IRJET- Bit Error Rate (BER) Performance Evaluation of Reference Channel for Power Line Communication (PLC) Channel Under Multipath Modeling Technique

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Bit Error Rate (BER) Performance Evaluation of Reference Channel for
Power Line Communication (PLC) Channel under Multipath Modeling
Technique
Shubham Pandey1
1MTECH, NITTTR, Bhopal , India
---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - Power Line Communication (PLC) is a substituteto
wireless communication for providing high-speed broadband
multimedia services within the office or home with the
advantage of abolishing the requirement for additionalpower
cables and reducing the communication infrastructure cost.
The development of power line communication requires
sufficient information of the PLC physical properties and
characteristics in order to choose suitable transmission
methods. This paper presents analysis of Multipath technique
which is based on Time Domain Modeling technique [3]. In
order to evaluate the performance of PLC, this thesissimulates
practical multipath PLC channel model on the basis of
reference channels and provides the Bit-Error-Rate (BER) vs.
Signal-to-Noise Ratio (SNR) curves for Orthogonal Frequency
Division Multiplexing (OFDM). Hence by comparingtheBERof
the data transmitted through these reference channels, a
practical reference channel is proposed forward which can be
used effectively for Power Line.
Key Words: Power Line Carrier Communication (PLCC),
Transmission Line Model, Multipath Channel Model,
Reference Channels, OFDM, BER
1. INTRODUCTION
Among those communication technologies, Power Line
Communication (PLC) is getting a tremendous amount of
research interest. The advantage is that there is no
requirement for new infrastructure, which is both tedious
and costly to introduce. PLC utilizesthe in building electrical
wiring as a local area network over IP and home
entertainment service at power socket in home or business
premises. The most important elements that influence
communications over electrical cables are attenuation,
multipath fading, and noise, which increases with the
increase in channel length, thus limiting the long distance
communication.
One more inconvenience is that the data signal infused to
PLC could not go through the transformer. So there is a need
of bypass devices across the transformer which increases
complexity and cost. From past decades, PLC is used for
electrical signal transmission and distribution, But till now,
communication capacitiesof power line cable are restricted.
Now there is a need for communication capabilities is
remote metering and operation management.
Since late 1980’s, a lot of research is being done in the field
of PLC because of its various advantages. The power cables
exist all over, therefore PLC makes the internet accessible
from each room through every socket. Security is one of the
major issuesin any telecommunication system. But in a case
of shared medium like power line channel, its effect is
significantly large, However in PLC the physical medium is
difficult to get retrieved so, it is more secure channel
compared to the wireless network. There are various
applications of Power Line Communication such as
Automatic Meter Reading (AMR), Home Automation,
Demand Side Management (DSM), Vehicle to Grid
Communication in electric vehicles and many more.
This paper is divided into four topics. In first topic,
introduction regarding power line, it’s advantage
disadvantage is provided. Then in the methodology,
Multipath Model is discussed and it’s transfer function is
derived on the basis of our experimental analysis. Moving
forward OFDM technique is discussed in brief.
Then the schematic representation and BER calculation are
explained. In the third the Bit Error Rate (BER) performance
evaluation of the PLC using BPSK-OFDM and QPSK-OFDM
under multipath effect using two reference channels which
are derived from multipath model has been done through
the simulations in the MATLAB. Then at last the conclusions
of this present work is drawn.
2. METHODOLOGY USED:
A power line channel model is represented to show the
attenuation and delay over the transmitted signals. A power
line medium is characterized by Impedance discontinuities
and various branches. Due to this, the transmitted signals in
the power line cables go through several reflections that
bring a multipath effect.
Thus a power line cables can be well modeled by using
Multipath Model. In Multipath Model [2], the propagation of
signals does not takes place only between transmitter and
receiver, but other paths are also considered. Let, X is the
point of transmission and Z is the point of reception.
The channel has a branch at point Y. The branch ends at
point W. The cable lengths are and
characteristic impedances are . Reflection
coefficients are and and are
transmission parameters.
