Coordinated multicast and unicast transmission in V2V underlay massive MIMO

This paper investigates coordinated multicast and unicast transmission for vehicle-to-vehicle (V2V) underlay massive multiple-input multiple-output (MIMO). First, the achievable ergodic multicast rate for the cellular link and the achievable ergodic unicast rate for all the V2V links are summed with weight to formulate the rate optimization problem, with the assumption that the statistical channel state information (CSI) is known at the base station and the transmitters of the V2V communication pairs. We then derive the optimal transmitting directions in closed-form for the cellular link and all the V2V links, respectively, which converts the original optimal problem to a simpler power allocation problem in the beam domain. Via invoking the concave-convex procedure, an efficient iterative algorithm with guaranteed convergence is proposed for the power allocation problem. Furthermore, we replace the objectives which contain high-complex expectation operations with their deterministic equivalents in each iteration of the proposed algorithm to achieve lower algorithm complexity. Simulation results show the fast convergence speed of the proposed power allocation algorithm and the significant performance gains of the proposed transmission design for V2V underlay massive MIMO.