BER PERFORMANCE IMPROVEMENT USING MIMO TECHNIQUE OVER RAYLEIGH WIRELESS CHANNEL with DIFFERENT EQUALIZERS Amit Kumar Sahu * , Sudhansu Sekhar Singh # * Kalam Institute of Technology, Berhampur, Odisha, India amit.wmc@gmail.com # KIIT University, Odisha, India Sudh_69@yahoo.com Abstract Wireless communication using Multiple-Input Multiple-Output (MIMO) links has emerged as one of the most significant breakthroughs in modern communications because of the huge capacity and reliability gains promised even in worst fading environment. This paper presents an overview of some important behaviors of MIMO systems under Rayleigh channel environments. This work describes the basic ideas of MIMO transmission systems and focused and investigated the BER performance. All analysis was performed under ideal identical independent fading conditions by the use of MATLAB. At the initial stage of the work we related the SNR and the error performance of MIMO systems with the diversity schemes, in the later part of the paper, implementations of different equalizers are also verified for the improvement of the BER performance. Each chapter is rounded by a number of simulations to deepen the understanding of the performance with the use of multiple antennas and equalizers in wireless communication over Rayleigh wireless radio channels. MIMO fading channels are correlated to observe mutual coupling between antenna elements. Receiver diversity is analyzed especially with the Maximal Ratio Combining(MRC) technique and fair comparison is done with Equal Gain Combining(EGC) and Selection- Combing(SC). Further study is done with integration of Maximum Likelihood (ML), Maximum Mean Square Equalization(MMSE) and Zero Forcing(ZF). All the results obtained are simulated by using the MATLAB, under Rayleigh channel conditions. Keywords: MIMO,EGC,MRC techniques, ZF, MMSE and ML equalizers, SNR BER. I. INTRODUCTION The wireless communications is evolving rapidly for high data rates and better quality of services,. It can also be done by increasing transmit power but there is a limitation for the biological hazards, interference and also it is technically difficult and costly to create linear receivers with sensitivity more than 30-35 dB [1]. The information theoretic capacity of the MIMO wireless channel has been characterized under various assumptions since the prominent works of Foschini [2] and Telatar [3]. The performance improvement of wireless connection by the use of array of antenna elements is an old technique. It was used by Guglielmo Marconi in 1901 to get the better gain of the Atlantic transmissions of Morse codes [4] .This paper discuses the merits of the MIMO System and the BER Performance of the Rayleigh Wireless channel under BPSK modulation scheme. Different diversity techniques like EGC, MRC, SC has been analyzed here. Again various equalization techniques are also implemented to achieve even better link performance. II. ANALYTICAL MODEL FOR MIMO MIMO is a narrowband technology. For the H Channel matrix we have y = Hx + n. The number of independent channels that a signal travels from the sender to the receiver is called as the diversity gain[5]. The proper operation of MIMO systems requires careful design, with the encoded signals received from each transmitting antenna and the multiple communication channels achieving specified orthogonality conditions.[6]. The better combination of number of transmitting and receiving antenna for MIMO systems in BPSK modulation technique that satisfy the good SNR is to be investigated primarily. Amit Kumar Sahu et al. / International Journal of Engineering and Technology (IJET) ISSN : 0975-4024 Vol 4 No 5 Oct-Nov 2012 333