IJCA Special Issue on “2nd National Conference- Computing, Communication and Sensor Network” CCSN, 2011 22 Design and Simulation of COFDM for High Speed Wireless Communication and Performance Analysis Arun Agarwal ITER College, Siksha ‘O’ Anusandhan University Department of Electronics and Communication Engineering Bhubaneswar-751030, India Kabita Agarwal C.V. Raman College of Engineering Department of Electronics and Telecommunication Engineering Bhubaneswar-751052, India ABSTRACT Coded Orthogonal Frequency Division Multiplexing (COFDM) is one of the dominant techniques of present day wireless (mobile) communication. The main advantage of OFDM is that it makes the receiver highly robust against Multipath fading environments. Due to orthogonal properties of the sub-carriers used, OFDM also provides efficient spectrum utilization by use of single frequency networks (SFNs) and use of simple equalizers. OFDM has become the standard for physical layer implementation of various digital audio and video wireless communications such as DAB/DVB, wireless local access networks (WLANs) and wireless metropolitan area networks (WMANs). In this paper, we present a performance analysis of a (COFDM) using convolutional coding, interleaving with different digital modulation techniques in diverse transmission channels. The results show that COFDM is well suited for high speed data transmission in mobile environment and interleaving is essential for reducing bit error rate (BER) for high speed transmission. General Terms Wireless (mobile) digital communication. Keywords COFDM, multipath fading, channel coding, interleaving, bit error rate. 1. INTRODUCTION With the rapid growth of digital communication in recent years, the need for high-speed data transmission has increased. Over the last few years, there has been increasing demand on extending the services available on wired public telecommunications networks to mobile/movable non wired telecommunications users [1]. At present, in addition to voice services, only low-bit-rate data services are available to mobile users. However, demands for wireless broadband multimedia communication systems are anticipated within both the public and private sectors. Wired networks are cannot support extension to wireless mobile networks because mobile radio channels are more contaminated than wired data-transmission channels [1]. We also cannot preserve the high Quality of service in wired communications network. The mobile radio channel is always characterized by multipath reception. The signal picked up by the receiver contains not only a direct line-of-sight (LOS) radio wave, but also a large number of reflected radio waves that arrive at the receiver at different time‘s instants. Delayed signals are due to the result of reflections from terrain features such as trees, hills, mountains, vehicles, or buildings. These reflected, delayed waves interfere with the direct wave and cause intersymbol interference (ISI), which in turn causes significant degradation of network performance [1]. ISI occurs when a transmission interferes with itself and the receiver cannot decode the transmission correctly. As communication systems increase their information transfer speed, the time for each transmission necessarily becomes shorter. Since the delay time caused by multipath remains constant, this ISI becomes a limitation in high-data-rate communication. A wireless network should be designed to minimize these adverse multipath effects to avoid signal degradation. To overcome such a multipath-fading environment with low complexity Equalizers and to achieve wireless broadband multimedia communication systems, this paper presents a detailed overview and simulation of the orthogonal frequency division multiplexing (OFDM) parallel data transmission scheme. OFDM is a kind of Multi Carrier Transmission system where a single data stream is transmitted over a number of subcarriers. Since many communication systems being developed use OFDM, it is a worthwhile research topic. Some examples of current applications using OFDM include GSTN (General Switched Telephone Network), Cellular radio, DSL & ADSL modems, DAB (Digital Audio Broadcasting) radio, DVB-T (Terrestrial Digital Video Broadcasting), HDTV broadcasting, HYPERLAN/2 (High Performance Local Area Network standard), and the wireless networking standard IEEE. In this paper we designed and implemented an interleaving based channel coding technique for improved performance of OFDM system in different transmission channels. In this paper we developed an OFDM transmission system based on IEEE 802.11a standard [5] [6]. The design consists of energy dispersal scrambler, QPSK/QAM symbol mapping, convolutional encoder (FEC), interleaving and OFDM signal generator (IFFT) in the transmitter side and in the receiver corresponding inverse operations is carried out. A frame based processing is used in this work. Bit error rate (BER) has been considered as the performance index in all analysis. The analysis has been carried out with simulation studies under MATLAB environment.