1. WF on CB-group based retransmission
3GPP TSG RAN1#88bis
Spokane, USA, 3rd – 7th, April, 2017
Agenda Item:
R1-17xxxxx
WF on CB-group based retransmission
Samsung, [Ericsson, KT, ZTE, ZTE Microelectronics, SEQUANS], …

2. Background In RAN1#88, the following working assumption was made.
CBG-based transmission with single/multi-bit HARQ-ACK feedback is supported in Rel-15, which shall have the following characteristics:
Only allow CBG based (re)-transmission for the same TB of a HARQ process
CBG can include all CB of a TB regardless of the size of the TB – In the such case, UE reports single HARQ ACK bits for the TB
CBG can include one CB
CBG granularity is configurable

3. Proposal Confirm the working assumption as below.
CBG-based transmission with single/multi-bit HARQ-ACK feedback is supported in Rel-15, which shall have the following characteristics:
Only allow CBG based (re)-transmission for the same TB of a HARQ process
CBG can include all CB of a TB regardless of the size of the TB – In the such case, UE reports single HARQ ACK bits for the TB
CBG can include one CB
CBG granularity is configurable

4. Proposal
The UE is semi-statically configured by RRC signaling to enable CBG-based retransmission.
The above configuration to enable CBG-based retransmission is separate for DL and UL.
For initial transmission of a PDSCH or PUSCH, the CBs of the PDSCH or PUSCH transmission are grouped into the configured number of CBGs based on a rule on how to group CBs.
The rule on how to group CBs is described in the L1 specs.
FFS how to operate CBG-based retransmission when the number of CBs is smaller than the configured number of CBGs.
FFS how to group CBs for retransmission of the PDSCH and PUSCH