A Comparison on Different Techniques for PAPR and BER Reduction in OFDM Communication Systems

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
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A Comparison on Different Techniques for PAPR and BER Reduction in
OFDM Communication Systems
Shristi Shukla1, Rishi Sharma2, D P Singh3
1 M Tech Scholar, Oriental Institute of Science and Technology, Bhopal, India
2 Asst. Professor, Electronics and Communication, OIST Bhopal, India
3 Asst. Professor, Electronics and Communication, OIST Bhopal, India
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Abstract - Orthogonal Frequency Division Multiplexing
(OFDM) is an environment friendly multicarrier modulation
scheme in wi-fi communication. It is used in functions like 4G
(fourth generation) cellular Communications, wi-fi networks,
digital television, electricity line networks and audio
Broadcasting. It gives each benefits and hazards for
multicarrier transmission. Themostimportantbenefitsarethe
removal of Inter Carrier Interference (ICI) and Inter Symbol
Interference (ISI) in the signal. But OFDM’s one of the most
important harmful componentsareexcessivePeak-to-Average
Power Ratio (PAPR) price of the transmitted sign which
relatively impacts the strength amplifiers complexity. Several
strategies to overcome and decrease PAPR such as Tone
Reservation (TR), selective mapping (SLM), clipping and
filtering, partial transmit sequence (PTS), etareproposed and
implemented. Detailed description and comparisons of all
methods are mentioned in this paper.
Key Words: PAPR; BER; PTS; OFDM; SLM;
1.INTRODUCTION
With extended demand for excessive first-rate verbal
exchange offerings in 4G and 5G, it’s been a top notch
undertaking to enhance the Quality of Service (QoS) and
reduces the extend time. To overcome and fulfil this
requirement, a method known as Orthogonal Frequency
Division Multiplexing(OFDM)isencountered.Itovervarious
outfalls like preserving excessiveinformationrate,excessive
bandwidth efficiency, low computational complexity and
casting off multipath fading [1].
OFDM is a unique case of thefrequencydivisionmultiplexing
(FDM), which is used with the aid of the American National
Defense Department for navy communications. Compared
with the traditional FDM, OFDM lets in the spectrums from
exclusive subcarriers that are orthogonal to be overlapped
with every other, which improves the spectral effectivity of
the system. The idea of OFDM methods used to be first
proposed by using RW Chang in 1965. In 1967, Saltcberg
analyced the overall performanceofOFDMsystems.In1970,
OFDM science was once patented at the USPD and then after
it was once used in navy verbal exchange systems. In 1971,
SB Weinstern and PM Ebert employed the Discrete Fourier
Transform (DFT) into the MCM. in practice, the Fast Fourier
Transform (FFT) implementation of the DFT has made
OFDM modulation and demodulation possible and very
successful. In the 1980s,ISI wasoncediminishedwhenPeled
and Ruic delivered cyclic prefix (CP) into the simple OFDM
indicators to have the orthogonality renovation amongst
subcarriers [2].
The demand for information transmission in cellular
conversation has improved consistently. OFDM device has
won pastime in the fourth-generation cell conversation due
to its potential to grant excessive bandwidth effectivity and
excessive information price in each digital audio and video
broadcasting wi-fi communication.
The fundamental precept of OFDM is to cut up a high-data
charge circulate into a variety of decrease statistics price
streams in parallel the use of a number of orthogonal
subcarriers. When the subcarriers have excellent spacing
and fulfill the orthogonality, their spectra will overlap
[1,2,3]. The use of orthogonal subcarriers allowed the
subcarrier’s spectra to overlap, as a consequence growing
the spectral efficiency. As lengthy as orthogonality is
maintained, it is feasible to recover the man or woman
subcarriers’ sign notwithstandingtheiroverlappingspectrIf
the product of two deterministic alerts is equal tozero,these
indicators are stated to be orthogonal to every different [1].
OFDM affords many blessings over service modulation;
however, the principal situation with the scheme is the
excessive peak-to-average strength ratio (PAPR) that
distorts the sign if the transmitter includes nonlinearfactors
such as electricity amplifier, influences the sign and
consequences in the attenuation of the acquired sign [4].
