International Journal of Computer Engineering and Information Technology

VOL. 11, NO. 8, August 2019, 164–171

Available online at: www.ijceit.org
E-ISSN 2412-8856 (Online)

The Analysis of Improved Sinc Power Pulse and Rectangular Pulse on

OFDM System through Frequency Selective Fading Channel
Kadek Agus Mahabojana Dwi Prayoga1, Ni Made Esta Dewi Wirastuti2 and Nyoman Pramaita3

1, 2, 3
Electrical Engineering Department, Engineering Faculty, Udayana University, Indonesia
1
mahabojanadwi1@gmail.com, 2dewi.wirastuti@unud.ac.id, 3pramaita@unud.ac.id

ABSTRACT
The combination of OFDM (orthogonal frequency division However, in such OFDM technique there are several
multiplexing)and Pulse Shaping system can reduce Inter Carrier flaws, one of which is the highly sensitivity towards
Interference (ICI) and the occurred error. This research aimed at frequency offset which may cause ICI. The presence of
investigating the performance comparison of OFDM system ICI will reduce the performance of the OFDM system [2].
without pulse shaping and OFDM with pulse shaping Improved
Sinc Power (ISP) pulse as well as Rectangular pulse through
Therefore, an accurate and efficient ICI reduction is
Frequency Selective Fading channel, viewed from BER (bit highly required for the obtained data demodulation.
error rate) compared to Eb/No (energy per bit to noise power Several methods have been proposed in reducing ICI, one
spectral density ratio). This research utilized simulation method of which is pulse-shaping method.
by using Matlab R2018a program. The obtained result of the One of the methods in overcoming the main cause of ICE
simulation for the OFDM system performancewith pulse is pulse shaping, which in the OFDM system, the
shaping ISP pulse gained better result than the OFDM subcarriers are filtered when they are still in the
Rectangular pulse and OFDM without pulse shaping. On the orthogonal state so that when it is in the interference
Frequency Selective Fading transmission channel, in order to effect receiver from the side lobe the other subcarrier has
gain BER value of 10-1, the OFDM system with pulse shaping
ISP pulse required Eb/No of 2 dB. Meanwhile, the Rectangular
been reduced[3].The combination of OFDM with Pulse
pulse OFDM system and OFDM without pulse shaping required Shaping using Improved Sinc Power(ISP) pulse and
Eb/No of 6 dB and 10 dB respectively. Rectangular pulse was expected to produce better system
by combining the advantages of each system.
Keywords: OFDM, Pulse Shaping, ICI, ISP pulse, Thus, in this research a simulation on the work of OFDM
Rectangular pulse, Frequency Selective Fading. system without using Pulse Shaping technique and
OFDM using Pulse Shaping technique, namely ISP pulse
and Rectangular pulse on the Frequency Selective Fading
1. INTRODUCTION channel would be conducted. Consequently, the
performance of the each system would be compared to
LTE (Long Term Evolution)technology is a kind of
investigate which system has better performance.
technology that is used in actualizing a fast and good
communication service on wireless communication. This
LTE technology utilizes OFDM (Orthogonal Frequency 2. OFDM, PULSE SHAPING AND
Division Multiplexing) for downlink and SC-FDMA
(Single-Carrier Frequency Division Multiple Access) for FREQUENCY SELECTIVE
uplink. OFDM is a multicarrier modulation technique, in FADINGINTRODUCTION
which each subcarrier to another is orthogonal. Due to
such orthogonal nature, thus between subcarrier an 2.1 OFDM (Orthogonal Frequency Division
overlapping is made without creating any ISI (inter Multiplexing)
symbol interference) effect. With multiplexing subcarrier
Orthogonal Frequency Division Multiplexing (OFDM)
which was done in overlap, the bandwidth can be reduced.
is a multiplexing technique that is used on digital
The conducted process is similar to multicarrier
modulation technique. However, the difference is on the
communication system by using several frequencies
use of orthogonal subcarrier on each sub-channel [1]. that divide the bandwidth into several orthogonal
 International Journal of Computer Engineering and Information Technology (IJCEIT), Volume 11, Issue 8, August 2019
K. A. M. D. Prayoga et. al 165

subcarriers. The OFDM divides the serial data by the receiving device is called Additive White Gaussian
highest bit rate into N numbers of parallel data by the Noise(AWGN). The meaning of additive is that the noise
lowest bit rate that would later be transmitted through is in the nature of adding power spectral density from the
such subcarriers [4]. transmitting signal, white means that it has even
distribution on all bands, and is a type of noise occurred
with Gaussian distribution with mean value of zero and
deviation standard in the value of one[6].

