Massive MIMO (M-MIMO) is one of the most promising technologies towards fifth generation (5G) wireless systems. M-MIMO use a large number of antennas at the base station (BS) serving multiple user terminals (UTs). Therefore, it presents an exceptional performance in terms of the ergodic capacity and bit error rate (BER) using simpler linear detectors when time-invariant channels (TIC) and perfect channel state information (CSI) are considered. However, impairments introduced by the time-variant channel (TVC) and the imperfect channel estimation limit the M-MIMO performance. In this work, the impairments introduced by the multiplexed pilot estimation (MPE), superimposed pilot estimation (SPE), and hybrid pilot estimation (HPE), using the minimum-mean-square error (MMSE) estimator are analyzed for M-MIMO in TVCs. Furthermore, the system performance is evaluated in terms of the BER for the zero-forcing (ZF) detector. Closed-form expressions and simple lower bounds are derived. The results show that the average BER in TVCs is far from the average BER obtained for TICs. Moreover, MPE and HPE are more susceptible to the impairments of TVCs, and even increasing a considerable number of BS antennas, the BER improvement is negligible in some time-slots. Finally, the BER using SPE outperforms the other estimation techniques.

大规模MIMO（M-MIMO）是第五代（5G）无线系统中最有前途的技术之一。M-MIMO在为多个用户终端（UT）服务的基站（BS）使用大量天线。因此，当考虑时不变信道（TIC）和完美信道状态信息（CSI）时，使用更简单的线性检测器，在遍历容量和误码率（BER）方面表现出卓越的性能。然而，由时变信道（TVC）引入的损害和不完美的信道估计限制了M-MIMO性能。在这项工作中，使用最小均方误差（MMSE）估计器分析了由复用导频估计（MPE），叠加导频估计（SPE）和混合导频估计（HPE）引入的损伤，以进行M-MIMO TVC。此外，系统性能是根据零强制（ZF）检测器的BER评估的。得出封闭形式的表达式和简单的下界。结果表明，TVC中的平均BER与TIC的平均BER差距很大。而且，MPE和HPE更容易受到TVC的损害，甚至增加了相当数量的BS天线，在某些时隙中BER的改善也可以忽略不计。最后，使用SPE的BER优于其他估计技术。BER的改善在某些时隙中可忽略不计。最后，使用SPE的BER优于其他估计技术。BER的改善在某些时隙中可忽略不计。最后，使用SPE的BER优于其他估计技术。