Satellite Communication for the Adaptable Railway Communication System, Lab-Test Results and Field Test Preparation

This paper reports the activities of the X2Rail-5 WP3 work done on an adaptable communication system (ACS) in relation to satellite communication (SatCom). The ACS connects trackside applications with on-board side. Since coverage along the lines with a dedicated system (railway operator owned) is expensive, it can be supplemented using available public networks or other technologies. The paper presents the resutls of a SatCom prototype and the ACS field test preparation

Analytical Model of ALOHA and Time- and Frequency-Asynchronous ALOHA with Forward Error Correction for IoT Systems

The blooming of internet of things (IoT) services calls for a paradigm shift in the design of communications systems. Short data packets sporadically transmitted by a multitude of low-cost low-power terminals require a radical change in relevant aspects of the protocol stack. For example, scheduling-based approaches may become inefficient at the medium access (MAC) layer, and alternatives such as uncoordinated access policies may be preferred. In this context random access (RA) in its simplest form, i.e., additive links on-line Hawaii area (ALOHA), may again become attractive as also proved by a number of technologies adopting it. The use of forward error correction (FEC) can improve its performance, yet a comprehensive analytical model including this aspect is still missing. In this paper, we provide a first attempt by deriving exact expressions for the packet loss rate and spectral efficiency of ALOHA with FEC, and extend the result also to time- and frequency-asynchronous ALOHA aided by FEC. We complement our study with extensive evaluations of the expressions for relevant cases of study, including an IoT system served by low-Earth orbit (LEO) satellites. Non-trivial outcomes show how time- and frequency-asynchronous ALOHA particularly benefit from the presence of FEC and become competitive with ALOHA

A SDR SatCom Prototype for Railway Communication

The public private partnership Shift2Rail is looking for innovations and solutions supporting railways core business and increasing the capacity of the rail system. Therefore, one aspect is the development of a new communication system that improves shortcomings of the current GSM-R system with an adaptable multi-bearer communications system (ACS) considering multiple applications. Multiple bearers like, 5G, LTE, Wi-Fi or SatCom are used to increase the availability, capacity and security of the railways communications by adaptively switching between bearers or using them in parallel, both depending on Quality of Service (QoS). For testing such a system we developed a prototype focusing on railway signalling application that models a SatCom bearer based on Software Defined Radio (SDR). SDR offers a flexible solution and can be adapted to different technologies and future application

Satellite Communication Prototype Based on SDR

The railways industry is at the moment looking for innovations and solutions supporting their core business and increasing the capacity of the rail system. One aspect is the development of a new communication system that improves shortcomings at the European Train Control System (ETCS) with an adaptable multi-bearer train-to-ground communications system. The idea is to increase the capacity and improve the availability of the communication system by using multiple bearers or providers like, 5G, LTE, WiFi or SatCom. Testing these solutions can become cumbersome since multiple networks must be set up and especially in the SatCom case there are multiple options for bearers. SDR offers a solution for this: the bearer can be implemented in software and adapted if needed to model other technologies. We present here a prototype design that modules a satellite channel and can be used to model a satellite bearer

Les méthodes de détermination des [math] des bases faibles. Application au cas des cetones α, β-ethyleniques

La mesure des [math] de vingt six cyclohexéne-2 ones 1 diversement substituées en 3, dans l’acide sulfurique aqueux, à partir de l’évolution des courbes d’adsorption UV, permet d’examiner plusieurs méthodes de détermination de pK fondées sur des hypothèses différentes ainsi que plusieurs méthodes de correction des “effets de milieu” ; ceci conduit à dégager les avantages et inconvénients des diverses méthodes. La méthode de correction des “effets de milieu” de Davis-Geissman s’avère être la plus simple et son efficacité est comparable à celle de l’analyse factorielle des courbes UV de Reeves. L’application de l’équation de Hammett-Deyrup montre que ces cétones suivent la fonction d’acidité HA. Les [math] obtenus à partir de cette équation sont en excellent accord avec les valeurs issues des équations de Bunnett-Olsen et de Cox-Yates

Next-Generation Connectivity in a Heterogenous Railway World

Global System for Mobile communication - Railway (GSM-R) is widely used for operational communications between train and signaler. However, there is a need to define a successor that addresses: obsolescence, radio spectrum demand and the enabling of a range of emerging digital applications such as radio-based signaling and Automatic Train Control (ATC). Therefore, the International Union of Railways (UIC) started the initiative to develop the Future Railway Mobile Communication System (FRMCS). This paper describes an Adaptable Communication System (ACS) that is being developed jointly by industry and railway operators as a possible successor covering all types of railways and all aspects of the FRMCS. A pragmatic approach is suggested that considers diverse railway settings and makes use of various radio access technologies. Countries, geographical regions and infrastructure managers differ concerning available radio technologies, but use of a suitable ACS could pave the way towards innovation in the railway sector. For this adaptive concept we discuss several network models and enhancements including satellite communications (SatCom), Software-Defined Networking (SDN) integration and antenna systems that support multiple bearers in one. For SatCom a software defined radio (SDR) prototype using random access is presented that is able to fulfill the requirements of ETCS. We found that SDN can be used for dynamically changing the access technology for critical and non-critical railway use cases. Furthermore, we present an antenna prototype that can be used for 5G, GSM, WLAN and LTE in parallel which saves limited mounting surface on the train