A tractable model for optimizing device-to-device communications in downlink cellular networks

In this paper, we develop a tractable and accurate framework for a Device-to-Device (D2D) enabled downlink cellular network with a dedicated spectrum approach, meaning that D2D links use a frequency band orthogonal to the cellular users. Using stochastic geometry, we provide accurate expressions for SINR distributions and average rates, under an assumption of interference randomization via time and/or frequency hopping. The obtained analytical results allow us to easily explore and optimize the impact of system parameters. For example, we find the optimal frequency hopping probability for the D2D users, i.e. how often they should randomly access a subband. We also propose an optimization approach for mode selection, i.e. when should potential D2D users transmit directly, and when should they fall back to the cellular mode. This can be viewed as an optimized lower bound to other more sophisticated scheduling schemes.