This document evaluates the performance of digital modulation techniques in a WCDMA radio over fiber communication system. It discusses how radio over fiber combines wireless and optical networks to increase network capacity and mobility while decreasing costs. The document specifically looks at 64-PSK modulation and analyzes its performance based on metrics like bit error rate, eye diagrams, and scatter plots. Radio over fiber is presented as a promising technique for next generation wireless networks as it can support high data transmission rates and seamlessly integrate various communication services.

1. ISSN: 2277 – 9043
International Journal of Advanced Research in Computer Science and Electronics Engineering
Volume 1, Issue 4,June 2012
Performance Evaluation of Digital Modulation
Techniques in a WCDMA-based Radio-over-
Fiber Communication System
Amanjot Kaur, Jasbir Singh
Abstract-The demand of mobile communications in the The distributed antenna system (DAS) provides an
modern world is increasing day by day and subscribers infrastructure that brings the radio interface very
for the mobile communication technologies are growing close to the users. It gives the benefit such as better
rapidly. The data transfer rate should be maximum for coverage, higher capacity and easier installation.
uninterruptable communication .Therefore, the Radio
over fiber system along with wireless communication, is
Other benefits are low attenuation loss, larger
used for the high speed data transfer. This combination bandwidth and immunity to radio frequency. One of
will increase the capacity for the cellular base stations the most promising approaches to 3G is to combine a
to change dynamically and meet the traffic Wideband CDMA (WCDMA) air interface with the
requirements. To better understand the M-ary PSK radio over fiber technology. Several proposal
system, a Simulink-based simulation system is designed supporting WCDMA were submitted to the
for M-ary PSK for M=64 using communication toolbox International Telecommunication Union (ITU) and its
in Simulink. In this paper we propose the suitability of International Mobile Telecommunications for the
64 PSK Digital Modulation Technique for transmission year 2000(IMT2000) initiative for 3G. All these
and the results are analyzed on the basis of BER, scatter
plot and eye diagram like performance measures.
schemes try to take advantage of the WCDMA radio
techniques. The standard that has emerged is based
on ETSI's Universal Mobile Telecommunication
Index Terms---Digital Modulation Techniques,Eye
Diagram, Scatter Plot and 64 psk using rof.
System (UMTS) and is commonly known as UMTS
Terrestrial Radio Access (UTRA). WCDMA signal
modulation & conversion of electrical to optical
I. INTRODCTION signal happen in central station. After transmission
through various length of step index single mode
Radio over fiber (RoF) is an analog optical link fiber (SI-SMF), the receiver signal is analysed.PIN
transmitting modulated RF signals. It serves to photo diode is used to detect the optical signal&
transmit the RF signal downlink and uplink, to and convert it back to electrical signal. Demodulation
from central station (CS) to base station (BS) called then performed. Fig. 1 shows the Simulink diagram
also radio ports. The main requirements of radio over of WCDMA using Radio over fiber.
fiber Link architecture are duplex operation (i.e.
downlink-uplink), reasonable length (a few tens of
kilometers), and need a few millimeter-wave
components only in the base stations and also need of
only few high-performance Optical components. RoF
systems are now being used extensively for enhanced
cellular coverage inside buildings such as offices,
shopping malls and airport terminals.
Amanjot Kaur, Department of Electronics and communication
Engg., Yadavindra College of Engineering, Talwandi Sabo, India,
Phone/MobileNo.09465504021.(email:amanjotmann.04@gmail.co Fig.1: Block Diagram for WCDMA using RoF
m).
The combination of wireless and optical networks is
Jasbir Singh, Department of Electronics and communication a potential solution for increasing capacity and
Engg., Yadavindra College of Engineering, Talwandi Sabo, India, mobility as well as decreasing costs in the access
Mobile No.09501011864.(jasbirsingheng@yahoo.com). network. The concept of RoF means to transport
information over optical fiber by modulating the light
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All Rights Reserved © 2012 IJARCSEE

2. ISSN: 2277 – 9043
International Journal of Advanced Research In Computer Science and Electronics Engineering
Volume 1, Issue 4, June 2012
with the radio signal. This modulation can be done techniques have proposed in recent years for ultra
directly with the radio signal or at an intermediate long distance digital optical transmission. Because of
frequency. Radio-over-Fiber (RoF) system is a fiber- it’s easy to modulate and demodulate.
fed distributed antenna network which is expected to
be a fundamental supporting technique for 3G III. PSK
development. Greater end user demand for improved
3G services .It provides wider coverage & better Phase shift keying is another form of angle
indoor broadband quality. It supports high data rate modulated, constant amplitude digital modulation.
transmission. The goal for the next generation with Psk is an M-ary digital modulation scheme.64 psk is
mobile communication system is to seamlessly an M-ary encoding technique where M=64; there are
integrate a wide variety of communication services 64 different output phases possible. With 64-psk six
such as high speed data, video & multimedia traffic bits are combined, producing 32 different output
as well as voice signals. This was a topic of phases. With 64 PSK, n=6 and M=64; therefore, the
investigation Khasjori and H.S A.I Raweshidy. minimum bandwidth and baud equal one –sixth the
Description of the MATLAB simulation of multiuser bit rate (fb/6).
