Adaptive subcarrier allocation for increasing the capacity of multiuser spatial multiplexing based OFDM systems

In this paper, the subcarrier allocation problems for downlink transmission of spatial multiplexing based OFDM systems are investigated. With the goal of maximizing the instantaneous capacity, two categories of subcarrier assignment criteria are derived, that is, exclusive manner based criteria which allocate each subcarrier to a single user, and shared manner based criteria which allow multiple users to share a subcarrier. Simulation results demonstrate that both the presented criteria are capable of utilizing the multiuser diversity to enhance the capacity of spatial multiplexing based OFDM systems significantly. Furthermore, via experiments we find that compared with shared criteria, allocating each subcarrier to a single user is a feasible choice to achieve tradeoff among complexity, overhead, and capacity enhancement