This paper proposes a flexible pilot assignment method to jointly optimize
the uplink and downlink data transmission in multi-cell Massive multiple input
multiple output (MIMO) systems with correlated Rayleigh fading channels. By
utilizing a closed-form expression of the ergodic spectral efficiency (SE)
achieved with maximum ratio processing, we formulate an optimization problem
for maximizing the minimum weighted sum of the uplink and downlink SEs subject
to the transmit powers and pilot assignment sets. This combinatiorial
optimization problem is solved by two sequential algorithms: a heuristic pilot
assignment is first proposed to obtain a good pilot reuse set and the data
power control is then implemented. Numerical results manifest that the proposed
algorithm converges fast to a better minimum sum SE per user than the
algorithms in previous works.

本文提出一种灵活的载波分配方法，能够联合优化具有相关瑞利衰落信道的多小区大规模多输入多输出系统中的上行和下行数据传输，在最小化加权上下行谱效率之和的约束下，通过利用最大比处理获得的符号误差率的闭式表达式进行优化问题的建模，并使用两种连续的算法来解决组合优化问题和功率控制。数值结果表明，所提出的算法比以前的算法更快地收敛到更好的用户最小和谱效率。