Figure 1: VDES Frequency Plan and Subsystem Definitions [1]
The aim of this special issue of IJSC&N has been to shed light on potential use cases and relevant technologies applicable to VDES. The first part of this special issue brings together six papers selected among manuscripts submitted to this call addressing verity of topics ranging from channel modelling, antenna technologies, random access protocol as well as geo-localization and ranging applications.
In the paper titled “Satellite forward VDES channel modeling and impact on higher‐layer performance”, G. Giambene et al. use the collected data from a measurement campaign to develop an ON-OFF model for the VDE-SAT downlink channel taking into account the multipath due to the surface reflections and wide-beam receiving antenna. The channel model is subsequently used to assess the effect of link layer coding schemes to combat packet loss during deep signal fading. The proposed technique is particularly important for VDE-SAT downlink broadcasting content such as ice charts to multiple users.
A review of the state-of-the art regarding on-board antenna technologies in VHF bands, particularly for small satellites and CubeSats in Low Earth Orbit (LEO), has been reported by V. Gomez-Guillamon Buendía et. al in their paper titled “Review of antenna technologies for very high frequency Data Exchange Systems”. The paper provides a comparative study of antennas for VDES applications taking into account relevant performance metrics.
The third paper in this special issue entitled “Performance bounds for VDE‐SAT R‐Mode” by J. Safar et al., reports on the growing interest to utilize VDES satellite and terrestrial components to deliver positioning and timing services to vessels, as commonly referred to as ranging mode or R-Mode. The paper in particular investigates the feasibility of using satellite VDES transmission by establishing statistical performance bounds on the ranging error. Reported results complement previous findings of the same authors on the performance bounds obtained for terrestrial VDE waveforms.
The fourth paper entitled “VDES R‐Mode performance analysis and experimental results” by M. Wirsing et al., applies signal processing techniques such as Kalman filtering for position and velocity tracking based on experimental data collected from VDES terrestrial trails. Using the experiment results, authors remark that terrestrial VDES R-Mode is capable of achieving a 95th-percentile horizontal position error of 22 m.
In the paper entitled, “VDES R‐Mode: Vulnerability analysis and mitigation concepts” F. Lázaro et al., report on the use of VDES and its potential vulnerability as a contingency for maritime positioning and navigation systems in case of disruption of the Global Navigation Satellite Systems (GNSS). Authors propose an authentication method for VDES navigation messages.
Finally, in the sixth paper of this special issue R. Andreotti et al. in their paper titled “On-Field Test Campaign Performance of VDE-SAT Link ID 20 over Norsat-2 LEO Satellite”, analyse experiment results of their test campaign based on VDE-SAT uplink random access channel transmissions. The paper also reports on the use of demodulation techniques to successfully decode overlapping messages, confirming the robustness of the VDES protocol against self-interference from random access channel transmissions.
In closing this editorial message, we would like to thank all authors of submitted manuscripts for their excellent contributions. We would also like to recognize the contribution of reviewers for their valuable comments and suggestions to enhance the quality of the papers.