Performance Analysis of A Ds-Cdma System by using Rayleigh and Nakagami-M Fading Channel

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 06 | June -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 3039
PERFORMANCE ANALYSIS OF A DS-CDMA SYSTEM BY USING RAYLEIGH
AND NAKAGAMI-M FADING CHANNEL
Neha .S Patel1 (PG Student), Prof. R.G.Zope2
Dept. Of Electronics and Telecommunication Engineering, Sanjivani College of Engineering, Kopargaon, India.
---------------------------------------------------------------***------------------------------------------------------------------
Abstract— In this paper, we studytheexpressionsforSignal
to- Noise plus Multi AccessInterferenceRatio(SINR)without
and with receive diversity considering Nakagami-m fading
channel. The analysis is also extended to Rake receiver with
Maximal Ratio Combining (MRC) technique with multiple
receiving antenna. The results are presented intermsof BER
and improvement of receiver sensitivity due to diversity.
Finally, optimum values ofsystemparameterslikenumber of
orthogonal frequency division multiplexing (OFDM) sub-
carrier, optimum code length and order of receive diversity
for a given BER are determined. It is noticed that there is
significant improvement due to receive diversity, higher
order code length as well as OFDM sub-carrier in a Multi-
carrier direct sequence code division multiple access (MC-
DS-CDMA) system. In Proposed work we will work on the
relationship between MRC diversityandNakagami-mfading
is investigated. The error performances of several
modulation schemes with diversity over Rayleighfadingand
without diversity over Nakagami-m fading is analyzed and
compared. The analysis is further extended to diversity over
Nakagami-m fading channel. An attempt has been made to
find the physical interpretation of Nakagami-m with MRC
diversity over Rayleigh fading channel. A novel equivalence
is obtained between diversity orders over Rayleigh fading
and Nakagami parameter m.
Keywords— MAI, SINR, OFDM, MRC
I. INTRODUCTION
With the tremendous incrementintheuserscountand
introduction of new features including web browsing. In
the past few years, the request for bandwidth has started
to surpass the availability in wireless networks. Different
techniques have been studied to improve the bandwidth,
efficiency and increase the number of users that can be
accommodated within each cell [2]. The International
Telecommunication Union (ITU) likewise characterized
recommendations for mobile communication framework
for fourth era (4G).In these recommendations,information
rates up to 100 Mbps for high portability and up to 1 Gbps
for low versatility or nearby wireless are anticipated.
Frameworks satisfying these prerequisites are typically
considered as 4G frameworks. Be that as it may, third
generation (3G) frameworks give information rate of
around 3.6-7.2 Mbps. Existing multiple access techniques
used in 1G/2G/3G systems (such as FDMA/TDMA/CDMA
respectively) are basically suitable for voice
communication only and unsuitable for high data rate
transmission and burst data traffic which would be the
dominant portion of traffic load in 4G system [2]. In
present day communication framework Code-Division-
Multiple –Access (CDMA) has had its effect in remote
correspondence. It offers surely understood components,
for example, dynamic channel sharing ,delicate capacity,
reuse variable of one, low dropout rate and expansive
scope (because of delicatehandover),easeofcell arranging,
vigor to channel hindrances and insusceptibility against
obstruction and so on. These points of interest are
accessible because of spreading the data over an extensive
transmission capacity. The execution of regular CDMA
framework is restricted by numerous get to obstruction
(MAI) and in addition Inter image Interference (ISI) [4].
Likewise, the intricacy of CDMA multiuser location has
dependably been a genuine worry for extensive no. of
clients. DS-CDMA is the most famous method of CDMA
procedures. The DS-CDMA transmitter duplicates every
client's flag by a particular code waveform. The finder gets
a signal composed out of the aggregate of every one of
clients' signs which cover in time and frequency [2] [10].
DS-CDMA demonstrates a few favorable advantageswhich
are simple frequency arranging, high resistance against
obstruction if a high handling increase is utilized,
adaptable information rate adaption and so forth.
II. LITERATURE SURVEY
A. Sudhir Babu and Dr.K.V.Sambasirao in their paper,
“Evaluation of BER for AWGN, Rayleigh and Rician
presumed that from the reenactment comes aboutthatthe
BER of computerized correspondence framework is a
critical figure of legitimacy used to evaluate the
trustworthiness of information transmitted through the
framework. By actualizing the distinctive tweak [11]
methods, the standard is examination of variety of BER of
various for various SNR. It is watched that the BER is least
for AWGN and most extreme for Rayleigh and Rician.
Sidratul Moontaha, Farhana Akter,AKMNazrul Islam,
Farhana Rahman composed paper "BER Performance of
DS-CDMA System over a Multipath Rayleigh Fading
Channel Considering Path Gain Component and Noise
Variance". In this paper, wehaveattemptedtodiminishthe
bit blunder rate of an uplink (switch connect) DS-CDMA
framework. For this reason, recurrence specific and
multipath Rayleigh blurring channel with power control

