Massive MIMO, a key technology for increasing area spectral efficiency in cellular systems, was developed assuming moderately sized apertures. In this article, we argue that massive MIMO systems behave differently in large-scale regimes due to spatial non-stationarity. In the large-scale regime, with arrays of around 50 wavelengths, the terminals see the whole array but non-stationarities occur because different regions of the array see different propagation paths. At even larger dimensions, which we call the extra-large scale regime, terminals see a portion of the array and inside the first type of non-stationarities might occur. We show that the non-stationarity properties of the massive MIMO channel change several important MIMO design aspects. In simulations, we demonstrate how non-stationarity is a curse when neglected but a blessing when embraced in terms of computational load and multi-user transceiver design.

中文翻译：

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超大规模大规模MIMO中的非平稳性

在假设孔径适中的前提下，开发了大规模MIMO，这是提高蜂窝系统中区域频谱效率的关键技术。在本文中，我们认为大规模MIMO系统由于空间的非平稳性而在大规模方案中的行为有所不同。在具有大约50个波长的阵列的大规模系统中，终端看到整个阵列，但由于阵列的不同区域看到的传播路径不同，所以会出现不稳定现象。在更大的维度上（我们称其为超大规模机制），终端会看到阵列的一部分，并且在第一类非平稳性内部可能会发生。我们表明，大规模MIMO信道的非平稳性会改变MIMO的几个重要设计方面。在模拟中