In this paper, we investigate the strategy of transmission mode switching for device-to-device (D2D) communication in both single-cell scenario and multi-cell scenarios, which selects the transmission mode to guarantee the maximum ergodic achievable sum-rate among three transmission modes. We first introduce the basic operation principles of three communication transmission modes which are named as traditional cellular communication mode, direct D2D communication mode and two-way decode-and-forward (DF)-relayed D2D communication mode. Then we derive the corresponding expressions for the ergodic achievable sum-rates of each transmission mode, and get the crossing points of different transmission modes to attain maximum ergodic achievable sum-rate of the system. From the analytical results, we can see that the proper operating region of each transmission mode is related to different interference level and distance of the D2D users. Based on the analytical results, we obtain a reliable communication transmission mode switching strategy which guarantees the system to choose the mode with the maximum ergodic achievable sum-rate so as to improve the performance of D2D communication. Numerical results demonstrate that by applying mode switching, the ergodic achievable sum-rate of the system achieves a remarkable enhancement.
['Yiyang Ni', 'Dan Qiao', 'Xiao Li', 'Shi Jin', 'Hongbo Zhu']
Transmission mode switching for device-to-device communication aided by relay node