Basic RF measurement quantities: Definitions and measurement Soc Classification level 1 © Nokia Siemens Networks LTE OPT Training Last Updated: April 10 th , 2012 Version 1.9 Presentation / Author / Date
Basic RF measurement quantities: Definitions and measurement
Soc Classification level 1 © Nokia Siemens Networks
LTE OPT TrainingLast Updated: April 10th, 2012Version 1.9
Presentation / Author / Date
Content
• RSRP: Reference Signal Received Power
• RSSI: Reference Signal Strength Indicator
• RSRQ: Reference Signal Received Quality
• SINR / CINR / SNR etc
– Definition and measurement
Soc Classification level 2 © Nokia Siemens Networks Presentation / Author / Date
– Definition and measurement
– Mapping RSRP / RSRQ to SINR
• MIMO variants of the RF quantities and use cases
• 3GPP defined measurement accuracy for UEs
Reference signal from three 2Tx cellsRecap (1/2)
• RS frequency shift based on PCI modulo-3
0R
0R
0R
0R
1R
1R
1R
1R
0R
0R
0R
0R
1R
1R
1R
1R
0R
0R
0R
0R
1R
1R
1R
1R
R0: tx antenna 1R1: tx antenna 2
Soc Classification level 3 © Nokia Siemens Networks
00
0R
0R
0R
0R
1 1
1R
1R
1R
1R
00
0R
0R
0R
0R
1 1
1R
1R
1R
1R
00
0R
0R
0R
0R
1 1
1R
1R
1R
1R
Reference signal from three 2Tx cellsRecap (2/2)
• RS as seen by UE from cells of a 3-sector site � no RS-RS interference since PCImod3 are different
0R
0R
1R
1R
0R
0R
1R
1R
0R
0R
1R
1R
Sector 1: blueSector 2: greenSector 3: red
R : tx antenna 1
Soc Classification level 4 © Nokia Siemens Networks
0R
0R
0R
0R
0R
0R
1R
1R
1R
1R
1R
1R
0R
0R
0R
0R
0R
0R
1R
1R
1R
1R
1R
1R
0R
0R
0R
0R
0R
0R
1R
1R
1R
1R
1R
1R
R0: tx antenna 1R1: tx antenna 2
RSRPDefinition in 3GPP TS 36.214
• RSRP is the linear average of received power of RS resource elements• UE measures the rx power of multiple RS REs and takes average of them• Reporting range -44…-140 dBm
Definition 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 [3] shall be used. If the UE can reliably detect that R1 is available it may use R1 in addition to R0 to determine RSRP.
R0: tx antenna 1R1: tx antenna 2
Soc Classification level 5 © Nokia Siemens Networks
The reference point for the RSRP shall be the antenna connector of the UE. If receiver diversity is in use by the UE, the reported value shall not be lower than the corresponding RSRP of any of the individual diversity branches.
Applicable for RRC_IDLE intra-frequency, RRC_IDLE inter-frequency, RRC_CONNECTED intra-frequency, RRC_CONNECTED inter-frequency
Note1: 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.
RSRP mapping 3GPP TS 36.133 V8.9.0 (2010-03)
• 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:
Reported value Measured quantity value Unit
RSRP_00 RSRP < -140 dBm
RSRP_01 -140 ≤ RSRP < -139 dBm
Soc Classification level 6 © Nokia Siemens Networks
RSRP_01 -140 ≤ RSRP < -139 dBm
RSRP_02 -139 ≤ RSRP < -138 dBm
… … …
RSRP_95 -46 ≤ RSRP < -45 dBm
RSRP_96 -45 ≤ RSRP < -44 dBm
RSRP_97 -44 ≤ RSRP dBm
RSRP measurement using different devices
-70
-651 31 61 91 121 151 181 211 241 271 301 331 361 391
RSRP measurement, idle cell and fully loaded cell
• Comparison of Samsung UE and R&S TMSW / PCTel EX scanners– UE inside car and scanners using the same antenna mounted on car roof
Soc Classification level 7 © Nokia Siemens Networks
-90
-85
-80
-75
RS
RP
[d
Bm
]
time, seconds
PCTel RSRPR&S RSRPUE RSRP
Measured RSRP depends on scanner
UE starts downloading
Quiz: RSRP vs CPICH RSCP• Below a measurement of 2.1GHz CPICH RSCP versus 1.8GHz/20MHz
RSRP using a multi-RAT multi-band scanner. • Q: Should RSRP be scaled somehow to make it comparable to RSCP?
