NR-RSRP

RSRP stands for Reference Signal Recieved Power. The basic definiton of NR RSRP is same as LTE RSRP. The major difference from LTE RSRP is that NR RSRP is measured from the reference signal in SSB whereas LTE RSRP is measured from CRS(Cell Reference Signal).

RSRP Report Mapping

Before the table itself, it helps to know what its two data columns are for. 38.133 defines two separate reporting ranges for RSRP, one for L3 reporting and one for L1 reporting, and the table carries both of them side by side.

When you get the RSRP value from measurement report (e.g, Measurement Report RRC message), it gives a positive integer value, not the dBm value. The mapping between the reported value and real power (measured quantity value) is defined in 3GPP as follows.

Following is based on 38.133 v20.0.0 (Release 20)

< 38.133-Table 10.1.6.1-1: SS-RSRP, CSI-RSRP measurement report mapping and P-L1-RSRP report mapping >

NOTE : You may do quick convert from Reported Value to Measured value by taking (Reported Value - 157)

Reported Value	Measured Quantity value(L3 SS-RSRP) and CSI-RSRP	Measured Quantity value(L1 SS-RSRP and CSI-RSRP, P-L1-RSRP)	Unit
RSRP_0	SS-RSRP < -156	Not valid	dBm
RSRP_1	-156 ≤ SS-RSRP < -155	Not valid	dBm
RSRP_2	-155 ≤ SS-RSRP < -154	Not valid	dBm
RSRP_3	-154 ≤ SS-RSRP < -153	Not valid	dBm
RSRP_4	-153 ≤ SS-RSRP < -152	Not valid	dBm
RSRP_5	-152 ≤ SS-RSRP < -151	Not valid	dBm
RSRP_6	-151 ≤ SS-RSRP < -150	Not valid	dBm
RSRP_7	-150 ≤ SS-RSRP < -149	Not valid	dBm
RSRP_8	-149 ≤ SS-RSRP < -148	Not valid	dBm
RSRP_9	-148 ≤ SS-RSRP < -147	Not valid	dBm
RSRP_10	-147 ≤ SS-RSRP < -146	Not valid	dBm
RSRP_11	-146 ≤ SS-RSRP < -145	Not valid	dBm
RSRP_12	-145 ≤ SS-RSRP < -144	Not valid	dBm
RSRP_13	-144 ≤ SS-RSRP < -143	Not valid	dBm
RSRP_14	-143 ≤ SS-RSRP < -142	Not valid	dBm
RSRP_15	-142 ≤ SS-RSRP < -141	Not valid	dBm
RSRP_16	-141 ≤ SS-RSRP < -140	RSRP < -140	dBm
RSRP_17	-140 ≤ SS-RSRP < -139	-140 ≤ RSRP < -139	dBm
RSRP_18	-139 ≤ SS-RSRP < -138	-139 ≤ RSRP < -138	dBm
RSRP_19	-138 ≤ SS-RSRP < -137	-138 ≤ RSRP < -137	dBm
RSRP_20	-137 ≤ SS-RSRP < -136	-137 ≤ RSRP < -136	dBm
RSRP_21	-136 ≤ SS-RSRP < -135	-136 ≤ RSRP < -135	dBm
RSRP_22	-135 ≤ SS-RSRP < -134	-135 ≤ RSRP < -134	dBm
RSRP_23	-134 ≤ SS-RSRP < -133	-134 ≤ RSRP < -133	dBm
RSRP_24	-133 ≤ SS-RSRP < -132	-133 ≤ RSRP < -132	dBm
RSRP_25	-132 ≤ SS-RSRP < -131	-132 ≤ RSRP < -131	dBm
RSRP_26	-131 ≤ SS-RSRP < -130	-131 ≤ RSRP < -130	dBm
RSRP_27	-130 ≤ SS-RSRP < -129	-130 ≤ RSRP < -129	dBm
