Potential use of wireless networking in trains

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Stanley Hines
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1 P.O. Box 9 Tel.: AA VENLO The Netherlands Technical article FAST WIRELESS ACCESS ON BOARD Potential use of wireless networking in trains Top-speed data communication is taken for granted in many areas today. So it is all the more remarkable that even very recently designed trains pay almost no attention to wireless technology. This article explains the difficulties that have to be faced and what shape a solution might take. Frequent train commuters will know the situation: the train arrives on time, but even before it reaches the platform it is announced that the cars are not in the order shown. Sometimes there are even cars missing. The result of this is that passengers on the platform, and subsequently in the train, have extreme difficulty locating their reserved seats. When some of the expected cars are not included, the corresponding reservations will also be missing. If trains were equipped with broadband Ethernet networking, it would be possible to implement this and numerous other applications that airline passengers, for instance, have learned to take for granted: onboard entertainment with a selection of different films that can be shown on request; access to or internet from the train; up-to-date information about connections, delays and so on. A broadband network would enable staff on board to improve the proffered service by providing a central overview of the occupancy of individual cars. Video monitoring and fastresponse emergency services could also serve to improve safety. But even now, trains are equipped only with cable-based networking. There are two reasons for this their robustness and their durability. Any broadband connection on board a train suffers primarily from the fact that each of the couplings between cars acts as a bottleneck, Page 1

2 substantially slowing down the data transfer. They are the most heavily used connections, and are subjected to a great deal of wear and tear. Changing temperatures, rain, snow and sleet, contamination with dirt, and impacts from loose chippings all demand extremely robust, welldesigned plugs and sockets for the cable connections that have to pass through the couplings. This is why, to date, trains have, at most, digital bus technology or modulated Ethernet using the UIC line. For many years, Ethernet has been gradually ousting conventional bus technology from the field of industrial automation. Bus technology is relatively simple and extremely reliable, but it does not lend itself to networking, and many of the available forms are mutually incompatible. Ethernet has the advantage of allowing the individual subscribers to be networked, and is also a standardized technology (IEEE 802.3), meaning it can be upgraded with additional modules anywhere in the world at relatively low cost. Ethernet networking not only permits high data speeds, it also facilitates fast recognition of the train configuration and is readily extensible. To date, however, connections through train couplings have at best achieved rates of 10 MBit/s. A wireless network is the obvious solution to this problem. Wireless LAN (WLAN), as described in the IEEE standard, is a wireless Ethernet network. Thus far, the WLAN standard has diversified into four variants, from the venerable but still common IEEE802.11b standard, offering gross data rates of up to 11Mbit/s, right up to the brand new IEEE802.11n standard, which currently offers up to 300Mbit/s, and is scheduled to reach 450Mbit/s in a subsequent stage. These rates are perfectly adequate for implementing the desired facilities and services in the train, and for future requirements such as electronic rear-view mirrors or front cameras to improve passenger comfort. A wireless network can be installed in an existing network the existing cables and couplings do not need to be modified. Page 2

3 In practice, we find that there are some technical problems that remain to be solved even with a wireless LAN. Installing WLAN access points, and particularly antennas, in an existing train can be quite a challenge. Every inch of space is already taken up. Naturally, small, easy-toinstall units will be advantageous here. A further advantage can be achieved by reducing the number of units required through the integration of more than one WLAN interface into a single access point. The units naturally also have to meet all the standards required for equipment that is installed in trains. These are stringent requirements, and cannot be fulfilled by just any device. But the greatest challenge is caused, of all things, by the simple fact that a wireless network has no external boundary. Electromagnetic waves do not stop when they reach the side of the train. Setting up a connection between two cars or train sections needs only to bridge a very short distance. It is particularly important to prevent two neighboring trains from setting up an unwanted connection. And, naturally, there have to be safeguards to prevent unauthorized persons from gaining access to a train s internal network. Modern WLAN equipment is perfectly able to meet these requirements. Authentication and encryption are mechanisms that are described in the WLAN IEEE802.11i safety standard, which is supported by almost all modern products. The solution to the second task setting up correct one-to-one connections between one train section and another calls for equipment features above and beyond those stipulated by the standards. The embedded operating systems in the WLAN access points are capable of supporting the verification of connections, thereby supplying a certain native intelligence. With appropriate programming of the system, and powerful management software to monitor and control the wireless and cable-based network, the solution is as good as complete. As a manufacturer of both industrial standard Ethernet hardware and powerful management software, Belden offers such complete solutions from its range of Hirschmann products. The management software uses LLDP to recognize the topology of the train s on-board network. This information can then be used to flexibly assign numbers to cars, seats, etc. The industry s tried-and-tested redundancy mechanisms reinforce the reliability of the network. Hirschmann WLAN access points support all the usual rail standards, and also offer the very latest WLAN standard. Page 3