The excessive PAPR of OFDM potential that if the signisnow
not to be distorted, many of the factors in the transmitter
and receiver need to have a broad dynamic range. The
output amplifier of the transmitter should be very linear
over a broad vary of sign levels. In wi-fi system,thepriceand
energy consumption of these amplifiers are frequently the
vital layout constraints [5, 6]. Moreover, the presence of a
giant wide variety of subcarriers with various amplitude
effects in excessive peak-to-average energy ratio of the
device (OFDM) and has implication in the effectivity of the
radio frequency amplifier. This degrades the bit error fee
and will increase the fee of the system.

To reply to the abovementioned problems, distinctive
techniques andmethodshavebeenproposedvia researchers
such as coding techniques, tone injection, filtering,
oversampling and a couple of sign representation. The
fundamental cause of this find out about is to endorse
methods for the reduction of peak-to-averageenergyratio in
OFDM device with emphasis on 4G network. In this paper,
two methods are proposed to clear up the hassle discovered
when the usage of the OFDM system: the height windowing
and the clipping techniques.
2. OFDM AND PAPR
2.1 OFDM system
Orthogonal frequency division multiplexing (OFDM) is a
most environment friendly and broadly used multiplexing
and modulation science for 4G and 5G telecommunications
requirements which consists of digital radio broadcasting,
digital terrestrial tv (DTT), wi-fi neighborhood region
networks (LANs), et OFDM structures consist of two
components the transmitter aspect and the receiver aspect
[3].
OFDM transceiver
The integral precept of OFDM is to break up the reachable
bandwidth into more than one sub-carriers. As the quantity
of subcarriers increases, it receives extra immune to
frequency selectivefading,andstatisticsfeesareadditionally
increasing. However, quantity of sub-carriers can't be
extended arbitrarily due to the fact it will increase the
complicated structure of the machine and image intervals
that make transmission extra touchytothetimeincoherence
of the channel.
The hassle of the complicated plan of the gadget used to be
treated via Weinstein and Ebert with the implementation of
OFDM modulation through Inverse Discrete Fourier
Transform (IDFT) and demodulation by means of Discrete
Fourier Transform (DFT). To illustrate this considers one
OFDM image with N one-of-a-kindsubcarriersandanticipate
that s(t) is sampled at each time interval Ts=N (Figure 1).
Fig -1: OFDM Modulation block diagram
OFDM machine transmitter
The incoming serial facts is the data that wishes to be
transmitted thru the channel the use of OFDM system. The
serial records is transformed into N special parallel records
streams with the aid of the use of serial to parallel converter.
These symbols can be modulated with the aid of the use of
extraordinary modulation strategies and given to the IFFT
block as an enter [3].
IFFT block offers the digital time area sign for the given
input, and this parallel informationistransformedintoserial
records by using the usage of parallel toserial converter.The
cyclic prefix is added between two OFDM symbols to cancel
the impact of ISI due to channel dispersion. Now this digital
time sign is transformed into actual time waveform with the
use of digital to analog converters. The accessible baseband
sign is up transformed to an RF ignore band sign with the
use of a mixer or modulators.
Channel model
The phenomenon of noise and multipath surroundings can
be expected by means of the use of channel model.
Generation of noise can be carried out by way of including
few random information to the OFDM image and multipath
surroundings canbegeneratedthroughincludingattenuated
and delayed copies of the OFDM signal.
OFDM receiver
At the receiver end, the acquired OFDM signal is down
transformed the use of the demodulator and sampled with
analog-to-digital converters to acquire the digital time area
signal. The digital time area sign is demodulated bymeans of
the usage of FFT, and the records that is transmitted can be
extracted via the use of image demapper [4] (Figure 2).
Fig- 2: OFDM System receiver.
Characteristics
OFDM has quite a few facets which entice builders to plan a
number preferred applications. Even OFDM reveals severa
benefits over the household of traditional serial modem
schemes which are as follows:
A. Implementation complexity: The complexity is
considerably decrease evaluatingtothesingleservicegadget
for a unique extend spread.
B. Robustness in oppositiontoslimbandinterference:An
interferer can smash the conversation hyperlink in single
service whilst a small quantity of sub providergetaffected in
multicarrier.

C. Spectral efficiency: The conduct of orthogonality
accommodated a massive wide variety of sub provider in a
very slender spectral place therefore will increase the
spectral efficiency.
D. Immunity in opposition to frequency selective fading:
Each subcarrier has slim bandwidth in evaluation to usual
bandwidth of the signal. It converts a frequency selective
fading channel into a number of almost flat fading channels.