RSRP_28	-129 ≤ SS-RSRP < -128	-129 ≤ RSRP < -128	dBm
RSRP_29	-128 ≤ SS-RSRP < -127	-128 ≤ RSRP < -127	dBm
RSRP_30	-127 ≤ SS-RSRP < -126	-127 ≤ RSRP < -126	dBm
RSRP_31	-126 ≤ SS-RSRP < -125	-126 ≤ RSRP < -125	dBm
RSRP_32	-125 ≤ SS-RSRP < -124	-125 ≤ RSRP < -124	dBm
RSRP_33	-124 ≤ SS-RSRP < -123	-124 ≤ RSRP < -123	dBm
RSRP_34	-123 ≤ SS-RSRP < -122	-123 ≤ RSRP < -122	dBm
RSRP_35	-122 ≤ SS-RSRP < -121	-122 ≤ RSRP < -121	dBm
RSRP_36	-121 ≤ SS-RSRP < -120	-121 ≤ RSRP < -120	dBm
RSRP_37	-120 ≤ SS-RSRP < -119	-120 ≤ RSRP < -119	dBm
RSRP_38	-119 ≤ SS-RSRP < -118	-119 ≤ RSRP < -118	dBm
RSRP_39	-118 ≤ SS-RSRP < -117	-118 ≤ RSRP < -117	dBm
RSRP_40	-117 ≤ SS-RSRP < -116	-117 ≤ RSRP < -116	dBm
RSRP_41	-116 ≤ SS-RSRP < -115	-116 ≤ RSRP < -115	dBm
RSRP_42	-115 ≤ SS-RSRP < -114	-115 ≤ RSRP < -114	dBm
RSRP_43	-114 ≤ SS-RSRP < -113	-114 ≤ RSRP < -113	dBm
RSRP_44	-113 ≤ SS-RSRP < -112	-113 ≤ RSRP < -112	dBm
RSRP_45	-112 ≤ SS-RSRP < -111	-112 ≤ RSRP < -111	dBm
RSRP_46	-111 ≤ SS-RSRP < -110	-111 ≤ RSRP < -110	dBm
RSRP_47	-110 ≤ SS-RSRP < -109	-110 ≤ RSRP < -109	dBm
RSRP_48	-109 ≤ SS-RSRP < -108	-109 ≤ RSRP < -108	dBm
RSRP_49	-108 ≤ SS-RSRP < -107	-108 ≤ RSRP < -107	dBm
RSRP_50	-107 ≤ SS-RSRP < -106	-107 ≤ RSRP < -106	dBm
RSRP_51	-106 ≤ SS-RSRP < -105	-106 ≤ RSRP < -105	dBm
RSRP_52	-105 ≤ SS-RSRP < -104	-105 ≤ RSRP < -104	dBm
RSRP_53	-104 ≤ SS-RSRP < -103	-104 ≤ RSRP < -103	dBm
RSRP_54	-103 ≤ SS-RSRP < -102	-103 ≤ RSRP < -102	dBm
RSRP_55	-102 ≤ SS-RSRP < -101	-102 ≤ RSRP < -101	dBm
RSRP_56	-101 ≤ SS-RSRP < -100	-101 ≤ RSRP < -100	dBm
RSRP_57	-100 ≤ SS-RSRP < -99	-100 ≤ RSRP < -99	dBm
RSRP_58	-99 ≤ SS-RSRP < -98	-99 ≤ RSRP < -98	dBm
RSRP_59	-98 ≤ SS-RSRP < -97	-98 ≤ RSRP < -97	dBm
RSRP_60	-97 ≤ SS-RSRP < -96	-97 ≤ RSRP < -96	dBm
RSRP_61	-96 ≤ SS-RSRP < -95	-96 ≤ RSRP < -95	dBm
RSRP_62	-95 ≤ SS-RSRP < -94	-95 ≤ RSRP < -94	dBm
RSRP_63	-94 ≤ SS-RSRP < -93	-94 ≤ RSRP < -93	dBm
RSRP_64	-93 ≤ SS-RSRP < -92	-93 ≤ RSRP < -92	dBm
RSRP_65	-92 ≤ SS-RSRP < -91	-92 ≤ RSRP < -91	dBm
RSRP_66	-91 ≤ SS-RSRP < -90	-91 ≤ RSRP < -90	dBm
RSRP_67	-90 ≤ SS-RSRP < -89	-90 ≤ RSRP < -89	dBm
RSRP_68	-89 ≤ SS-RSRP < -88	-89 ≤ RSRP < -88	dBm
RSRP_69	-88 ≤ SS-RSRP < -87	-88 ≤ RSRP < -87	dBm
RSRP_70	-87 ≤ SS-RSRP < -86	-87 ≤ RSRP < -86	dBm
RSRP_71	-86 ≤ SS-RSRP < -85	-86 ≤ RSRP < -85	dBm
RSRP_72	-85 ≤ SS-RSRP < -84	-85 ≤ RSRP < -84	dBm
RSRP_73	-84 ≤ SS-RSRP < -83	-84 ≤ RSRP < -83	dBm
RSRP_74	-83 ≤ SS-RSRP < -82	-83 ≤ RSRP < -82	dBm
RSRP_75	-82 ≤ SS-RSRP < -81	-82 ≤ RSRP < -81	dBm
