Leveraging tinyos for integration in process automation and control systems

The number and complexity of networked sensors and actuators in industrial monitoring and control systems is rapidly increasing. This calls for flexible yet efficient methods (w.r.t. time and money) for designing, deploying and maintaining such systems. To this end, Service Oriented Architectures (SOAs) and wireless technologies are foreseen to play important roles. In the area of Wireless Sensor Networks (WSNs), TinyOS (TOS) has gained wide spread use, mainly because it offers a simple programming model. Moreover TOS comes with a ready made code base (e.g., protocol stacks needed to implement SOA enabled devices) and is available for a large number of light-weight target platforms. However, TOS has yet to make its way into industrial applications where real-time operation is required (which is typical to monitoring and control systems). As being designed primarily with simplicity in mind, the TOS execution model for tasks is non-preemptive, limiting system responsiveness and schedulability. To overcome this problem preemptive TOSThreads has been introduced. However, this introduces the additional complexity of traditional multi-thread programming, thus the main benefit of TOS is lost. In this paper we present an alternative execution model for TOS, that allows preemptive execution while preserving the simplicity of vintage TOS. We exemplify the impact of scheduling to a typical sensor/actuator node scenario. Our results indicate that the proposed preemptive execution model is capable of reducing both delay and drop rate for the given scenario.