Long-term power allocation for multi-channel Device-to-Device communication

In underlay Device-to-Device (D2D) communication, a D2D pair reuses the cellular spectrum and creates interference to regular cellular users. Achieving potential improvements in underlay D2D communication requires joint consideration for the achieved D2D rate and the interference to cellular users. In this work, we present stochastic optimization solutions to allocate the D2D transmission power over multiple resource blocks (RBs), to maximize the D2D rate, under a long-term sum-power constraint and long-term individual power constraints over each RB at the D2D transmitter. The long-term sum-power constraint limits the battery usage of the D2D transmitter, and the per-RB constraints give probabilistic guarantees on the interference to regular cellular users. The proposed optimization is applicable to both uplink and downlink cellular spectrum sharing. We present two dynamic algorithms to solve this stochastic optimization problem: a Lagrange dual based algorithm that is optimal but has high computational complexity, and a low-complexity heuristic based on dynamic time averaging. Through simulation, we show that the performance gap between optimal and heuristic algorithms is small, and effective long-term stochastic power optimization over the D2D shared RBs can lead to substantial gains in the ergodic sum rate between D2D and cellular users.