RSRP 3GPP Definition
RSRP or Reference Signal Received Power, is defined as the linear average over the power contributions (in [W]) of the resource elements (REs) that carry cell-specific reference signals within the considered measurement frequency bandwidth. For RSRP determination the cell-specific reference signals RE0 according TS 36.211 shall be used. If the UE can reliably detect that RE1 is available it may use RE1 in addition to R0 to determine RSRP.
where Prs,k is the estimated received power (in Watts) of the kth Reference Signal Resource Element (REs) transmitted from the first BTS antenna port.
In the figure beside, these REs are denoted with RE0. To improve the accuracy of the RSRP estimate, the UE may optionally also measure the RS transmitted from the second antenna port (RE1), if present.
In case of four BTS transmit antennas, Reference Signals of the third and fourth BTS antenna ports are not used in the RSRP measurement.
Since all LTE UEs have at least two receive antennas, RSRP must be equal or higher than the stronger of the two receive antennas’ individual measured RSRP.
The maximum number of PRBs over which RSRP should be measured is sent to the UE over RRC signalling, and is denoted in this paper with Nprb.
Applicable for: RRC_IDLE intra-frequency, RRC_IDLE inter-frequency, RRC_CONNECTED intra-frequency, RRC_CONNECTED inter-frequency
- Note 1: The number of resource elements within the considered measurement frequency bandwidth and within the measurement period that are used by the UE to determine RSRP is left up to the UE implementation with the limitation that corresponding measurement accuracy requirements have to be fulfilled
- Note 2: The power per resource element is determined from the energy received during the useful part of the symbol, excluding the CP
In other words, RSRP is the average power of Resource Elements (RE) that carry cell specific Reference Signals (RS) over the entire bandwidth, so RSRP is only measured in the symbols carrying RS.
In other words:
- RSRP is the average received power of a single RS resource element
- UE measures the power of multiple resource elements used to transfer the reference signal but then takes an average of them rather than summing them
- the reporting range of RSRP is defined from -140 dBm to – 44 dBm with 1 dB resolution. The mapping of measured quantity is defined in the table below: RSRP mapping 3GPP TS 36.133 V8.9.0 (2010-03)
- RSRP does a better job of measuring signal power from a specific sector while potentially excluding noise and interference from other sectors
- RSRP levels for usable signal typically range from about -75 dBm close in to an LTE cell site to -120 dBm at the edge of LTE coverage
- the lowest RSRP value having reported value of ’RSRP_00’
- under normal operating conditions, absolute measurement accuracy is allowed to have up to 6dB error for intra-frequency RSRP measurement
- measured RSRP difference between serving and a neighbour cell on the same carrier frequency should have at most 3dB error.
- for inter-frequency RSRP measurement, the absolute and relative error under normal conditions should both be less than 6dB. It can be seen that inter-frequency RSRP measurement is considerably less accurate for “power budget” type handover triggering than intra-frequency RSRP measurement.
The above cited measurement accuracy requirements hold for SNR = −6dB and without any higher layer measurement filtering. Higher SNR and application of L3 filtering results in improved measurement accuracy. Therefore, in typical network conditions, measurement error can be expected to be smaller.
RSRP and RSRQ Measurement in LTE