Reduced complexity LPTV-aware bit loading for channel adaptation in broadband PLC

The power line communications (PLC) channel has been shown to be linear periodically time varying (LPTV) with the duration of the AC cycle of the mains. Therefore, channel adaptive bit-loading algorithms used in broadband (BB) orthogonal frequency division multiplexing (OFDM) PLC often operate on so-called microslots, which are a fraction of the AC mains cycle duration. In previous work, we have demonstrated that data rates can be improved if bit-loading is performed across microslots, assuming an average instead of per-microslot transmit power constraint. In this paper, we present a number of extensions and improvements to our original LPTV-aware loading algorithm. First, we derive a modified version that accomplishes rate improvements through better power allocation. Secondly, we tackle the numerical complexity of LPTV-aware loading and propose a reduced-complexity version. Finally, we consider the use of power clipping to reduce peak power levels. Numerical results demonstrate that the reduced complexity LPTV-aware bit loading algorithm with power clipping improves the performance of the original LPTV-aware bit loading significantly, rendering it an attractive solution for high data-rate BB OFDM PLC.