5G NR RSRP Measurement Report Mapping

Author 5G, 5G Network Architectures, 5G Network Planning, 5G Physical Layer, Call Flow, LTE, New Radio, Radio Resource Management, RF Basics, RRC, RRC Signalling, Tech Fundas

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:

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