Marina Aguado

Railway signaling systems and new trends in wireless data communication

With the increment of passenger railway traffic especially in high speed lines, improvements in railway transportation safety become even more crucial. This paper presents technological and commercial trends in this area, enumerates innovative on-going related projects and proposes the application of new wireless communication standards such as, DSRC - WAVE (Dedicated Short Range Communications and Wireless Access in Vehicular Environment) or 802.11p; 802.16 or WiMAX; and MBWA (Mobile Broadband Wireless Access) or 802.20, in train control communications networks. In order to validate this proposal, we have designed a model for a wireless communication system deployed in a fully redundant configuration. The application of these new open-standard technologies will allow an affordable deployment, ubiquitous, always-on and interoperable muti-vendor mobile broadband train control communication system that supports new safety services and applications. Railway, signaling, wireless, 802.11b/g, MBWA

End-to-End Multipath Technology: Enhancing Availability and Reliability in Next-Generation Packet-Switched Train Signaling Systems

The migration of railway signaling systems based on circuit switching toward Internet protocol (IP) is on the way. Consequently, new strategies to promote reliability in packet-?switching networks must be studied. In this article, we propose the use of multipath technology to enhance the availability and reliability of these communications. To our knowledge, this is the first time that multipath strategies are customized for the railway train-control domain. We present the basic requirements that a multipath protocol must fulfill to increase the reliability and evaluate different related multipath proposals and provide our own customized protocol, the reliable multipath transmission control protocol (RMPTCP). Finally, we demonstrate the availability improvement that our proposed multipath strategy introduces.

The WiMAX ASN Network in the V2I Scenario

This article presents a mobile WiMAX network deployment as a candidate for broadband and low latency V2I communication architecture. Firstly, it looks over the current state of development of the standards involved, outlining the newest trends (i.e. 802.16m support for 500 km/h). Secondly, the opportunities and the main characteristics that this technology offers are highlighted. Thirdly, by stressing this network in two highly demanding scenarios, the challenges that this WiMAX network deployment faces are also identified. Network simulation modeling techniques have been used to carry out the corresponding performance analysis. The inter ASN handover is identified as the critical point to be tackled, so that, the proposed mobile WiMAX architecture meets the WiMAX radio system profile release 1.0 and RNM (reference network model) requirements when the class 2 group real time applications (VoIP & video conference) are deployed.

SCADA Systems in the Railway Domain: Enhancing Reliability through Redundant MultipathTCP

Reliability is a key research issue to promote the role of rail in the transportation system. An important set of critical and vital railway services, such as Traction Power Supply and Supervision Systems, relay currently on modern Supervisory Control and Data Acquisition (SCADA) systems. At the same time, these large scale and networked SCADA systems are deployed over heterogeneous wide area networks. Current strategies to warrant reliability on these systems focus on costly equipment redundancy or retransmission techniques with associated delay penalization. In this paper, we propose a MultiPath strategy with redundant policy to increase reliability in railway SCADA over TCP/IP systems. We built a hybrid simulation tool with real Modbus over TCP/IP equipment and validate our approach comparing the obtained results with three alternative strategies (default TCP/IP, backup and default delivery policy).

Design and formal security evaluation of NeMHIP

NEtwork MObility Basic Support (NEMO BS) is a standardized protocol for managing the mobility of a set of nodes that move together as a whole while having continuous connectivity to the Internet through one or more Mobile Routers (MRs). Because it is based on Mobile IPv6 (MIPv6), it inherits the properties of MIPv6, such as the use of IPsec. However, NEMO BS does not address all the features required by the demanding Intelligent Transportation Systems (ITS) scenario to provide an integrated and global secure mobility management framework. In addition, unlike MIPv6, the routing in NEMO BS is suboptimal, which makes difficult the provision of an adequate service performance. These characteristics make the application of the NEMO BS protocol not optimum in this scenario. An interesting strategy to provide security and good service performance is to consider a protocol that establishes and maintains Security Associations (SAs), such as the Host Identity Protocol (HIP). Different HIP-based approaches have been defined. However, these HIP-based network mobility solutions still present unsolved issues. In this article, we present a secure and efficient network mobility protocol named NeMHIP. NeMHIP provides secure and optimum mobility management and efficient end-to-end confidentiality and integrity protection apart from the basic security properties inherited from HIP. To evaluate the security provisions of NeMHIP, we have conducted a belief-based formal evaluation. The results demonstrate that the defined security goals are achieved by the protocol. Furthermore, we have performed an automated formal evaluation to validate additional security aspects of NeMHIP. Thus, we have modeled NeMHIP using the AVISPA tool and assessed its security when an intruder is present. The results confirm that NeMHIP is a secure protocol that ensures end-to-end confidentiality and integrity without introducing security leaks to the basic HIP. Thus, we have addressed the need found in the literature for providing security and efficiency in the network mobility scenario.

Scanning on handover enhancement issues in video application deployments on WiMAX mobile networks

WiMAX evolution is expected to go through Wireless broadband last mile access, backhaul solutions ending with handset integration. This paper outlines the challenging scenario WiMAX networks face when deploying mobile Internet applications, including the most demanding in terms of latency and data rate: the video applications. The proposed strategy to enhance global network performance has been to apply new handover policies. Several validation methodologies have been approached: testbeds, simulation scenario and a mixed real-to- simulation scenario.