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 05 Issue: 08 | Aug 2018 www.irjet.net p-ISSN: 2395-0072

Fig - 1: Power Line Cable Topology
There are two possibilities for the signal is transmittedfrom
X to Z. The initial one is an immediate way from X over YtoZ.
Second way is X → Y → W → Y → Z. Refection of signals
appears at point W. Except direct path all other signal
experience numerous reflections at W before reaching Z.
With these assumptions, an infinite number of propagation
paths are possible in principle, because of numerous
reflections. Every path has weighing factor which is the
product of reflection coefficient and transmissioncoefficient
along the path. All refection and transmissioncoefficientsare
always less than or equal to 1. Consequently the weighing
factor , a result of multiplication of transmission and
reflection coefficient along the path, is also lessorequivalent
to one i.e.
Also each path experience different delay defined as
Where,
is the length of path,
is the speed of light
is dielectric constant of insulating material.
From this topology only N dominant path considered for
analyzing power line channel.
The formulas for all reflection and transmission coefficients
along the paths are following
 Reflection Coefficients
 Transmission Coefficients
Where,
Table 1: Multipath in PLC Topology
Possibe
Path (i)
Signal
Propagating
Nodes
Reflection
Factor ( )
Propagatio
n Length
( )
1 X→Y→Z I1 + I2
2
X→Y→W→Y→
Z
I1 + 2I2 + I3
3
X → (Y
→W→)2 → Y
→ Z
I1 + 4I2 + I3
.
.
.
.
.
.
.
.
.
.
.
.
N
X→(Y→W→)N-
1 →Y→Z
I1 + 2(N-1)I2
+ I3
In this Table, all the N possible paths are listed along with
their respective reflection factors ( ) and length of
propagation ( )
2.1. PLC Channel Transfer Function on the basis on
Multipath Model
The transmitted signals are affected by attenuation A(f,d)
that is increased with length and frequency.Thesignalsfrom
the all individual paths have to be combined by using
superposition principle. Therefore, the frequency response
H(f) from X to Z can be expressed as:
Where
: weighing factor

: Attenuation Portion
: Delay Portion
Following table describes the parameters included in the
transfer function:
Table 2: Description of the Parameters of the Transfer
Function
Parameters Description
I Number of paths, where the path
with shortest delay has index i=1
Attenuation (cable) parameters
K Exponent factor of attenuation
(theoretically between 0.5 to 1)
Weighing factor
Length of each link i
Delay of each link i
N Number of dominant paths
2.2. Power Line Reference Channels (RC)
Ever communication link exhibits its restrictive unique
profile, because of individual system structure, dominant
effects of signal propagation and an individual noise
spectrum. In any case, the link can be assigned to groups
depending on length, type of cable and number of branches.
To every group a normal reference channel is assigned. In
this chapter, four reference channels [1] areproposedwhich
are based on Multipath Model. The figures below represent
silent characteristics of the reference channels, observed in
various estimations. The reference channels might be
utilized directly for the evaluation of channelcharacteristics,
for system rating and for standardization. Here we are
showing the Frequency Responses of these Reference
Channels.
Fig - 2: Frequency Response of Reference Channel 1
RC1 is a representation of a decent power line station. In
depends on a link at a length of roughly 100m – without
branches. This kind of link acquires just a few reflection
points. In residential areas with equidistant column houses
and house interfering cables of comparable length. The
frequency response may show deep notches.
RC2 is a type of link, which has a length of 110 m – with 6
branches. With extending length, this regular network
structure may brings abrupt frequency response along with
deep fading.
RC3 is a type of link that relates to a network having length
of 210m – with 8 branches. This link demonstrates an
exceptionally abrupt fading with increase of attenuation.
RC4 is a type of link which is typically found in residential
areas without significant general system structure. Because
of various branches this link exhibits a large attenuation.
