Wireless communications networks are handling increasing amounts of data, with each user depending upon their mobile communications devices as a form of starting point for daily activities. To facilitate data transfers from wireless networks to mobile devices, data kiosks are being developed for use at frequencies with wide available bandwidths, such as millimeter-wave and terahertz frequencies. Due to the small wavelengths at these high frequencies, channel modeling is essential to ensure high data rates between kiosk transmitter and mobile handset receiver.
In pursuit of a short-distance, stochastic channel model that can be applied in such applications at millimeter-wave and terahertz frequencies, an international team of researchers from Germany, Japan, and China analyzed a number of wireless kiosk scenarios. They studied existing wireless data kiosk setups based on material compositions and for the different geometrical link configurations each presented between transmitter and receiver, performing ray-tracing (RT) simulations to determine key channel parameters.
The researchers based their studies on the work of the IEEE 802.15.3 task group 3d (TG3d) and on an amendment of the standard for 100-Gb/s point-to-point data links operating at 252 to 325 GHz. The amendment of the standard applies to various wireless short-distance links, including kiosk terminals in airports and train stations. Even though the typical transmission range of these systems is on the order of centimeters, the multiple paths between the kiosk transmitter and the handheld receiver can result in problematic multipath signal conditions that can degrade short-haul data rates. By developing channel models for these millimeter-wave and terahertz-frequency-band signals, it is possible to optimize the data rates for a variety of kiosk operating conditions.
To acquire RT data for the models, measurements were performed with a commercial vector network analyzer (VNA) operating from 220 to 340 GHz in an anechoic chamber with commercially available horn antennas to determine radiation patterns. S21 measurements were made at various distances between the transmitter and the receiver to emulate the conditions between a user at a data kiosk with a handheld mobile wireless device. Since users may also hold a mobile wireless device at different angles to the kiosk transmitter’s faceplate, these different angles of departure (AoDs) and angles of arrival (AoAs) between the transmitter and receiver were also considered in extracting the kiosk channel characteristics.
The collected data were applied to the development of a three-dimensional (3D) RT simulator that can model the different potential positions and angles between the kiosk transmitter and the handheld receiver. The model includes various delays, phases, and multipath components and has been evaluated for accuracy at different frequencies and with different bandwidths with good results, showing that it is possible to achieve a target data rate of 100 Gb/s for the three data kiosk scenarios under the right conditions and communications distances.
See “Stochastic Channel Modeling for Kiosk Applications in the Terahertz Band,” IEEE Transactions on Terahertz Science and Technology, Vol. 7, No. 5, September 2017, p. 502.