Power Control for Massive MIMO Systems with Nonorthogonal Pilots

TL;DR

This paper proposes a joint optimization of transmit power and nonorthogonal pilot design in massive MIMO systems, significantly reducing pilot contamination and enhancing uplink throughput.

Contribution

It introduces a deterministic and a stochastic optimization approach for power control with nonorthogonal pilots, improving over conventional orthogonal pilot schemes.

Findings

Significant throughput improvement with optimized nonorthogonal pilots and power control.

The stochastic optimization method outperforms baseline approaches.

Simulation confirms reduced pilot contamination and enhanced system performance.

Abstract

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.