The database of these reference channels are considered
from the European 3-phase underground distribution
system using PVC isolated cables. These Reference Channels
are summarized [6] as follows:
 RC 1: excellent channel, length 100m, with zero
branch

 RC2: good channel, length 110m, with 6 branches
 RC3: average channel, length 210, with 8 branches
 RC4: bad channel, residential space and strong
branching
2.3. Bit Error Rate (BER):
When some bits are transmitted from a transmitter, some of
these bits are changed in the course of travelling from
transmitter to receiver due to the noise present in the
channel, hence these bitsare received as errored bits eg. 1 is
changed to 0. So the BER is defined asthe ratio of number of
bitsin error to the total number of transmitted bits. For eg,if
10000 bits are transmitted and out of which 100 bits are
received in error, then we can say the average Bit Error Rate
equals the number of bits in error i.e. 100 divided by the
total number of bits transmitted i.e. 10000. Then the Bit
Error Rate is 0.01 or 1%
BER = = = 0.01 or 0.01%
2.4. Orthogonal Frequency Division Multiplexing:
OFDM is basically a multi carrier modulatedsystem [4].Here
the bandwidth of the channel is split into N parallel sub-
bands, and each of these sub-bands are having different N
subcarriers. The frequency of these subcarriersarespacedat
the fundamental frequency Fo i.e. Fo, 2Fo, 3Fo….(N-1)Fo. The
high-speed data symbols are spitted into slower data
streams, thus increasing the symbol duration and hence
reducing the effect of impulsive noise which producesdueto
various electrical equipments connected in the power line.
This also lessens the impact of multipath and Inter Symbol
Interference as the symbol duration becomes more than the
time delay i.e. Each of these slower data streams are used to
modulate the subcarriers. By using cyclic prefix efficiency
can be further increased by eliminating Inter Block
Interference by converting the frequency selective fading
into flat fading channel.. We require multiple oscillators to
generate carrier frequencies, and to maintain the
ortogonality of the sub-carriers these carrier frequencies
must be precisely centered at the fundamental frequency.
Now, if we require thousand bits to be transmittedinparallel
then we require thousand such oscillators. We can replace
the use of these oscillators by performing IFFT/IDFT
operation at the transmitter side. At the receiversidewewill
perform the inverse of IDFT/IFFT i.e. Discrete Fourier
Transform (DFT) or Fast Fourier Transform(FFT)torecover
back the transmitted symbols without using multiple
coherent detectors.
2.5 Overall System Configuration:
To analyze and study the performance of the multipath
power line channel model, OFDM modulation scheme used
with BPSK and QPSK. The figure illustrate Orthogonal
Frequency Division Multiplexing (OFDM). System block
diagram is used for this purpose.BPSKandQPSKmodulation
are used as the modulation scheme.
Fig - 6: PLC-OFDM System Architecture
Various steps in PLC-OFDM transmitter are given asfollows:
i. Modulation
In initial step serial data is modulate by using any
modulation scheme such as Binary Phase Shift Keying
(BPSK) or Quadrature Phase Shift Keying (QPSK). In this
thesis both schemes are used.
ii. Serial-to-Parallel (S/P) Converter
The modulated data is a serial data which is converted into
parallel data by using serial to parallel converter. Because
IFFT requires the parallel data streams of data for further
processing.
iii. Inverse Fast Fourier Transform (IFFT)
After generation of parallel streams, IFFT block convert
frequency domain signal into a time domain signal. The
output sequences of the IFFT are orthogonal to each other.
With the absence of local oscillators, the OFDM system
complexity has been significantly reduced.
iv. Cyclic Prefix Insertion
The Cyclic Prefix is a technique in which last part of OFDM
symbol is copied to the beginning of the OFDM symbol. It is
used to avoid Inter Block Interference (IBI).
v. Parallel to Serial (P/S) Converter
Again the OFDM signal is converted back to serial data in
order to send it through the channel.
vi. PLC Channel and Noise
The channel under consideration is multipath power line
channel. The OFDM signal experiences variation in phase
and amplitude of subcarriers due to power line channel
characteristics and noise which adds up in the channel.
vii. Receiver end
At the receiver end, all the above mentioned steps are
performed in exactly reverse manners. And the message
signal is recovered back.

