Ben A. Witvliet

Medium usage model for the design of dynamic spectrum management in ISM bands

This paper presents a new approach for dynamic spectrum management for heterogeneous wireless devices. Local congestion degrades the reliability of wireless applications in the License Exempt bands. This leads to the research questions: (1) how to realize equal spectrum sharing between dissimilar systems, and (2) how to improve the collective spectrum efficiency. A solution is in dynamic distribution of the available spectrum between contesting devices. Politeness mechanisms embedded in the individual devices are considered as building blocks for the creation of a distributed dynamic spectrum management system. Medium Usage defines the medium occupied by each transmitter and receiver. A regulatory view is chosen, favoring technology neutrality and including receiver parameters.

Multiyear trans horizon radio propagation measurements at 3.5 GHz: System design and measurement results over land and wetland paths in the Netherlands

The design, realization, and measurement results of a high-accuracy multiyear 3.5 GHz trans-horizon radio propagation measurement system are discussed, with both emphasis on the results and implemented technical measures to enhance the accuracy and overall reliability of the measurements. The propagation measurements have been performed on two different paths of 253 and 234 km length, using two transmitters and one receiver in the period September 2013 till November 2016. One of the paths travels over wetland; the other path can be considered as a land path. On each path, an additional transmitter is placed at 107 km (in the 253 km path) and 84 km (in the 234 km path) from the receiver. With this arrangement, the correlation between two nonaligned paths of comparable length, and two aligned paths of dissimilar length, was studied. The measurements show that for the land path, the predicted ITU-R P.452-16 cumulative distribution function (CDF) typically shows 5 dB higher path loss than the actual measured CDF for the region of interest; anomalous propagation. This means that the measured signal is on average weaker than predicted (a higher path loss). For the wetland path, the actual CDF is very close to the predicted CDF. Also, the measurements reveal that typically 30% of the anomalous propagation occurrences are correlated with other paths.

Special Issue on HF Radio Systems and Techniques [Guest Editorial]

The articles in this special issue are dedicated to high-frequency (HF) radio systems and techniques. Up to the 1960s, most telecommunication between the continents was realized by large HF (3–30-MHz) radio systems built especially for that purpose. The ionosphere was used as a natural high altitude reflector to obtain the large operation distances. Inventions such as adaptive beamforming, antenna diversity, and frequency diversity stem from the 1930s, an impressive achievement considering the technology of that time.