2.4 Frequency Selective Fading

A signal is said to be through frequency selective fading if
the transmitted signal has a bandwidth greater than the
bandwidth of the radio channel and the channel impulse
response has greater delay spread than the symbol period.
The received signal consists of several transmitted signals,
which have been muffled and there is a delay so that the
received signal will be distorted. Frequency Selective
Fading causes time dispersion from the transmitted
Fig. 1. The comparison of FDM and OFDM symbol. This kind of channel causes inter-symbol
interference (ISI), [7].Figure 2shows the characteristics of
2.2 Pulse Shaping frequency selective fading channel.
On the OFDM spectrum, each subcarrier consists of main
lobe and many side lobes. When the orthogonality among
the subcarriers is reduced, the side lobe would have a
potential to bring out ICI power in the center area of each
subcarrier. The ICI power will increase when the offset
frequency increases. The objective of the pulse shaping
use is to eliminate the side lobe so that the ICI would be
reduced and would later increase the performance of the
OFDM system [5].
 Improved Sinc power Pulse(ISP) as the modification
of the pulse shape is described into the equation
of , later on the frequency
offset is substituted into the following equation:
Fig. 2. The Characteristics of Frequency Selective Fading

(1)
2.5 Rayleigh Distribution
 Rectangular pulse as the type of pulse shaping used in On the moving channel, Rayleigh distribution is common
the equation of , later on the to be used to describe time alteration from the received
frequency offset is substituted into the following flat lading signal sheath or the sheath of one of the
equation: multipath components that has previously been assumed
into Rayleigh Distribution. Rayleigh Distribution is used
(2) to describe the state on a channel in which the Rayleigh
distribution has density function probability as shown in
In which the represents the carrier frequency offset the following equation (3) [8]:
between the transmitting and the receiving oscillators,
and represents the value of normalized frequency
offset. The a parameter is used to adjust the amplitude and (3)
n represents the sinc function degree.

2.3 AWGN (Additive White Gaussian Noise) 2.6 ICI (Inter Carrier Interference)
A type of noise in communication system is noise thermal. ICI occurs due to the shifting of work frequency of the
This noise disturb the signal in the additive form, i.e. OFDM system, commonly called as offset frequency. The
added into the main signal. Thus, noise thermal in the cause of the offset frequency is the Doppler shift caused
 International Journal of Computer Engineering and Information Technology (IJCEIT), Volume 11, Issue 8, August 2019
K. A. M. D. Prayoga et. al 166

by the relative movement between the transmitter and the Tabel 1: Simulation Parameter
receiver and by the difference between the frequency of
the receiving and transmitting oscillators [9]. Parameter The used value
The number of subcarriers 64
The number of FFT
64
symbols
Modulation Type QPSK
Zero Padding 14
bit per OFDM value 50
Guard interval type Cyclic prefix
cyclic prefix length 16
Eb/No Value -10 : 1 : 10
Input bit value 100.000 bit (Random)
Pulse Shaping type ISP pulse& Rectangular pulse
AWGN + Frequency selective
Channel Type
fading

3.3 OFDM System Modeling with Pulse Shaping

In this research, the OFDM system modeling which was
combined with pulse shaping Improved Sinc Power (ISP)
pulse on the Frequency Selective Fading channel is shown
Fig 3: Inter Carrier Interference in Figure 4.
1 1 1 1
: : : :
Data 1...N 1...M Serial to Parallel to 1...80 Pulse Shaping
Data Mapping : Zero pedding : IFFT : Cyclic Prefix :
3. RESEARCH METHOD Generator Paralel
:
:
:
:
:
:
:
:
Serial ISP Pulse

50 64 64 80
1...N (Dikirim)

1...80
This research utilized simulation method aiming at
investigating the performance of the Improved Sinc Kanal Selective
BER vs Eb/N0 fading + noise
Power (ISP) pulse and the Rectangular pulse on the AWGN

OFDM system through Frequency Selective Fading

1...N (Diterima)

1...80
channel. The first conducted simulation was by using 1 1 1 1
pulse shaping, which later ran OFDM system simulation Data yang 1...N Data
1...M Parallel to
:
: Remove Zero
:
: FFT
:
:
Remove Cyclic
Prefix
:
: Serial to 1...80 Pulse Shaping
diterima Demapping Serial pedding Parallel ISP Pulse
using pulse shaping Improved Sinc Power (ISP) pulse and :
50
:
64
:
64
:
80

Rectangular pulse. Then the performances of the three

systems were compared. Fig. 4. OFDM System Modeling with ISP pulse

3.1 Research Steps

The conducted steps of this research was initiated by
conducting system modeling in Matlab R2018a software.
The result of the conducted simulation in the Matlab
R2018a software was in the form of graph of BER value
compared to Eb/No, which was later analyzed.

