Abstract: MIMO (Multiple-input, multiple-output) systems are an essential component of future wireless communication systems, due to their promising improvement with regards to performance and bandwidth efficiency. A significant research topic is study regarding multi-user MIMO systems. Such systems have the possibility to combine the top throughput achievable with MIMO processing with the main advantages of space division multiple accesses (SDMA). In this paper, a Bit Error rate analysis is presented for multiple-input–multiple-output (MIMO) system with two way multiple relay system with 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 and zero-forcing beam forming. This paper considers both one-way and two -way relaying systems with multiple relays between two terminal nodes where all nodes have MIMO antennas.

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