Abstract
Discrete multitone (DMT) modulation is a suitable technique to cope with main impairments of broadband indoor power-line channels: spectral selectivity and cyclic time variations. Due to the high-density constellations employed to achieve the required bit-rates, synchronization issues became an important concern in these scenarios. This paper analyzes the performance of a conventional DMT timing recovery scheme designed for linear time-invariant (LTI) channels when employed over indoor power lines. The influence of the channel cyclic short-term variations and the sampling jitter on the system performance is assessed. Bit-rate degradation due to timing errors is evaluated in a set of measured channels. It is shown that this synchronization mechanism limits the system performance in many residential channels. Two improvements are proposed to avoid this end: a new phase error estimator that takes into account the short-term changes in the channel response, and the introduction of notch filters in the timing recovery loop. Simulations confirm that the new scheme eliminates the bit-rate loss in most situations.
Highlights
The increasing demand for home networking capabilities, along with the recent provisioning of triple-pay services by digital subscriber line operators, has generated considerable interest in high-speed indoor power-line communications
The shortcomings of the conventional strategies designed for Discrete multitone (DMT) systems that operate in linear time-invariant (LTI) channels are firstly revisited [8]
The reason is that according to the statistics of the Doppler spread bandwidth shown in [4], the taps of a onestage frequency equalizer (FEQ) should be adapted at a rate comparable to that of the synchronization system
Summary
The increasing demand for home networking capabilities, along with the recent provisioning of triple-pay services (internet, video, and telephony) by digital subscriber line operators, has generated considerable interest in high-speed indoor power-line communications. The most common procedure to accomplish synchronization is by means of a fixed frequency sampling and a digital phase-locked loop (PLL) [5, 6] This system performs two main tasks: timing. A new timing recovery scheme for indoor PLC is proposed To this end, the shortcomings of the conventional strategies designed for DMT systems that operate in LTI channels are firstly revisited [8]. The shortcomings of the conventional strategies designed for DMT systems that operate in LTI channels are firstly revisited [8] This analysis suggests two direct improvements: to design a phase error estimator that takes into account the magnitude of the cyclic short-term changes in the channel response, and to modify the loop response so that higher attenuation is provided to the harmonics of the cyclic channel variations.
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