A Distributed Mode Selection Scheme for Device-to-Device Communications

The introduction of device-to-device (D2D) communication may provide higher energy efficiency and spectrum efficiency to the traditional cellular network. One important question coming out of this introduction is how to select the transmission mode for user equipment (UE). In this work, we investigate the mode selection problem in a distributed way which gives a rule for determining the transmitter to use cellular transmission or D2D transmission. Firstly, the link performances are analyzed for UE under cellular transmission mode and D2D transmission mode, respectively, and closed-form expressions are presented. Then the optimum mode selection metric is derived to maximize the successful transmission probability for the transmission link. Lastly, a distributed mode selection scheme is proposed which can determine the transmission mode by UE itself without frequent information exchanges. In addition, the link performance can be optimized by using this scheme. Simulation results show that the link performance is dependent on many wireless environment factors such as numbers of existing D2D links and cellular links, channel quality, decoding threshold at the receiver and power control. However, the optimum link performance can be achieved by the proposed scheme under these different deployment conditions and wireless environments. Compared with the random mode selection methods, the proposed scheme can at most improve the link performance by seven times .