STBC (Space Time Block Code) schemes are widely used in MIMO-OFDM systems for communicational link or antenna link performance enhancements. For more than two transmit antenna systems, QOSTBC (Quasi Orthogonal STBC) is found to be very effective. In general QO-STBC lowers decoding complexity and higher BER performance is achieved. In this paper the output for the bit-error-rate (BER) performance of quasi-orthogonal space time block code (QOSTBC) with L=4 and M=1 antennas over the frequency flat Rayleigh block fading channel has been analyzed. For encoding and decoding processes, Alamouti scheme and (ML) maximum likelihood decoding scheme has been used simultaneously. Also we consider the throughput problem of a wireless fading network with relaying scheme, where n single antenna source-destination pairs communicate through a set of single antenna relays using detect-and-forward, decode- and-forward along with amplify-and-forward strategies. Finally the performance of all has been evaluated along with AWGN, Rayleigh fading channels with MRC with two sender strategy.