Soc Classification level 8 © Nokia Siemens Networks
Content
• RSRP: Reference Signal Received Power
• RSSI: Reference Signal Strength Indicator
• RSRQ: Reference Signal Received Quality
• SINR / CINR / SNR etc
– Definition and measurement
Soc Classification level 9 © Nokia Siemens Networks Presentation / Author / Date
– Definition and measurement
– Mapping RSRP / RSRQ to SINR
• MIMO variants of the RF quantities and use cases
• 3GPP defined measurement accuracy for UEs
0R
0R
1R
1R
RSSI
• RSSI is internal to UE, not reported in uplink to eNB• RSSI measures all power within the measurement bandwidth
– hence it includes thermal noise, interference and serving cell power• Measured over those OFDM symbols that contain RS for antenna port R0
Soc Classification level 10 © Nokia Siemens Networks
0R
0R
0R
0R
0R
0R
1R
1R
1R
1R
1R
1R
OFDM symbol containing R0
Relation between RSSI and RSRPTheory
• RSSI = wideband power= noise + serving cell power + interference power
• Without noise and interference, 100% DL PRB activity:
Where:– N is number of PRBs across the RSSI is measured and depends on the BW
RSSI=12*N*RSRP
Soc Classification level 11 © Nokia Siemens Networks
• Based on the above, under 100% PRB utilization and high SNR:
Presentation / Author / Date
RSRP (dBm)= RSSI (dBm) -10*log (12*N)
Relation between RSSI and RSRPField measurement in fully loaded 10MHz cell
RSRP versus RSSI for fully loaded cell, 10MHz system bandwidth (100% of REs active)
-85
-75
-93 -88 -83 -78 -73 -68 -63 -58 -53 -48
RS
RP
[dB
m]
Soc Classification level 12 © Nokia Siemens Networks Presentation / Author / Date
-125
-115
-105
-95
RSSI [dBm]
RS
RP
[dB
m]
Measurement: slope ~28 dB �
agrees with theory (27.8dB)
Relation of RSSI and RSRPImpact in cell load
• RSSI increases about 5dB when PRB activity increases to 100%,10MHz cell -70
-60
-50
-40
1 6 11 16 21 26 31 36
Po
wer
, d
Bm
30
40
50
60
Nu
mb
er o
f R
Bs
SCell-RSSI(Com)
SCell-RSRP(Com)
RB Num(DL)
RSRP
Soc Classification level 13 © Nokia Siemens Networks
100%,10MHz cell
• RSRP is independent of cell load
-100
-90
-80
-70
Time, seconds
Po
wer
, d
Bm
0
10
20
30
Nu
mb
er o
f R
Bs
RSSI increases
about 5-6dB
RSRP independent of cell load
UE starts downloading
Content
• RSRP: Reference Signal Received Power
• RSSI: Reference Signal Strength Indicator
• RSRQ: Reference Signal Received Quality
• SINR / CINR / SNR etc
– Definition and measurement
Soc Classification level 14 © Nokia Siemens Networks Presentation / Author / Date
– Definition and measurement
– Mapping RSRP / RSRQ to SINR
• MIMO variants of the RF quantities and use cases
• 3GPP defined measurement accuracy for UEs
RSRQ 3GPP TS 36.214
Where:
• RSSI is pure wide band power measurement, including serving cell power, interference and thermal noise
• N: RSSI measurement bandwidth in PRBs
RSRQ = N x RSRP / RSSI
Soc Classification level 15 © Nokia Siemens Networks Presentation / Author / Date
