Abstract: In this paper, a Bit Error rate analysis is presented for multiple-input–multiple-output (MIMO) system with two way multiple relay system with amplify and forward (AF) considered in QPSK modulation technique, where a transmitted signal consists of a pre-coders followed by an space–time block code (STBC), such as dirty paper code (DPC). DPC primarily helps transmit data efficiently even though the communication channel offers interference. Its objective is always to send as much readable information on a channel with interference as you can. The BER performance of this method is compared with the pre-coder based methods like Minimum Mean Square Error (MMSE) and zero-forcing beam forming (ZF-BF). This paper considers both one-way and two -way relaying systems with multiple relays between two terminal nodes where all nodes have MIMO antennas. Simulation effects we advise a fresh practical scheme leads with low computation complexity and BER performance and faster convergence with better system utilization.

Keywords: Amplify-and-forward, MIMO, Space time block coding, Pre-coder (DPC), two ways relay, CSI, MMSE.