Pilot Allocation and Power Control in D2D Underlay Massive MIMO Systems

In this letter, we propose pilot reuse among device-to-device (D2D) users (DUs) in a D2D underlay massive MIMO system to shorten pilot overhead. First, we derive a lower bound on the average signal-to-interference-plus-noise ratio of DUs. Then, a revised graph coloring-based pilot allocation (RGCPA) algorithm is proposed to mitigate the pilot contamination. Finally, a power control problem to minimize D2D links' data transmit power is formulated and an iterative scheme is adopted to solve the problem. The simulation results show that pilot overhead can be shortened greatly by pilot reuse, and the effect of pilot contamination can be almost cancelled using the proposed RGCPA algorithm. In addition, the power control scheme converges rapidly.