Downlink Multi-User MIMO Transmission for Reconfigurable Antenna Systems

摘要

This paper proposes an efficient downlink multi- user MIMO (MU-MIMO) scheme for multiple antenna transmission systems comprised of reconfigurable antenna (RA) elements. MU-MIMO schemes typically require a combined user pairing and precoding scheme where the channels of the selected users have to satisfy certain conditions to reduce interference among the users. Therefore, MU-MIMO typically requires a large number of users so that suitable user-tuples can be found. In this work, instead of relying on this requirement, we employ RAs at the transmitter to create multiple channel states for each user. An RA system accomplishes this by its dynamically changeable operation modes each of which creates a different channel realization. The availability of multiple channel states allow for an expanded search space for user pairing. We develop a joint user and antenna mode selection algorithm minimizing the error rates. A low-complexity iterative mode selection scheme is introduced to simplify the joint optimization problem. Simulation results indicate that one would need a lower number of users to benefit from MU-MIMO transmission if RAs are employed at the transmitter.