This document summarizes a research paper that proposes a scheme for image transmission over OFDM systems using LDPC coding and trigonometric transforms. It aims to improve OFDM performance by reducing peak-to-average power ratio (PAPR) and enhancing image quality. The scheme uses SPIHT for image source coding, BPSK modulation, and inserts DCT or DST transforms after IFFT. Simulation results show the DST transform most effectively reduces PAPR compared to DCT. Reconstructed images also have improved visual quality with DST. The scheme thus enhances OFDM systems for image transmission applications.

1. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 3, March (2014), pp. 01-07 © IAEME
1
PERFORMANCE EVALUATION AND IMAGE TRANSMISSION OVER
OFDM SYSTEM
Nasheet Fatima Sukanya A Kulkarni
EXTC Department, EXTC Department,
Sardar Patel Institute of Technology, Sardar Patel Institute of Technology,
Andheri West, Mumbai Andheri West, Mumbai
ABSTRACT
In this paper a scheme is proposed for image transmission over Orthogonal Frequency
Division Multiplexing (OFDM) systems using LDPC.As High PAPR overcomes the advantages of
OFDM so Trigonometric transforms are used in this scheme for improving the performance of the
OFDM systems by reducing the Peak to Average Power Ratio (PAPR) of OFDM signal. SPIHT is
used for source coding of images to be transmitted. Then, the transmitted data of each parallel
subchannel is modulated by Binary phase Shift Keying (BPSK) modulation because it provides high
throughput and best performance when combined with the OFDM. Finally, the modulated data are
fed into an IFFT circuit, such that the OFDM signal is generated.In the proposed scheme the transmit
data sequence of the OFDM signal after Inverse Fast Fourier Transform (lFFT) is grouped into in-
phase and in-quadrature components, then each component is transformed using either the Discrete
Cosine Transform (DCT) or the Discrete Sine Transform (DST). The simulation results show that
adding the DST to the system reduces the PAPR of OFDM signal more than the DCT. which The
simulation results show that adding the DST to the system improves the visual quality of
reconstructed image.
Keywords: OFDM, PAPR, SPIHT, Trignometric Transforms.
1. INTRODUCTION
1.1 OFDM
Orthogonal frequency division Multiplexing (OFDM) has a promising future as a new
modulation scheme in many next generation wireless communication systems due to its several
significant advantages [2]:
INTERNATIONAL JOURNAL OF ELECTRONICS AND
COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)
ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
Volume 5, Issue 3, March (2014), pp. 01-07
© IAEME: www.iaeme.com/ijecet.asp
Journal Impact Factor (2014): 7.2836 (Calculated by GISI)
www.jifactor.com
IJECET
© I A E M E

2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 3, March (2014), pp. 01-07 © IAEME
2
1. Robust to multipath fading, intersymbol interference, cochannel interference and impulsive
parasitic noise.
2. Lower implementation complexity than the single carrier solution.
3. High bandwidth efficiency
The main disadvantage of OFDM is its large PAPR. When N signals are added with the same
phase they produce a peak power which is N times the average power. The large peaks at the
transmitter occasionally force its amplifier into saturation and result in signal distortion and hence
lead to degradation in the system performance. High PAPR requires [4] a linear High Power
Amplifier otherwise nonlinear signal distortion occurs and leads to high adjacent channel
interference and poor system performance. HPA requires large back off from the peak power to
reduce the distortion caused by the nonlinearity of HPA and these results in low power efficiency.
High PAPR also causes sophistication of analog to digital converter (ADC) and digital to analog
converter (DAC).Thus reduction of PAPR is very crucial in OFDM systems.
1.1.1 PAPR
In OFDM systems, total bandwidth is divided into many overlapping orthogonal sub
channels, which are transmitted in parallel synchronously[2].
Let A=[A0 A1…..AN-1]T
denote an input symbol vector in frequency domain, where Ak is
complex data of the kth
subcarrier and N is the number of subcarriers. The OFDM signal is generated
by summing all the N modulated subcarrriers each of which is separated by 1/NTs in the frequency
domain. Here Ts is OFDM symbol duration.
A continuous time OFDM signal is represented as
(1)
A Discrete time OFDM signal obtained by sampling above signal at Nyquist rate is
represented as
(2)
However, the main concept of orthogonality comes from the linear relationship between IFFT
and FFT which have been implemented in transmitter and receiver, respectively. Jones goes on to
say, "By the use of the Fast Fourier Transform (FFT) algorithm, it can be better because it allows
precise control of all those multiple simultaneous frequencies (carriers) used to simultaneously carry
many data bits in parallel on different frequencies."
1.1.2 APPLICATIONS
OFDM is a promising modulation technique that is considered for adoption by 4G
community to provide 10-20 Mbps and at least 2 Mbps in the moving vehicles. Presently OFDM is
applied in Digital Television Broadcasting, European digital audio Broadcasting (DAB) and Digital
Video Broadcasting (DVB-T), the European telecommunications standard (ETSI) HIPERLAN/2
standard, the IEEE 802.11 a standard for wireless local area networks (WLANs) and IEEE 802.16
standard for wireless metropolitan area networks (WMANs).[2]

