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RSRP(Reference Signal Recieved Power)

 

RSRP is the linear average of reference singal power (in Watts) accorss the specified bandwidth (in number of REs). This is the most important item UE has to measure for cell selection, reselection and handover. You can think of this as the one similar to CPICH RSCP in WCDMA.

 

The formal definition of RSRP in 3GPP 36.214 is as follows :

 

Reference signal received power (RSRP), is defined as the linear average over the power contributions (in [W]) of the resource elements that carry cell-specific reference signals within the considered measurement frequency bandwidth. For RSRP determination the cell-specific reference signals R0 according TS 36.211 shall be used. If the UE can reliably detect that R1 is available it may use R1 in addition to R0 to determine RSRP.

 

Note : R0 is the Cell Specific Reference Signal for Antenna Port 0 and R1 is the Cell Specific Reference signal for Antenna Port 1 (Refer to 36.211 Figure 6.10.1.2-1. Mapping of downlink reference signals (normal cyclic prefix))

 

Following is an example of one downlink radio frame. The red part is the resource elements in which reference signal is being transmitted. RSRP is the linear average of all the red part power.

 

 

Since this measures only the reference power, we can say this is the strength of the wanted signal. But it does not gives any information about signal quality. RSRP gives us the signal strenth of the desired signal, not the quality of  the signal. For quality of the signal information another parameter called 'RSSQ' is used in some case.

 

UE usually measures RSRP or RSRQ based on the direction (RRC message) from the network and report the value. When it report this value, it does use the real RSRP value. It sends a non-negative value ranging from 0 to 97 and each of these values are mapped to a specific range of real RSRP value as shown in the following table from 36.133.

 

 

For practical calculation example, refer to RSRQ Calculator (YouTube)

 

Just to relieve a little of headache to figure out the mapping between the reported RSRP and measured value in dBm, I just made precalculated table as shown below.

 

RSRP

From

To

Unit

00

-140

dBm

01

-140

-139

dBm

02

-139

-138

dBm

03

-138

-137

dBm

04

-137

-136

dBm

05

-136

-135

dBm

06

-135

-134

dBm

07

-134

-133

dBm

08

-133

-132

dBm

09

-132

-131

dBm

10

-131

-130

dBm

11

-130

-129

dBm

12

-129

-128

dBm

13

-128

-127

dBm

14

-127

-126

dBm

15

-126

-125

dBm

16

-125

-124

dBm

17

-124

-123

dBm

18

-123

-122

dBm

19

-122

-121

dBm

20

-121

-120

dBm

21

-120

-119

dBm

22

-119

-118

dBm

23

-118

-117

dBm

24

-117

-116

dBm

25

-116

-115

dBm

26

-115

-114

dBm

27

-114

-113

dBm

28

-113

-112

dBm

29

-112

-111

dBm

30

-111

-110

dBm

31

-110

-109

dBm

32

-109

-108

dBm

33

-108

-107

dBm

34

-107

-106

dBm

35

-106

-105

dBm

36

-105

-104

dBm

37

-104

-103

dBm

38

-103

-102

dBm

39

-102

-101

dBm

40

-101

-100

dBm

41

-100

-99

dBm

42

-99

-98

dBm

43

-98

-97

dBm

44

-97

-96

dBm

45

-96

-95

dBm

46

-95

-94

dBm

47

-94

-93

dBm

48

-93

-92

dBm

49

-92

-91

dBm

50

-91

-90

dBm

51

-90

-89

dBm

52

-89

-88

dBm

53

-88

-87

dBm

54

-87

-86

dBm

55

-86

-85

dBm

56

-85

-84

dBm

57

-84

-83

dBm

58

-83

-82

dBm

59

-82

-81

dBm

60

-81

-80

dBm

61

-80

-79

dBm

62

-79

-78

dBm

63

-78

-77

dBm

64

-77

-76

dBm

65

-76

-75

dBm

66

-75

-74

dBm

67

-74

-73

dBm

68

-73

-72

dBm

69

-72

-71

dBm

70

-71

-70

dBm

71

-70

-69

dBm

72

-69

-68

dBm

73

-68

-67

dBm

74

-67

-66

dBm

75

-66

-65

dBm

76

-65

-64

dBm

77

-64

-63

dBm

78

-63

-62

dBm

79

-62

-61

dBm

80

-61

-60

dBm

81

-60

-59

dBm

82

-59

-58

dBm

83

-58

-57

dBm

84

-57

-56

dBm

85

-56

-55

dBm

86

-55

-54

dBm

87

-54

-53

dBm

88

-53

-52

dBm

89

-52

-51

dBm

90

-51

-50

dBm

91

-50

-49

dBm

92

-49

-48

dBm

93

-48

-47

dBm

94

-47

-46

dBm

95

-46

-45

dBm

96

-45

-44

dBm

97

-44

dBm

 

 

Reference :

 

[1] 3GPP - 36.214 Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer - Measurements  

[2] 3GPP - 36.133  Evolved Universal Terrestrial Radio Access (E-UTRA);Requirements for support of radio resource management

[3] For practical calculation example, refer to RSRQ Calculator (YouTube)

[4]  RSRP and RSRQ Measurement in LTE