Moderate loading in bit-rounding algorithms for multicarrier systems

Bit-rounding algorithms are practically attractive for their computational efficiency and suitability for integer-bit loading. However, because of the concave nature of the rate-energy relationship, these algorithms often tend to load bits aggressively, which leads to the performanceconstraint violation. In addition, for BPSK and 8-QAM cases, the anomalous behaviour of the SNR-gap rate function also contributes to the performance constraint violation of the existing bit-rounding algorithms. This paper presents an efficient moderate algorithm for estimating the optimum biasing parameter for round-off operation, using exact SNR values instead of the SNR-gap rate function in order to ensure that both the performance and total power constraints are satisfied while rate optimality is achieved. Simulation results show that the proposed moderate algorithm can maintain the optimum rate and avoid the performance constraint violation of its aggressive counterparts for 75 tested cases.