Scheduling DTX Time for Densely Deployed Femtocell Networks

Abstract

To reduce rapidly growing power consumption in wireless network infrastructure, cell downlink discontinuous transmission (DTX) has been considered as a promising candidate under discussion by standardization organization. DTX is also regarded as an ideal solution to avoid inter-cell interference, especially when the cell is under low load condition. We proposed a graph-coloring based scheme to mitigate the femto-to-femto interference of densely deployed femtocell networks with the goal of minimizing supply power consumption while they utilize the DTX operation. If femtocell access points (FAPs) choose different slots to transmit their data and leave the other slots in the DTX mode, then femtocells could reduce mutual interference to achieve high SINR thereby resulting in the reduction of power consumption. FAPs report their interferers to femtocell management system (FMS), FMS then constructs an interference graph according to their reporting information. Based on the constructed interference graph, FMS determines which FAPs to include in which color groups (CGs) using our proposed graph-coloring algorithm. Then FMS allocates certain amounts of consecutive slots dedicated to FAPs in each CG and reusable slots to the unsatisfied FAPs by means of our proposed slots allocation algorithm. The simulation results indicate that our proposed solution has better performances than existing schemes in terms of mean power consumption, mean SINR and mean outage probability with a little introduction of signal overhead. In particular, compared with the state-of-the-art scheme, our scheme conserves 15% of power consumption and diminishes almost 85% outage probability.