Energy-Efficient D2D Communication Based Retransmission Scheme for Reliable Multicast in Wireless Cellular Network

In the traditional reliable multicast schemes of wireless cellular network, base station (BS) repeatedly transmits the same packet until it is received by all receivers. The use of device-to-device (D2D) communication can greatly offload the traffic of BS. This paper considers D2D communicationbased multicast from BS to a cluster of devices which are close to one another (e.g., in the same building). So far, the efficient D2D retransmission scheme available is to associate each NACK-device (which did not correctly receive the data from BS) to some near ACK-device (which correctly received the data) for forming subclusters, and let ACK-devices retransmit the data to their respective associated NACK-devices in the FDMA mode by using multiple channels, aiming to minimize the time-frequency resource cost. Noticing that the total available channels are very limited and the devices' energy is a very precious resource, in this paper, we first present the subcluster-based single-channel D2D retransmission way where the ACK-devices use the same channel in the TDMA mode. Then, aiming to minimize the total energy consumption of retransmitters, we formulate the joint optimization of NACK-devices' association and retransmitters' transmission powers to be a mixed integer programming problem. Finally, we propose an efficient algorithm for this problem to find a good association pattern and transmission powers. Simulation results show that, using D2D communication greatly reduces multicast traffic load of BS. Moreover, compared to its counterparts with a fixed number of retransmitters, our retransmission scheme greatly reduces the total energy consumption of retransmitters.