Joint Pilot Sequence Design and Power Control for Max-Min Fairness in Uplink Massive MIMO

摘要

This paper optimizes the pilot assignment and pilottransmit powers to mitigate pilot contamination in MassiveMIMO (multiple-input multiple-output) systems. While priorworks have treated pilot assignment as a combinatorial problem,we achieve a more tractable problem formulation by directlyoptimizing the pilot sequences. To this end, we compute alower bound on the uplink (UL) spectral efficiency (SE), forRayleigh fading channels with maximum ratio (MR) detectionand arbitrary pilot sequences. We optimize the max-min SEwith respect to the pilot sequences and pilot powers, under powerbudget constraints. This becomes an NP-hard signomial problem,but we propose an efficient algorithm to obtain a local optimumwith polynomial complexity. Numerical results manifest the nearoptimality of the proposed algorithm and show significant gainsover existing suboptimal algorithms.