Reliable Middleware for Wireless Sensor-Actuator Networks

Many important and critical applications use wireless sensor/actuator networks (WSAN). These applications are spanning widely that range in several environments, including industrial, commercial, and residential. Most of these applications need a certain level of real-time communication in addition to reliable data delivery service. Data distribution service (DDS) is a known standard for supporting real-time distributed systems based on the publish/subscribe model. The DDS specification offers two disparate quality-of-service levels of data reliability, namely: best-effort and fully-reliable. TinyDDS is a lightweight and partial porting of DDS middleware to sensor-based platforms, specifically for platforms with limited resources. However, TinyDDS in its current form lacks the reliability support for data delivery. In this paper, we extended the DDS data reliability service and integrated it into TinyDDS, which resulted in Reliable TinyDDS. Moreover, we provide a prototype and comprehensive performance evaluation of the reliability functions taking into account: number of hops, number of publishers, and several other network parameters. The achieved results indicate that reliable data delivery in real-time for WSAN is possible with optimized system parameters, such as retransmission time-out value of 400ms and number of hops not exceeding 10 for an end-to-end delay ranging from 10 to 100s of milliseconds.