Challenges in using Wireless Sensor Networks in Railway Signalling

The use of Wireless Sensor Networks in a safety critical Domain like Railways signalling poses challenges in implementation and Operation. Some of the issues and challenges are discussed in this chapter.

 

1. Sensor network communications must prevent disclosure and undetected modification of exchanged messages. Due to the fact that individual sensor nodes are anonymous and that communication among sensors is via wireless links, sensor networks are highly vulnerable to security attacks.

 

2. The gateway nodes are prone to failures just like any sensor node, and they consume significantly more energy since they transmit over longer distances compared with sensor-to-sensor links. Failure of a Gateway node results to catastrophic results because, there not information regarding the yard status to the base station

 

3. Sensor nodes have limited computing power and memory sizes. This restricts the amount of intermediate result a node can hold, also the type of data processing algorithm on a Sensor node.

 

4. Signals detected at physical sensors might have errors. Malfunction sensors might repeatedly generate false signals, also there could be bias caused by the placement of the sensor.

 

5. Sensor Nodes, Driver Node and Gate Way node have to work in High EMI Environment. Since sensor networks can be deployed in different situations, wireless medium can be greatly affected by noisy environments, and thus the signal attenuates in regard to the noise. Note that an adversary can intentionally interfere and cause enough noise to affect the communication. It is vital to ensure that communication is on time to respond to emergencies.

 

6. Wireless sensor networks at times may add delay in sending data to the base station due to the routing algorithms, etc, but Railway Signalling is very time critical job, any delay in receiving the data leads to Catastrophic results.

 

7. If a sensor node fails due to a technical problem or consumption of its battery, the rest of the network must continue its operation without a problem. Researchers must design adaptable protocols so that new links are established in case of node failure or link congestion. Furthermore, appropriate mechanisms should be designed to update topology information immediately after the environment changes so as to minimize unnecessary power consumption. 

 

8. The network should be scalable and flexible to the enlargement of the network's size. The communication protocols must be designed in such a way that deploying more nodes in the network does not affect routing and clustering. Rather, the protocols must be adapted to the new topology and behave as expected. In other words, the network must preserve its stability. Furthermore, introducing more nodes into the network means that additional communication messages will be exchanged, so that these nodes are integrated into the existing network. This must be done in a way that a minimum number of messages need to be exchanged among the sensor nodes, and thus battery is not wasted unreasonably.

 

9. As in Wireless Sensor Networks Both Ground based signalling (Way Side Signalling) and On-Board Signalling (Cab Signalling) get merged, so there is the complexity of linking the ground based control laws to the inputs received from the On-Board Sensors in the train

 

10. Design and development of failsafe, fault tolerant and energy saving  network routing algorithms is a complex design