Modeling latency and reliability of hybrid technology networking

Operational safety and security are the key concerns of the North American railroad industry. Of growing importance is the ability for real-time identification, monitoring, and fault alerting of freight railcars and their myriad components. This vision of an Internet of Things applied to the transportation industry has widespread benefits and applications. Wireless sensor networks (WSNs) have been extensively used for addressing such challenges. However, the nature of a train's arrangement requires the sensors to be placed in a long linear network topology. Given the limitations in radio transmission range and network depth of common WSN solutions like ZigBee, it is infeasible to use them for such applications. Furthermore, due to its low throughput, severe packet loss and high latency may occur, which is unacceptable, especially for failure alert messages. Therefore, we have proposed a heterogeneous multihop network approach called hybrid technology networking (HTN) that employs WiFi together with ZigBee. In this paper, we derive a mathematical model to illustrate HTNs superior performance compared with conventional ZigBee-based WSNs. Specifically, we analyze the delay and reliability of HTN and ZigBee and verify the analytical results against our simulations.