I. Introduction
High-speed data transmissions over power lines (PL) constitute a real challenge for engineers and researchers. The low voltage grid has been recently proposed as a potential medium for the “last mile” access network, due to its ability to offer a low-cost existing solution. Various classic modulation schemes, such as multi-carrier modulation, spread spectrum or combinations of these two techniques [1] [2], could be adapted for power line channels. The key benefit of multi-carrier modulation methods (orthogonal frequency division multiplexing (OFDM) or discrete multi-tones (DMT)) is their ability to turn a frequency-selective channel with additive colored noise into a set of independent narrowband subchannels with additive white noise, which greatly simplifies the channel equalization process. In addition, given a stationary channel, it is possible to use a loading algorithm to adapt the sub-carrier modulation parameters to the channel conditions [3] [4], which improves the data rate performance substantially. In both cases, it's clear that final performance is highly dependent on the quality of the channel estimation. In this paper, we focus on most popular channel estimation techniques, which use pilot sub-carriers and piecewise polynomial interpolations.