detection in code division multiple access (CDMA)
Hailil Tanyer Eyyuboglu ,to reach low bit error rate IV. PERFORMANCE MEASURES
(BER) levels within reasonable computation times,
the method of sampling is utilized. Sonia Aissa and The right choice of the performance evaluation
Martin Maier demonstrated the ultimate goal of criteria for the characterization of optical
networks providing access to information when transmission links represents one of the key issues for
needed, wherever needed and in whatever format it is an effective design of future long-haul optical
needed. The vision of technological convergence of systems. The evaluation criteria should provide a
wireless and optical networks is not only becoming a precise determination and separation of dominant
necessity but also plays a key role in future system limitations, making them crucial for the
communications networks. suppression of propagation disturbances and a
performance improvement. The most widely used
II. DIGITSL MODULATION TECHNIQUES performance measures for performance evaluation
are the BER and eye opening.
To meet the explosive demands of high-capacity and
broadband wireless access, radio over fiber (RoF) A. EYE DIAGRAM
technology has been proposed to be the best solutions
for the implementation of the reduced cell size and The Discrete-Time Eye Diagram Scope block
cost-effective system. For the high speed data rate displays multiple traces of a modulated signal to
like 10 GB/s or 40 GB/s per channel linear and produce an eye diagram. In telecommunication, an
nonlinear degrading effects will be severe. The eye pattern, also known as an eye diagram, is an
Performance Evaluation of Digital Modulation oscilloscope display in which a digital data signal
Techniques for WCDMA using Radio over fiber from a receiver is repetitively sampled and applied to
selection of a suitable optical modulation format is a the vertical input, while the data rate is used to trigger
key issue to ensure optimum system the horizontal sweep. It is so called because, for
performance[1].An optimal modulation format which several types of coding, the pattern looks like a series
is more tolerant to linear and nonlinear impairments of eyes between a pair of rails. Several system
can improve dramatically the capacity of light wave performance measures can be derived by analyzing
system, bit rate-distance product.[2] To combat both the display. If the signals are too Long, too short,
the linear and the nonlinear impairments over the poorly synchronized with the system clock, too high,
transmission fiber, an optimal modulation format is too low, too noisy, or too slow to change, or have too
desired. The advanced modulation schemes with much undershoot or overshoot, this can be observed
other key technologies, like low noise optical from the eye diagram. An open eye pattern
amplifiers, new advanced optical fibers and forward corresponds to minimal signal distortion. Distortion
error correction techniques, can realize high spectral of the signal waveform due to intersymbol
efficient, high-capacity optical transport networks
[3].several advanced optical digital modulation
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All Rights Reserved © 2012 IJARCSEE

3. ISSN: 2277 – 9043
International Journal of Advanced Research in Computer Science and Electronics Engineering
Volume 1, Issue 4,June 2012
interference and noise appears as closure of the eye D. SCATTER PLOT
diagram.
The Discrete-Time Scatter Plot Scope block displays
B. BIT ERROR RATE (BER) scatter plots of a modulated signal, to reveal the
modulation characteristics, such as pulse shaping or
channel distortions of the signal. The Discrete-Time
In digital transmission the number of bit errors is the
Scatter Plot Scope block has one input port.
number of received bits of a data stream over a
communication that have been altered due to noise,
V. SYSTEM DESCRIPTION AND RESULTS
interference Distortion bit or synchronization errors.
The BER can be estimated from following equation. In this system we will use matlab Simulink. Fig2.
The BER gives the upper limit for the signal because Shows the Matlab simulation model of the 64 PSK
some degradation occurs at the receiver end. digital modulation technique. The Performance of 64
PSK is measured and Eye diagram, signal trajectory,
BER is scatter plot and BER graph for 64 PSK is evaluated.
1 Q exp( Q 2 / 2)
 erfc( ) 
2 2 Q 2
The bit error rate or bit error ratio (BER) is the
number of bit errors divided by the total number of
transferred bits during a studied time interval. BER is
a unit less performance measure, often expressed as a
percentage. The bit error probability pe is the
expectation value of the BER. The BER can be
considered as an approximate estimate of the bit error
probability. This estimate is accurate for a long time
Interval and a high number of bit errors. In a
communication system, the receiver side BER may
be affected by transmission channel noise
Fig 2.Simulink Model for 64 PSK Digital Modulation
interference, distortion, bit synchronization problems,
Technique using WCDMA and RoF.
attenuation, wireless multipath fading, etc. In a noisy
channel, the BER is often expressed as a function of
the normalized carrier-to-noise ratio measure denoted
Eb/N0, (energy per bit to noise power spectral
density ratio), or Es/N0 (energy per modulation
symbol to noise spectral density).