3.2 Simulation Parameters

The utilized simulation parameters in the OFDM system
modeling without pulse shaping and OFDM with pulse
shaping Improved Sinc Power(ISP) pulse as well as with Fig. 5. OFDM System Modeling with Rectangular pulse
Rectangular pulse are shown on Table 1.
Each diagram block of the OFDM system with the
application of pulse shaping method is explained as
follows:
 International Journal of Computer Engineering and Information Technology (IJCEIT), Volume 11, Issue 8, August 2019
K. A. M. D. Prayoga et. al 167

 Transmitting Block According to this research, the length of the used CP was
The transmitted data was in the form of random binary 16 rows so that the length of the OFDM symbol would
number input where the data transmission was through change from 1 to 80.
diagram blocks explained as follows: 7. Parallel to serial
1. Input Data This block functioned to combine the parallel data in the
Input data was a string of data raised on single user using form of IFFT output into serial data that referred to as one
randint function in Matlab, so that the string of data has OFDM symbol where if the IFFT output had a matrix
random pattern in the form of binary data with the value measurement of 80x1 then the output matrix of the
of 0 and 1. On the simulation 100,000 bits of transmission parallel to serial data would be 1x80.
was conducted. The number was initiated from 1 to N, 8. ICI modeling
where N is valued 100.000. The system modeling that experienced Inter Carrier
2. Mapping Data Interference (ICI) effect is represented in the following
In this block, the binary data would be transformed into equation (2.19):
data symbols in accordance to the used digital modulation =
constellation. The used signal mapper in this research was
QPSK where the constellation of QPSK mapper produced (4)
2 bits per symbol to be modulated. Thus, the initial 1 to N
bit would produce symbols as many as N/2 which would The presence of ICI effect on the received symbol is
later denoted with 1 to M (M = N/2). represented with Δf variable that is referred to as carrier
3. Serial to parallel frequency offset. Later on, such carrier frequency offset
value would be normalized against the value of the
Serial to parallel block functioned to alter the string of
subcarrier spacing which later referred to as normalized
serial data into the string of parallel data where the
frequency offset in the value of ΔfT. This value of ΔfT or
objective is to increase the time period of the data string
ε would show how great the shifting of the subcarriers
with the incoming signal so that there would be rate
which was detected by the receiving oscillator where the
reduction. This serial to parallel process produced a
matrix of 50 rows and several columns where the number value of |ΔfT| 1. In the modeling simulation, such
of the columns was adjusted according to the result of the formula was done after the output of the parallel to serial.
X variable division by 50 (subcarriers). Each column that 9. Pulse Shaping Function
consisted of 50 rows in the resulting matrix was a symbol This block functioned to form pulse from the existing
of OFDM. symbols. Each transmitted symbol would be multiplied by
4. Add Zero Padding the used pulse function where in this simulation pulse
On the Zero Padding(ZP), an insertion of zero bit was shaping Rectangular Pulse type was used and compared to
conducted on each symbol to prevent Inter Carrier the pulse shaping Improved Sinc power Pulse(ISP). The
Interference(ICI) so that the string of the parallel data objective of the use of pulse shaping method was to
would be in accordance to the number of the IFFT eliminate the side lobe power that was potential to
symbols. The number of the used zero padding was 14, so generate ICI power whereby the use of Pulse Shaping
that each OFDM symbol had 64 rows. could reduce the ICI power.
5. IFFT (Invers Fast Fourier Transform)  Channel Modeling
The IFFT block functioned as baseband modulator that On this OFDM system simulation, Frequency selective
generated the value of the orthogonal subcarrier where in fading was used which was distributed using Rayleigh
the simulation the mapper result would be processed by distribution where each channel response distributed with
using the ifft function in Matlab. In this research, the used Rayleigh distribution was added with AWGN noise.
number of IFFT points or the number of the used  Receiving Block
subcarriers was 64. After undergoing the process on the channel, the data was
6. Add Cyclic Prefix then processed in the receiving part which process was
The addition of Cyclic Prefix(CP) was aimed at the inverse function of the transmitting block. The
preventing Inter Symbol Interference(ISI) that could be diagram blocks of the receiving part or receiver are
done by periodically adding symbol or known as pilot explained as follows:
addition. This pilot addition can reduce the occurrence of 1. Pulse Shaping Function
Inter Carrier Interference(ICI) and could help maintain On the receiver end there was also pulse-shaping process
the orthogonality of the signal. The number of the added where this occurring pulse shaping process in the receiver
symbols was a quarter of the number of the used was the inverse of the pulse shaping process on the
subcarriers where the pilot signal would be eliminated on transmitter end.
the receiving end so that the received one would only be
the signal or the string of information data only.
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K. A. M. D. Prayoga et. al 168

