Flow-table updating strategy for efficient use of renewable energy in software defined wireless relay networks

Software defined networking (SDN) is revolutionizing the telecommunication networking industry by providing flexible and efficient management. Because of energy cost and environmental concerns, green networking technologies are being developed to increasing energy efficiency and making use of renewable energy, for both wired and wireless networks. Relay nodes (RNs) are widely used in wireless networks to increasing energy efficiency as well as the network coverage. In this paper, we consider an SDN-enabled wireless relay network, in which the relay nodes are powered by renewable energy. In the beginning, all the users can connect to a BS or an RN in the most energy efficient way, however, the availability of renewable energy is unpredictable, and users connected to an RN will have to be handed over to base stations (BSs) when there is not enough renewable energy to power the RN. There are also occasions when an RN harvested more renewable energy than required to server the users connected to it, in these cases users connected to BS or other RNs can be transferred to connect through this RN, otherwise the harvested surplus renewable energy will be wasted as it cannot be stored. We transform the problem of optimizing the use of harvested renewable energy into a flow-table management problem. A model of harvested renewable energy available for RNs is built first, then we propose a dynamic flow-table updating strategy (DFTUS), which is driven by the availability of renewable energy, to maximize the use of the harvested renewable energy and thus minimize the use of traditional energy. DFTUS can be integrated as an application on top of an SDN controller. Simulation results show that DFTUS can make more efficient use of renewable energy thus make the overall relay network more energy efficient compared with other routing strategies such as the capacity limited strategy (CLS) and the optimal path strategy (OPS).