R0: tx antenna 1R1: tx antenna 2
RSRQ mapping 3GPP TS 36.133 V8.9.0 (2010-03)
• RSRQ reporting range -3…-19.5dB• Some devices report values < -20dB
Reported value Measured quantity value Unit
RSRQ_00 RSRQ < -19.5 dB
RSRQ_01 -19.5 ≤ RSRQ < -19 dB
RSRQ_02 -19 ≤ RSRQ < -18.5 dB
Soc Classification level 16 © Nokia Siemens Networks Presentation / Author / Date
RSRQ_02 -19 ≤ RSRQ < -18.5 dB
… … …
RSRQ_32 -4 ≤ RSRQ < -3.5 dB
RSRQ_33 -3.5 ≤ RSRQ < -3 dB
RSRQ_34 -3 ≤ RSRQ dB
RSRQ Theoretical values in idle / fully loaded cell
• Idle cell:When there is no traffic, and assuming only the reference symbols aretransmitted (there are 2 of them within the same symbol of a resource block) froma single Tx antenna then the RSSI is generated by only the 2 reference symbolsso the result becomes:– RSRQ = -3 dB for 1Tx
RSRQ = N x RSRP / RSSI, N = measured bandwidth in PRBs
Soc Classification level 17 © Nokia Siemens Networks
– RSRQ = -3 dB for 1Tx– RSRQ = -6dB for 2Tx
• Fully loaded cell: Cell with 100% PRB utilizationIf all resource elements are active and are transmitted with equal power then– RSRQ = -10.8 dB for 1Tx– RSRQ = -13 dB for 2Tx (assumption: rx div not used!)
In practice, UEs seem to report RSRQ ~11dB for fully loaded cell, assuming no other-cell interference
RSRQ/R measurement, 2Tx cell
Idle cell RSRQ=
• Only serving cell on-air, FDD ZTE (QC)
Soc Classification level 18 © Nokia Siemens Networks
UE starts downloading
RSRQ= neg6dB
-6
-4
-2
01 31 61 91 121 151 181 211 241 271 301 331 361 391
RS
RQ
[d
B]
RSRQ measurement, idle cell and fully loaded cell
RSRQ measurement using different devices
• Comparison of Samsung UE and TMSW / PCTel EX scanners– UE inside car, scanners on car roof using the same antenna
Soc Classification level 19 © Nokia Siemens Networks
-20
-18
-16
-14
-12
-10
-8
RS
RQ
[d
B]
time, seconds
PCTel RSRQR&S RSRQUE RSRQ
NOTE: R&S RSRQ independent of cell load!! (a bug?)
Measured RSRQ depends
on deviceUE starts
downloading
Content
• RSRP: Reference Signal Received Power
• RSSI: Reference Signal Strength Indicator
• RSRQ: Reference Signal Received Quality
• SINR / CINR / SNR etc
– Definition and measurement
Soc Classification level 20 © Nokia Siemens Networks
– Definition and measurement
– Mapping RSRP / RSRQ to SINR
• MIMO variants of the RF quantities and use cases
• 3GPP defined measurement accuracy for UEs
SINR / SNR / CINRDefinition and Measurement
• Usually SINR=SNR=CINR unless the receiver is able to separate interference from thermal noise• Example: IRC receiver can separate dominant interferer from noise
• The actual measurement definition must be checked for every measurement device• which signal the ‘S’ measures?
SINR = S / (I+N)
Soc Classification level 21 © Nokia Siemens Networks
• which signal the ‘S’ measures?• what is the measurement bandwidth?• is the measured SNR instantaneous or average value?• if the average SNR is measured, what is the number of samples averaged?
