iosr-JECE   Volume-7 ~ Issue-4

Abstract: Orthogonal Frequency division multiplexing (OFDM) is a very popular technique in wireless communications which provides excellent robustness to channel fading and immune to interference. OFDM is one of a popular modulation technique for transmitting large amounts of digital data over radio carriers. One of the major problems that had been observed in this is the Peak-To Average power Ratio (PAPR). PAPR is a distortion that had occurred due to large number of sub carriers that are used in OFDM for modulating the digital data. Many techniques were available to reduce the PAPR in OFDM systems, among them the companding technique can be used to enhance the OFDM transmission performance by decreasing the PAPR effectively and hence BER. Here we proposed "Bessel Companding Algorithm" to reduce this significant drawback in OFDM Systems.

Keywords : Orthogonal Frequency Division Multiplexing (OFDM), peak to average power ratio (PAPR), bit error rate (BER), Out Band Interference (OBI), Additive White Gaussian Noise (AWGN), Bessel Companding Algorithm, Quadrature Amplitude Modulation (QAM) and Multi Carrier Modulation (MCM).

[1] B.S. Krongold and D.L.Jones, "PAR Reduction in OFDM via active constellation extension" IEEE Trans. Broadcast. vol. 49, pp. 258-268, Sep. 2003.

[2] D. Lowe and X. Huang, "Optimal adaptive hyperbolic companding for OFDM," in Proc . IEEE Second Intl Conf. Wireless Broadband and Ultra Wideband Commun., pp. 24-29, Aug. 2004.

[3] Hikmet Sari and Fabien Buda, "An Analysis of OFDM Peak Power Reduction Techniques for WiMAX Systems" Sequans Communications, 19 Le Parvis, 92073 Paris La Defense, France2009.

[4] I.N.Bronshtein, K. A. Semendyayev, G. Musiol, and H. Muehlig, Handbook of Mathematics, 5th ed. New York: Springer, 2007, p. 422.

[5] J.Akhtman, B.Z. Bobrovsky , and L.Hanzo, "Peak-to-average power ratio reduction for OFDM modems," in Proc. 57th IEEE Semi- Annual Vehicular Technology Conf. (VTC ‟03), vol. 2, Apr. 2003. pp 1188-1192.

[6] Nishar Ahamed Gugudu, "Evaluation of Channel Coding in OFDM Systems", a thesis in "Telematics and Signal Processing may 2006.

Abstract:Today in the world of communication systems the most widely researched area is of wireless technology and a study of communication systems is incomplete without an understanding of the operation of the antennas. In the recent years of development in communication systems a need for the development of lightweight, compact and cost-effective antennas that are capable of maintaining high performance over a wide spectrum of frequencies. This technological trend has focused much effort into the design of a Micro strip patch antenna. In this work, the simulation tool of IE3D is used to study the performance and gain of the rectangular Microstrip patch antenna. The design and simulation of patch antennas is widely used in mobile cellular phones today, and our emphasis in this work is on optimization of a 2.4 GHz rectangular Microstrip patch antenna. The return loss and the various gain plots have been studied along with the radiation patterns.