2. Serial to Parallel the Frequency Selective Fading transmitting channel

After going through the channel, the information data in according to BER vs Eb/No parameters. The graphs of the
the serial form would be received and would later be OFDM system performance without pulse shaping on the
divided into each arm into parallel data. AWGN channel and the Frequency Selective Fading are
3. Remove Cyclic Prefix shown on Figure 6.
The Cyclic Prefix symbols that had been inserted on the According to Figure 6, Eb/No with the value of 12 dB
previous data in the transmitter part would be separated was required to gain BER value of 10-2on the AWGN
and removed so that the obtained data would only be the transmitting channel for the OFDM system without pulse
actual transmitted input data. This process was the inverse shaping,. Meanwhile, on the Frequency Selective Fading
of the cyclic prefix addition process on the transmitting transmitting channel the required Eb/No value was 20dB.
block. Thus, the number of the OFDM rows, which
previously was 80 rows in one symbol, became 64 rows
in one OFDM symbol.
4. Fast Fourier Transform (FFT)
FFT was the inverse of the IFFT process where FFT was
used to analyze the signal on the frequency domain. The
measurement of this FFT was equal to the measurement
of the IFFT that was 64 and used the data in the parallel
stream.
5. Remove Zero Padding
The Zero Padding symbol that was inserted previously on
the transmitter part would be separated on this block so
initial input data would be obtained. Thus, one OFDM
symbol would generate 50 rows.
6. Parallel to Serial
This block functioned to recombine the information data
Fig. 6. BER OFDM without pulse shaping on the AWGN channel and
of each arm in the parallel form into a string of serial data. Frequency Selective Fading
Later on, the added pilot on the transmitting end would be
removed after the data in the serial form so that the Based on Figure 6it can be seen that the AWGN
received output would be in the form of information data transmitting channel had lower value of BER than the
only. Frequency Selective Fading transmitting channel. This
7. De-mapping Data was because the AWGN modeling did not skip the
De-mapping functioned to reconstruct the transmitted data received data transmitted on a channel or a
according to the value of the received data symbol in communication channel that had fading effect, but only
order to match the used modulation constellation on the added AWGN noise effect in the transmission process
transmitter end. between the transmitter and the receiver.
 BER calculation
One way to investigate the performance of a 4.2 The Result of OFDM ISP Pulse System
communication system was by calculating the number of Simulation
error data on the receiver known as Bit Error Rate (BER).
BER was done by comparing the received data to the The OFDM system simulation with pulse shaping
transmitted data that would later be compared to the Improved Sinc Power (ISP) pulse was conducted in
Eb/No (Energy Bit per Noise). accordance to OFDM ISP pulse system modeling on
Figure 4. This simulation was aimed at investigating the
performance of OFDM system using pulse shaping ISP
4. RESULTS AND DISCUSSION pulse on the Frequency Selective Fading transmitting
channel according to the BER vs Eb/No parameters. The
4.1 The Result of OFDM System Simulation graphs of the performance of the OFDM system with
without Pulse Shaping pulse shaping ISP pulse on the AWGN and the Frequency
Selective Fading transmitting channel are shown on
The OFDM simulation without pulse shaping was aimed Figure 7.
at investigating the performance of the OFDM system on
 International Journal of Computer Engineering and Information Technology (IJCEIT), Volume 11, Issue 8, August 2019
K. A. M. D. Prayoga et. al 169

Fig. 7. BER OFDM ISP pulse on AWGN and Frequency Selective Fig. 8. BER OFDM ISP pulse on AWGN and Frequency Selective
Fading channel Fading Channels

