For better wireless communications, diversity technique becomes a very important topic. Receiver diversity is already a very recognized topic for frontier researchers. Now for the next generation wireless system, high voice quality and high bit rate data service, are the prerequisite for cheaper, small, lightweight pocket communicators, which are suitable to any acceptable environment. After considering all of these issues and looking at fading channel problems, a simple two-branch transmit diversity technique is proposed by Alamouti. Tarokh and Naguib later have included space-time coding, and shown an efficient method for fading channels and that realizes the benefit of multiple transmit antenna. For this, they studied space-time codes for high data rate wireless communications and come out with performance criteria in the presence of channel estimation errors, mobility, and multiple paths. After that, Tarokh and Jafarkhani use a new technique called, space-time block codes with the multiple transmit antenna over Rayleigh fading channel and proved a better performance result with a simple technique. They reviewed encoding and decoding algorithms for various codes and provide simulation results demonstrating their performance that is better than conventional techniques. These provide a new paradigm for diversity technique.