International Journal of Wireless & Mobile Networks (IJWMN) Vol. 4, No. 5, October 2012 DOI : 10.5121/ijwmn.2012.4509 125 Study and Simulation of Quasi and Rotated Quasi Space Time Block Codes in MIMO systems using Dent Channel model Priyanka Mishra 1 ,Rahul Vij 2 ,Gurpreet Singh 3 and Gaurav Chandil 4 1 Department of Electronics Engineering, United Group of Institution,Allahabad mishrapriyanka6@gmail.com 2 Department of Electronics Engineering, L R of Institute of Engineering,Solan rahulvij2@gmail.com 3 Department of Electronics Engineering, Shaheed Bhagat Singh State Technical Campus, Ferozpur, Punjab gurpreet2828@hotmail.com 4 Department of Electronics Engineering, United Group of Institution,Allahabad gaurav.iiitm18@gmail.com ABSTRACT Multiple Input Multiple Output (MIMO) has become one of the most exciting field in modern engineering.It has become one of the key technologies for wideband wireless communication systems.It is mainly used to increase capacity and data rate of any wireless systems.In this paper,we exploit the space and time diversity to decode the quasi and rotated quasi space time block codes (QOSTBC) based on dent channel model.For doppler shifting and rayleigh distribution we make use of dent channel model.A general Quasi and rotated quasi Space-Time Block Coded (STBC) MIMO structure is presented in this paper. BER analysis is presented in terms of code rate and diversity achieved using Quasi and Rotated quasi STBC methods. Furthermore, simulations are carried out using above two OSTBC methods with various modulation schemes in quasi static dent channel model and then optimum coding method is suggested for 4×2 quasi and rotated quasi Space time block coded MIMO systems.This provide fast decoding and gives better performance of communication system.BER analysis is presented in terms of diversity and code rate. KEYWORDS MIMO, QUASI ORTHOGONAL SPACE-TIME BLOCK CODES (QOSTBC), ROTATED QOSTBC,MAXIMUM LIKELIHOOD (ML) DECODING. 1. INTRODUCTION MIMO technology constitutes a breakthrough in wireless communication system that offers a number of benefits that helps in improving the reliability of link. The advantage of MIMO technology includes improvement in array gain, spatial diversity gain, multiplexing gain and interference reduction. MIMO systems provide diversity to mitigate fading, that is realized by providing the receiver with multiple copies of the transmitted signal in space, frequency or time. By increasing number of signal replicas, the probability of getting least faded signal is increased. The information capacity of a system is increased by employing multiple transmit and receive antennas. An effective and practical way to gain the capacity of the multiple input multiple output (MIMO) is to employ Space Time (ST) Coding. Space-Time (ST) coding schemes combines coding along with transmit diversity to achieve high diversity performance. It can be implemented in two forms ST-Trellis and ST-Block codes.