utilizing standard Gaussian estimate (SGA) has been
considered. Here, the way pick up segment has been
viewed as Rayleigh appropriation.[7] Thefinal observation
of our simulation is that the BER performance of DS-CDMA
system is highly influenced by this path gain component
and noise variance. This work can be further extended
considering path gain component and other parametersin
multicarrier direct sequence CDMA (MC-DS-CDMA) and
orthogonal frequency division multiplexing(OFDM). Mr. G.
A. Bhalerao and Prof.R.G.Zope in their paper,” BER
Improvement of DS CDMA with rake receiver using
Multipath fading channel”, had studied the performanceof
DS CDMA system for various users.
By studying all the above papers, we can have the
performance of communication system for various
parameters like BER, various fading channels, modulation
techniques.
III. METHODOLOGY
A. BPSK Modulation
Modulation is an important step of communication
framework. Modulation is characterized as the procedure
whereby a few attributes (line plentifulness, frequency,
stage) of a high recurrence flag wave is shifted agreement
with prompt esteem power of low frequency signal wave
which is balancing wave. There are many sorts of
modulation, for example, APSK, QPSK, QAM, BPSK. Be that
as it may, here we are utilizing BPSK modulation
procedure.
BPSK (additionally once in a while called PRK, stage
different keying, or 2PSK) is the most straightforwardtype
of stage move keying (PSK). .This modulation is the most
strong of all the PSKs since it takes the largest amount of
clamor or twisting to make the demodulator achieve an
inaccurate choice. It is, nonetheless, just ready to balance
at 1 bit/image as is unsatisfactoryforhighinformationrate
applications. Consider a sinusoidal bearer.Intheeventthat
it is modulated by a bi-polar bit stream as indicated by the
plan delineated in Figure 1, its polarity will be reversed
each time the bit stream changes extremity. This, fora sine
wave, is proportional to phase reversal (shift). The
multiplier output is a BPSK 1 signal. The data about the bit
stream is contained in the progressions of period of the
transmitted signal. A synchronous demodulator would be
delicate to these stage inversions. A depiction of a BPSK
motion in the time space is appeared in Figure 2 (lower
follow). The upper follow is the binary message grouping.
Fig.1 Generating BPSK Signal
Fig.2 BPSK Signal
The upper follow is the paired message succession. There
is something exceptional aboutthewaveformofFigure4.2.
The wave shape is "symmetrical" at each stage move. This
is on the grounds that the bit rate is a sub-different of the
bearer recurrence 1/(2π). Furthermore, the message
moves have been planned to happen at a zero-intersection
of the carrier. While this is referred to as 'extraordinary',it
is normal by and by. It offers the benefitofstreamliningthe
bit clock recuperation from a got flag. Once the bearer has
been procured then the bit clock can be determined by
division.
The Nakagami fadingmodel wasinitiallyproposedbecause
it matched empirical results for short wave ionospheric
propagation. In current wireless communication,themain
role of the Nakagami model can besummarizedasfollows:
1. It describes the amplitude of received signal after
maximum ratio diversity combining.
2. The sum of multiple independent and identically
distributed (i.i.d.) Rayleigh-fading signals have a
Nakagami distributed signal amplitude. This is
particularly relevant to model interference from
multiple sources.
3. The Nakagami distribution matches some empirical
data better than other models
The Rician and the Nakagami model behaveapproximately
equivalently near their mean value. This observation has
been used in many recent papers to advocate the
Nakagami model as an approximation forsituationswhere
a Rician model would be more appropriate.

