ORTHOGONAL SIGNAL ALIGNMENT WITH VARIABLE RATE AND POWER IN MIMO Y CHANNELS

Abstract

The multiple-input multiple-output (MIMO) Y channel employs signal alignment (SA) to improve spectral efficiency of wireless networks. In this system of three nodes exchanging data via the relay, cooperation of terminals allows the data transfer of six messages in two phases, medium access control (MAC) and broadcast, each taking one time slot thus achieving up to three times the rate of the conventional relaying system without SA. The antenna configuration in the original MIMO Y channel imposes limitations on controlling the minimum distance between signaling points representing network coded messages and this affects symbol error rate performance. To mitigate this problem, this thesis proposes to add one redundant antenna at every user and designs corresponding precoding vectors to obtain flexibility in the selection of orthogonal signaling dimensions and to simplify decoding at the relay. Additionally, the thesis develops adaptive power allocation and bit loading to optimize the system performance.