• Typically UEs measure SNR from RS• Exact measurement method uncertain, since UE chipset vendors don’t typically reveal
technical data
• Scanners measure SNR from PSS/SSS and/or RS
50
60
70
80
SIN
R d
Bm
/ th
roug
hput
Mbp
s
SINR measurement, idle cell and fully loaded cell
PCTel SSS SINR
PCTel RS SINR
SINR measurement using different devices
• Comparison of Samsung UE and TMSW / PCTel Ex scanners
DL starts, PRB
utilization to100%
Soc Classification level 22 © Nokia Siemens Networks
0
10
20
30
40
50
1 31 61 91 121 151 181 211 241 271 301 331 361 391
SIN
R d
Bm
/ th
roug
hput
Mbp
s
time, seconds
PCTel RS SINR
R&S SSS SINR
UE SINR
DL Throughput
Secondary Sync Signal SNR much worse than RS SNR
RS CINR and RSRP measured by FDD scanner
RS CINRRS CINR
Soc Classification level 23 © Nokia Siemens Networks
Content
• RSRP: Reference Signal Received Power
• RSSI: Reference Signal Strength Indicator
• RSRQ: Reference Signal Received Quality
• SINR / CINR / SNR etc
– Definition and measurement
Soc Classification level 24 © Nokia Siemens Networks
– Definition and measurement
– Mapping RSRP / RSRQ to SINR
• MIMO variants of the RF quantities and use cases
• 3GPP defined measurement accuracy for UEs
Mapping RSRP to SNR
• Motivation: Sometimes might be useful to be able to map RSRP to SNR
• Assuming only thermal noise, RSRP can be mapped approximately to SNR– Quiz: How?
• In practical field conditions, this does not seem to work very well:
Soc Classification level 25 © Nokia Siemens Networks
– Insufficient averaging for fading signal by measurement equipment– Tx signal nonlinearities cause EVM that saturates measured SNR to ~25-
30dB. – Receiver non-idealities, such as carrier frequency offset, Doppler spread,
oscillator, phase noise etc also saturate SNR– Interference
• Example on next slide
Mapping RSRP to SNRSamsung XCAL measurement in lab, non-fading channel
•Lab measurement in shielded box, UE-reported RSRP versus UE-reported SINR
Soc Classification level 26 © Nokia Siemens Networks
In 100% loaded cell SINR saturates sooner, probably
due to subcarrier leakage or other imperfections.
Mapping RSRP to SNRXCAL field measurement, fading channel
• Fading channel measurement, drive test.
SINR versus RSRP, measurement
-85
-75
-7 -2 3 8 13 18 23
Samsung measurement values are instantaneous
snapshots � high variance due to fading.
Soc Classification level 27 © Nokia Siemens Networks
-125
-115
-105
-95
SINR [dB]
RS
RP
[d
Bm
]
Mapping RSRQ to SINRTheory (1/2)
• RSRQ depends on own cell traffic load, but SINR doesn’t depend on own cell load.– Used Resource Elements per Resource Block (RE/RB) in serving cell is an
input parameter for RSRQ -> SINR mapping– Assumption: RSRP doesn’t contain noise power
NRSRPSINR
12*
+=
Soc Classification level 28 © Nokia Siemens Networks
RSSI
RSRPNRSRQ
PxNRSRPPRSSI
RBsN
usedRBREx
xNPP
PPSINR
Nni
REnxNn
Nni
*
*
#
_/
12_
__
12_
=
++==
=
∗=
+=
xRSRQ
xNRSRPRSRQ
RSRPNNRSRP
SINR−
=−
=1
12
**
12*
Mapping RSRQ to SINRTheory (2/2)
• Equation used:
Where x=RE/RB
• 2RE/RB equals to empty cell. Only Reference Signal power is
xRSRQ
SINR−
=112
RSRQ vs SINR
-10.00
-5.00
0.00
5.00
10.00
15.00
20.00
25.00
30.00
-20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3
RSRQ (dB)
SIN
R (
dB
)
2 RE/RB
4 RE/RB
6 RE/RB
8 RE/RB
10 RE/RB
12 RE/RB
Soc Classification level 29 © Nokia Siemens Networks
Only Reference Signal power is considered from serving cell.
