and Computer Engineering 2(2): 155-159(2013) BER Performance in MIMO OFDM System for Rayleigh Fading Channel

ABSTRACT: In this paper we show the Channel coding plays a very important role in OFDM systems performance. The structure of OFDM systems makes channel coding more effective in confronting fading channels. Sometimes Coded OFDM is known as COFDM. The role of channel coding in conjunction with frequency and time interleaving is to provide a link between bits transmitted on separated carriers of the signal spectrum, in such a way that the information conveyed by faded carriers can be reconstructed in the receiver. Frequency selectivity, currently known to be a disadvantage, is then turned into an advantage that can be called frequency diversity. Using Channel State Information (CSI), channel coding can yield some additional gain. Channel state information is frequency response of the channel or signal to noise ratio in each carrier. This paper presents Space-Time Coded OFDM system consisting of two transmitters and a single receiver. Simple space time code is used. 4- PSK modulation is used to modulate the symbols across an OFDM channel. We also proposed a variation of the scheme which tries to spread additional symbols across time frequency attempting to increase the rate of transmission without changing the type of modulation employed or increasing the bandwidth. A Rayleigh frequency selective slow fading channel is assumed throughout the analysis. SER performance of the above systems is carried out with emphasis on the modulation scheme and number of carriers. Index Terms: MIMO-OFDM, BER, SNR Outage Capacity I