An energy efficient multicast transmission scheme with patching stream exploiting user behavior in wireless networks

The widespread requirement of multimedia application, especially Video-on-Demand (VoD), has lead to rapidly rising energy consumption. User behavior brings a great effect on the energy consumption of traffic transmissions. In wireless networks user behavior in terms of user request frequency follows power-law distribution, which indicates that some media streams are requested more frequently than the others. There-fore, exploiting multicast transmission technique for multimedia can significantly reduce the transmission power consumption. However, due to user requests occurs at different moment, in multicast transmission a subsequent user will miss the pervious part of the media stream that has been already transmitted for the early-arriving user. In order to guarantee the quality of service (QoS), the transmitter can deliver the missing fraction of the media stream through initiating separate patching stream. In this paper, we propose an energy efficient multicast scheme with patching stream which enable the transmitter to deliver both patching stream through unicast transmission and shared stream through multicast transmission with dynamic bandwidth allocation. Closed-form formula for power consumption of this scheme is established, in which the impact of the time window length, the user requests distribution are considered. We also derive a tight upper bound on the minimum power consumption under the optimal time window length. Compared to the traditional unicast transmission power consumption which grows like O(e^λ), power consumption in the proposed scheme grows like O(e^√λ), where λ represents the user request rate. Simulation results validate the theoretical analysis and demonstrate that our scheme can lead to 73% and 20% power deduction compared with the traditional unicast transmission scheme and traditional patching multicast transmission scheme.