Millimeter-Wave Channel Sounding: Exploring the Wireless Highway of Tomorrow

October 11, 2022

Robbert Schulpen defended his PhD thesis at the department of Electrical Engineering on October 11th.

A millimeter-wave channel sounder in action (Image credit: Robbert Schulpen).

Slow internet is something that many of us have experienced at one moment or another. This can be caused by congested cellular network, particularly when the network is subject to increased local demands at a stadium or a festival, for example. In the future, the number of devices connected to the internet will only increase, as the ‘Internet of Things’ will see cars, home appliances, and even augmented reality devices all vying to connect to the internet. Higher capacity is needed, and one way is to turn to millimeter-wave signals in the internet of the future. For his PhD research, Robbert Schulpen explored techniques to accurately measure millimeter-waves – which look set to be used in the networks of the future.

The Internet of Things (IoT) is here, and set to get bigger over the coming years. Cars, trains, boats, home appliances, and lots more will all need to connect to the internet, along with traditional devices like computers and smartphones. To prevent congestion, we need a higher capacity cellular network. Besides, new applications will require even higher data rates than the current network can support.

Higher frequencies, so called millimeter-waves, will be used in 5G and 6G networks to increase the capacity of the cellular network and to enable even higher data rates.

Millimeter-wave challenges

The use of millimeter-waves poses several challenges though. Millimeter-waves require directional communications in cellular networks. Furthermore, millimeter-waves experience higher attenuation and blockage in general. The small wavelengths at millimeter-waves also cause small and dynamic objects to have a more significant impact at these frequencies.

For these reasons, it is essential to characterize and understand the millimeter-wave channel between a transmitter and receiver to enable a higher capacity and higher data rates.

Robbert Schulpen (Image credit: Vincent van den Hoogen).

Channel measurements

For his PhD research, Robbert Schulpen explored the techniques needed to accurately measure the millimeter-wave channel. Multiple millimeter-wave channel sounders were developed to measure several properties of the millimeter-wave channel, such as Doppler frequencies and angular characteristics.

Millimeter-wave channel measurements were conducted by Schulpen and his colleagues in several non-line-of-sight environments, which showed that millimeter-wave propagation heavily relies on specular reflections. In addition, an uncertainty analysis methodology to accurately determine uncertainties in wideband millimeter-wave channel measurements is proposed. This is important for the validation of measurement results and drawn conclusions.  

Another exciting topic investigated by Schulpen is millimeter-wave human blockage. After all, we, humanity as a whole, are all part of the millimeter-wave channel. It’s quite easy to attenuate or block millimeter-wave signals with the human body. The impact of dynamic human blockage in indoor environments has been examined. Schulpen found that there are typically other strong paths available for the millimeter-wave signal when the dominant path is blocked by a person. This is an important conclusion for the future of millimeter-wave communications, because human blockage is often regarded as a major challenge for the success of millimeter-wave communications.

Title of PhD thesis: Millimeter-Wave Channel Sounding: Exploring the Wireless Highway of Tomorrow. Supervisors: Bart Smolders, Ulf Johannsen, and Sander Bronckers.

Barry Fitzgerald
(Science Information Officer)

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