IV. SYSTEM ARCHITECTURE
The framework outline for performance examination
of DS CDMA with various fading channels is as appeared in
figure 3. At the transmitter, the data is encoded utilizing
codes. The encoded data isthenchangeintoaninformation
modulated symbol arrangement with a base band
modulator. The modulated symbol arrangement is spread
in time space by a chip sequence of PN code generator,
generally Walsh code and PN succession. The data is
molded and gone through channel for transmission. At the
beneficiary end, the data is increased with chip grouping
by the connections in the Rake recipient. The data is then
summed and increased by nearby created spreading code,
which is de spreading. The data is demodulated and
decoded and unique information can be recuperated.
Transmitter
Channel
Receiver
Fig.3 System Architecture
V. EXPERIMENTAL RESULTS
a. Simulating BER vs SNR in MATLAB
For the analysis of the proposed system following
steps will be carried out:
1. Random BPSK signals will be generated and passed
through the AWGN channel, Nakagami channel, and
Rayleigh channel.
2. Received signal is demodulated.
3. Numbers of errors will be counted.
4. For Nakagami channel by varying M factor number of
BER values can be obtained.
5. Result will be plotted.
VI. OBSERVATIONS WITH RESULTS
Following table no.1 shows the BER values for different
SNR values without Rake receiver using BPSK modulation
and PN code for AWGN and Nakagami-m fading channel.
AWGN channel is good in terms of BER as compared to
Nakagami-m fading channel.
Table No. 1 BER values for fading channels
Sr.No SNR
Values
(dB)
BER
Rayleigh
channel
BER AWGN
Channel
1 1 0.4000 0.2666
2 2 0.4500 0.2476
3 3 0.4700 0.2225
4 4 0.5200 0.2050
5 5 0.5300 0.1714
6 6 0.5400 0.1428
7 7 0.5500 0.1161
8 8 0.4800 0.0882
9 9 0.5000 0.0652
10 10 0.5100 0.0464
Below figures shows the output of the DS CDMA
System by using Rayleigh fading, Nakagami-m fading,
AWGN fading Channel. It shows that the BER is less for
AWGN Channel as compared to theRayleighandNakagami
channel. The performanceunderRayleighfadingchannel is
very uneven.
0 5 10 15 20 25 30
10
-0.32
10
-0.31
10
-0.3
10
-0.29
10
-0.28
BER Versus SNR plot
SNR Values
BERValues
Fig.4 Using Rayleigh fading channel

0 0.5 1 1.5 2 2.5 3 3.5 4
10
-4
10
-3
10
-2
BER Versus SNR plot
SNR Values
BERValues
Fig.5 Using Nakagami-m Fading channel (m=1)
0 2 4 6 8 10 12 14 16
10
-4
10
-3
10
-2
10
-1
10
0
BER Versus SNR plot
SNR Values
BERValues
Fig.6 Using AWGN Channel
Following table no.2 shows the BER values for
different SNR values without Rake receiver using BPSK
modulation and PN code for different values of m- factor
using Nakagami-m fading channel. AWGN channel is good
in terms of BER as compared to Nakagami-m fading
channel. It is observed that for higher values of m BER
values are less. For negative values of m it shows spikes
which are not good for efficient communication system.
Table No. 2 BER values for Nakagami-m fading channels
SNR
Value
s
(dB)
BER
Nakagam
i channel
(m=1)
BER
Nakagam
i channel
(m=2)
BER
Nakagam
i channel
(m=0)
BER
Nakagam
i channel
(m=0.5)
1 0.0210 0.0738 0.0784 0.0905
2 0.0138 0.0503 0.0573 0.0715
3 0.0078 0.0287 0.0411 0.0456
4 0.0031 0.0171 0.0263 0.0298
5 0.0015 0.0082 0.0120 0.0173
6 0.0004 0.0030 0.0056 0.0079
7 0.0000 0.0005 0.0020 0.0035
8 0.0001 0.0004 0.0009 0.0012
9 0.0000 0.0000 0.0001 0.0005
10 0.0000 0.0000 0.0001 0
VII.CONCLUSIONS
The performance of the framework will be
compared at by utilizing the parameters like BER andSNR.
We can improve the performance of wireless
communication system with parameters BER, SNIR for
various fading channels and different modulation
techniques. For better productive framework the BER
ought to as little as would be prudent. The rake receiver is
utilized to diminish the BER because of multipath
impedance over channels utilized. The framework
demonstrates that how Nakagami-m channel is good as
compared to both Rayleigh and AWGN channel. The
execution of framework is better for AWGN channel when
contrasted with Rayleigh channel. Diverse estimations of
BER will be watched for Nakagami channel by shifting m-
factor.
REFERENCES
[1] M. A. Rahman1, M. M. Alam1, Md. KhalidHossain2*,Md.
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of Engineering and Technology, 2016, 4, 1-9
[2] Sidratul Moontaha, Farhana Akter,Farhana Rahman,
“BER Performance of DS-CDMA System over a Multipath
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Performance Analysis of A Ds-Cdma System by using Rayleigh and Nakagami-M Fading Channel

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Performance Analysis of A Ds-Cdma System by using Rayleigh and Nakagami-M Fading Channel