Uplink Pilot Allocation for Multi-Cell Massive MIMO Systems

Wanming HAO  Osamu MUTA  Haris GACANIN  Hiroshi FURUKAWA  

IEICE TRANSACTIONS on Communications   Vol.E102-B   No.2   pp.373-380
Publication Date: 2019/02/01
Publicized: 2018/08/13
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2017EBP3312
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
pilot contamination,  massive MIMO,  pilot allocation,  

Full Text: FreePDF

Pilot contamination due to pilot reuse in adjacent cells is a very serious problem in massive multi-input multiple-output (MIMO) systems. Therefore, proper pilot allocation is essential for improving system performance. In this paper, we formulate the pilot allocation optimization problem so as to maximize uplink sum rate of the system. To reduce the required complexity inherent in finding the optimum pilot allocation, we propose a low-complexity pilot allocation algorithm, where the formulated problem is decoupled into multiple subproblems; in each subproblem, the pilot allocation at a given cell is optimized while the pilot allocation in other cells id held fixed. This process is continued until the achievable sum rate converges. Through multiple iterations, the optimum pilot allocation is found. In addition, to improve users' fairness, we formulate fairness-aware pilot allocation as maximization problem of sum of user's logarithmic rate and solve the formulated problem using a similar algorithm. Simulation results show that the proposed algorithms match the good performance of the exhaustive search algorithm, meanwhile the users' fairness is improved.