Jelena Senic

A Radio Channel Sounder for Mobile Millimeter-Wave Communications: System Implementation and Measurement Assessment

We describe a state-of-the-art channel sounder to support channel-model development for mobile millimeterwave (mm-wave) communications. The system can measure the complex amplitude, delay, and angle of arrival of the multipath components of indoor and outdoor channels. Specifically, a custom multiplexer (MUX) records the channel impulse response across a 16-element receive (RX) antenna array in 65.5 μs, while the channel is static. The delay resolution of the system is 1 ns and, because the elements are oriented in a 3-D space, both azimuth and elevation angles can be extracted. The robust link budget, comprising high-gain directional RX antennas, enables indoor link measurement beyond 150 m in line-of-sight and 20 m in non-line-of-sight conditions. The RX array is mounted on a location-aware robot, which is battery operated. Combined with the speed of the MUX, untethered acquisition of mobile-channel data is possible. To the best of our knowledge, this paper contributes the first sounder that is capable of mobile measurements at mm-wave frequencies. The hardware implementation of a functional 83.5-GHz system is described in this paper, and some illustrative results, including small-scale statistics and Doppler, are presented.

Measurement Challenges for 5G and Beyond: An Update from the National Institute of Standards and Technology

In less than a decade since the mainstreaming of cellular wireless technology, spectrum has become saturated by data-intensive smartphones, driving the so-called spectrum crunch. As a solution, the wireless community is pursuing the use of alternatives to current wireless technologies, including multiple-input/multipleoutput (MIMO) antenna arrays that allow increased simultaneous transmission capacity; the millimeter-wave (mmW) spectrum (30-300 GHz) to alleviate the spectrum crunch in current frequency bands; and ultradense networks transmitting wide-band modulated signals to allow short-range, high-speed data transfer.

Quasi-Deterministic Model for Doppler Spread in Millimeter-Wave Communication Systems

The most salient feature differentiating millimeter-wave communication systems from their predecessors will be electronically steerable pencilbeam antennas at the transceivers. Due to their extremely narrow beamwidth and the sparse millimeter-wave channel, few multipath components will be captured by the pencilbeams. Although each component has a unique Doppler-frequency shift, the combination of shifts across the detected multipath components captured will give rise to a Doppler spread. The width of the spread is uncertain because, to our knowledge, there are no such measurement results for millimeter-wave systems in open literature to date. To fill this void, we have designed an 83.5-GHz channel sounder that can measure the shift of multipath components in a mobile environment with super-resolution. In this letter, we develop a parameterized model for the Doppler spread by synthesizing the measured frequency shifts through a simulated antenna with variable beamwidth.

Pathloss Models for Indoor Hotspot Deployment at 83.5 GHz

Conventional pathloss models are based on the received power from an omnidirectional antenna. Millimeter-wave receivers, conversely, will feature highly directional antennas that can be steered towards the angle with maximum power, exploiting their high gain in order to compensate for the greater pathloss witnessed in the upper spectrum. Hence models for the maximum power are also valuable. In this paper, we present both model types for indoor hotspot deployment at 83.5 GHz. The environments considered - a basement, lobby, and hallway in line- and non-line-of-sight conditions up to 24 m range - are typical of such deployments. To fit the models, a measurement campaign with over 1500 different transmitter- receiver configurations was conducted using a correlation-based channel sounder. Computation of the maximum-power model is enabled by the sounders custom-designed antenna array which can resolve the receiver power into three-dimensional angles-of-arrival.