• 12RE/RB equals to fully loaded serving cell. All resource elements are carrying data.
• In practice, mapping from RSRQ to SINR seems difficult– Currently available measurement
UEs and scanners report SINR directly
RSRP vs. SNR
-15.00
-10.00
-5.00
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
-135 -130 -125 -120 -115 -110 -105 -100 -95 -90 -85 -80 -75 -70
RSRP (dBm)
SN
R (
dB
)
SNR
Mapping RSRQ to SINRLab measurements
• Lab measurements match well the calculated results
• Measured with Agilent scanner– RSRP– RSRQ– Reference signal SINR
• Cable connection between BTS and scanner
SINR vs. RSRQ
-10
-5
0
5
10
15
20
25
30
35
-20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0
RSRQ
SIN
R
Measured - full traffic Caculated - no traffic Calculated - full traffic load Measured - no traffic
Soc Classification level 30 © Nokia Siemens Networks
scanner– Attenuator used to reduce signal
level– No traffic: only control channels and
reference signals– Full traffic load: data send in each RB
Note: Validity of formulae have been proven in lab under above conditions and with only one cell on air ( i.e. no other cell interference). Measurements from the field will differ as exact load can not be set
SNR vs. RSRP
-15
-10
-5
0
5
10
15
20
25
30
35
40
-140 -135 -130 -125 -120 -115 -110 -105 -100 -95 -90 -85 -80
RSRP
SN
R
Measured-full traffic
Calculated
Measured - no traffic
Mapping RSRQ to SINRField measurement
• Samsung BT-3730 + XCAL
-3
-1
1
0 5 10 15 20 25 30
SINR versus RSRQ, field measurement
Soc Classification level 31 © Nokia Siemens Networks
-15
-13
-11
-9
-7
-5
RS
RQ
[d
B]
CINR [dB]
RSRQ�SINR mapping unreliable in practice.
(depends on meas device!)
RSRQ�SINR mapping unreliable in practice.
(depends on meas device!)
Content
• RSRP: Reference Signal Received Power
• RSSI: Reference Signal Strength Indicator
• RSRQ: Reference Signal Received Quality
• SINR / CINR / SNR etc
– Definition and measurement
Soc Classification level 32 © Nokia Siemens Networks
– Definition and measurement
– Mapping RSRP / RSRQ to SINR
• MIMO variants of the RF quantities and use cases
• 3GPP defined measurement accuracy for UEs
MIMO variants
• Terminals and scanners may report RSRP, RSSI, RSRQ, SINR per receiver antenna
• Example: RSRP– RSRP0 measured at rx. antenna 0 – RSRP1 measured at rx. antenna 1
• Measurement capabilities should be checked case-by-case
Soc Classification level 33 © Nokia Siemens Networks
• Measurement capabilities should be checked case-by-case
• Some devices measure even more MIMO quantities– Altair chipset measures four SINR values for a 2Tx BTS, one value per Tx-Rx
pair– The old LG chipset measures antenna correlation coefficient
• Question: How can these multi-antenna measurements be used in practical field testing?
