Frequency domain resources can be allocated for the PUSCH using Downlink Control Information (DCI) Formats 0_0 and 0_1. DCI is transferred to the UE using the PDCCH physical channel. Alternatively, in the case of Type 1 Configured Grants, frequency domain resources are allocated for the PUSCH using RRC signaling.
The ‘Frequency Domain Resource Assignment’ field within the DCI is used to specify the set of allocated Resource Blocks. Similarly, the ‘frequencyDomainAllocation’ information element within the RRC signaling protocol can be used to specify the set of allocated Resource Blocks when using Configured Grants resource allocations.
3GPP defined two schemes for the allocation of frequency resource allocations: Type 0 and Type 1.
Type 0: This scheme uses a bitmap to allocate specific RBGs (Resource block groups). RBG is a set of contiguous virtual resource blocks. These RBGs need not be contiguous.
This scheme cannot be used with DCI format 0_0 and/or with transform pre-coding.
Type 1: This scheme uses the resource indication value (RIV) to configure a set of virtual resource blocks. This scheme is used with DCI format 0_0/0_1 or RRC signaling.
‘resourceAllocation’ IE is used to specify resource allocation scheme. In case of dynamic resource allocations, this IE is included in PUSCH-Config IE.
In case of configured grant resource allocations, this information is included in ConfiguredGrantConfig IE.
‘resourceAllocation’ IE can have values of Type0, Type1 and dynamicSwitch. In case of Type 1 configured grant resource allocation, this IE cannot switch dynamically.
When using dynamicSwitch one additional bit added within DCI to indicate the scheme being used.
RRC signaling can be used to configure upto 4 bandwidth parts in addition to initial bandwidth part.
When UE receives the frequency domain resource allocation(FDRA), UE first identifies bandwidth part and then identifies the corresponding resource allocation.
Uplink resource allocation Type 0
Uplink resource allocation Type 0 can be signaled on the PDCCH using DCI Format 0_1 or on RRC in case of Type 1 Configured Grant. This scheme uses a bitmap to indicate a set of allocated Resource Block Groups (RBG).
A Resource Block Group (RBG) is a set of contiguous Virtual Resource Blocks (VRB) within a Bandwidth Part. The number of Resource Blocks within an RBG is dependent upon the Bandwidth Part size and the ‘rbg-Size’ information element in PUSCH-Config IE. The ‘rbg-Size’ can be ‘configl ’ or ‘config2’. Below table shows the values:
In frequency range 1, only ‘almost contiguous allocation’ defined in [3GPP TS 38.101–1] is allowed as non-contiguous allocation per component carrier for UL RB allocation for CP-OFDM.
3GPP TS 38.101–1 introduces the concept of an ‘almost contiguous’ Resource Block allocation. A resource allocation is categorized as ‘almost contiguous’ if the following conditions are satisfied:
Nrb_gap /(Nrb_alloc + Nrb_gap) <= 0.25 AND (Nrb_alloc + Nrb_gap) > X
where, ‘X’ = {106, 51, 24} for subcarrier spacings of 15, 30 and 60 kHz respectively. Nrb_alloc is the total number of allocated Resource Blocks, and Nrb_gap is the total number of unallocated Resource Blocks between allocated Resource Blocks.
In frequency range 2, non-contiguous allocation per component carrier for UL RB allocation for CP-OFDM is not supported.
Uplink resource allocation Type 1
Uplink resource allocation Type 1 can be signaled on PDCCH DCI Format 0_0/0_1 or on RRC in case of Type 1 Configured Grant. This scheme uses RIV (Resource Indicator Value) to specify the set of VRBs within active bandwidth part.
An uplink type 1 resource allocation field consists of a resource indication value (RIV) corresponding to a starting virtual resource block ( RBstart ) and a length in terms of contiguously allocated resource blocks LRBs . The resource indication value is defined by following equation:
