WSAN demonstrator in Frankfurt/Oder

Steffen Peter
IHP microelectronics
peter(at)ihp-microelectronics.com

Gerd Weber
FWA mbH
gerd.weber@fwa-ffo.de

Drinking water provision is a critical infrastructure that can benefit from Wireless Sensor and Actuator Networks (WSANs). As part of the WSAN4CIP project, we implemented a demonstrator to prove the feasibility of WSANs. This technology cannot only increase the economic efficiency of the pipeline network, but also improve its safety and security.

Nowadays pipeline networks need to be monitored, in order to ensure the quality of the drinking water and to react quickly in case of accidents, e.g. if pipelines are broken. This type of monitoring is integrated into a Supervisory Control and Data Acquisition (SCADA) management system, operating 24 hours, 7 days a week. In addition, drinking water reservoirs are considered to be also a very sensible part of the network. In the worst case, manipulating the drinking water quality and supply could have immediate impact on the population in the provided area.

The demonstrator is deployed in the waterworks system of FWA (Frankfurter Wasser- und Abwassergesellschaft), the local water provider in the city of Frankfurt/Oder, Germany, about 100 km east of Berlin. The demonstrator monitors the operation of water mains between the waterworks in Briesen and the elevated tank in Rosengarten using a fail-safe and secure data transmission. Between these two facilities, two parallel water pipes run over a total length of 17.5 km. For a primary scenario, data is collected from several pipe access points. The deployed nodes can process the sensed flow rate and pressure measurement data.

Technical realisation

For setting up the demonstrator, each of the access points will be equipped with a sensor node which is able to transmit the sensed data wirelessly. A sensor node consists of a small microcontroller, a radio, and an interface to connect the sensors and actuators. For this demonstrator, the microcontroller is the 16bit TI MSP430, and the radio uses the 868 MHz band, in which sending data is permitted with a power of up to 500 mW. This setup allows wireless transmissions of data for distances of up to 5 km in practice. The node is shown in the figure.

Figure: Node from the FWA water pipeline network

The distance between the furthest nodes and the base station is larger than 5 km. Under bad weather conditions, such as rain or fog, the transmission range can drop to less than 2 km. Thus, it is necessary to send the data hop-by-hop. This means that intermediate nodes have to forward the data packets. However, large distances and several hops increase the possibility of transmission errors significantly.

To cope with those reliability issues, the reliable middleware TinyDSM has been implemented in the project on top of a secure routing and medium access control (MAC) protocol. TinyDSM implements the concept of reliable data storage that helps to assure data availability despite well-known wireless sensor network resource problems. Thereby it adds data redundancy within the network and takes care of the quality of service of the data, e.g. ensuring that alarms are propagated faster than periodic status updates.

Another important requirement for such large networks is the possibility of remote code updates. New node configurations have to be distributed in the network without the need to access each node physically. The FWA demonstrator has integrated a novel secure code update mechanism that not only allows remote configurations but also ensures the correctness of the distributed software.

Conclusion

The novel software modules together with the new sensor nodes promise to fulfil the initial requirements for a secure and cost-efficient wireless surveillance and control network for drinking water pipelines. The practicability of the implementation will be shown in a six-month demonstration starting in summer 2011.

Further information is available at www.wsan4cip.eu/demonstrators/demonstrator-2-water-distribution.html

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