Cell-free widely distributed massive multiple-input multiple-output (MIMO) systems utilize radio units spread out over a large geographical area. The radio signal of a user equipment (UE) is coherently detected by a subset of radio units (RUs) in the vicinity of the UE and processed jointly at the nearest baseband processing unit (BPU). This architecture promises two orders of magnitude less transmit power, spatial focusing at the UE position for high reliability, and consistent throughput over the coverage area. All these properties have been investigated so far from a theoretical point of view. To the best of our knowledge, this work presents the first empirical radio wave propagation measurements in the form of time-variant channel transfer functions for a linear, widely distributed antenna array with 32 single antenna RUs spread out over a range of 46.5 m. The large aperture allows for valuable insights into the propagation characteristics of cell-free systems. Three different co-located and widely distributed RU configurations and their properties in an urban environment are analyzed in terms of time-variant delay-spread, Doppler spread, path loss and the correlation of the local scattering function over space. For the development of 6G cell-free massive MIMO transceiver algorithms, we analyze properties such as channel hardening, channel aging as well as the signal to interference and noise ratio (SINR). Our empirical evidence supports the promising claims for widely distributed cell-free systems.
翻译:用户设备(UE)的无线电信号由UE附近的一组无线电单位(RUs)一致检测,并在最近的基带处理单位(BPU)联合处理。这一结构可以提供两个数量级的输电量较少的信号,空间聚焦于UE位置,具有高度可靠性,而且覆盖区的传输量一致。所有这些特性都从理论角度进行了研究。根据我们的最佳知识,这项工作展示了第一个实验性无线电波传播测量,其形式为线性、分布广泛的天线阵列和32个单一天线RUs分布在46.5米的范围。大孔可以对无细胞系统的传播特性有宝贵的洞见。三个不同的共同地点和广泛分布在UE位置的空间配置及其在城市环境中的特性,从时间差异性延迟分布、多普勒扩散、路径丢失和当地分散式无线电波传播波传播波传播功能,其形式为线性、广泛分布式天线阵列传输功能,其范围分布在46.5米范围内。大孔能够对无细胞系统的传播特性进行有价值的洞察。我们作为无声势分析系统进行大规模分析。