International Journal of Science and Advanced Technology (ISSN 2221-8386) Volume 1 No 3 May 2011 http://www.ijsat.com PERFORMANCE OF MIMO-OFDM SYSTEM FOR RAYLEIGH FADING CHANNEL Fig 1. Block diagram of MIMO system Pallavi Bhatnagar 1 , Jaikaran Singh 2 , Mukesh Tiwari 3 Department of Electronics & Communication, Sri Satya Sai Institute of Science &Technology, Sehore, MP (India) pallavi_sx@rediffmail.com 1 , jksingh81@yahoo.co.in 2 , tiwari_mukesh79@yahoo.in 3 Abstract- This paper proposes a simple and efficient simulation method for MIMO-OFDM system with channel equalization.BPSK modulation is used to detect the behavior of the Rayleigh fading channel in presence of additive white Gaussian noise and then its performance is evaluated. Obtained result is then compared with adding MLSE equalizer. This paper shows that the addition of equalizer reduces the BER (Bit Error Rate) and the channel output becomes more pronounced. Though the total channel is a frequency selective channel, the channel experienced by each subcarrier in an OFDM system is a flat fading channel with each subcarrier getting independent Rayleigh fading. Keywords- MIMO system, channel, equalization, Rayleigh fading. I. INTRODUCTION The rising demand of multimedia services and the development of Internet related contents lead to increasing curiosity to high speed communications. In the ceaseless search for increased capacity in a wireless communication channel it has been shown that by using MIMO (Multiple Input Multiple Output) system architecture it is possible to increase that capacity considerably. The combination MIMO-OFDM is very likely and beneficial since OFDM enables support of more antennas and larger bandwidths since it simplifies equalization in MIMO systems. Usually fading is considered as a problem in wireless communication but MIMO channels uses the fading to increase the capacity of entire system. Fading of the signal can be mitigated by different diversity techniques. II. OVERVIEW OF MIMO- OFDM SYSTEM The MIMO system transmits different signals from each transmit element so that the receiving antenna array receives a superposition of all the transmitted signals. All signals are transmitted from all elements once and the receiver solves a linear equation system to demodulate the message. Multiplexing (MIMO-OFDM) system is an effe- Fig 1. Block diagram of MIMO We consider the system where the transmitter has t n antennas and the receiver has r n antennas. Let n m h , be a complex number corresponding to the channel gain between transmit antenna n and the receive antenna m. If at a certain time instant complex signals   nt x x x ,..., , 2 1 are transmitted via the t n antennas, the received signals at antenna m can be expressed as     t n n m n n m m e x h y 1 ,  where m e is a noise signal. This relation is easily expressed in a matrix structure. Let x and y be t n and r n vectors containing the transmitter and receiver data, respectively. Define the following r n x t n channel gain matrix H =               nt nr nr nt h h h h , 1 , , 1 1 , 1 ....... . ......... .......... .........   . tive solution to improve communication quality, performance, capacity, and transmission rate. MIMO- OFDM is under intensive investigation by researchers.