RSRP_76	-81 ≤ SS-RSRP < -80	-81 ≤ RSRP < -80	dBm
RSRP_77	-80 ≤ SS-RSRP < -79	-80 ≤ RSRP < -79	dBm
RSRP_78	-79 ≤ SS-RSRP < -78	-79 ≤ RSRP < -78	dBm
RSRP_79	-78 ≤ SS-RSRP < -77	-78 ≤ RSRP < -77	dBm
RSRP_80	-77 ≤ SS-RSRP < -76	-77 ≤ RSRP < -76	dBm
RSRP_81	-76 ≤ SS-RSRP < -75	-76 ≤ RSRP < -75	dBm
RSRP_82	-75 ≤ SS-RSRP < -74	-75 ≤ RSRP < -74	dBm
RSRP_83	-74 ≤ SS-RSRP < -73	-74 ≤ RSRP < -73	dBm
RSRP_84	-73 ≤ SS-RSRP < -72	-73 ≤ RSRP < -72	dBm
RSRP_85	-72 ≤ SS-RSRP < -71	-72 ≤ RSRP < -71	dBm
RSRP_86	-71 ≤ SS-RSRP < -70	-71 ≤ RSRP < -70	dBm
RSRP_87	-70 ≤ SS-RSRP < -69	-70 ≤ RSRP < -69	dBm
RSRP_88	-69 ≤ SS-RSRP < -68	-69 ≤ RSRP < -68	dBm
RSRP_89	-68 ≤ SS-RSRP < -67	-68 ≤ RSRP < -67	dBm
RSRP_90	-67 ≤ SS-RSRP < -66	-67 ≤ RSRP < -66	dBm
RSRP_91	-66 ≤ SS-RSRP < -65	-66 ≤ RSRP < -65	dBm
RSRP_92	-65 ≤ SS-RSRP < -64	-65 ≤ RSRP < -64	dBm
RSRP_93	-64 ≤ SS-RSRP < -63	-64 ≤ RSRP < -63	dBm
RSRP_94	-63 ≤ SS-RSRP < -62	-63 ≤ RSRP < -62	dBm
RSRP_95	-62 ≤ SS-RSRP < -61	-62 ≤ RSRP < -61	dBm
RSRP_96	-61 ≤ SS-RSRP < -60	-61 ≤ RSRP < -60	dBm
RSRP_97	-60 ≤ SS-RSRP < -59	-60 ≤ RSRP < -59	dBm
RSRP_98	-59 ≤ SS-RSRP < -58	-59 ≤ RSRP < -58	dBm
RSRP_99	-58 ≤ SS-RSRP < -57	-58 ≤ RSRP < -57	dBm
RSRP_100	-57 ≤ SS-RSRP < -56	-57 ≤ RSRP < -56	dBm
RSRP_101	-56 ≤ SS-RSRP < -55	-56 ≤ RSRP < -55	dBm
RSRP_102	-55 ≤ SS-RSRP < -54	-55 ≤ RSRP < -54	dBm
RSRP_103	-54 ≤ SS-RSRP < -53	-54 ≤ RSRP < -53	dBm
RSRP_104	-53 ≤ SS-RSRP < -52	-53 ≤ RSRP < -52	dBm
RSRP_105	-52 ≤ SS-RSRP < -51	-52 ≤ RSRP < -51	dBm
RSRP_106	-51 ≤ SS-RSRP < -50	-51 ≤ RSRP < -50	dBm
RSRP_107	-50 ≤ SS-RSRP < -49	-50 ≤ RSRP < -49	dBm
RSRP_108	-49 ≤ SS-RSRP < -48	-49 ≤ RSRP < -48	dBm
RSRP_109	-48 ≤ SS-RSRP < -47	-48 ≤ RSRP < -47	dBm
RSRP_110	-47 ≤ SS-RSRP < -46	-47 ≤ RSRP < -46	dBm
RSRP_111	-46 ≤ SS-RSRP < -45	-46 ≤ RSRP < -45	dBm
RSRP_112	-45 ≤ SS-RSRP < -44	-45 ≤ RSRP < -44	dBm
RSRP_113	-44 ≤ SS-RSRP < -43	-44 ≤ RSRP	dBm
RSRP_114	-43 ≤ SS-RSRP < -42	Not valid	dBm
RSRP_115	-42 ≤ SS-RSRP < -41	Not valid	dBm
RSRP_116	-41 ≤ SS-RSRP < -40	Not valid	dBm
RSRP_117	-40 ≤ SS-RSRP < -39	Not valid	dBm
RSRP_118	-39 ≤ SS-RSRP < -38	Not valid	dBm
RSRP_119	-38 ≤ SS-RSRP < -37	Not valid	dBm
RSRP_120	-37 ≤ SS-RSRP < -36	Not valid	dBm
RSRP_121	-36 ≤ SS-RSRP < -35	Not valid	dBm
RSRP_122	-35 ≤ SS-RSRP < -34	Not valid	dBm
RSRP_123	-34 ≤ SS-RSRP < -33	Not valid	dBm
RSRP_124	-33 ≤ SS-RSRP < -32	Not valid	dBm
RSRP_125	-32 ≤ SS-RSRP < -31	Not valid	dBm
RSRP_126	-31 ≤ SS-RSRP	Not valid	dBm
RSRP_127	Infinity	Infinity	dBm

