Power- and bandwith-efficient relay-assisted communications

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As estimated by the European Commission, the total annual energy consumed by broadband technologies (to provide access to homes) will soon approach 50,000,000,000 KWh (or 50 TWh), out of which 70% is consumed in homes, twice as much energy as spent in servers and across the networks [1]. Taking into account that network data rates are expected to almost double every one and a half years, the power consumption for broadband access technologies and the associated costs are rising exponentially. Driven by these facts, we expect significant changes to occur in the way we communicate today: we are moving from wire-line to wireless access at an exponential rate. As information and communication technologies are driving engines for our society, the profound impacts of such changes are inevitable. Currently, our wireless infrastructure has a rather rigid architecture where communication resources, such as transmit power and radio spectrum at a certain location, are left unused if the user devices are not utilizing these resources to their fullest extent. As such, our wireless networks appear highly inefficient due to its non-dynamic resource allocation strategy. Thus, it becomes very expensive to keep up with the ever increasing demand of ``communicating anywhere anytime''. Alternative network architecture is based on collaboration between different user devices in the network. In co-operative networks, the user devices participate in a collaborative communication strategy to forward/route a message originated from one of these devices and deliver it to the intended destination. Such networks are often called ad-hoc relay networks. While the design of relay networks is still in its infancy, it is essential to consider resource (power and radio spectrum) restrictions at this early stage of the network design to ensure that future relay networks will make highly-efficient use of the available resources, thus providing sustainable communication services to our society. The time to develop ``green networks'' of the future is now and that is what this research focuses on.