Improving The Spectral Efficiency
Improving The Spectral Efficiency
Improving The Spectral Efficiency
Reyaz Ahmed
Abstract- The current research trends towards mobile System has been designed which imposes the RRC
broadband communications highly focused on mitigating the filter mechanism to improve the signal to noise ratio [3]
power spectral analysis and frequency localization issues [4]. The proposed method also ensures a better signal
associated with Orthogonal Frequency Division Multiplexing
namely OFDM signals. There are various existing research quality in the receiver end where the proposed f-OFDM
works have been found ensure less efficient communications achieves bandwidth utilization regarding frequency
strategies. Therefore to address various interference problems localization and considering inter-symbol interference
during transmission data filter, OFDM has been and inters carrier inference within an acceptable limit.
conceptualized and implemented. Most of the f-OFDM The proposed model also has been designed to establish a
techniques have been designed without coding. The proposed secure and efficient wireless communication to provide
study aims to develop a higher order modulations e.g.
QAM/PSK based filtered OFDM system to mitigate the inter-
30 to 40 megabits per sec data in a wireless medium
symbol interference issues of channel properties. The [5][6]. In this pr5posed study an RRC filter oriented
proposed system has been configured and simulated in a real- OFDM model has been designed and implemented
time test bed (Matlab). The proposed system uses Root Raised where, the design specification of RRC filters highlights
Cosine (RRC) filter design specification and it also integrated that it can be integrated with the OFDM system to limit
the filter modules in the transmitter and the receiver side. The the Inter symbol Interference (ISI). However, the
experimental outcomes of the proposed system show that it
achieves very higher signal quality on less amount of bit error proposed model also constructs a spectrally-localized
rates and the huge amount of power spectral density at the multicarrier waveform which achieves very active signal
receiver end. It also achieves a high data transfer rate, well to noise ratio and better spectral density of the signal at
utilization of bandwidth as well as frequency localization the receiver end. Therefore, the use of RRC filter in the
factors as compared to the conventional OFDM models. proposed model minimizes the bit error rate and enhances
Index Terms - Filtered Orthogonal Frequency Dvision the spectral density of the received signal. It can also be
Multiplexing (f-OFDM); Root Raised Cosine (RRC)Filter ,
PSK(Phase Shift Keying) , Frequency Localization.
seen that the proposed model reduces the occurrence of
Inter symbol interference and inter-carrier interference
I. INTRODUCTION during the signal transmission through a channel. The
performance evaluation of the proposed model has been
The mobile broad band communications services require evaluated considering the signal to noise ratio and the
a very efficient and fast data transfer technology therefore in computation of bit error rate (BER).
order to enhance the broadband communications in terms of The current research trends focused on minimizing
high speed, interoperable and secured access of microwave the bit error rate and enhancing the spectral efficiency
channels various existing state of art studies have been associated with an OFDM Signal. The proposed study
introduced[1]. aims to design a novel filtered OFDM namely f-OFDM
The existing state of art studies towards wireless system for channel interference avoidance. It also
communication standards highlights that most of the current considers the concept of IFFT and FFT in the transmitter
multicarrier modulation techniques use higher order and receiver end for performing data encryption and
orthogonal frequency division multiplexing (OFDM) decryption respectively. The proposed system achieves
scheme which widely used like a multi-carrier modulation. an efficient signal quality with very less amount of bit
In the recent times, the concept of the filter based OFDM error rate and very less amount of computational cost.
namely f-OFDM is gaining popularity, where a specific The performance analysis of the proposed system
filter is designed considering higher order filter length to shows the output signal spectrum contains more power
exceed the cyclic prefix such as Root-raised-cosine(RRC) spectral density as compare to conventional OFDM
based OFDM[2]. Filtered OFDM is conceptualized to communications systems.
enhance the broadband communications regarding high- The paper is organized as follows Section II
speed, interoperable and secure access to microwave discusses about the recent studies towards efficient filtered
channels. In this project, an efficient filtered based OFDM OFDM communication systems which is followed by
problem statement in Section III. Section IV discusses
about proposed system followed by discussion of algorithm
implementation in Section V. Section VI discusses about
the result analysis followed by conclusion in Section VII.
