Design and prototype of a train-to-wayside communication architecture

Telecommunication has become very important in modern society and seems to be almost omnipresent, making daily life easier, more pleasant and connecting people everywhere. It does not only connect people, but also machines, enhancing the efficiency of automated tasks and monitoring automated processes. In this context the IBBT (Interdisciplinary Institute for BroadBand Technology) project TRACK (TRain Applications over an advanced Communication networK), sets the definition and prototyping of an end-to-end train-to-wayside communication architecture as one of the main research goals. The architecture provides networking capabilities for train monitoring, personnel applications and passenger Internet services. In the context of the project a prototype framework was developed to give a complete functioning demonstrator. Every aspect: tunneling and mobility, performance enhancements, and priority and quality of service were taken into consideration. In contrast to other research in this area, which has given mostly high-level overviews, TRACK resulted in a detailed architecture with all different elements present

Traffic differentiation: a basic step towards providing end-to-end QoS on the train-to-wayside wireless communication system

We developed a network platform that is responsible for an uninterrupted and seamless connectivity from the train to the wayside through heterogeneous wireless access technologies. However, limiting the offered services to only an onboard Internet is not a feasible business case. A viable one should extend to a broad spectrum of railway communication services like: train control, diagnostics, real time passenger information, entertainment, security CCTV surveillance etc. In a highly dynamic environment (from the communication link point of view) such a fast moving train, it is neccesary to introduce prioritization among different traffic classes. This will implicitly determine under what conditions a certain flow should get suspended or dropped in order to preserve the flows of a higher priority as long as possible and to ensure that they meet their QoS demands. The first step towards this goal is data traffic differentiation

A novel network architecture for train-to-wayside communication with quality of service over heterogeneous wireless networks

In the railway industry, there are nowadays different actors who would like to send or receive data from the wayside to an onboard device or vice versa. These actors are e.g., the Train Operation Company, the Train Constructing Company, a Content Provider, etc. This requires a communication module on each train and at the wayside. These modules interact with each other over heterogeneous wireless links. This system is referred to as the Train-to-Wayside Communication System (TWCS). While there are already a lot of deployments using a TWCS, the implementation of quality of service, performance enhancing proxies (PEP) and the network mobility functions have not yet been fully integrated in TWCS systems. Therefore, we propose a novel and modular IPv6-enabled TWCS architecture in this article. It jointly tackles these functions and considers their mutual dependencies and relationships. DiffServ is used to differentiate between service classes and priorities. Virtual local area networks are used to differentiate between different service level agreements. In the PEP, we propose to use a distributed TCP accelerator to optimize bandwidth usage. Concerning network mobility, we propose to use the SCTP protocol (with Dynamic Address Reconfiguration and PR-SCTP extensions) to create a tunnel per wireless link, in order to support the reliable transmission of data between the accelerators. We have analyzed different design choices, pinpointed the main implementation challenges and identified candidate solutions for the different modules in the TWCS system. As such, we present an elaborated framework that can be used for prototyping a fully featured TWCS

The use of freeze-dried blood samples affects the results of a dried blood spot analysis

Dried blood spot (DBS) microsampling has several advantages over venous blood sampling. In a clinical validation study of tacrolimus microsampling it was noted that tacrolimus DBS concentrations ([Tac]DBS) were systematically higher than tacrolimus whole-blood concentrations ([Tac]WB). This observation was explored by investigating the effect of using freeze-dried standards (STFD) for [Tac]DBS measurement. For all experiments, both non-frozen whole-blood samples and whole-blood samples that were frozen and thawed (to simulate freeze-drying) of 10 patients were analyzed. Multiple tacrolimus concentrations were measured: 1) [Tac]WB, 2) [Tac]DBS, where 15 μL was volumetrically applied to a pre-punched DBS disk, and 3) [Tac]DBS, where 50 μL was applied before a 6 mm DBS disk was punched from the card. All tacrolimus concentrations were determined independently using STFD and standards made of non-frozen blood spiked with tacrolimus (STSP). In both non-frozen and frozen and thawed whole-blood samples, [Tac]WB measured with STFD appeared similar to [Tac]WB measured with STSP (Ratios 1.061 and 1.077, respectively). In non-frozen samples, the median ratio between the [Tac]DBS measured with STFD, and [Tac]WB measured with STFD (the reference method), was 1.396. When blood was volumetrically applied to the DBS card (to eliminate the effect of the spreading over the filter paper), this ratio was 1.009. In conclusion, when using DBS microsampling to quantify concentrations of analytes, one should be aware that using the commercially available freeze-dried blood samples for the preparation of standards may affect the spreading of blood on the filter-paper, leading to a systematic error in the results