2.2 PAPR
The transmitted sign of OFDM famous a excessive height
strength when brought in the equal section at IFFT. When
these indicators excite the nonlinear traits of the HPA, it
motives out-of-band radiation, whichinadditiondistortsthe
indicators in adjoining bands and its regions. This excessive
height energy reduces the effectivity of HPA and degrades
the overall performance of the OFDM system. To estimate
the distortion which is brought on with the aid of
nonlinearity, a commonplace parameter used is PAPR.
The PAPR of OFDM non-stop time baseband transmitted
sign x(t) is represented as the ratio of maximum on the spot
strength to common power. Its equation is:
The important consequences of excessive PAPR are
A. Increased complexity in the ADC and DA
B. Reduced effectivity of RF (radio frequency) amplifiers[5].
3. RELATED WORK
To come out with a suitable reduction in PAPR, researchers
proposed the recursive Golay complementary sequence [7]
and the consequences confirmed that the PAPR of the
sequence is bounded up to 3.6 dB and the records price is
bounded up to 3.6 d The writer of [8] proposed a PAPR
reduction technique with low computation complexity
primarily based on a mixture of cuckoo search optimization
algorithm with top windowing scheme in OFDM system. In
[9], the writer proposed that new segmentation schemes to
beautify the PAPR mitigation overall performance of the top
windowing algorithm remember upon the range of
partitioned sub-blocks, the variety of the segment rotation
vectors, and the form of the segmentation scheme utilized.
The consequences show that the PAPR values at the
complementary cumulative distribution characteristic
(CCDF) 10−3 are 10.96 dB for unique OFDM, 7.62 dB for
random search algorithm, 7.45 dB for PSO algorithm, 6.8 dB
for cuckoo search algorithm and 6.37 dB for foremost
algorithm.
A systematic evaluation of specific PAPR reduction
techniques in OFDM structures was once carried out [10].
The lookup proposed easy methods for the reduction of
excessive peak-to-average energy ratio based totally on
clipping and differential scaling, in orthogonal frequency
division multiplexing (OFDM). The proposed up- and
downscaling strategies had been to acquire PAPR reduction
of the order of 8.5 dB from 12 dB PAPR initially. A reduction
of 3.5 dB was once done for PAPR when keepingthebiterror
price (BER) inside a margin of three instances the BER price
at the overall performance certain at signal-to-noise ratio
(SNR) of 10 d The overall performance contrast of two
clipping-based filtering strategies for PAPR reduction in
OFDM sign [11] was once proposed to remedy theimportant
universal trouble of OFDM strategies which is excessive
peak-to-average electricity ratio describedastheratioof the
top energy to the common strength of the OFDM sign [12].
To remedy the predominant hassle in OFDM, the excessive
peak-to-average energy ratio, the usage of windowing
approach and to enhance the BER, the approach proposed is
Kaiser and Hamming which makes use of cumulative
distribution function.Theendresultsimulationsuggeststhat
Hamming and Kaiser have a lot of variations on the equal
spectrum attribute [13]: in Hamming windowing technique,
at normalized frequencies − 1 and 0.9989 MHz, the spectral
densities are − 81.5 and − 46.05; in Kaiser windowing
technique, at normalized frequencies − 2 and 1.998, the
spectral densities are − 81.5 and−46.05.Theenergyspectral
frequency is equal for one of a kind normalized frequency
however they are equal for most value.
To the research, one-of-a-kind literature and work has been
reviewed. Lee & Kim [6], proposed scheme makes use of
clipping operation to acquire more suitable PAPR reduction
of OFDM signals. Since the top regrowth of sign is mitigated
via adaptively enhancing the CT, the proposed scheme can
efficiently decorate the PAPR reductionoverall performance
and additionally decrease the quantity of iterations. Wang&
Luo [7] investigates.
A convex optimization approachtodynamicallyregulatethe
filter response in an ICF manner which limit the PAPR of
OFDM symbols. Also, in March 2011 creator Jeon [8] used
the similarity amongst the required indicators generated in
PTS to advance a new algorithm which achieves low
computational complexity in contrast to that of a traditional
PTS algorithm.
