Bit and Power Allocation for Multiuser MIMO OFDM Systems with Subcarrier Reuse

MIMO systems may achieve spatial multi-user access using singular value decomposition (SVD) MIMO techniques [J.Z. Ying and K.B. Letaief, 12005; J. Kim and J.M. Cioffi, 2000]. The MIMO OFDM systems multiplex the users both in the frequency and the spatial domains. Hence, the co-channel interference caused by the sub-carrier reuse may lower the system´s performance. For MIMO OFDM systems with co-channel interference, the combination of power control with adaptive modulation is desirable to reduce the effect. Zhang and Letaief proposed an allocation algorithm [1] by starting an OFDMA-based allocation procedure, so the amount of the co-channel interference is mitigated by the sub-carrier allocation. The scheme used a neighborhood search scheme to obtain additional power efficiency. However, the proposed scheme has the limitation on the affordable maximum data rate even without transmit power constraint. The paper presents an enhanced version of the scheme to remedy the problem. The proposed scheme aims to minimize the total user transmit power while satisfying the required data rate, the maximum transmit power constraint, and the bit error rate of each user. The proposed algorithm offers better spectrum efficiency than the high complexity multi-user greedy algorithm [5] as illustrated in the simulation results.