Reyaz Ahmed, Department of Electronics and Communication, S.E.A
College of Engineering and Technology, Bengaluru, India.
45 www.ijntr.org
Improving the Spectral Efficiency of OFDM System Using Raised Cosine Filter
II. RELATED WORK explored and simulated over a real-time test bed. The
proposed system also compared with the experimental
This section introduces various states of art studies
outcomes of Nyquist sampled, the two over inspected
towards efficient higher order multi-carrier f-OFDM-based
signal had a superior execution in diminishing PAPR. The
modulation schemes for achieving high data transfer rate
bit blunder rate (BER) mistake stream research had been
and greater spectral efficiency of the received signal. The
finished with transmitting the cut sign in nonlinear twisted
followings are the existing research trends in wireless
ROF join. Also, the QAM had been affirmed for the favored
communication and multicarrier modulation.
procedure in OFDM-ROF links.
The study of Li et al. [7] introduced a novel DSP-
Kim et al. [11] designed a channel and-forward
based SSBI alleviation strategy, with lower intricacy than
(FF) hand-off for orthogonal recurrence division
already proposed policies, is proposed and surveyed through
multiplexing (OFDM) transmission frameworks is
mathematical recreations surprisingly. The execution
considered for enhancing context execution over
change is measured by reproductions of 9 × 112 Gb/s 16-
straightforward increase and-forward (AF) handing-off. Not
QAM SSB-OFDM signal with a net optical ISD of 2.1
at all like customary OFDM have transfers performing
(b/s)/Hz. The execution is appeared to be like that of the
OFDM demodulation and modulation, to lessen preparing
more mind-boggling collector based iterative SSBI pay
multifaceted nature, the proposed FF hand-off correctly
procedure. Recreations foresee an 8.7 dB decrease in the
channeled the approaching sign in the time area with a
required OSNR at the 7% overhead HD-FEC edge, and
limited drive reaction (FIR) and advances the separated sign
increments up to 100% in greatest scope over
to the destination. Three configuration criteria are
uncompensated standard single-mode fiber utilizing the
considered for improving the hand-off channel. The primary
proposed rearranged SSBI pay strategy.
model is the minimization of the transfer transmits power
Lee and Yoo [8] presented a polyphase sifted
subject to per-subcarrier sign to-clamor proportion (SNR)
orthogonal recurrence division multiplexing (PF-OFDM)
requirements, the second rule is the expansion of the most
The proposed structure uses a changed discrete Fourier
exceedingly bad subcarrier channel SNR subject to source
change trans-multiplexer to accomplish more prominent
and hand-off transmits power limitations, and the third
phantom productivity than an OFDM framework while
paradigm is the amplification of the information rate subject
saving in reverse similarity with it. The model PF-OFDM
to source and hand-off transmits power imperatives.
channel has phenomenal time and recurrence restriction
A clipping and filtering technology for OFDM
properties, which make it conceivable to kill a gatekeeper
systems has been studied and simulated in the work of
interim and effortlessly smother interchannel obstruction.
Wang et al [12] where the radio over fiber system has been
In the study of Gutman et al. [9] introduced three
demonstrated to the best contender for the remote access
noteworthy execution criteria of the framework: (i) power
innovation, and the orthogonal recurrence division
productivity of the PA, (ii) otherworldly virtue of the
multiplexing (OFDM) strategy has been acknowledged as
transmitted sign communicated by neighboring channel
the center transmitting innovation, so the OFDM-ROF
obstruction, and (iii) transmission execution demonstrated
system is the interesting issue in the global the educated
by shared data or image blunder rate. So as to satisfy the
community. An OFDM-ROF framework reenactment model
initial two criteria, it is proposed to utilize iterative cutting
basing on IEEE 802.16a physical layer convention had been
and sifting (ICF) at the transmitter together with low
developed. Unique consideration had been paid on the high
contribution back-off while the third rule is acquired by an
peak-to-average power proportion (PAPR) of the OFDM
adjusted iterative recipient (MIR). The proposed MIR
signal which significantly compelled the execution of the
depends on the evidently understood iterative beneficiary,
OFDM-ROF framework.
