Joint pilot assignment and pilot contamination precoding design for massive MIMO systems

This paper investigates the joint design of pilot assignment and pilot contamination precoding (PCP) to combat pilot contamination in multi-cell multi-user massive MIMO systems. The system performance of the downlink transmission in massive MIMO with PCP is investigated and an optimization problem is formulated to find the best pilot assignment solution in PCP assisted massive MIMO systems that can maximize the sum rate of the system. Two heuristic pilot assignment schemes are proposed to combine with zero forcing PCP (ZF-PCP) including a greedy scheme and a swapping-based scheme. The complexities of the both schemes are analyzed. Simulations are done and results indicate that the proposed two schemes perform well and can greatly outperform the ZF-PCP scheme and an existing enhanced PCP scheme with random pilot assignment. Results also show that obvious performance gain can be obtained by joint designing the pilot assignment and PCP.