International Journal of Computer Applications (0975 – 8887) Volume 69– No.16, May 2013 40 Implementation and Analysis of Various PAPR Reduction Techniques using MATLAB Ankit Bass Student, SECE Lovely Professional University Jalandhar, INDIA Sudipta Ghosh Student Member IEEE Lovely Professional University Jalandhar, INDIA Vikas Singh Student, SCS Lovely Professional University Jalandhar, INDIA ABSTRACT Orthogonal Frequency Division Multiplexing is a new and emerging technology that provides us with high data rate. But every coin has two sides, pros and cons. So does OFDM. On the better side it provides us with high data rate but on the down side we have PAPR. The main obstacle for OFDM to work more efficiently is PAPR i.e. peak to average power ratio which is nothing but several sinusoidal leads. The purpose of this paper is to provide a MATLAB simulation of PAPR using some reduction techniques so that better performance could be achieved. General Terms Fast fourier transform (FFT), Inverse fourier Transform (IFFT), Pulse Shaping, Filters .Keywords Orthogonal Frequency Division Multiplexing (OFDM) ,Peak Average to Power Ratio(PAPR), Systematic Odd Parity Checking Coding(SOPC), Power Amplifier(PA). 1. INTRODUCTION Orthogonal frequency-division multiplexing (OFDM) is the modulation technique for European standards such as the Digital Audio Broadcasting (DAB) and the Digital Video Broadcasting (DVB) systems. As such it has received much attention and has been proposed for many other applications, including local area networks and personal communication systems. OFDM is a type of multichannel modulation [9] that divides a given channel into many parallel sub channels or subcarriers, so that multiple symbols are sent in parallel. Multiuser systems that use OFDM must be extended with a proper multiple-access scheme as must single carrier transmission systems. Compared to single carrier systems, OFDM is a versatile modulation scheme for multiple access systems in that it intrinsically facilitates both time-division multiple access and frequency-division multiple access .The communication track must be linear for OFDM to work properly and that too within the dynamic range that fits the PAPR distribution. Usually there is a problem with a linear Power Amplifier (PA) due to fact that its power efficiency is upper bounded and this upper bound decreases as the PAPR (the dynamic range of the PA) increases. This is the main reason why many PAPR reduction schemes have been proposed. 2. ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING (OFDM) OFDM is a Multicarrier Transmission technique which divides the available spectrum into many carriers each one being modulated by a low data rate stream. OFDM is similar to Frequency Division Multiple Access (FDMA) in that the multiple user access is achieved by sub-dividing the available bandwidth into multiple channels, which are then allocated to users. However OFDM uses the spectrum much more efficiently by spacing the channels more closer together. This is achieved by making all the carriers orthogonal to one another, preventing interference between the closely spaced channels. [6] -10 -8 -6 -4 -2 0 2 4 6 8 10 -55 -50 -45 -40 -35 -30 -25 frequency, MHz power spectral density Transmit spectrum OFDM (based on 802.11a) Figure 1. Normalized power spectrum of an OFDM signal 3. Peak To Average Power Ratio (PAPR) The output of the OFDM modulator is given by: 1 0 0 (_ ) | | cos[( ) ] N n n n St x a n t           , 0 t T   (1) where 0 a a  ,……, 1 n a  and | | n j n n a a e   , n=0,1,2 3……., N-1. All symbols a n , n=0,1,2,……N-1 are taken from constellation { a (1) , a (2) , ….., a (M) }. Let, ( ) max 1 max | | m mM A a    (2)