  This letter shows that optimizing the transmit powers along with optimally
designed nonorthogonal pilots can significantly reduce pilot contamination and
improve the overall throughput of the uplink multi-cell massive multiple-input
multiple-output (MIMO) system as compared to the conventional schemes that use
orthogonal pilots. Given the optimized nonorthogonal pilots, power control as a
function of the large-scale path-loss can be thought of as a stochastic
optimization problem due to the presence of fast fading. This paper advocates a
deterministic approach to solve this problem, then further proposes a
stochastic optimization method that utilizes successive convex approximation as
a benchmark to quantify the performance of the proposed approach. Simulation
results reveal significant advantage of using optimized nonorthogonal pilots
together with power control to combat pilot contamination.
