Description
The Resource Indication Value (RIV) is an encoding mechanism defined in the LTE (3GPP TS 36.213) and NR (3GPP TS 38.214) specifications for signaling resource block allocations in the downlink and uplink grants carried by the Downlink Control Information (DCI). When the scheduler at the gNB (or eNodeB) decides to allocate a contiguous set of Physical Resource Blocks (PRBs) to a UE, it needs to communicate this allocation efficiently. Transmitting the start and length of the allocation as two separate numbers would be wasteful of the precious DCI payload bits. The RIV solves this by combining the starting resource block (RB_start) and the length of the allocation in contiguous PRBs (L_RBs) into a single integer value.
The encoding algorithm is defined such that for a given bandwidth part of size N_RB PRBs, any valid combination of a starting index and a length (where start + length <= N_RB) maps to a unique RIV. The formula is: if (L_RBs - 1) <= floor(N_RB / 2) then RIV = N_RB * (L_RBs - 1) + RB_start, else RIV = N_RB * (N_RB - L_RBs + 1) + (N_RB - 1 - RB_start). This creates a one-to-one mapping. The UE, upon receiving the DCI, extracts the RIV field and decodes it using the known N_RB to derive the exact RB_start and L_RBs values, thus understanding its allocated frequency resources.
This mechanism is a key component of resource allocation Type 0 (bitmap-based) and Type 1 (RIV-based for contiguous allocations) in LTE, and similar principles apply in NR for resource allocation Type 1. Its role is critical for dynamic scheduling efficiency. By minimizing the control signaling overhead for the most common type of allocation (contiguous blocks), it preserves DCI capacity, allowing the network to schedule more users per control channel region, thereby increasing overall system capacity and reducing latency.
Purpose & Motivation
The RIV was created to address the problem of control channel overhead in OFDMA-based cellular systems like LTE and NR. The control channels (PDCCH in LTE, PDCCH in NR) have limited capacity. Every bit used to signal a resource allocation is a bit that cannot be used for other purposes, limiting the number of users that can be scheduled per subframe/slot. A naive method of signaling resource allocation would require up to log2(N_RB) bits for the start index and another log2(N_RB) bits for the length, which is inefficient.
The RIV provides a compact, lossless encoding that leverages the constraint that allocations are contiguous. It solves the limitation of verbose signaling by packing two pieces of information into a single value whose maximum size is just enough to uniquely represent all possible contiguous allocations within the bandwidth. This optimization was motivated by the need for highly efficient dynamic scheduling, which is a cornerstone of the packet-switched, low-latency design of LTE and NR. It allows the network to make fast, granular scheduling decisions without being burdened by excessive control signaling, directly contributing to the high spectral efficiency and user multiplexing capabilities of 4G and 5G networks.
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (58 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the Resource Indication Value (RIV) function was extended to support a wider range of values, now ranging up to 63, with specific attention to uplink resource allocation type 1 and PUSCH transmissions scheduled by a RAR UL grant. Corrections were made to ensure proper alignment of frequency domain resource allocation with the specifications, particularly for configured grant Type 1 uplink transmissions and PUSCH with SP CSI. The updates also clarified the application of RIV for in-band emissions testing, referencing specific bitmap values like '00001' and '00100' for verification.
- Correction on uplink resource allocation type 1 TS 38.214CR0010
- Correction on determination of the resource allocation table for PUSCH with SP CSI TS 38.214CR0011
- Correction on PUSCH resource allocation TS 38.214CR0012
- Change Request for alignment of frequency domain resource allocation with 38.213 for a PUSCH transmission scheduled by a RAR UL grant TS 38.214CR0013
- CR on PDSCH beam indication TS 38.214CR0017
- Correction on TCI indication for multi-slot PDSCH TS 38.214CR0018
+ 2 more changes
In Release 16, the RIV (Resource Indication Value) function was extended to support a wider range of values, now ranging up to 63, to accommodate more granular resource allocation configurations. This change is particularly noted for its application in defining specific uplink resource allocations, such as `L = 10` corresponding to `RIV = 19`, for calculating A-MPR (Additional Maximum Power Reduction) requirements in new bands like Band 49. Furthermore, the RIV's role was clarified for in-band emissions testing, where specific RIV bitmaps (e.g., '00001', '00100') are used to verify different emission components like IQ image and LO leakage.
