  Multi-user Orthogonal Frequency Division Multiplexing (OFDM) and Multiple
Output Multiple Output (MIMO) have been widely adopted to enhance the system
throughput and combat the detrimental effects of wireless channels. Recently,
interference alignment was proposed to exploit interference to enable
concurrent transmissions of multiple signals. In this paper, we investigate how
to combine these techniques to further enhance the system throughput. We first
reveal the unique characteristics and challenges brought about by using
interference alignment in diagonal channels. We then derive a performance bound
for the multi-user (MIMO) OFDM/interference alignment system under practical
constraints, and show how to achieve this bound with a decomposition approach.
The superior performance of the proposed scheme is validated with simulations.
