Orthogonal Multi-beam Techniques for Multi-user Diversity and Multiplexing Gain in Packet-based Wireless Systems

In this paper, we consider the use of orthogonal multiple beams (OMBs) to simultaneously achieve multi-user diversity and multiplexing gain in a packet-based wireless system. Previous schemes consider the use of a fixed number of OMBs according to the number of transmit antennas. However, unless the number of active users is sufficiently large, the use of multiple beams may not provide desired performance mainly due to the interference from other users´ signals, being even worse than the use of a single beam. To alleviate this problem, we consider the adjustment of the number of beams in use to maximize the spectral efficiency according to the operating condition. Simulation results show the validity of the proposed scheme.