yet with ICF in the input way. They got results and
Chini et al. [13] presented a use of a sifted choice
demonstrated that the proposed framework is superior to
condemnation channel estimator for OFDM-based DTV
anything its rivals while considering the three execution
frameworks utilizing big request QAM tweaks. The
criteria together. The investigation and results are centered
execution and the execution of the channel estimator are
on OFDM; be that as it may happen that, the proposed
examined. PC reproductions were directed to assess the
methodology might be connected to a single carrier.
implementation of the channel estimator. The channel
In the study of Wang et al. [10] a radio-over-
estimation misfortune is around 1.2 dB from the perfect
fiber(ROF) system has been demonstrated to the best
situation where the channel is thought to be known by the
contender for the remote access innovation, and the
recipient. For a given multipath spread, the misfortune can
orthogonal recurrence division multiplexing (OFDM)
be further diminished by expanding the FFT size. The FFT
procedure has been acknowledged as the center transmitting
size is, however, subject to the furthest point of confinement
change, so the OFDM-ROF system is the intriguing issue in
forced by the Doppler spread.
the worldwide the educated community. An OFDM-ROF
Li et al. [14] investigated, through broad PC recreations, the
framework reenactment model basing on IEEE 802.16a
impacts of section and sifting on the execution of OFDM,
physical layer convention had been developed.
including the force unearthly thickness, the peak variable,
Extraordinary consideration had been paid on the high top
and the bit-mistake rate. Our outcomes demonstrate that cut-
to-normal force proportion (PAPR) of the OFDM signal
out and separating is a promising strategy for the
which incredibly obliged the execution of the OFDM-ROF
transmission of OFDM signs utilizing practical straight
framework. A cut-out and sifting innovation had been
enhancers.
46 www.ijntr.org
International Journal of New Technology and Research (IJNTR)
ISSN: 2454-4116, Volume-2, Issue-6, June 2016 Pages 45-51
The proposed system also computes the impulse response
III. PROBLEM STATEMENT associated with the f-OFDM spectrum and it also filters the
modulated data for maximizing the SNR and to minimize
The previous section introduced various existing studies
the BER.
towards efficient broadband communication techniques
using higher order sub carrier modulation techniques. B. f-OFDM Signal Transmission Module:
Accuracy, in order to compute Bit Error Rate and In this module, it has been shown that when a
denoising the OFDM, transmitted Signal in receiver end modulated signal is transmitting through channel thus noise
has become one of the recent issues in the field of Signal is bound to come for the purpose of this project the
Processing and Communications. Lack of proper Gaussian noise has been computed and added to the signal
analysis associated with various higher order modulations during the transmission phase over a wireless channel.
schemes such as (QAM/PSK) creates a very problematic
scenario during the computation of bit error rates and C. f-OFDM Receiver (Rx) Module:
Signal to Noise Ratio (SNR) regarding various channel In the f-OFDM receiver module the modulated signal
condition scenarios and channel correlation factors. It has is received and unfiltered the modulated data after that the
a great impact on the spectral estimation of Digital reverse process which has been performed in the transmitter
Signals. The high-speed data access in a multi-user model as mentioned above module has been evaluated to reshape
for transmitting data simultaneously over different and retrieve the original image. Here the received
subcarriers using different types of modulation modulated and a noisy signal is first processing through
techniques (QAM/PSK) results in allocative inefficiency, ODFM and QAM demodulation respectively after that it
handover latency, frequency selective fading, and passes through a vertibri decoder for reshaping. The original
frequency flat fading, etc. image is received at the receiver side.