WiMAX Role on CBTC Systems

The recent progresses in mobile telecommunications technologies have allowed railway telecommunications technology to go a step forward, and, in the same way, the railway control systems. In this sense, while the mobile telecommunications technology evolved from the first generation of analogue mobile communication systems to what is known today as B3G (Beyond 3G), the same occurred with the telecommunication systems used in railways, from those based on analogue telecommunications, to the most recent ones based on 2G such as GSM-R or TETRA. Till recently, there was a technological gap regarding high mobility environments, high transmission rate and high interactivity (low latency). However, new emerging telecommunications technologies have shortened this gap significantly. This way, the train control systems will be affected by the availability of telecommunications technologies capable of offering earth-train broadband communications in real time. This article presents a telecommunications network architecture based on WiMAX (Worldwide Interoperability for Microwave Access) mobile technology (IEEE 802.16e) that fulfils the telecommunications needs in the railway environment. The WiMAX mobile technology most relevant features are: transmission rates up to 30Mbps at 15 km distance; mobility support up to 200km/h; QoS, security, low latency, fast, scalable and cost effective deployment, mainly compared to GSM-R deployment. In the mobile node design of this network telecommunications architecture, the multipath fading effect, and the Doppler effect, present in high speed mobility scenarios, have been taken into account. An improvement in the handoff between BSs, through a neighbouring and predictive mobility algorithm, is included. The architecture proposed supports the functional and system requirements identified in the UIC Project EIRENE (European Integrated Railway Radio Enhanced Network), and demanded to GSM-R technology. Measures on a real testbed and a model developed with the discrete event simulation tool, Opnet, have been employed in this work.Copyright

A high performance link layer mobility management strategy for professional private broadband networks

Abstract In this paper, we present an innovative approach to solving the mobility management problem in the context of professional private broadband networks in the vehicular scenario. These heterogeneous communication networks are commonly deployed and managed by mission-critical organisations with the aim of supporting their specific and highly demanding services. Taking advantage of the specific characteristics of these networks, we propose to solve the mobility problem at Layer 2. This way, the mobility management overhead is reduced compared to solutions that operate at Layer 3 or above and therefore, shorter handover delays and better end-to-end application performances are achieved. The core element of our proposal is an intelligent mobile switch that makes use of the services provided by the IEEE 802.21 protocol to enhance vertical or heterogeneous handover performance. To validate our approach, we have developed a prototype implementation of the designed mobile switch with IEEE 802.11 and IEEE 802.16 support. Using this mobile switch implementation, we have carried out a set of experiments over a real testbed and measured some key indicators to assess the mobility management process. The obtained results show that our handover strategy comfortably meets the requirements of the ITU-T Y.1541 recommendation for highly demanding applications and ITU-R report M.2134 for high-speed handover. To the best of our knowledge, our contribution is the first proposal that solves the mobility management problem at Layer 2 while addressing the multi-access technology context in the vehicular professional private network scenario.

The cross layer RMPA handover: a reliable mobility pattern aware handover strategy for broadband wireless communication in a high-speed railway domain

Enhancing the handover process in broadband wireless communication deployment has traditionally motivated many research initiatives. In a high-speed railway domain, the challenge is even greater. Owing to the long distances covered, the mobile node gets involved in a compulsory sequence of handover processes. Consequently, poor performance during the execution of these handover processes significantly degrades the global end-to-end performance. This article proposes a new handover strategy for the railway domain: the RMPA handover, a Reliable Mobility Pattern Aware IEEE 802.16 handover strategy “customized” for a high-speed mobility scenario. The stringent high mobility feature is balanced with three other positive features in a high-speed context: mobility pattern awareness, different sources for location discovery techniques, and a previously known traffic data profile. To the best of the authors’ knowledge, there is no IEEE 802.16 handover scheme that simultaneously covers the optimization of the handover process itself and the efficient timing of the handover process. Our strategy covers both areas of research while providing a cost-effective and standards-based solution. To schedule the handover process efficiently, the RMPA strategy makes use of a context aware handover policy; that is, a handover policy based on the mobile node mobility pattern, the time required to perform the handover, the neighboring network conditions, the data traffic profile, the received power signal, and current location and speed information of the train. Our proposal merges all these variables in a cross layer interaction in the handover policy engine. It also enhances the handover process itself by establishing the values for the set of handover configuration parameters and mechanisms of the handover process. RMPA is a cost-effective strategy because compatibility with standards-based equipment is guaranteed. The major contributions of the RMPA handover are in areas that have been left open to the handover designer’s discretion. Our simulation analysis validates the RMPA handover decision rules and design choices. Our results supporting a high-demand video application in the uplink stream show a significant improvement in the end-to-end quality of service parameters, including end-to-end delay (22%) and jitter (80%), when compared with a policy based on signal-to-noise-ratio information.

A novel architecture for secure, always-best connected ship-shore communications

Together with the IMOs future navigation system implementation strategy, the e-navigation, wireless access technologies are proliferating on the maritime scenario, covering last mile communications. In the near future, we foresee that communication technologies will coexist and will be available in overlapping areas through the maritime last mile. Therefore, in order to enhace ship-shore communications, always-best-connected procedures and an efficient mobility management protocol is required to satisfy maritime context peculiarities such as safety and security. In this article we analyze the most suitable mobility management protocol in terms of security and handover efficiency and propose a novel architecture that integrates the HIP protocol and always-best-connected procedures to best achieve maritime context specifications.