Practical Implementation of Bit Loading Schemes for Multiantenna Multiuser Wireless OFDM Systems

This paper provides useful insights into the practical design of bit allocation algorithms in multiantenna multiuser orthogonal frequency-division multiplexing (OFDM) systems. With the degrees of freedom obtained with multiple antennas and multiple subcarriers, the performance might be enhanced at the expense of a higher complexity. Since the scheduling with realistic integer mappings is an NP-complete combinatorial problem, suboptimum solutions based on the scalar product are shown to be good candidates for yielding a realizable scheduler at a wireless physical layer. Additionally, a power reuse strategy is proposed to lower the computational requirements of such a system. Besides the tradeoff between performance and complexity, there exists the tradeoff between performance and signaling. Therefore, we show that the required signaling might be reduced either by a user-subcarrier clustering or by using a scheme that forces an equal mapping for all the users at the same subcarrier, which might be well-suited if instantaneous fairness is required. The proposed strategies are evaluated for typical OFDM-based wireless LAN scenarios.