47 www.ijntr.org
Improving the Spectral Efficiency of OFDM System Using Raised Cosine Filter
V. SYSTEM ARCHITECTURE
PSK/QAM Mod
Tx Message
IFFT/Data Encryption
OFDM Modulation
RRC-Filter
Compute BER Channel
RRC-Filter
OFDM Demodulation FFT/Data Decryption
QAM/PSK
Demondulation
Rx Message
The stated figure 1 shows the system architecture of the the receiver end while increasing the SNR values. The
proposed f-OFDM model to perform an efficient and fast performance metrics shows the effectiveness of the
wireless broadband communication. The proposed model proposed system.
has been designed with four different types of sub modules
1. f-OFDM Transmitter Module 2. f-OFDM receiver VI. IMPLEMENTATION
module 3. Signal transmission through channel and 4.
The implementation of the proposed system has been
Computation of Bit Error Rate. The above-stated figure also
carried out using MATLAB,
shows how an image has been transmitted through a
This project aims to develop a scalable and faster higher
wireless medium using OFDM/QAM Modulation and
order subcarrier modulation and RRC filter based OFDM
Demodulation. The proposed system also computes the
system for achieving high spectral efficiency and high data
Signal to noise ratio (SNR) and BER in order to evaluate the
transmission rate in the wireless communication medium. In
performance graph. The input image is converted into
this project, a higher order modulation such as QAM/PSK,
binary data representation and process through convolution
OFDM, and RRC filter based communication system is
encoding. However, before performing the convolution
prototyped and simulated considering MATLAB test bed
encoding parallel to serial conversion of the binary data is
environment. The proposed model is designed using three
evaluated. Quadrature Amplitude Modulation (QAM) is
different types of modules which are
conducted on the binary data, and it generates another bits
1. f-OFDM transmitter module
representation of the signal which is again further processed
2. f-OFDM Channel and
through the OFDM modulation, after that the signal is dealt
3. f-OFDM receiver module
with by an RRC filtered for filtering modulated data.
The modules as mentioned above are simulated over a real-
Finally, the OFDM modulated signal is transmitted over the
time test bed where the Matlab tool has been considered for
wireless communication medium, during the transmission
integrating different modules. The design specifications and
through the channel the signal gets affected by the presence
the implementation strategies associated with each and
of Gaussian noise. The proposed model can detect and
every module components are discussed below.
compute the presence of Gaussian noise in an OFDM signal
whereas at the receiver end the modulated signal is again
f-OFDM Transmitter (Tx) Module
preprocessed with the filter and demodulation (QAM and
The proposed f-OFDM model enables the concept of
OFDM) then a decoder is used to perform the decoding of
Orthogonal Frequency Division Multiplexing as well as
the received information which is further reshaped to
Orthogonal Frequency Division Multiple Access
retrieve the noisy image at the receiver end. The proposed
mechanism. In the transmission module Message of the
system utilizes a concept of reducing the bit error rates at
OFDM signal to be transmitted over a wireless channel is
48 www.ijntr.org
International Journal of New Technology and Research (IJNTR)
ISSN: 2454-4116, Volume-2, Issue-6, June 2016 Pages 45-51
various low pass, filters have been integrated where the use
of raised-cosine filter gained most of the attention. Usually, RRC Filter
The raised cosine filters satisfy the Nyquist equation and Signal Tranmission
signal and enhance the signal to a ratio (SNR) with respect RRC Filter
In T T T T
Reshape Image
49 www.ijntr.org
Improving the Spectral Efficiency of OFDM System Using Raised Cosine Filter
50 www.ijntr.org
International Journal of New Technology and Research (IJNTR)
ISSN: 2454-4116, Volume-2, Issue-6, June 2016 Pages 45-51
IX. ACKNOWLEDGMENT
I am greatly indebted to our guide and Head of the
Department Mr. Pradeep Kumar N.S Associate Professor,
Department of Electronics and Communication,
S.E.A.C.E.T Bengaluru for his valuable suggestions,
guidance, moral support and encouragement in completion
of this project successfully. I have been fortune for having
his precious help.