3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 3, March (2014), pp. 01-07 © IAEME
3
1.2 SPIHT
The SPIHT algorithm has been introduced by Said and Pearlman [7]. It is algorithm based on
the wavelet Transform and restricts the necessity of random access to the whole image to small sub
images. The success of this algorithm in compression efficiency and simplicity makes it well known
as a benchmark for embedded Wavelet image coding. SPIHT displays exceptional characteristics
over several properties all at once including: Good image quality with a high PSNR (Peak Signal to
Noise Ratio), fast coding and decoding, a fully progressive bit-stream, can be used for lossless
compression, may be combined with error protection ability to code for exact bit rate or PSNR,
flexibility of code rate and simplicity.
1.3 LDPC Codes
LDPC codes have attracted much attention particularly in the field of coding theory. LDPC
codes are a class of linear block codes which provide a reliable transmission for coding performance
that is very close to the Shannon's limit. A (N, K) LDPC code can be represented by a very sparse
parity-check matrix having M rows, N columns and code rate R=K/N, where K=N-M. It was
originally invented by Gallager in 1963 [8] and rediscovered by Mackay and Neal recently [9].
LDPC has been adopted as the DVB-S2 standard.
The rest of this paper is organized as follows: the system description, the simulation results and
finally, the conclusions followed by the relevant references.
2. SYSTEM DESCRIPTION
The paper concentrates on two targets reducing the PAPR of the OFDM signal and improving
the quality of the reconstructed images. It considers the trigonometric transforms as a way for
reducing the PAPR by using the character of the DCT/DST energy focused in the low component.
The data of OFDM signal is modulated by IFFT then using DCT/DST, which can reduce the PAPR.
At the same time, the proposed method reduces the PAPR greatly and the system has character of
low complexity hardware.
Fig.1 Image Transmission and Reception System
SPIHT
Encoding
LDPC
Encoder S/P
Replacement
and Inverse
Transform
Transform
and
replacement
IFFT
BPSK
Mapping
LDPC
Decoder
BPSK
Demapping
P/S FFT
SPIHT
Decoding
Add CP
Remove
CP
AWGN
Channel

4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 3, March (2014), pp. 01-07 © IAEME
4
2.1 Image Transmission
1. The SPIHT divides the image stream into several layers.
2. Then the image stream is converted to a binary format.
3. Afterwards the information bits are LDPC encoded at the LDPC encoder.
4. The baseband data is BPSK modulated
5. Then, the transmitted data of each parallel sub channel is modulated by Binary phase shift
keying (BPSK) modulation because it provides high throughput and best performance when
combined with the OFDM.
6. Finally, the modulated data are fed into an IFFT circuit, such that the OFDM signal is
generated. This is SystemI.
7. In SystemII and System III the output of IFFT is split into two components in-phase and in-
quadrature. And then DCT (SystemII) or DST (SystemIII) is applied.
2.2 AWGN Channel
Additive white Gaussian noise (AWGN) is a basic noise model used in information theory to
mimic the effect of many random processes that occur in nature. The modifiers denote specific
characteristics:
• 'Additive' because it is added to any noise that might be intrinsic to the information system.
• 'White' refers to idea that it has uniform power across the frequency band for the information
system. It is an analogy to the color white which has uniform emissions at all frequencies in
the visible spectrum.
• 'Gaussian' because it has a normal distribution in the time domain with an average time
domain value of zero.
2.3 Image Reception
1. The replacement and inverse transform are then applied to the received samples.
2. OFDM subchannel demodulation is implemented by using a (FFT) then the Parallel-to-Serial
(P/S) conversion is implemented.
3. This received OFDM symbols are demodulated at the demodulator.
4. The demodulated bits are decoded with each LDPC encoded block and data bits are restored.
These data are converted into image format, such that SPIHT decoding can be performed
2.4 Trigonometric Transformation process
The output of IFFT is split into two components in-phase and in-quadrature. And then DCT
(SystemII) or DST (SystemIII) is applied to both components, separately. The first half of samples of
the in-phase component after the transform (Li) is concatenated with the first half of samples of the
in-quadrature component after the transform (Lq) to form the new in-phase component. Similarly,
the second half of samples of the in-phase component after the transform (Hi) is concatenated with
the second half of samples of the in-quadrature component after the transform (Hq) to form the new
in-quadrature component. Finally, the new components are added to produce the OFDM signal.
2.5 Proposed Schemes
SystemI: The system which consists of coded OFDM
SystemII: The system I with the DCT transforms for the transmitted signal.
SystemIII: The system I with the DST transform for the transmitted signal.

