Timing recovery scheme for a discrete multitone transmission system

Abstract

A random access data network in accord with the invention will utilize discrete multi-tone (DMT) transmission over a link within a home or other premises, such as over existing in-house telephone wiring. Discrete multi-tone communication in a random access implementation raises a number of timing issues. To address these issues, all packet transmissions through the network will begin with one or more cycles of a defined periodic signal, typically a sinusoid at a specified frequency. All timing of decoding of subsequent signals, such as ID signals and DMT symbols, is based on counting signal sampling intervals following the detected timing mark. The preferred embodiment utilizes differential modulation of the tones within the DMT symbol. Each packet may include a reference symbol to enable demodulation of the first DMT data symbol. Also, the preferred embodiment of the DMT symbol includes a prefix code followed by the actual DMT waveform carrying the modulated information. The prefix code corresponds to a fixed number of samples of time-domain data, such as a copy of the last thirty-two samples used to generate the actual DMT waveform.