C. SIGNAL TRAJECTORY
The Discrete-Time Signal Trajectory Scope displays
the trajectory of a modulated signal in its signal space
by plotting its in-phase component versus its
quadrature component. The Discrete-Time Signal
Trajectory Scope block has one input port. The input
signal must be complex. The block accepts signal of
type double, single, base integer, and fixed-point for
input, but will cast it as double. The input signal must
be a sample-based scalar in sample-based mode. The Fig 3.Signal Trajectory Scope for 64 psk
input must be a frame-based column vector or a
scalar in frame-based mode.
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4. ISSN: 2277 – 9043
International Journal of Advanced Research In Computer Science and Electronics Engineering
Volume 1, Issue 4, June 2012
Fig 6.BER Graph for 64 psk
VI. CONCLUSIONS
This paper describes the performance of 64 psk
Digital Modulation Technique using the WCDMA
and RoF. The Results are carried out using Matlab
Simulink. The results include the Eye Diagram,
scatter plot, Signal trajectory and BER graph for 64
psk Digital Modulation Technique.
REFERENCES
[1] Nazem Khashjori, H.S. AI-Raweshidy, A.Bajwa, “Macro
diversity Performance in the uplink of WCDMA with radio over
fibre access network” PlMRC 2002, Lisbon.
[2] Harri Holma, Toskala “WCDMA for UMTS radio Access for
the UMTS radio access for the third generation mobile
communications,” JOHN WILEY & SONS, LTD, 2000
[3]Theodore S.Rappaport.,“Wireless Communications Principles
and Practice”. Prentice Hall, 2000
Fig4.Eye Diagram for 64 psk [4] Holma, H., A. Toskala, “WCDMA for UMTS”. New York:
Wiley, eds. 2000.
[5] Affida M. Zin, Sevia M. Idrus, and Nadiatulhuda Zulkifli, “The
Characterization of Radio-over-Fiber Employed GPON
Architecture for Wireless Distribution Network”, International
Journal of Machine Learning and Computing, Vol. 1, No. 5,
December 2011
[6] M. A. Masud, M. Samsuzzaman, M. A.Rahman,” Bit Error
Rate Performance Analysis on Modulation Techniques of
Wideband Code Division Multiple’, Journal of
Telecommunications, volume 1, issue 2, March 2010
[7] Y.BhanupakashReddy, A.Alphones,”Asynchronous W-CDMA
Uplink Performance in Double Spread Cascaded RoF systems”,
ICICS-PCM, 15-18 Singapore 2003
[8] D.Opatic, "Radio over Fiber Technology for Wireless Access,"
Ericsson Zagreb, Technology2004 titution of Electrical Engineers,
Fig 5.scatter Plot for 64 psk London, 1995, pp 202-227.
[9] K.S. Ju, U.S. Goni' and A.M.D. Turkmani,” Comparative
Evaluation of the Performance of Anti-multipath Modulation
Techniques for Digital Mobile Radio Systems”, 1994 IEEE
[10] John A. C. Bingham, “Multicarrier Modulation for Data
Transmission: An Idea Whose Time Has come”, IEEE
Communications Magazine, Vol. 28, Issue 5, pp 5-14, 1990.
[11] G. C. Yang, W. C. Kwong, “Performance comparison of
multiwavelength CDMA and WCDMA+CDMA for fiber optic
Network”, IEEE Trans. Commun., vol. 45, pp. 1426, Nov.
1992
[12] D. K. Mynbaev, L. L. Scheiner, “Fiber-optic communications
technology”, Prentice-Hall Inc., New Jersey, USA, 2001
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All Rights Reserved © 2012 IJARCSEE

5. ISSN: 2277 – 9043
International Journal of Advanced Research in Computer Science and Electronics Engineering
Volume 1, Issue 4,June 2012
[13] Y. Luo et al., “Integrating Optical and Wireless Services in Convergence of Optical and Wireless Access Networks, vol. 25,
the Access Network,Proc. OFC/NFOEC, Anaheim, CA, Mar. 2006 no. 11, Nov. 2007, pp. 3428–42.
[14] L. G. Kazovsky et al., “Next-Generation Optical Access
Networks,”IEEE/OSA J. Light wave Tech., special issue on
Amanjot Kaur received the Bachelor’s
degree in E.C.E. from Yadavindra
College of Engineering, Talwandi .
Sabo, Bathinda, Punjab in 2010. She is
currently persuing Masters Degree in
Electronics and Communication
Engineering from Yadavindra College
of Engineering, Talwandi Sabo,
Bathinda, Punjab, under Punjabi
University Patiala. Her Research area
is Communication System.
Jasbir Singh is working as Assistant
Professor in E.C.E Dept., Yadavindra
College of Engineering, Talwandi
Sabo. He has done M.E. in Electronics
Product Design and Technology From
PEC, Chandigarh. His areas of interest
include Communication System and
Electronics Product Design. He has
published 4 papers in national
conferences.
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