2018 年 7 巻 5 号 p. 154-159
This paper proposes a hardware configuration for uplink multiuser multiple-input multiple-output (MU-MIMO) transmissions with distributed antenna systems (DASs) in real indoor environments. Beam-forming (BF) technology is used in the DAS with massive MIMO. In massive MIMO transmission, signal processing becomes complicated because of the massive antennas. Therefore, in general, a technique known as digital beamforming (DBF) is adopted, in which the weight values are calculated through digital signal processing. Massive MIMO systems applying DBF, which requires receivers for all massive antennas, have problems related to power consumption and cost because the access point becomes large.
We propose an analog–digital hybrid configuration, which selects antennas using a many-to-one switch connected to the antenna. In the proposed configuration, it is possible to reduce the number of receivers required, by grouping antennas using many-to-one switches. In this paper, we evaluate the effect of the proposed configuration through computer simulations using the propagation channels obtained from experiments conducted in real indoor environments. The effectiveness of the proposed configuration is demonstrated by comparing the basic characteristics, when antennas are selected according to the conventional full-digital configuration and the proposed analog–digital hybrid configuration.
