical Downlink Shared Channel, PDSCH transmission associated with the MBS session; and
in case of determining a failure in decoding the received TB:
starting the at least one Retransmission Timer based on the configuration message; and
monitoring, before the at least one Retransmission Timer expires, a PDCCH for at least one PTM retransmission for the failed TB requested by the one or more UEs in the connected state via at least one Hybrid Automatic Repeat Request, HARQ, feedback to the network node.
16. The method according to claim 15 , wherein the at least one Retransmission Timer comprises a HARQ Round-Trip-Time, RTT, Timer and a Discontinuous Reception, DRX, Retransmission Timer,
wherein the UE, in the inactive or idle state, performs the following:
receiving, via the PDCCH transmission, Downlink Control Information, DCI, comprising a timing indicator for indicating a time slot for the at least one HARQ feedback,
starting the HARQ RTT Timer after a predetermined symbol in the indicated time slot; and
starting the DRX Retransmission Timer after the HARQ RTT Timer expires.
17. The method according to claim 16 , wherein:
the indicated time slot comprises a plurality of symbols,
the UE is pre-configured with a fixed number indicating a corresponding symbol comprised in the indicated time slot as the predetermined symbol that is default for all MBS sessions.
18. The method according to claim 16 , wherein:
the indicated time slot comprises a plurality of symbols,
the configuration message further configures the UE with a specific number indicating a corresponding symbol of the indicated time slot as the predetermined symbol for a specific MBS session or default for all MBS sessions.
19. The method according to claim 16 , wherein the UE performs the following:
extending the configured DRX Retransmission Timer with at least one additional time slot, when the predetermined symbol is the first symbol in the indicated time slot.
20. The method according to claim 15 , wherein the configuration message is per Temporary Mobile Group Identity, TMGI, or a corresponding identifier identifying a specific multicast service or all multicast services of the group of UEs.