Comparison of cm- and mm-Wave Channel Characteristics between Autonomous Mobile Robots in a small I4.0 Manufacturing Facility

The use of millimeter wave communication for replacing wires in industrial environments has received much interest as part of the Industry 4.0 revolution. MM-wave communication may be used to have manufacturing entities communicate device to device in a decentralized private communication network, e.g. for letting autonomous mobile robots cooperate for improved efficiency and speed. Our objective in this paper is to understand how the device to device channel may be different from the characteristics reported in the literature on the infrastructure-based communication channel, as well as between cm- and near mm-wave. By transmitting and measuring a 5G synchronization signal burst, time-synchronized with the position of two moving robots, we characterize the large- and small-scale propagation characteristics as a function of the line of sight distance within a cluttered manufacturing space. Overall, we find only small differences between 3.8 and 26.4 GHz, however, with a clear indication that propagation at 26.4 GHz is more dominated by the geometric line of sight condition. For distances up to 35 m, path loss characteristics at the two frequencies are almost identical, close to free space propagation, and with shadowing decorrelation according to the (Gaussian) exponential decay model.