viii. BER Calculation:
At the last the received signal is compared with the
transmitted signal to calculate the Bit-Error-Rate(BER) for
different values of SNR.
3. SIMULATION AND RESULT ANALYSIS
Here we are using MATLAB for simulation, which is a high-
performance language for technicalcomputing.Stepsusedin
MATLAB Simulation
1. Save all the target equations.
2. Write a program code in MATLAB to perform the
simulation, the code is written for the performance
evaluation of the PLC-OFDM.
3. Now in code input the values of Rference Channels
parameters.
4. Save & compile the program in MATLAB.
5. Get the final result after simulation done by
MATLAB.
3.1. Flowchart For Simulation:
Steps involve for the proposed simulation are as follows:
1. Generation of the Random Binary Sequence
2. QPSK/BPSK modulation
3. Serial to Parallel Conversion
4. Performing Inverse Fast Fourier Transform
5. Cyclic Prefix Addition
6. Parallel to Serial Conversion
7. Convolving this data with the Reference Channel
coefficients
8. Adding White Gaussian Noise
9. Serial to Parallel Conversion
10. Cyclic Prefix Removal
11. Performing Fast Fourier Transform
12. Parallel to Serial conversion
13. QPSK/BPSK Demodulation
14. Counting the number of bits in error
15. Repeating for the multiple values of Eb/No
Fig - 7: Flowchart of Simulation
3.2.Reference Channels:
The reference channels are used for the study of physical
properties of the channels and overall performance
variation. Here two reference channels are used RC1 and
RC4. RC1 is an ideal reference channel which is proposed in
this thesis, and RC4 is the existing type of reference channel,
which is used in the electrical network of residential areas.
The parameters of these reference channels are given in the
table. We are going to compare the BER of the data
transferred from both there Reference Channels and find
out which Reference Channel is better and can be used for
the transmission of data over Power Line Cables.
3.3. Parameters of Reference Channels:
Table 3: Parameters for Reference Channel 1 and
Reference Channel 4
REFERENCE CHANNEL 1 REFERENCE CHANNEL 4
Attenuation Terms: Attenuation Terms:
K =
1
ao = 0
a1 =
1.5*10^-9
K=
1
ao =
8*10^-3
a1 =
3.5*10^-9
Path Parameters: Path Parameters:
i gi di i gi di
1 +0.60 100 1 +0.26 300
2 -0.08 130 2 +0.05 350
3 +0.08 160 3 -0.30 370
4 -0.08 190 4 +0.25 450
5 +0.15 300 5 -0.35 510
3.4.Result Analysis:
The results obtained from the simulation of the MATLAB
program is analyzed [5] in this part. The results are in form
of BER v/sSNR curve. In the graphsthe comparisonbetween
various plots are made for two different modulation
techniques i.e. BPSK and QPSK. Additive White Gaussian
Noise is used to corrupt the channel. TheBERperformanceis
achieved by adding the PLC impulse response into the
system, in a realistic PLC environment.
Now power line channel performance is evaluated using a
Multipath Channels i.e. RC1 and RC4 across the same signal
to noise ratio (SNR) values. The comparison isdonebetween
four plots for both the modulations i.e. BPSK and QPSK.
Among these four plots, the first plot refers to the
BPSK/QPSK-OFDM transmission overtheReferenceChannel
4 with an AWGN noise, which is our existing reference
channel that represents topology of residential area with
large branching and channel length of around 500 meters.
The second plot refers to the BPSK/QPSK-OFDM
transmission over the Reference Channel 1 with an AWGN
noise, which is our proposed reference channel, with no

branches and cable length of 100 meters only. Third plot
refers to the BPSK/QPSK-OFDM over the ideal channel with
AWGN noise only. The fourth plot refers to theoretical BER
of BPSK which is given by the formula i.e. it’s minimum BER
for any type of communication.
