Laboratory 2: Analysis of Measurement Data

Aims:

This laboratory is for the students to gain skills

to analyse raw measurement data

that have been recorded from a live LTE network. St

udents will represent raw data in

well-presented graphical formats and analyse the me

asurement results using Excel and/or

MATLAB.

Outline:

Section 1 “ Introduction to Laboratory and Paramet

er Definitions

Section 2 “ Laboratory Exercises

Appendix A “ MATLAB Codes

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Section 1: Introduction to Laboratory and Parameter

Definitions

The measurement was conducted using a œNEMO Handy

in the same network as

Laboratory 1. The attached file (Lab2_Data.xls) con

tains a measurements of a LTE

handset downloading a file. The handset was moving

at a pedestrian speed from an area

with a good signal quality to the cell boundary whe

re there is no adjacent cell to hand-

over to (death-spot). The LTE network used is Tel

stra LTE with a bandwidth of 10 MHz

which is equivalent to 50 PRBs as per Laboratory 1.

Parameter Definitions:

RSRP (Reference Signal Received Power)

The RSRP measurement provides a cell-specific signa

l strength metric. This

measurement is used mainly to rank different LTE ca

ndidate cells according to their

signal strength and is used as an input for handove

r and cell reselection decisions. RSRP

is defined for a specific cell as the linear averag

e over the power contributions (in Watts)

of the Resource Elements (REs) which carry cell-spe

cific RS within the considered

measurement frequency bandwidth. Normally the RS tr

ansmitted on the first antenna port

are used for RSRP determination, but the RS on the

second antenna port can also be used

if the UE can determine that they are being transmi

tted. If receive diversity is in use by

the UE, the reported value is the linear average of

the power values of all diversity

branches.

Refer also 3GPP TS 36.214 subclause 5.1.1.

Range: -140 “ 0

Unit: dBm

RSRQ (Reference Signal Received Quality)

This measurement is intended to provide a cell-spec

ific signal quality metric. Similarly to

RSRP, this metric is used mainly to rank different

LTE candidate cells according to their

signal quality. This measurement is used as an inpu

t for handover and cell reselection

decisions, for example in scenarios for which RSRP

measurements do not provide

sufficient information to perform reliable mobility

decisions. The RSRQ is defined as the

ratio:

RSRQ = N Â· RSRP/(LTE carrier RSSI),

*¦*

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where N is the number of Resource Blocks (RBs) of t

he LTE carrier RSSI measurement

bandwidth. The measurements in the numerator and de

nominator are made over the same

set of resource blocks. While RSRP is an indicator

of the wanted signal strength, RSRQ

additionally takes the interference level into acco

unt due to the inclusion of RSSI. RSRQ

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therefore enables the combined effect of signal str

ength and interference to be reported in

an efficient way.

The measurements in the numerator and denominator a

re made over the same set of

resource blocks. Refer also 3GPP TS 36.214 subclaus

e 5.1.3.

Range: -30 “ 0

Unit: dB

RSSI (Carrier Received Signal Strength Indicator)

Carrier RSSI (frequency scanning mode)

The LTE carrier RSSI is defined as the total receiv

ed wideband power observed by the

UE from all sources, including co-channel serving a

nd nonserving cells, adjacent channel

interference and thermal noise within the measureme

nt bandwidth . LTE carrier RSSI is

not reported as a measurement in its own right, but

is used as an input to the LTE RSRQ

measurement described below.

Range: -140 “ -10

Unit: dBm

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Section 2: Laboratory Exercises

As part of the lab submission, the students should

submit a report containing graphs, and

answers of the following questions.

1. Plot the following graphs (for antenna port 1 an

d port 2 where applicable):

“ RS SNR vs measurement slots

“ RSRP vs measurement slots

“ RSRQ vs measurement slots

“ RSSI vs measurement slots

1.a Compare RSRP and SNR graphs. Express the differ

ence and similarity of the trends

of these graphs. [20]

Hint: Plot a graph showing the relationship betwee

n RSRP and SNR (RSRP minus

SNR in dB) which can provide an approximation of th

e interface level. You may use

either MS Excel or MATLAB to create the graphs. Sel

ect the corresponding columns

in the Excel data. In MATLAB, use the codes below:

Figure(11)

SNR=[x1];

% Replace x1 by data in Column H in the Lab2_Data (

SNR)

plot(SNR)

title(

˜SNR vs Measurement Slots’

)

xlabel(

˜Measurement Slots’

)

ylabel(

˜SNR in dB’

)

Adjust the codes accordingly for other parameters.

1.b Compare the trends of RSRP, RSRQ and RSSI and p

rovide explanation. [15]

2. Plot the following graphs:

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“ Throughput vs measurement slots

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“ The relationship between SNR (x-axis) and through

put (y-axis).

Hint: Plot graph in logarithm scale (x-axis in dB a

nd semilog in y-axis using semilogy in

MATLAB). Use the following codes:

Figure(20)

semilogy(SNR,throughput)

% SNR in the data in Columm H and

throughput is in Column K

title(

˜SNR vs Throughput’

)

xlabel(

˜SNR in dB’

)

ylabel(

˜Throughput in bps’

)

Make sure the SNR used is a larger value between SN

R values on Antenna port 1 and

port 2 in each measurement slot

2.a Find the maximum and minimum throughput (consid

er the measurement slots [20:180])

[10]

Hint: Use following MATLAB commands

“ max(x) and find(x==max(x))

“ min(x([20:180])) and find(x==min(x[20:180]))

Make sure you find the maximum (and minimum) throug

hput and its

corresponding measurement slot(s)

2.b Find the value of SNR at which the throughput s

tarts to degrade (i.e. when the

throughput is lower than 10 Mbps for more than 10 m

easurement slots). Explain how

the result relates to RSRP level. [15]

2.c Consider the measurement slots that the lowest

throughout occurs (t

min

) and when the

peak throughput occurs (t

max

). Plot the following graphs for each t

min

and t

max

:

“ PRB percentage.

“ Modulation percentage

Compare and analyse the results. [20]

Hint: Use similar data to the following. The measur

ement slots should be as obtained

from Question 2.a.

% Example Data from Measurement Slot 78

% modmax=[2 2 2 2 6 6 6 6 2 2 2

2 2 4 4 4

4 4 4 6 6 6 6 6 6 6 6];

% pmodmax=[54.7 2.4 4 0.2 0.3 0.2 0.2 0.2 1.1 0.3

0.3 0.3 0.3 0.3 0.2

0.6 1.8 2.3 5.2 9.9 3.7 5.5 1.8 1 0.3 1.3 1 0.6

];

% nrb=[0 3 6 9 12 15 27 29 30 33 36

38 39 41 42 44

45 47 48 50];

% prb=[54.7 6.8 0.2 0.2 0.5 0.2 0.2 0.6 0.2 0.2 0.2

0.2 3.6 0.3 1.3 0.3

0.2 3.4 1.3 25.7];

*¦*

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