4 This IEEE802.11n standard offers transmission rates of up to 300Mbit/s plus markedly increased transmission stability. A further benefit of a WLAN is the option of video transmissions. This new standard is supported, for instance, by Hirschmann BAT300 access points/access clients, which are available in both IP40 (BAT300-Rail) and IP65/67 (BAT300-F) versions. The integrated MIMO technology (multiple input multiple output) ensures a stable radio connection even in the event of reflections or other forms of interference. The units possess a compact metal housing and can be used at temperatures from -30 C to +50 C or +55 C (BAT 300-F). This makes it possible to set up fast and stable infrastructure networks, wireless distribution systems (WDS), or point-to-point connections, even in harsh environments. While BAT300-Rail, which can be latched onto a top-hat rail, is designed for use inside a switch cabinet, the BAT300-F can be used both indoors and outdoors. This version, which has a housing that is also able to withstand salt water, can be attached magnetically to the outside wall of a wind power station without affecting the station s static equilibrium. Both versions possess a radio module that operates in the 5GHz waveband (BAT300-Rail) or in either the 5GHz or 2.4GHz waveband (BAT300-F). Fast roaming facilitates an uninterrupted connection when transferring from one radio cell to another. The antenna connections use N (BAT300-F) or R-SMA sockets (BAT300-Rail), and the LAN ports (10/100 BASE-TX) are connected via M12 (BAT300-F) or RJ45 (BAT300-Rail), which support PoE as specified in the IEEE802.3af standard. A serial V.24 interface is also available. A redundant power supply is provided by two 24 VDC and one 48 VDC PoE connections (BAT300-F) or two 24 VDC, two 48 VDC PoE and one 12 VDC connections (BAT300-Rail). With an integrated IP router, it is possible to set up as many as eight subnetworks, which can be assigned to corresponding ports and interfaces in the access points / access clients. It is also possible to connect both analog and DSL modems, for instance for WAN routing or remote maintenance. Management functions can be carried out via the web interface, Telnet, TFTP, FTP or SNMP V2. The redundancy protocols Rapid Spanning Tree and VRRP ensure high availability of the network. Among other features, the quality-of-service functions specified by IEEE e provide for the prioritization of voice or video streams. Page 4

5 Both BAT300-Rail and BAT300-F support all the standardized encryption and identification methods specified by IEEE i and 802.1x/EAP, plus WEP, WPA, WPA2, TKIP, and AES. LEPS can be used to make WPA2/PSK even more secure, and there are also WLAN port and protocol filters, a radius server, and a firewall equipped with intrusion detection. Rogue AP detection is also available by means of background scanning and WLAN monitor. With the WLAN access points / access clients of its Hirschmann BAT range, Belden offers a comprehensive product program for wireless data transmission that was especially designed for indoor and outdoor applications in an industrial environment. Two product versions (BAT54-FX2 and BAT 300-FX2) can even be used in potentially explosive atmospheres. Page 5

6 All BAT devices have a robust metal housing, an extended temperature range, M12 sockets, and a high protection class. Since they also possess two WLAN interfaces they can operate simultaneously in the 2.4GHz and 5GHz wavebands. They also offer particularly robust antennas that support the multiple input multiple output (MIMO) technology used in the IEEE802.11n standard, without which worthwhile data rates cannot be achieved over long distances. Conclusion The use of Ethernet networks in trains offers numerous ways of increasing passengers safety, and convenience, and their acceptance of rail transport. Existing trains can also be equipped without needing to rethink or modify their cabling, which is a considerable potential advantage in terms of time and money when trains are retrofitted and/or redesigned. Combining a cablebased Ethernet network with its wireless counterpart can provide an elegant solution to one of the core problems of on-board networks for trains, namely the couplings between cars, but it is necessary to use robust hardware and industrial-standard management software for long-term, secure operations. Pictures Railroad operators can use Ethernet technology and its wireless counterpart WLAN to make many of their processes and services more flexible and more agreeable for their passengers. Page 6

WLAN can be used to set up a broadband Ethernet connection

7 An on-board Ethernet network makes it possible to rapidly recognize the configuration of the train. WLAN can be used to set up a broadband Ethernet connection from one car to another, thus avoiding the obstacle represented by the coupling. Page 7

8 Hirschmann BAT access points and antennas are suitable for use in trains. Belden is also a certificated manufacturer of on-board equipment for trains. Page 8

9 The Author Olaf Schilperoort Product Manager Industrial Networking Responsible for Belden s Hirschmann series. Stuttgarter Strasse Neckartenzlingen Germany Phone: +49 (0) Fax: +49 (0) olaf.schilperoort@belden.com Olaf Schilperoort is a graduate engineer and MBA, who was born in Luxembourg on July 1, After graduating from high-school and training as an electronics technician for power equipment at OSRAM GmbH, he went on to study electrical engineering, specializing in communications engineering, at the RWTH and Aachen university of applied sciences. In November 2005, he successfully completed a supplementary course in MBA Entrepreneurship at the Aachen university of applied sciences. At the end of 1997 Mr. Schilperoort commenced work at ELSA AG, in 1999 taking over product management and project management for Wireless LAN technology in the Communication Systems business area. In 2003 Mr. Schilperoort took over product management of the wireless LAN portfolio at LANCOM Systems GmbH, where he was instrumental in setting up the Industrial Ethernet business area. Since September 2006 Mr. Schilperoort has been responsible for the product area Wireless LAN at Hirschmann. He manages the entire product portfolio, comprising WLAN access points, clients, antennas, controllers and accessories. Page 9

Mass Transit Systems for Rail On Board Applications

Mass Transit Systems for Rail On Board Applications Cost Saving Meeting and exceeding all data rate requirements for today and tomorrow Reliability Wired/wireless Ethernet systems designed to deliver total