Chen Ye [9], developed a modified SLM scheme with
decreased complexity for lowering PAPR is proposed. This
scheme performs the addition of mapped sign sequences to
OFDM sign sequences. Li & Wang [10], proposed two low-
complexity SLM schemes. Although the proposed
architectures have positivePAPRoverall performancelosses
when in contrast to the common SLM scheme however have
decrease complexities and their BER performances are
precisely the equal as the standard SLM scheme.
4. CONCLUSION
In this paper, we have analyzed and in contrast eight PAPR
reduction techniques. Among above analyzed techniques, it

was once discovered out that from existing methods no
method is totally positive in reduction of PAPR and is the
first-rate for the OFDM system. As earlier than deciding on
the splendid PAPR technique,a numberofdifferent elements
like preserving records rate, computational complexity,BER,
sign strength have to additionally be taken into
acknowledgement. So, it is recommended to recommend
height to common energy ratio (PAPR) reduction scheme
and sketch a network/model assisting it for OFDM
structures after evaluating present traditional methods.
Table I Comparison of PAPR and BER Reduction Techniques [1].
REDUCTION TECHNIQUES MERITS DEMERITS
1
Clipping and filtering
This is the easiest method used for a PAPR reduction
[12,13]. In this method the amplitude of the enter sign
is frozen to a specific valu Supposex[n]signifytheenter
signal, and the clipped model of x[n] is denoted by way
of xc[n], so expression is described as: Where, A is the
clipping level
This is a Simple approach.
Have excessive PAPR
reduction capability.
No facet facts is require
No alternate at receiver side
Introduce greater distortion.
Degrade BER performance
2
Coding
In the coding technique, some code phrases are used to
reduce or limit the PAPR of the signal. It does no longer
motive any distortion and no out-of-band radiation
production, [1] however it has a downsideofdecreased
bandwidth effectivity as the informationpriceisreduce
It additionally suffersfromcomplexityissues,duetothe
fact it requires giant reminiscence for discovering the
fantastic codes and to save massive look up tables, in
particular for a massive quantity of subcarriers [1,14].
Have much less distortion.
High PAPR reduction
capability.
No aspect facts is require
The complexity is very high.
Data price loss.
Require change in each Tx
and Rx.
3
Active constellation extension (ACE)
In ACE, for decreasing PAPR in a specific block, some
outer sign constellation factors in every block are
prolonged outdoor of the constellation [15].
It is obvious to receiver.
There is no loss of statistics rat
No facet statistics is require
Less distortion of theauthentic
signal.
Require addition operations
after FFT operation in
receiver.
4
Tone reservation (TR)
TR works by way of reserving a few tones inside the
transmitted bandwidth and assign them terrific values
[14].
No distortion is added to the
records bearing tones
No facet records is require
Increase in the common
electricity per bit, which
would possibly limit the BER
overall performance
improvement.
Loss of spectral effectivity
due to tone reservation.
5
Selected mapping (SLM)
In SLM, from the unique information block numerous
candidate statistics blocks are generated and the one
with lowest PAPR is transmitte At the receiver the
reverse operation is carried out to get better the
authentic statistics block [15,16].
No distortion is introduce
Independent of number of
carriers.
Side information is require
Degrade BER performanc

6
Partial transmit sequences (PTS)
The authentic records block i s partitioned into V
disjoint sub blocks. The subcarriers current in every of
these sub blocks are turned around by way of the equal
section factor, so the PAPR of the mixture is minimize
Also, the reverse operation is carried out at the
receiver, to get better the authentic information block
[17-19].
Less distortion is introduce
Less complex.
Side data is require
Degrade BER performanc
Involve complicated vector
sums at Tx.
7
Companding
In Companding technique, we make bigger the small
indicators whilst compressing the giant alerts so that
the immunity of small alerts from noise will increas
This compression is carried out at the transmitter stop
after the output is taken from IFFT block. Compression
of the sign reduces excessive peaks, sointhiswayPAPR
reduction of enter sign takes region [20].
Less distortion is introduce
Loss of statistics rate
8
Tone injection (TI)
The TI technique, simple concept is to enlarge the
constellation dimension so every factor current in the
authentic constellation ought to be mapped into more
than a few equal points. In an authentic constellation
point, the equal constellation factors are brought so
PAPR reduce The calculation of the sub-carrier time
area alerts additionally offers reduced PAPR [20].
No statistics charge loss.
Require modulo-D addition,
after an FFT operation in the
receiver.
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