This type of resource allocation is mainly
used for contiguous RB allocations for uplink (RA Type0) and for
compact scheduling of downlink assignments (RA Type 2).

In this type, the resource block
assignment information indicates to a scheduled UE a set of contiguously
allocated localized VRBs or distributed VRBs.

In case of resource allocation
signaled with PDCCH DCI format 1A, 1B or 1D, one bit flag indicates whether
localized VRBs or distributed VRBs are assigned (value 0 indicates Localized
and value 1 indicates Distributed VRB assignment) . In the case of resource
allocation signaled with PDCCH DCI format 1C, only distributed VRBs are assigned.

Localized VRB allocations for a UE
vary from a single VRB up to a maximum number of VRBs spanning the system
bandwidth.

For indicating contiguous RB
assignment, starting position of the RB (RB

_{start}) and the number of RBs is required. Let us consider RB_{start}=_{ }0^{th}RB, the number of combinations possible = N_{RB}. Similarly when RB_{start}=_{ }1^{st}RB, then the number of possible combinations are N_{RB}– 1 and so on. There are**N**combinations possible in total._{RB}.(N_{RB}+ 1)/2
For downlink, PDCCH DCI format 1A, 1B
or 1D, a type 2 resource allocation field consists of a Resource Indication Value
(RIV) corresponding to a starting resource block (RB

_{start}) and a length in terms of virtually contiguously allocated resource blocks L_{CRBs}.
For uplink, a resource allocation (type 0) field in the scheduling grant consists of a resource indication value (RIV)
corresponding to an RB

_{start}and a length in terms of contiguously allocated physical resource blocks (L_{CRBs}≥ 1). The RIV value for both uplink and downlink is defined by:

*RIV*

**=**

**N**if (L

_{RB}(L_{CRBs}— 1) + RB_{start }_{CRBs}— 1) ≤ ⎿ N

_{RB}/2⏌

**=**

**N**otherwise

_{RB}(N_{RB}— L_{CRBs}+ 1) + (N_{RB}— 1 — RB_{start})**Example**:

Let us consider N

_{RB}= 6 ⇨ N_{RB}.(N_{RB}+ 1)/2 = 21 ⇨ 5-bits are required for indicating any RIV value ranging from 0 to 20. The RIV values for N_{RB}= 6 are illustrated below. Let RB_{start}= 2 and L_{CRBs}= 3, from the above equations RIV = 14
Reference: 3GPP TS 36.213