Cellular systems evolved from a dedicated mobile communication system to an almost omnipresent system with unlimited coverage anywhere and anytime for any device. The growing ubiquity of the network stirred expectations to determine the location of the mobile devices themselves. Since the beginning of standardization, each cellular mobile radio generation has been designed for communication services, and satellite navigation systems, such as GPS, have provided precise localization as an add-on service to the mobile terminal. Self-contained localization services relying on the mobile network elements have offered only rough position estimates. Moreover, satellite-based technologies suffer a severe degradation of their localization performance in indoors and urban areas. Therefore, only in subsequent cellular standard releases, more accurate cellular-based location methods have been considered to accommodate more challenging localization services. This survey provides an overview of the evolution of the various localization methods that were standardized from the first to the fourth generation of cellular mobile radio, and looks over what can be expected with the new radio and network aspects for the upcoming generation of 5G.

Absolute positioning of vehicles is based on Global Navigation Satellite Systems (GNSSs) combined with on-board sensors and high-resolution maps. In cooperative intelligent transportation systems, the positioning performance can be augmented by means of vehicular networks that enable vehicles to share location-related information. This paper presents an implicit cooperative positioning (ICP) algorithm that exploits the Vehicle-to-Vehicle (V2V) connectivity in an innovative manner, avoiding the use of explicit V2V measurements such as ranging. In the ICP approach, vehicles jointly localize non-cooperative physical features (such as people, traffic lights, or inactive cars) in the surrounding areas, and use them as common noisy reference points to refine their location estimates. Information on sensed features are fused through V2V links by a consensus procedure, nested within a message passing algorithm, to enhance the vehicle localization accuracy. As positioning does not rely on explicit ranging information between vehicles, the proposed ICP method is amenable to implementation with off-the-shelf vehicular communication hardware. The localization algorithm is validated in different traffic scenarios, including a crossroad area with heterogeneous conditions in terms of feature density and V2V connectivity, and a real urban area by using Simulation of Urban MObility (SUMO) for traffic data generation. Performance results show that the proposed ICP method can significantly improve the vehicle location accuracy compared to the stand-alone GNSS, especially in harsh environments, such as in urban canyons, where the GNSS signal is highly degraded or denied.

This work presents an overview of the radio interface of VHF Data Exchange System (VDES), which is currently on its way to become an ITU standard supported by International Association of Marine Aids to Navigation and Lighthouse Authorities. VDES includes the already existing collision avoidance tracking system Automatic Identification System and the messaging system Application Specific Messages. Additionally, a new third component for digital maritime communications of any kind, named VHF Data Exchange is included. On the one hand, there is a traditional terrestrial component, on the other hand, a satellite communication link is also envisioned partly by the same spectrum usage. In this article, focus is given towards the technical design aspects and challenges of this hybrid communications transmission scheme.

The delay power spectrum is widely used in both communication and localization communities for characterizing the temporal dispersion of the radio channel. Experimental investigations of in-room radio environments indicate that the delay power spectrum exhibits an exponentially decaying tail. This tail can be characterized with Sabine's or Eyring's reverberation models, which were initially developed in acoustics. So far, these models were only fitted to data collected from radio measurements, but no thorough validation of their prediction ability in electromagnetics has been performed yet. This paper provides a contribution to fill this gap. We follow Sabine's original experimental approach, which consists in comparing model predictions to experimental observations in a room, while varying its mean absorption coefficient and total room surface. We find that Eyring's model provides a more accurate prediction of the parameters characterizing the decaying tail, such as the reverberation time, than Sabine's model. We further use the reverberation models to predict the parameters of a recently proposed model of a distance-dependent delay power spectrum. This model enables us to predict the path loss, mean delay, and root mean square (rms) delay spread versus transmitter-receiver distance. We observe good agreement between predictions and experimental results.

This paper presents a geometric stochastic channel model designed for analyzing maritime communication and navigation services between moving ships using the C-band or sub-6 GHz spectrum, which aligns with the focus of emerging 5G networks on land. The channel model is validated through channel measurements conducted both on the sea and land. A software tool has been developed to integrate and analyze these measurements, which is included with this publication. The main challenge in developing the channel model for maritime services lies in the dynamic nature of the sea surface, leading to constantly changing reflection conditions due to varying reflectors and scatterers on the water. Additionally, the motion conditions of the transmitter and receiver on ships change in all three dimensions, depending on the sea state. To address these complexities, data from several measurement campaigns in diverse areas were collected. The analysis involved examining the propagation conditions over the sea with variations in sea surface roughness, antenna heights, and used bandwidths. Moreover, additional propagation conditions over nearby land were also taken into account. The study demonstrates that the changing antenna height on the ship, influenced by sea conditions, significantly affects the reflection and scattering conditions. The research aims to develop reliable, high-data rate, and broadband marine communication systems. Therefore, a measurement bandwidth of 120MHz was employed to derive the propagation model. This model not only offers absolute timing information but can also be used for time-based ranging or positioning systems. The proposed geometric stochastic channel model provides valuable insights into the complex maritime communication and navigation environment. By accounting for the continuously evolving sea surface and its impact on antenna height, the model offers a robust framework for studying and optimizing marine communication systems. The availability of a software tool integrating real-world measurements further enhances the usability and practicality of the channel model for future maritime communication research and deployment.

Summary: Global Navigation Satellite Systems (GNSS) have become an essential part of maritime navigation, in particular to improve situational awareness and vessel traffic management. The dependence on GNSS creates vulnerability for maritime shipping. Driven by this vulnerability, the desire for a backup system for maritime navigation has been emerging. The VHF Data Exchange System (VDES) standard provides communication capabilities for maritime applications. VDES is currently being revised. As part of this revision, VDES will be extended by ranging and navigation functionalities, called R‐Mode, as an alternative for maritime navigation. In this paper, we address system design aspects and evaluate the positioning performance of VDES R‐Mode. We derive estimation theory bounds on the accuracy of VDES R‐Mode distance and velocity. In a case study, we discuss and evaluate the benefit of satellite links to complement VDES R‐Mode positioning. Furthermore, we introduce a Kalman filter for position and velocity tracking, which we apply to experimental data. We describe an experiment we conducted at Lake Ammer, southwest of Munich, and evaluate the VDES R‐Mode positioning performance for this setup. Our experimental results show that VDES R‐Mode is capable of achieving a 95th‐percentile horizontal position error of 22 m. Thus, VDES R‐Mode is a promising approach for a maritime backup system that can meet the IALA accuracy requirements.