- Aperiodic CSI-RS Triggering for UE reporting beamSwitchTiming values of 224 and 336 TS 38.214CR0060
- 38.214 CR (Rel-16, F, Rel-15 originating) to fix configurable xOverhead values for TBS determination TS 38.214CR0134
- CR on Interference Measurement Resource for L1-SINR TS 38.214CR0139
- Correction on sidelink resource pool determination based on PSBCH TS 38.214CR0141
- CR on DL PRS resource prioritization for UE measurements TS 38.214CR0148
- Corrections related to the sidelink resource reservation period TS 38.214CR0164
+ 12 more changes
In Release 17, the RIV (Resource Indication Value) function was updated to support a wider range of values, now extending up to 63 for certain configurations, compared to the previous maximum. Specifically, the specification clarified the use of RIV for defining uplink resource allocations, including for contiguous allocations where RIV = 19, and its application for verifying in-band emissions masks. These changes provided more precise resource indication for features like configured grant transmissions and measurements under specific channel bandwidths.
- Correction on slot offsets of CSI-RS resource pairs for MTRP TS 38.214CR0320
- Correction on frequency resource for CSI-RS for tracking in TS 38.214 TS 38.214CR0351
- Correction on a minimum guard period between two SRS resources for antenna switching TS 38.214CR0363
- Correction on Type 1 configured grant PUSCH transmission associated with two SRS resource sets TS 38.214CR0365
- CR on UE TEG margin value report TS 38.214CR0373
- Correction on duplicated part on UE procedure for determining a resource conflict between TS 38.213 and TS 38.214 TS 38.214CR0390
+ 12 more changes
In Release 18, specific corrections were made to the RIV function for Sidelink resource allocation mode 2 and for the TRIV/FRIV resource indication of SL-U. Furthermore, the release introduced clarifications for contiguous resource block based resource allocation and defined specific RIV values, such as RIV = 19 for a contiguous allocation and RIV = 5 for certain uplink scheduling grants, within the context of channel bandwidth and emission requirements.
- CR on PDSCH resource mapping for dedicated spectrum less than 5 MHz TS 38.214CR0518
- Correction on TRIV/FRIV resource indication of SL-U TS 38.214CR0548
- Correction on contiguous RB based resource allocation TS 38.214CR0550
- Correction to Sidelink resource allocation mode 2 TS 38.214CR0568
- CR on active semi-persistent SRS resource configuration and transmission of SRS TS 38.214CR0650
- CR on Precoder Indication for 8 port CG-PUSCH TS 38.214CR0653
+ 4 more changes
In Release 19, the changes to the RIV (Resource Indication Value) function specifically pertained to its application in defining new network signalling (NS) values and associated power requirements. A new NS-value "NS_43" was defined for Band 49, with its Adjacent Channel Leakage Ratio (ACLR) requirements linked to specific RIV values, such as RIV = 19 for a contiguous allocation. Furthermore, the RIV's role was clarified for in-band emissions testing, where specific RIV bitmaps (e.g., '00001', '00100') are identified for verifying different unwanted emission components.
- TEI19 Counting of CSI-RS resource referred by N CSI reporting settings [SimCSI_count] TS 38.214CR0681
- TEI19 Simultaneous NZP-CSI-RS resource counting with NES [SimCSI_countNES] TS 38.214CR0689
- Clarification on the number of simultaneous L1 CLI-RSSI and simultaneous L1 SRS-RSRP measurement resources TS 38.214CR0745
- Correction on the maximum number of SRS-RSRP measurement resource sets and CLI-RSSI measurement resource sets TS 38.214CR0746
Explore further
Broader topics and technologies where RIV plays a role.
Defining Specifications
3GPP specifications that define or reference RIV, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 36.790 vf00 | LAA/eLAA for CBRS 3.5GHz Band in US | Rel-15 |
| TS 38.214 vj10 | NR Physical Layer Procedures for Data | Rel-19 |