Measuring, Modeling and Enhancing Power-Line Communications

Power-line communication (PLC) is a technology that has become increasingly popular in recent years, as it provides easy and high-throughput connectivity in residential and enterprise networks. The IEEE has standardized PLC with the 1901 standard, and the HomePlug Alliance certifies products and provides specifications for different data-rates and applications. Furthermore, tens of vendors offer hybrid solutions with both WiFi and PLC, thus yielding an extended coverage and relieving congestion in the network. Although it is commercially successful and widely adopted, PLC has received far too little attention from the research community. Two of the main reasons for this lack of research are the proprietary nature of the technology and the protocols’ complexity. We overcome these barriers and build the foundations for understanding, evaluating, measuring, exploiting and boosting PLC performance. In this dissertation, we explore PLC performance and dynamics in various time-scales and treat both best-effort and delay-sensitive applications towards enhancing quality of service. When deploying hybrid networks, there are two open questions that arise: Does PLC perform better than WiFi and to which extent can PLC augment network reliability? How can we accurately estimate PLC capacity for deciding to which medium data should be forwarded? To answer these questions, we conduct an experimental study with PLC and WiFi stations and delve into the spatio-temporal variations of PLC capacity. Our results uncover crucial differences between the two mediums, thus proving that PLC largely extends coverage and augments network reliability. We discover that PLC links are strongly asymmetric and that temporal variation occurs on three time-scales. There is a high correlation between link quality and its variability, which has a direct impact on probing overhead and on accurate link-metric estimations. Not only do we make it possible for the first time to understand the key features of PLC, but we also propose systematic guidelines for PLC link-metric estimation. The subsequent open questions are related to the efficiency of PLC, when stations contend for the medium. We investigate the PLC MAC layer and uncover that PLC employs a CSMA/CA mechanism that avoids wasting time for collisions, due to PHYlayer features, such as the significantly large frame duration with respect to the time-slot duration. This CSMA/CA bears a resemblance to that of WiFi, in the sense that it includes a binary exponential backoff. WiFi stations double the contention window only after experiencing a collision. In contrast, PLC enables the stations to also double their contention window before experiencing a collision. To this end, PLC introduces