1. Summary on CA Aspects Samsung 3GPP TSG RAN WG1#91
Reno, USA, Nov. 27 – Dec. 1, 2017
Agenda item
R1-17xxxxx
Summary on CA Aspects
Samsung

2. CA – General Activation/deactivation: MAC vs. L1
PUCCH cell: Can PUCCH transmission be configured on a SCell?
Cross-carrier scheduling: USS sharing in case of same DCI size?
Offline consensus is to support as an optional feature (UE capability for UEs that are capable of cross-carrier scheduling)
SRS switching: Inherit RRC parameters from LTE?
Multiple active UL cells in intra-band CA for a UE that is not expected to transmit simultaneously on the multiple cells but can transmit on different cells at different times
Decouple DL cells and UL cells in intra-band CA to allow a single UL cell to correspond to a DL SCell

3. Semi-static HARQ-ACK Codebook
Options for time domain configuration are:
Option 1: Semi-static configuration
DL association set is configured based on a maximum and minimum HARQ-ACK timing values (can be same in case of semi-static timing)
No need for counter DAI
HARQ-ACK codebook size is largest, DL/UL DCI overhead is smallest, simplest, no error cases
Offline consensus: For semi-static HARQ-ACK codebook, support option 1
DL association set is determined based on the configured set of HARQ-ACK timings
E.g. for configured set of timings of {7, 5, 3} the DL association set is (7, 5 ,3}
Option 2: Dynamic DL association set with/out HARQ-ACK codebook quantization
DL association set is based on a first PDCCH monitoring occasion where UE detects DL DCI until last PDCCH monitoring occasion where UE can report HARQ-ACK
May increase counter DAI to 3 bits for robustness - gNB may inflate DAI to reduce errors
If quantized, HARQ-ACK codebook is always a multiple of N (e.g. N=4 or N=8)
Can reduce HARQ-ACK codebook size, error cases exist (e.g. missed last DAI=1)
Option 3: HARQ-ACK codebook indication by PUCCH resource indicator
gNB needs to fix HARQ-ACK codebook size from start of DL association set – else, error cases
Option 4: Semi-static configuration of DL association set including maximum number of DL assignments in DL association set
Can reduce HARQ-ACK codebook size if gNB wants to semi-statically commit on maximum number of DL DCIs in DL association set
Counter DAI indicates number/location of DL DCI/HARQ-ACK bit in DL association set/CB

4. HARQ-ACK Codebook: CBGs in Some Cells
Option 1
Generate 2 HARQ-ACK sub-codebooks – one for transmissions with CBG-based HARQ-ACK (maximum number of CBGs/TB), one for cells with TB-based HARQ-ACK
No CBG-based DAI
Rather simple – FFS additional DL DCI overhead - robustness in case of 1 cell for TB-based or CBG-based HARQ-ACK may be an issue – other error cases exist requiring additional handling
Option 2
Generate 1 HARQ-ACK codebook regardless of CBG-based or TB-based HARQ-ACK for a cell
CBG-level DAI also in DL DCIs for cells without CBG-based HARQ-ACK feedback
Simple – minimum HARQ-ACK payload, requires log2(NCBG) more bits in counter/total DAIs for all cells (more likely to result to same DL DCI size for all cells) – less bits for coarser granularity
Option 3
Generate 2 HARQ-ACK sub-codebooks (afterwards joined into a single one) – one for cells with CBG-based HARQ-ACK, one for cells with TB-based HARQ-ACK
CBG-based DAI for cells in CBG-based HARQ-ACK codebook
Rather simple - minimum HARQ-ACK payload, requires log2(NCBG) more bits in counter/total DAIs for cells with CBG-based HARQ-ACK (less likely to result to same DL DCI size for all cells)
Option 4
CBG-based HARQ-ACK for all cells (based on maximum configured number of CBGs/TB)
No CBG-based DAI, TB level DAI
Simple – largest HARQ-ACK payload, no additional DL DCI overhead
No offline consensus to introduce CBG-level DAI

5. HARQ-ACK Codebook - Misc
Use of UL DAI for dynamic HARQ-ACK codebook in PUSCH
How many bits?
Can depend on decision for CBG-based HARQ-ACK codebook
Is it configurable (and is total DAI also configurable)?
Fallback DCI
Should it include counter/total DAIs?
Should it include timing indicator for HARQ-ACK?
HARQ-ACK bundling
Separate configuration of HARQ-ACK spatial bundling for PUSCH and PUCCH?
Across CBGs of different TBs?
Dynamic (e.g. HARQ-ACK code rate is larger than configured one in indicated resources)?
Across TBs of same PDSCH
Across CBGs of same TB
Across TBs of different PDSCHs in same cell (time domain) or different cells (cell domain)
Etc.

6. Different PDCCH Monitoring Periods per CG
For HARQ-ACK codebook
Counter DAI and total DAI updated at each PDCCH monitoring occasion
How is DL association set determined (for semi-static and dynamic HARQ-ACK codebooks)?
Any limit on the different PDCCH monitoring periodicities per CG
Is this according to RAN down-scoping?
‘Basic NR-NR CA’ (what does this mean?)
For scheduling/HARQ, same numerology within same PUCCH group including DL and UL (use of different numerology for SUL can be considered)
[Offline consensus: Different PDCCH monitoring periodicities per PUCCH cell group are supported unless a “significant” design problem is found.]

7. SUL SUL is considered to be collocated with NR carrier having DL/UL
e.g. for path-loss measurement
SUL in same TAG as UL
If/when dynamic switch is supported between UL and SUL, DCI includes a (configurable) 1-bit index field
Both UL and SUL of the PCell are primary CCs
UL and SUL of a same SCell are simultaneously activated/deactivated
UE can be configured two locations for TPC bits in DCI with TPC-PUSCH-RNTI; one for UL and one for SUL

8. References