5G NR RSRP Measurement Report Mapping

In 5G NR, RSRP measurement is performed and reported at Layer 1 (Physical Layer) and Layer 3 (RRC Layer). For example, 5G capable device can provide SS-RSRP measurements at Layer 1 when sending Channel State Information (CSI) and at Layer 3 when sending an RRC: Measurement Report to gNB.

How Measurement is performed

To generate SS-RSRP measurement results, 5G UE is allowed to measure PBCH-DMRS signal. DMRS and SS signals are transmitted with equal power so results can be averaged.

While performing SS-RSRP measurements for L1, UE can be configured to measure CSI-RS as well. CSI-RS may be transmitted with different transmit power compared to Sync Signals (SS) and PBCH-DMRS. In this case gNB shall provide offset information to UEs so that it can be taken into account during the measurement.

Measurement Characteristics

Layer 3 (L3) Measurement:
- - L3 measurements are useful for radio resource management decisions which require a long term view of channel conditions, e.g. handover procedures should be triggered after Layer 3 filtering to reduce the risk of ping-pong between serving cells
  - Measurements are filtered at Layer 3 to remove the impact of fast fading and to help reduce short term variations in results
  - L3 measurements can be either ‘beam level’ or ‘cell level’ which can be reported within an RRC message: Measurement Report (MR)
  - Beam level measurements are generated directly from the L1 measurements by applying L3 filtering
  - Cell level measurements are derived from the L1 measurements using the certain rules
  - L3 SS-RSRP reporting range is defined from -156 dBm to -31 dBm with 1 dB resolution
  - L3 report requires 7 bits payload to represent 128 value mapped to RSRP in dB
Layer 1 (L1) Measurement:
- - L1 measurements are useful for procedures which must react with minimal delay, e.g. beam management procedures which require the UE to rapidly switch between beams
  - Measurements are filtered at Layer 1 to help remove the impact of noise and to improve measurement accuracy
  - L1 measurements are ‘beam level’
  - L1 SS-RSRP and CSI-RSRP reporting range is defined from -140 to -40dBm with 1dB resolution
  - L1 measurement requires 7 bits payload to represent 128 value mapped to RSRP in dB

RSRP Measurement Report Mapping

Below table depicts the measurement report mapping for L3 SS-RSRP, L1 SS-RSRP and L1 CSI-RSRP. We have two table available from 3GPP specification 38.133 Table (A) for single value reporting and Table (B) for differential SS-RSRP and CSI-RSRP.

L3 measurement for SS-RSRP reporting range is defined from -156 dBm to -31 dBm with 1 dB resolution
- - Reported value of 0 means SS-RSRP is greater or equal to -156dB
  - Reported value of 126 means SS-RSRP is less than or equal -31 dBm
  - RSRP value rough estimation can be done with following thumb rule formula
    - RSRP value = Reported Value – 156
    - RSRP in dBm = 111 – 156 = -45 dBm
L1 measurement for SS-RSRP and CSI-RSRP reporting range is defined from -140 dBm to -40 dBm with 1dB resolution
- - Reporting range value of 0 to 16 and 113 to 127 is not valid for L1 measurement
  - Reported value of 17 means SS-RSRP is greater or equal to -156dB
  - Reported value of 112 means SS-RSRP is less than or equal -45 dBm
  - RSRP value rough estimation can be done with following thumb rule formula
    - RSRP value = Reported Value – 156
    - RSRP in dBm = 18 – 156= -138 dBm
The reporting range of differential SS-RSRP and CSI-RSRP for L1 reporting is defined from 0 dBm to -30 dB with 2 dB resolution

Table (A)

Table (B)

Reference:

3GPP TS 38.133 – 5G NR – Requirements for support of radio resource management

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