Abstract
This paper provides a comprehensive discussion about the characteristics of power line communication (PLC) channels related to its synchronization with the mains period. This fact constitutes an interesting and distinguishing feature of these kind of channels. Under the mains voltage presence, the behavior of some loads connected to the power network allows representing the transmission medium as a linear periodically time varying (LPTV) system. Some components in the received noise exhibit periodicity as well, in terms of impulsive waveforms synchronized with the mains period and other cyclostationary (CS) signals. This fact has been taken into account in the design of PLC systems, for instance by defining medium access control (MAC) frames synchronized with the mains period and by adapting the modulation to the cyclic signal-to-noise ratio (SNR) to improve the system performance. Hence, in PLC, it is of particular interest to describe the general relations of LPTV systems and CS signals when both have a common period, which is the purpose of this work. It is not aimed at providing new mathematical tools for the analysis of these cyclic signals and systems, which have been extensively developed over the last five decades, but to serve the readers of the PLC community more accessible mathematical relations that can be applied to the practical problems they have to face. A review of recent works dealing with the cyclic properties of PLC channels and transmission techniques aware of these strategies is included as well.
Highlights
The term cyclic used in the title of this work denotes in a synthetic way both: non-stationary random signals but with a periodical correlation, which are usually referred to as cyclostationary (CS) signals and, linear periodically time-varying (LPTV) systems.There exist valuable classical works devoted to CS signals properties [1], [2] and to LPTV systems [3]–[5] and, even more, works that contain a deep analysis of CS signals, LTPV systems and their interplay, from a comprehensive perspective [6]–[10]
There are many interesting publications that include discussions on cyclic signals and systems with a scope focused on signal processing for communications [11]–[14]. These studies may be too extensive and intricate for a reader attracted by this topic but mostly interested in power line communications applications (PLC) [15], The associate editor coordinating the review of this manuscript and approving it for publication was Naofal Aldhahir
The main contribution of this paper is to present general properties that cyclic signals and system exhibit but developed for the special case of PLC channels in which there is a dominant periodicity of the same period in both the CS random signals and LPTV systems
Summary
The term cyclic used in the title of this work denotes in a synthetic way both:. non-stationary random signals but with a periodical correlation, which are usually referred to as cyclostationary (CS) signals and,. In [25], the relation between these long-term channel variations and the appearance of strong impulsive noise events is studied Those are attributed to load changes in the power network, due to the connection and disconnection of appliances. Such variations occur in a larger time scale (with respect to the signal modulation time scale) and not necessarily imply a clear periodicity ( tendencies along the day can be observed). The main contribution of this paper is to present general properties that cyclic signals and system exhibit but developed for the special case of PLC channels in which there is a dominant periodicity of the same period in both the CS random signals and LPTV systems.
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