The NOTE above the table is worth stating precisely, because it holds everywhere except at the two ends. For a reported value of N between 1 and 126, the L3 range is N-157 dBm up to but not including N-156 dBm. So subtracting 157 gives you the lower edge of the bin, not its centre. RSRP_0 and RSRP_127 are the exceptions, since one is open at the bottom and the other means Infinity rather than a power.

38.133-10.1.6 states the two ranges in one sentence each. L3 reporting runs from -156 dBm to -31 dBm with 1 dB resolution. L1 reporting runs from -140 dBm to -44 dBm, also with 1 dB resolution. That difference is the whole reason the third column reads Not valid so often.

Reported value minus 157 gives the lower edge in dBm : it is the bottom of the bin rather than the middle. A reported RSRP_70 therefore means the measurement sat between -87 dBm and -86 dBm.
The two columns cover different ranges : L3 spans -156 to -31 dBm and L1 spans -140 to -44 dBm. The L1 column is therefore defined only between RSRP_16 and RSRP_113.
RSRP_127 means Infinity, not a very strong signal : 38.133 carries a note saying the value is applicable for an RSRP threshold. Meeting it in a report is not the same as measuring it.
The signalled range is wider than the guaranteed one : 38.133 warns that the range in the signalling may be larger than the guaranteed accuracy range. The extreme values are not promises about accuracy.

What SS-RSRP and CSI-RSRP Measure

The opening of this page says NR RSRP is measured from the reference signal in SSB. That is right, but 38.215 is more specific about which signal inside the SSB it means. It also defines a second RSRP that has nothing to do with the SSB at all.

38.215-5.1.1 defines SS-RSRP as the linear average over the power contributions, in watts, of the resource elements that carry secondary synchronization signals. So the measurement is taken on the SSS, and not on the SSB as a whole. The demodulation reference signal for PBCH may be used in addition. CSI reference signals may be used as well, when higher layers indicate it and the result feeds L1-RSRP.

Two constraints in the same clause matter in practice. SS-RSRP is measured only among reference signals belonging to SS/PBCH blocks with the same SSB index and the same physical-layer cell identity. Two different beams are therefore never averaged into one number. The measurement time is also confined to the SMTC window, except where SS-RSRP is being used for L1-RSRP, in which case that restriction does not apply.