5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 3, March (2014), pp. 01-07 © IAEME
5
3. SIMULATION RESULTS
3.1. Performance of OFDM system in terms of PAPR
In this section, simulation experiments are carried out to study the transmission of SPIHT
coded images on COFDM modified by Trigonometric transforms over AWGN channel. PAPR is
given by equation (1). Here x(t) is the OFDM signal and E[.] is the average power [2].
(3)
The parameters used in the simulation are: the number of subcarriers of a coded OFDM
system (N) is considered to be 1024, and Cyclic Prefix is taken 25% and rate is 0.2.Results are
shown in Table1,Table 2 and Table3.
Table 1: PAPR with Cyclic Prefix
Image Size System1 System2 System3
Lena.bmp (256×256) 13.8344 9.5581 7.6563
Cameraman. Tif (256×256) 13.7139 9.6206 7.8575
Girl.bmp (225×225) 13.7303 8.6907 7.3878
Lighthouse.jpg (768×1024×3) 13.7229 10.2994 7.5498
Table 2: PAPR without Cyclic Prefix
Image Size System1 System2 System3
Lena.bmp (256×256) 33.0747 15.2667 13.2011
Cameraman.tif (256×256) 35.3386 15.4356 12.8199
Girl.bmp (225×225) 31.4924 12.1586 11.1857
Lighthouse.jpg (768×1024×3) 36.8342 16.6390 13.7040
3.2 Performance for Image Transmission in terms of PSNR
The fidelity of image transmission is measured by the Peak Signal-to-Noise Ratio (PSNR),
which is usually expressed in terms of the logarithmic scale. It can be defined as follows:
PSNR=101og1o (PEAK2
/MSE) (4)
Where, MSE is the mean squared error between the original and the reconstructed image, and
Peak is the maximum possible magnitude for a pixel inside the image. The peak value is 255 for an 8
bits/pixel of original Image. Here N is taken as 256.

6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 3, March (2014), pp. 01-07 © IAEME
6
Table 3: PAPR (with Cyclic Prefix) for different values of N
Image Size System N=512 N=1024
Lena.bmp (256×256) System1 11.0578 13.8344
System2 5.5279 9.5581
System3 5.1909 7.6563
Cameraman.tif (256×256) System1 11.1146 13.7139
System2 6.2039 9.6206
System3 5.0711 7.8575
Girl.bmp (225×225) System1 11.0761 13.7303
System2 5.7373 8.6907
System3 5.1558 7.3878
Lighthouse.jpg (768×1024×3) System1 11.1163 13.7229
System2 5.9984 10.2994
System3 5.5561 7.5498
Table 4: PSNR for rate=0.2
Image Size System1 System2 System3
Lena.bmp (256×256) 27.6882 27.6882 37.8743
Cameraman.tif (256×256) 26.0853 26.0853 35.4933
Girl.bmp (225×225) 29.4518 29.4518 40.8864
Lighthouse.jpg (768×1024×3) 29.0779 29.0779 38.0979
Linux_256.jpg (256×256×3) 28.1374 28.1374 45.3756
Birds.jpg (800×554×3) 27.8079 27.8079 37.0346
Table 5: PSNR for rate=0.5
Image Size System1 System2 System3
Lena.bmp (256×256) 32.4240 32.4240 37.8743
Cameraman.tif (256×256) 30.4284 30.4284 35.4933
Girl.bmp (225×225) 35.0725 35.0725 40.8864
Lighthouse.jpg (768×1024×3) 33.3792 33.3792 38.0979
Linux_256.jpg (256×256×3) 35.7595 35.7595 45.3756
Birds.jpg (800×554×3) 32.0202 32.0202 37.0346

7. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 3, March (2014), pp. 01-07 © IAEME
7
4. CONCLUSION
Simulation results are obtained using MATLAB. The results show that PAPR reduction can
be achieved by using Cyclic Prefix. Also System II and System III have less PAPR as compared to
System I (From Table1 and Table2).Also for high values of N PAPR increases (Table 3). System III
is best in terms of PAPR reduction. For SystemI and SystemII PSNR increases with increase in rate.
System III gives best PSNR at all rates (refer Table4 and Table5).
5. REFERENCES
[1] Naglaa F. Soliman, Abd Alhamid, A. Shaalan, Mohammed M. Fouad.B, “Robust Image
Transmission with OFDM over an AWGN channel”, National Radio Science Conference,
April, 2011.
[2] Dae-Woon Lim, Seok-Joong Heo, and Jong-Seon No, “An Overview of Peak-to-Average
Power Ratio Reduction Schemes for OFDM Signals”, Journal of Communications And
Networks, Vol. 11, No. 3, pp. 229-239, June 2009.
[3] J. Kim and Y. Shin, “An Effective Clipped Companding scheme for PAPR Reduction of
OFDM Signals”, Proceedings of the IEEE ICC08, pp. 668-672, 2008.
[4] T. Jiang and G. Zhu, “Complement Block Coding for Reduction in Peak-to-Average Power
Ratio of OFDM Signals”, IEEE Communications Magazine, Vol. 43, no.9, pp. S17 - S22,
Sept. 2005.
[5] L. Guan, T. Jiang, D. Qu and Y. Zhou, “Joint Channel Estimation and PTS to Reduce Peak-
to-Average Power Ratio in OFDM Systems without Side Information”, IEEE Signal
Processing Letters, Vol. 17, No.10, pp. 883-886, October 2010.
[6] A.Rushdi and J. Tuqan, “Peak reduction in Trigonometric Based OFDM System",
Proceedings in ACSSC 2007, pp. 1747 - 1751, 2007.
[7] Said and W. A. Pearlman, “A New, Fast, and Efficient Image Codec Based on Set
Partitioning in Hierarchical Trees”, IEEE Transactions on Circuits and systems for video
technology, Vol.6, No.3, pp.243-250, June 1996.
[8] R.G. Gallager, “Low Density Parity check codes”, IEEE Transactions on Information
Theory, Vol. IT-8, pp. 21-28,Jan. 1962.
[9] Yuan Yang, Mong-Kai Ku, “LDPC coded OFDM modulation for high spectral efficiency
transmission”, Proceedings in ECCSC 2008, pp. 280- 284, July 2008.
[10] S.D. Giri and Prof. A.R. Salunke, “OFDM Based Wireless Lan Transmitter”, International
Journal of Electronics and Communication Engineering &Technology (IJECET), Volume 4,
Issue 2, 2013, pp. 469 - 476, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472.
[11] K.Muralibabu, Dr. K.Ramanaidu, Dr. S.Padmanabhan and Dr. T.K.Shanthi, “A Novel PAPR
Reduction Scheme using Discrete Cosine Transform Based on Subcarrier Grouping in
OFDM System”, International Journal of Electronics and Communication Engineering &
Technology (IJECET), Volume 3, Issue 3, 2012, pp. 251 - 257, ISSN Print: 0976- 6464,
ISSN Online: 0976 –6472.
[12] Ashok Kumar Kajla, Rupesh Sharma, Yash Walia and Sukoon Mishra, “Improve Peak To
Average Power Ratio (PAPR) Reduction Techniques in OFDM System”, International
Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4,
Issue 7, 2013, pp. 28 - 35, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472.