Uplink TDRA lookup tables in 5G NR

3 min readMar 9, 2022

The look-up table includes up to 16 rows and defines the slot offset (K2), the PUSCH Mapping Type, the starting symbol and the number of allocated symbols (the length).

3 lookup tables are used for uplink (UL) time domain resource allocations (TDRA). There are 3 types of lookup tables representing time domain resource allocations : Default A, PUSCH-TimeDomainAllocationList in PUSCH-ConfigCommon IE, PUSCH-TimeDomainAllocationList in PUSCH-Config IE.

PUSCH-TimeDomainAllocationList in pusch-ConfigCommon/pusch-Config
PUSCH-TimeDomainAllocationList is a list of time domain allocations for timing of UL assignment to UL data, defined in 3GPP TS 38.214. The IE PUSCH-TimeDomainAllocationList is used to configure a time domain relation between PDCCH and PUSCH. This contains one or more of PUSCH-TimeDomainAllocations (rows). The network indicates in UL grant that which of configured time domain allocations UE shall apply in that UL grant.
In other words PUSCH-TimeDomainAllocationList defines a lookup table with rows (PUSCH-TimeDomainAllocations) which can be selected when making a time domain resource allocation.

Each row or PUSCH-TimeDomainAllocations IE specifies a slot offset (K2), PUSCH mapping type (type A/type B) and startSymbolAndLength.
Slot offset (K2) defined in 3GPP TS 38.214,, values ranging from 0 to 32. When this field is absent, based on PUSCH SCS corresponding value can be used: 15/30 MHz — 1, 60 MHz — 2, 120MHz — 3.

PUSCH-TimeDomainAllocationList lookup table in PUSCH-ConfigCommon can be broadcast in SIB1 or sent to UE using dedicated signalling.

PUSCH-TimeDomainAllocationList lookup table in PUSCH-Config sent to UE using dedicated signalling.

PUSCH mapping type determines the allowed combinations of PUSCH starting symbol (S) and length (L). Length is a duration in terms of symbols.

PUSCH mapping types

Default PUSCH Time domain resource allocation A (default A)
Default A lookup table standardised by 3GPP TS 38.214 tables–2 and–3 for normal cyclic prefix and extended cyclic prefix. Slot offset specified in this table are increased by additional offset for MSG3 transmissions. The additional offset depends on subcarrier spacing: 2,3,4 or 6 slots for 15, 30, 60 and 120 kHz respectively.

table–2 Default A for normal CP
Default A for extended CP

Specific lookup table for time domain resource allocation
3GPP TS 38.214, defines the rules to select the specific lookup table for time domain resource allocations. If PUSCH scheduled by RAR (MSG3 transmission) and PUSCH-TimeDomainAllocationList received in PUSCH-ConfigCommon, PUSCH-TimeDomainAllocationList lookup table received in PUSCH-ConfigCommon is used. Else default table A lookup table is used.
Lookup table selection depends upon the RNTI, search space and availability of tables in rest of the cases:

lookup table selection for UL TDD rosources