CSI-RSRP is the other one, and 38.215-5.1.2 defines it as the linear average over the resource elements of the antenna ports carrying CSI-RS configured for RSRP measurement. It uses antenna port 3000, or ports 3000 and 3001 when the result is used for L1-RSRP.

	SS-RSRP	CSI-RSRP
Measured on	SSS, optionally PBCH DM-RS, and CSI-RS when used for L1-RSRP	CSI-RS configured for RSRP measurement
Antenna port	Not specified as a port number	3000, or 3000 and 3001 for L1-RSRP
Measurement time	Inside the SMTC window, unless used for L1-RSRP	The configured CSI-RS occasions
RRC states	RRC_IDLE, RRC_INACTIVE and RRC_CONNECTED	RRC_CONNECTED only
Usual purpose	Cell selection, reselection and cell level mobility	Beam management and beam refinement inside a connection

The RRC state row is the one to remember. A UE in RRC_IDLE or RRC_INACTIVE has no CSI-RS configuration at all, so CSI-RSRP does not exist for it. Every measurement a UE makes while it is choosing a cell is therefore SS-RSRP.

One more detail decides what the number actually refers to. For FR1 the reference point is the antenna connector of the UE. For FR2 the measurement is made on the combined signal from the antenna elements of a given receiver branch. In both frequency ranges, if the UE is using receive diversity, the reported value must not be lower than the value on any individual branch.

SS-RSRP is an SSS measurement : the SSB carries several signals, and 38.215 names the secondary synchronization signals as the ones that count.
Beams are never averaged together : only reference signals with the same SSB index and the same physical-layer cell identity go into one SS-RSRP value.
CSI-RSRP is a connected mode quantity : it needs a CSI-RS configuration, so an idle or inactive UE has only SS-RSRP to work with.
FR1 and FR2 measure at different points : FR1 refers to the antenna connector, and FR2 to the combined signal of a receiver branch. FR2 numbers are therefore not directly comparable with FR1 numbers.

L1-RSRP and L3-RSRP

The mapping table has two data columns, and the difference between them is not a detail. L1-RSRP and L3-RSRP are produced at different layers, they are filtered differently, and they travel to the network in different messages.

L1-RSRP is the raw physical layer measurement. L3-RSRP is what remains after the RRC layer has filtered it, and 38.331-5.5.3.2 gives that filter as a single expression.

Fn = (1 - a) × Fn-1 + a × Mn where a = 1 / 2^(k/4)

Mn is the latest measurement result from the physical layer, Fn is the updated filtered result that gets reported, and k is the filterCoefficient the network configures. When k is set to 0 no layer 3 filtering is applied, and the two quantities then differ only by where they are read.

	L1-RSRP	L3-RSRP
Produced by	The physical layer	RRC, after layer 3 filtering
Filtering	None beyond the L1 measurement period	The filter above, driven by filterCoefficient
Reporting range	-140 to -44 dBm, 1 dB resolution	-156 to -31 dBm, 1 dB resolution
Carried in	A CSI report, on PUCCH or PUSCH	An RRC MeasurementReport
Used for	Beam management and beam selection	Cell level mobility, handover and reselection

The reporting range row explains every Not valid entry in the mapping table. L1 reporting is defined only from -140 dBm to -44 dBm, so a reported value below RSRP_16 or above RSRP_113 carries no L1 meaning. That is not a hole in the table. It is the L1 range being narrower than the L3 range, and 38.133-10.1.6 states both ranges explicitly.

The filtering row is the one that catches people during drive tests. A phone that displays a fast moving RSRP is usually showing something close to Mn, while the value the network acts on is Fn. With a large filterCoefficient the two can disagree by several dB for seconds at a time, and neither of them is wrong.

Same quantity, two points in the chain : Mn is what the L1 column describes and Fn is what the L3 column describes, so the columns are not two different measurements.
filterCoefficient set to 0 disables L3 filtering : 38.331 says so directly, which is the setting to use when you want the reported value to track the radio quickly.
The Not valid entries are a range difference : L1 stops at -140 dBm and -44 dBm, so the rows outside RSRP_16 to RSRP_113 exist only for L3.
The two travel in different messages : L1-RSRP travels in a CSI report on PUCCH or PUSCH, and L3-RSRP in an RRC MeasurementReport. You will not find them in the same log line.

