01 RF Measurement and Optimization

Soc Classification level 1 © Nokia Siemens Networks Presentation / Author / Date

RF measurement quantities and optimization


Content

• LTE RF measurement quantities in field measurements– RSRP– RSSI– RSRQ– SINR

• RF optimization


SINR vs. RSSI vs. RSRP and RSRQ


Field measurement parameters

• 3GPP is defining following measurements:– RSRP (Reference Signal Received Power)– RSRQ (Reference Signal Received Quality)

• Scanners and terminals are typically measuring following RF quantities:– RSRP– RSRQ– RSSI (Received Signal Strength Indicator), Wideband channel power– P-SCH, S-SCH power– RS SINR, P-SCH/S-SCH SINR

• Understanding of different measurement quantities is very important for field performance analysis.


RSRP, 3GPP definition

• 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.

• 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. 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 limitat ion 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

RSRP_02 -139 RSRP < -138 dBm

… … …

RSRP_95 -46 RSRP < -45 dBm

RSRP_96 -45 RSRP < -44 dBm

RSRP_97 -44 RSRP dBm


RSSI

• RSSI not reported to eNodeB by UE– Can be computed from RSRQ and RSRP that are reported by UE

• RSSI measures all power within the measurement bandwidth– Measured over those OFDM symbols that contain RS

– Measurement bandwidth RRC-signalled to UE


RSSI and RSRP

• RSSI = wideband power= noise + serving cell power + interference power

• Without noise and interference, 100% DL PRB activity: RSSI=12*N*RSRP

– RSRP is the received power of 1 RE (3GPP definition) average of power levels received across all Reference Signal symbols within the considered measurement frequency bandwidth

– RSSI is measured over the entire bandwidth

– N: number of RBs across the RSSI is measured and depends on the BW

• Based on the above, under full load and high SNR:

RSRP (dBm)= RSSI (dBm) -10*log (12*N)


RSRQ

• RSRQ = N x RSRP / RSSI– N is the number of resource blocks over which the RSSI is

measured, typically equal to system bandwidth– RSSI is pure wide band power measurement, including intracell

power, interference and noise

• RSRQ reporting range -3…-19.5dB

Definition Reference Signal Received Quality (RSRQ) is defined as the ratio N×RSRP/(E-UTRA carrier RSSI), where N is the number of RB’s of the E-UTRA carrier RSSI measurement bandwidth. The measurements in the numerator and denominator shall be made over the same set of resource blocks. E-UTRA Carrier Received Signal Strength Indicator (RSSI), comprises the linear average of the total received power (in [W]) observed only in OFDM symbols containing reference symbols for antenna port 0, in the measurement bandwidth, over N number of resource blocks by the UE from all sources, including co-channel serving and non-serving cells, adjacent channel interference, thermal noise etc. The reference point for the RSRQ 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 RSRQ of any of the individual diversity branches.

Applicable for RRC_CONNECTED intra-frequency, RRC_CONNECTED inter-frequency


RSRQ reporting range

• RSRQ = N x RSRP / RSSI– N is the number of resource blocks over which the RSSI is

measured, typically equal to system bandwidth– RSSI is pure wide band power measurement, including intracell

power, interference and noise

• RSRQ reporting range -3…-19.5dB

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

… … …

RSRQ_32 -4 RSRQ < -3.5 dB

RSRQ_33 -3.5 RSRQ < -3 dB

RSRQ_34 -3 RSRQ dB


SINR definition

• SINR is the reference value used in the system simulation

• SINR can be defined:1. Wide band SINR

2. SINR for a specific subcarriers (or for a specific resource elements)

• SINR = S/(I+N), all measured over the same bandwidth

• Most drive test UEs and scanners support SINR or SNR measurement

Example: LG supports RS SNR measurement Example: Samsung BT-3710 measures CINR from RS (e-mail info from

Samsung)


SNR vs. RSRP

• RSRP to SNR mapping• RSRP is measured for a single subcarrier

– noisepower_for_15KHz= -125.2dBm Noise figure = 7 dB Temperature = 290 K

• Assumption: RSRP doesn’t contain noise power

powernoiseKHzP

P

RSRPSNR

REn

REn

__15_

_

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

This curve gives upper limit to SINR with certain RSRP.

SINR is always lower than SNR in live network due to

interference.


RSRQ to SINR mapping

• 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

RSSI

RSRPNRSRQ

PxNRSRPPRSSI

RBsN

usedRBREx

xNPP

PP

NRSRPSINR

Nni

REnxNn

Nni

*

*

#

_/

12*

12_

__

12_

xRSRQ

xNRSRPRSRQRSRPN

NRSRPSINR

112

**

12*


RSRQ to SINR mapping

• Equation used:

– x=RE/RB

• 2RE/RB equals to empty cell. 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

xRSRQ

SINR

112

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

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

Difficult to estimate SINR in this region from RSRQ, SINR very sensitive to RSRQ and

cell load


RSRP vs. DL throughput

Example measurement

•Drive test, 20MHz BW, ~2.6GHz

•FTP download, no other interfering traffic in the networkRSRP vs. throughput

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

-13

0

-12

8

-12

6

-12

4

-12

2

-12

0

-11

8

-11

6

-11

4

-11

2

-11

0

-10

8

-10

6

-10

4

-10

2

-10

0

-98

-96

-94

-92

-90

-88

-86

-84

-82

-80

-78

-75

dBm

Mb

ps


SINR vs. DL throughput

Example measurement

•Drive test, 20MHz BW, ~2.6GHz SINR vs. throughput

0

10

20

30

40

50

60

70

-4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

dB

Mb

ps


RF optimization

Basic RF planning is important

•Clear cell dominance areas

•Avoid sites shooting over large areas with other cells

Antenna tilting has big impact on other cell interference, at least in planning tool estimates

•No LTE reference measurements available


Example from 3HK trial – reusing 3G sitesImproving performance by blocking excess cells

• Overall SINR is improved due to reduction of inter-cell interference

• Locations with improved SINR are visible on the map

• Improvement in throughput is even more significant (see next slide)

FT_04.1 Mobility DT DL - SINR comparison

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

-11 -9 -7 -5 -3 -1 1 3 5 7 9 11 13 15 17 19 21 23 25 27

SI NR (dB)

CDF

% All cells

Blocked cells

All cells

Blocked cells

Ave SINR improved from 15.2dB to 17.4dB


Example from 3HK trial – reusing 3G sitesImproving performance by blocking excess cells

FT_04.1 Mobility DT DL - Throughput comparison

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64

Phy DL tput (Mbps)

CDF

% All cells

Blocked cells

Ave throughput improved from 23.34Mbps to 26.78Mbps, i.e. 14.7%

Key message:

• The number of LTE cells when converted from all existing 3G sites seem to be more than sufficient, and cell overlapping and hence inter-cell interference seems to be excessive in outdoor environment.

• Careful planning and cell/antenna selection process, and initial RF tuning is important to the LTE field performance

All cells

Blocked cells

Soc Classification level 20 © Nokia Siemens Networks

Quiz

Presentation / Author / Date

1. If RSRP = -100 dBm, Calculate SINR.

2. For the SINR obtained in (1), what is the value of RSRQ for:

i. Empty cell

ii. Fully loaded cell

01 RF Measurement and Optimization

Documents

Transcript of 01 RF Measurement and Optimization