X. REFERENCES
[1] V. Vakilian, T. Wild, F. Schaich, S. Ten Brink, and J.-F. Frigon,
“Universal-filtered multi-carrier technique for wireless systems
beyond LTE,” in IEEE Globecom Workshops (GC Wkshps), 2013,
pp. 223–228.
[2] T. Wild, F. Schaich, and Y. Chen, “5G air interface design based on
universal filtered (UF ) OFDM,” in Int. Conf. Dig. Sig. Proc. (DSP),
2014, pp. 699–704.
[3] 5G: A Technology Vision, Huawei Technologies Co., Ltd., Nov.
2013. [Online]. Available: www.huawei.com/ilink/en/download/HW
314849
[4] B. Le Floch, M. Alard, and C. Berrou, “Coded orthogonal frequency
division multiplex [TV broadcasting],” Proc. of the IEEE, vol. 83,
no. 6, pp. 982–996, 1995.
[5] M. Bellanger et al., “FBMC physical layer: a primer,” PHYDYAS,
January, 2010.
[6] M. J. Abdoli, M. Jia, and J. Ma, “Weighted circularly convolved
filtering in OFDM/OQAM,” in IEEE Int. Symp. Personal Ind. and
Mobi. Rad. Comm. (PIMRC), 2013, pp. 657–661.
[7] Li, Z., Erkılınç, M.S., Bouziane, R., Thomsen, B.C., Bayvel, P. and
Killey, R.I., 2016. Simplified DSP-Based Signal–Signal Beat
Interference Mitigation Technique for Direct Detection OFDM.
Journal of Lightwave Technology, 34(3), pp.866-872.
[8] Lee, C.S. and Yoo, K.Y., 2004. Polyphase filtered OFDM
transmission system. Electronics Letters, 40(11), p.1.
[9] Levitan, G., Levitan and Gutman, 1996. Virtual personal channel in
a television system. U.S. Patent 5,534,911.
[10] Wang, J., Zhou, X., Xu, Y. and Wang, W., 2008. Performance
improvement of OFDM-ROF system with clipping and filtering
technique. Consumer Electronics, IEEE Transactions on, 54(2),
pp.296-299.
[11] Kim, D., Seo, J. and Sung, Y., 2013. Filter-and-forward transparent
relay design for OFDM systems. Vehicular Technology, IEEE
Transactions on, 62(9), pp.4392-4407.
[12] Wang, J., Zhou, X., Xu, Y. and Wang, W., 2008. Performance
improvement of OFDM-ROF system with clipping and filtering
technique. Consumer Electronics, IEEE Transactions on, 54(2),
pp.296-299.
[13] Chini, A., Wu, Y., El-Tanany, M. and Mahmoud, S., 1998. Filtered
decision feedback channel estimation for OFDM-based DTV
terrestrial broadcasting system. Broadcasting, IEEE Transactions
on, 44(1), pp.2-11.
[14] Li, X. and Cimini Jr, L.J., 1997, May. Effects of clipping and
filtering on the performance of OFDM. In Vehicular Technology
Conference, 1997, IEEE 47th (Vol. 3, pp. 1634-1638). IEEE.
Reyaz Ahmed
M.Tech final Semester Student, In Digital
Communication and Networking from 2013-
2016 in SEA College of Engineering and
Technology Bengaluru, having completed
B.E in Electronics and Communications in
2013 from SEA College of Engineering and
Technology Bengaluru. As per VTU M.Tech
academics, have been industrially trained for
4 months on Web application during the year
2015 at Accent Tech Solutions Pvt. Ltd.
Bengaluru India.
51 www.ijntr.org