Transmit Diversity Technique for Wireless Communication over Rayleigh Channels Using 16 QAM Modulation Schemes

The increasing demand for higher data rates and higher quality in wireless communications has motivated the use of multiple antenna elements at the transmitter and single antenna at the receiver in a wireless link. Space-time block coding over Rayleigh fading channels using multiple transmit antennas was introduced. In this work Data is encoded using a space-time block code and the encoded data is split into n streams which are simultaneously transmitted using n transmit antennas. The received signal at each receive antenna is a linear superposition of the n transmitted signals perturbed by noise. Maximum likelihood decoding is carried out by dividing the signals transmitted from different antennas. This uses the orthogonal structure of the space-time block code and gives a maximum-likelihood decoding algorithm, which is based only on linear processing at the receiver. Space-time block codes are designed to achieve the maximum diversity order for a given number of transmit and receive antennas subject to the constrain of having a simple decoding algorithm. This paper presents a simple two-branch transmit diversity scheme. Using two transmit antennas and one receive antenna using QAM modulation technique the performance of OSTBC with Alamouti is compared with no STBC scheme at lower as well as higher SNRs. This paper evaluates the performance of the system by increasing data lengths in terms of blocks.