Differential RSRP Reporting

The second table answers a question the first one raises. When a beam report carries several RSRP values at once, sending each as a full 7 bit number wastes uplink. The beams being reported are usually within a few dB of each other.

The reporting range of differential SS-RSRP and CSI-RSRP for L1 reporting is defined from 0 dB to -30 dB with 2 dB resolution.

Following is based on 38.133 v20.0.0 (Release 20)

< 38.133-Table 10.1.6.1-2: Differential SS-RSRP, CSI-RSRP measurement (for L1 reporting) report mapping and P-L1-RSRP report mapping >

Reported Value	Measured Quantity Value (difference in measured RSRP from strongest RSRP)	Unit
DIFFRSRP_0	0 ≥ ΔRSRP > -2	dB
DIFFRSRP_1	-2 ≥ ΔRSRP > -4	dB
DIFFRSRP_2	-4 ≥ ΔRSRP > -6	dB
DIFFRSRP_3	-6 ≥ ΔRSRP > -8	dB
DIFFRSRP_4	-8 ≥ ΔRSRP > -10	dB
DIFFRSRP_5	-10 ≥ ΔRSRP > -12	dB
DIFFRSRP_6	-12 ≥ ΔRSRP > -14	dB
DIFFRSRP_7	-14 ≥ ΔRSRP > -16	dB
DIFFRSRP_8	-16 ≥ ΔRSRP > -18	dB
DIFFRSRP_9	-18 ≥ ΔRSRP > -20	dB
DIFFRSRP_10	-20 ≥ ΔRSRP > -22	dB
DIFFRSRP_11	-22 ≥ ΔRSRP > -24	dB
DIFFRSRP_12	-24 ≥ ΔRSRP > -26	dB
DIFFRSRP_13	-26 ≥ ΔRSRP > -28	dB
DIFFRSRP_14	-28 ≥ ΔRSRP > -30	dB
DIFFRSRP_15	-30 ≥ ΔRSRP	dB

38.214 sets out when this second mapping is used instead of the first. With nrofReportedRS set to one, the UE reports a single L1-RSRP as a 7 bit value in the range -140 to -44 dBm with 1 dB steps. When nrofReportedRS is larger than one, or when groupBasedBeamReporting is enabled, the UE switches to differential reporting.

In that mode the largest measured L1-RSRP in the reporting instance is quantised to that same 7 bit value. Every other value in the same report is then quantised to a 4 bit differential, with a 2 dB step, taken relative to that largest value.

The shape of the second table follows from those two numbers alone. Four bits give 16 values, and 16 steps of 2 dB span 30 dB below the strongest beam. Anything weaker than 30 dB below the strongest beam collapses into DIFFRSRP_15, which is why the last row has no lower bound.

Only the strongest beam is reported absolutely : it gets the full 7 bit value, and everything else in the report is expressed as a difference from it.
Four bits and 2 dB steps give exactly 30 dB : that is where the range in the second table comes from, rather than from any measurement limit.
The trigger is how many RS are reported : nrofReportedRS greater than one, or group based beam reporting, switches the UE from absolute to differential.
A differential value is meaningless on its own : without the absolute anchor from the same reporting instance, DIFFRSRP_6 tells you nothing about the received power.

Reference

[1] 38.133 v20.0.0 : NR - Requirements for support of radio resource management. Clause 10.1.6 and Tables 10.1.6.1-1 and 10.1.6.1-2 were read, and both tables on this page were checked against them.
[2] 38.215 v19.3.0 : NR - Physical layer measurements. Clauses 5.1.1 and 5.1.2 were read.
[3] 38.214 v19.4.0 : NR - Physical layer procedures for data. The L1-RSRP reporting text in clause 5.2.1.4 was read.
[4] 38.331 v19.3.0 : NR - Radio Resource Control (RRC) protocol specification. Clause 5.5.3.2 was read for the layer 3 filter.

Coverage is partial. Each of these documents is long, and I read the clauses listed above rather than the whole of any of them.