GREEN IPTV: a resource and energy efficient network for IPTV
Thesis
The distribution of television is currently dominated by three technologies: over-the-air broadcast, cable, and satellite. The advent of IP networks and the increased availability of broadband access created a new vehicle for the distribution of TV services. The distribution of digital TV services over IP networks, or IPTV, offers carriers flexibility and added value in the form of additional services. It causes therefore no surprise the rapid roll-out of IPTV services by operators worldwide in the past few years. IPTV distribution imposes stringent requirements on both performance and reliability. It is therefore challenging for an IPTV operator to guarantee the quality of experience expected by its users, and doing so in an efficient manner. In this dissertation I investigate some of the challenges faced by IPTV distribution network operators, and I propose novel techniques to address these challenges. First, I address one of the major concerns of IPTV network deployment: channel change delay. This is the latency experienced by users when switching between TV channels. Synchronisation and buffering of video streams can cause channel change delays of several seconds. I perform an empirical analysis of a particular solution to the channel change delay problem, namely, predictive pre-joining of TV channels. In this scheme each Set Top Box simultaneously joins additional multicast groups (TV channels) along with the one requested by the user. If the user switches to any of these channels next, switching latency is virtually eliminated, and user experience is improved. The results show that it is possible to eliminate zapping delay for a significant percentage of channel switching requests with little impact in access network bandwidth cost. Second, I propose a technique to increase the resource and energy efficiency of IPTV networks. This technique is based on a simple paradigm: avoiding waste. To reduce the inefficiencies of current static multicast distribution schemes, I propose a semi-dynamic scheme where only a selection of TV multicast groups is distributed in the network, instead of all. I perform an empirical evaluation of this method and conclude that its use results in significant bandwidth reductions without compromising service performance. I also demonstrate that these reductions may translate into significant energy savings in the future. Third, to increase energy efficiency further I propose a novel energy and resource friendly protocol for core optical IPTV networks. The idea is for popular IPTV traffic to optically bypass the network nodes, avoiding electronic processing. I evaluate this proposal empirically and conclude that the introduction of optical switching techniques results in a significant increase in the energy efficiency of IPTV networks. All the schemes I present in this dissertation are evaluated by means of trace-driven analyses using a dataset from an operational IPTV service provider. Such thorough and realistic evaluation enables the assessment of the proposed techniques with an increased level of confidence, and is therefore a strength of this dissertation.