Based on Figure 7, Eb/No with the value of 6 dB was

Based on Figure 8, Eb/No with the value of 8 dB was
required in order to gain BER value of 10-2on the AWGN
required to gain BER value of 10-2 on the AWGN
transmitting channel on the OFDM system with ISP pulse.
transmitting channel on the OFDM system with
Meanwhile on the Frequency Selective Fading
Rectangular pulse. Meanwhile, on the Frequency
transmitting channel the required Eb/No value was 14 dB.
Selective Fading transmitting channel the required Eb/No
It can be seen on Figure 7that the Frequency Selective
value was 16 dB.
Fading transmitting channel had greater BER value than
It can be seen on Figure8that the Frequency Selective
the AWGN transmitting channel. This was because on the
Fading transmitting channel had greater BER value than
Frequency Selective Fading transmitting channel the
the AWGN transmitting channel. This was because on the
transmitted data did not only go through the channel or
Frequency Selective Fading transmitting channel the
the communication channel with the fading effect, but
transmitted data did not only go through the channel or
there was also AWGN noise addition in the transmitting
the communication channel with fading effect, but there
process between the transmitter and the receiver.
was also AWGN noise addition in the transmitting
process between the transmitter and receiver.
4.3 The Result of OFDM System with Rectangular
Pulse 4.4 Performances Comparison of OFDM System
The simulation of OFDM system with pulse shaping without Pulse Shaping and OFDM System with
Rectangular pulse was conducted by following the OFDM Pulse Shaping
ISP pulse system modeling as seen on Figure 5. This
The comparison between the result of the OFDM system
simulation was aimed at investigating the performance of
simulation without pulse shaping and the OFDM system
the OFDM system using pulse shaping Rectangular pulse
simulation with pulse shaping Improved Sinc Power(ISP)
on the Frequency Selective Fading transmitting channel
pulse and Rectangular pulse according to the BER vs
according to the BER vs Eb/No parameters. The graphs of
Eb/No parameters. The graphs of the comparison between
the performance of the OFDM system with pulse shaping
OFDM system without pulse shaping and the OFDM
Rectangular pulse on the AWGN and Frequency Selective
system with pulse shaping are shown on Figure 9.
Fading transmitting channels are shown on Figure 8.
 International Journal of Computer Engineering and Information Technology (IJCEIT), Volume 11, Issue 8, August 2019
K. A. M. D. Prayoga et. al 170

Based on Figure 9, Eb/No with the value of 2 dB was transmitting channel. In order to obtain BER value of
required in order to gain BER value of 10 -1 on the 10-2on AWGN transmitting channel Eb/No with the
Frequency Selective Fading transmitting channel on the value of 12 dB was required. Meanwhile, on the
OFDM system with ISP pulse. Meanwhile, on the OFDM Frequency Selective Fading transmitting channel the
system with Rectangular pulse the required Eb/No value required Eb/No value was 20 dB.
was 6 dB and on the OFDM system without pulse shaping 2. On the performance of the OFDM system with pulse
the required Eb/No value was 10 dB. shaping Improved Sinc Power(ISP) pulse, the AWGN
The result of the simulation comparison showed that the transmitting channel had lower BER value than the
performance of the OFDM system with Pulse Shaping Frequency Selective Fading transmitting channel. In
had better performance than the OFDM system without order to obtain BER value of 10-2on the AWGN
pulse shaping on the Frequency Selective Fading transmitting channel Eb/No with the value of 6 dB was
transmitting channel. This was because the OFDM system required. Meanwhile, on the Frequency Selective
without pulse shaping in this research was an OFDM Fading transmitting channel the required Eb/No value
system that applied frequency offset which caused side was 14 dB.
lobe shifting from several subcarriers that generated ICI 3. On the performance of OFDM system with pulse
(Inter Carrier Interference) on such subcarriers. ICI would shaping Rectangular pulse, the AWGN transmitting
cause orthogonality loss from a subcarrier where the channel had lower BER value than the Frequency
subcarrier that had lost its orthogonality would cause its Selective Fading transmitting channel. In order to
side lobe to be no longer valued zero on the middle obtain BER value of 10-2on the AWGN transmitting
frequency of such subcarrier. This resulted in the channel Eb/No with the value of 8 dB was required.
worsening of performance of the OFDM system that was Meanwhile, on the Frequency Selective Fading
indicated by the increasing amount of the generated BER transmitting channel the required Eb/No value 16 dB.
value. Therefore, pulse shaping was applied to help
reducing the ICI on the OFDM system, where the ISP On the comparison of performances of the OFDM system
pulse had the best performance in eliminating the effect of without pulse shaping and OFDM with pulse shaping ISP
the side lobe shifting which had the potential to generate pulse and Rectangular pulse it was found that the
ICI so that the power of each subcarrier would not be performance of the OFDM system with pulse shaping ISP
interference by the side lobe of the other subcarriers. pulse was better. On the Frequency Selective Fading
transmitting channel, in order to obtain BER value of 10-
1
on the OFDM system with pulse shaping ISP pulse
Eb/No with the value of 2 dB was required. Meanwhile,
on the OFDM system with Rectangular pulse and OFDM
system without pulse shaping the required Eb/No value
were 6 dB and 10 dB respectively.

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