Analysis and Design of Timing Recovery Schemes for DMT Systems over Indoor Power-Line Channels
- PDF / 1,152,341 Bytes
- 11 Pages / 600.03 x 792 pts Page_size
- 36 Downloads / 184 Views
Research Article Analysis and Design of Timing Recovery Schemes for DMT Systems over Indoor Power-Line Channels ´ Luis D´ıez, Eduardo Martos-Naya, Francisco Javier Canete, ˜ Jose´ Antonio Cortes, and ´ Entrambasaguas Jose´ Tomas Departamento de Ingenier´ıa de Comunicaciones, Escuela T´ecnica Superior de Ingenier´ıa de Telecomunicaci´on, Universidad de M´alaga, 29071 M´alaga, Spain Received 31 October 2006; Accepted 23 March 2007 Recommended by Mois´es Vidal Ribeiro 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. Copyright © 2007 Jos´e Antonio Cort´es et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1.
INTRODUCTION
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. Applications range from audio/video distribution and traditional local area networking to the connection of computers and entertainment equipment to the network access gateway. The study presented in this paper concentrates on this scenario. However, it may be also useful for outdoor power-line applications because, since the user modem is located in an indoor network, it also experiences the characteristics of the indoor channels. The available bandwidth for broadband indoor powerline communications (PLC) extends up to 30 MHz [1]. Channels are frequency- and time-selective, with significant differences between the locations of a specific site. The frequency response introduces remarkably amplitude and phase distortion, with deep notches that appear in a priori unknown positions, and the noise is strongly colored [2, 3]. Time variations have a twofold origin: long-term changes caused by the connection and disconnec
Data Loading...