Fig - 8: BER performance of QPSK-OFDM PLC System
Fig - 9: BER performance of QPSK-OFDM PLC System
The plots shows the BER v/s SNR curve. The lower the plot
lower is the BER value and better is the communication.Also
with the increasing value of SNR the plot moves down i.e.
BER reduces, hence for better BER we need higher SNR.
Now from the graphs is clearly visible that the data which is
transmitted through the reference channel 4, which
represents an existing residential topology, the BER curve
doesn’t converge and goes straight i.e. higher BER andhence
poor communication channel. Thus certainly this channel
cannot be used for the data transfer through it. If done so,
out of total transmitted bits large number of bits will be
received in error, and definitely cannot be recovered back.
But if we look at the curve which represents the BER of the
signal transmitted over the reference channel1,whichisour
proposed reference channel with no branches and length
100 meters which is smaller than the presently used PLC
lengths, we can observe that this curve converges
downwards towards the theoretical BER of the BPSK/QPSK
modulation. This indicates that BER can be significantly
reduced if use this type of channel for communication
purpose. Thus we can clearly say, if we do the wiring in our
household, whose topology is similar to our proposed
Reference Channel 1 i.e. no branches and wire length only
upto 100 meters, we can definitely transmit the data signals
over the PLC successfully.
Now if we look at both the graphs we can see that the BER
for QPSK-OFDM is higher than BER for BPSK-OFDM,whichis
true because BER of QPSK lower than that of BPSK, but we
have compromise with the bandwidth. The BER of the BPSK
is twice that of QPSK but the bandwidth requiredfor BPSKis
twice to that of QPSK.
4. Conclusions drawn from Results:
The work presented in this paper mainly requires the
channel modeling of a power line communication channel.
An accurate channel model is needed for a complete
evaluation of any system. From the simulationgraphswecan
conclude that the Power Line Cables can be efficiently used
for the data communication if the length of the wire is kept
to be 100 meters and without branching. Also the BPSK-
OFDM is better compared to QPSK-OFDM in terms of BER.
REFERENCES
[1] Patric J. Langfeld, “The Capacity oftypicalPowerLine
Channels and Strategies for System Design”, in Proc.
of 5th Int’l. Symp. Power-Line Commun., Malmö,
Sweden, 4.4.-6.4., pp. 271–278, 2001
[2] Manfred Zimmermann and Klaus Dostert, “A
Multipath Model For The Powerline Channel”, IEEE
Transactions on Communications, vol. 50, no. 4,pp.
553-559, 2002
[3] Stefano Galli and Thomas C. Banwell, “A
Deterministic Frequency-Domain Model for the
Indoor Power Line Transfer Function”, IEEE Journal
on Selected Areas in Communications, vol. 24, no. 7,
pp. 1304-1316, 2006
[4] Amarisa Maneerung, Suvepon Sittichivapak and
Komsan Hongesombut, "Application of Power Line
Communication with OFDM to Smart GridSystem",in
Proc. of 8th International Conf. on Fuzzy Systems
and Knowledge Discovery (FSKD), pp. 2239-2244,
2011
[5] Charles U. Ndujiuba, Samuel N. John and Oladimeji
Ogunseye, “Improving Data Transmission Efficiency
over Power Line Communication(PLC) System Using
OFDM”, International Journal of Applied
Engineering Research, vol. 12, no. 5, pp. 705-710,
2017
[6] Matthis Gotz, Manuel Rapp and Klaus Dostert,
"Power Line Channel Characteristics and their Effect
on Communication System Design", IEEE
Communication Magazine, vol. 42, no. 4, pp. 78-86,
2004

IRJET- Bit Error Rate (BER) Performance Evaluation of Reference Channel for Power Line Communication (PLC) Channel Under Multipath Modeling Technique

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IRJET- Bit Error Rate (BER) Performance Evaluation of Reference Channel for Power Line Communication (PLC) Channel Under Multipath Modeling Technique