Use cases for multi-antenna RF quantities
• MIMO throughput is degraded by:
– Too large power imbalance between receiver branches– Tx/Rx antenna correlation
• In practice, only power imbalance can be measured by commercial devices
Soc Classification level 34 © Nokia Siemens Networks
Rx antenna power imbalanceField measurement• Note RSSI power imbalance between receive antenna branches
– This should be eliminated, if possible
-60
-55
-50
-45 02/18/2010
14:13:33.716 02/18/201014:15:16.143
02/18/201014:16:58.647
02/18/201014:18:40.153
02/18/201014:20:22.159
02/18/201014:22:03.167
Soc Classification level 35 © Nokia Siemens Networks
-95
-90
-85
-80
-75
-70
-65
time
RS
SI [
dB
m]
Average of SCell-RSSI(Com)
Average of RSSI(Ant0)
Average of RSSI(Ant1)
Time
Data
Rx antenna power imbalance: Impact on rank Field measurement
• Too large antenna power imbalance can reduce channel rank � tx falls to single stream even at high SNR
-85
-80
-75
-70
-65
RSSI0
RSSI1
Rx power imbalance
Soc Classification level 36 © Nokia Siemens Networks
50 100 150 200 250 300 350 400 450 500 550-90
-85
50 100 150 200 250 300 350 400 450 500 550-5
0
5
10Rank fluctuation at high RSSI (SNR)
Rx power imbalance dB
Rank indicator, {0,1}
seconds
seconds
Channel correlation
• High channel correlation degrades multi-stream throughput performance– Even high SNR won’t improve throughput if channel correlation is too high
• Typical problem case: Two vertical antennas on car roof � SNR is excellent but MIMO throughput is bad– Solution: use cross-polarized antennas, or take antennas inside car!
Soc Classification level 37 © Nokia Siemens Networks Presentation / Author / Date
• Problem: Channel correlation is not usually reported by DT tools or scanners
Channel correlation, drive test example• The same dt route driven twice, 2.6GHz@10MHz, Huawei E398, tm3
– vertical: two vertical scanner antennas mounted on car roof, mean tput = 29Mbps– x-pol: custom-made cross-polarized omni antenna on car roof, mean tput = 33Mbps
0.7
0.8
0.9
1x-pol versus two vertical
x-pol
verticalx-pol has
better peak
Soc Classification level 38 © Nokia Siemens Networks Presentation / Author / Date
0 10 20 30 40 50 60 700
0.1
0.2
0.3
0.4
0.5
0.6
0.7
MAC DL tput, Mbps
CD
F
verticalbetter peak tput
Vertical has better tput in
bad RF
Impact of channel correlation on MIMO Tput Measurement example, SINR=25dB• SINR=25dB, constant over the measurement• High spatial correlation causes rank-1 transmission even at very high SNR!!
(second stream tput goes to almost zero)
70
80
90PHY tput for substreams, EPA 3km/h, 2.6GHz, 3GPP low, medium, high correlation
stream 1
stream 2stream 1 + stream 2
High spatial correlation
low spatial correlation
Soc Classification level 39 © Nokia Siemens Networks Presentation / Author / Date
50 100 150 200 2500
10
20
30
40
50
60
time, seconds
PH
Y t
put
[Mbi
ts/s
ec]
correlation
medium spatial correlation
Impact of UE orientation Measurement in excellent RF
0
20
40
60
80
100
1
19
37
55
73
91
10
9
12
7
14
5
16
3
18
1
19
9
21
7
23
5
25
3
27
1
28
9
30
7
32
5
34
3
36
1
37
9
39
7
41
5
43
3
45
1
46
9
48
7
50
5
52
3
54
1
55
9
57
7
59
5
61
3
63
1
64
9
66
7
PH
Y t
pu
t [M
bp
s], C
INR
[d
B]
Time
PHY DL Throughput [Mbps]
CINR 0 [dB]
CINR 1 [dB]
Main message 1: MIMO throughput is very sensitive to UE orientation!
Main message 2: Eliminating power UE
Soc Classification level 40 © Nokia Siemens Networks
Time
-85
-80
-75
-70
-65
-60
-55
1
19
37
55
73
91
10
9
12
7
14
5
16
3
18
1
19
9
21
7
23
5
25
3
27
1
28
9
30
7
32
5
34
3
36
1
37
9
39
7
41
5
43
3
45
1
46
9
48
7
50
5
52
3
54
1
55
9
57
7
59
5
61
3
63
1
64
9
66
7
RS
RP
[d
Bm
]
Time
Antenna0 RSRP [dBm]
Antenna1 RSRP [dBm]
Eliminating power imbalance or channel correlation alone is not sufficient for good MIMO throughput. Both should be eliminated! In practice, this is a trial and error process in stationary measurements.
UE orientation changes