Design, analysis and implementation of a time-bounded spectrum handoff algorithm for real-time industrial wireless sensor and actuator networks

摘要

Industrial control applications require real-time communication systems with time-critical and safety-critical features, as well as the ability to operate in harsh propagation environments. This means that data communications need to be bounded both in time and reliability domains, while dealing with severe interference coming from other wireless communication systems, including jammers, and with signal degradation phenomena such as delay spread, deep fading or Doppler spread. The present work proposes a spectrum handoff (i.e. channel switching) mechanism for Industrial Wireless Sensor and Actuator Networks (IWSAN) which is capable of detecting interferences and hopping to another channel within a given time bound. This is possible because the spectrum handoff strategy is capable of detecting interference in the MAC layer with the high requirements demanded by real-time IWSAN applications in terms of time and reliability. A theoretical analysis has first been provided using Network Calculus, which determines the delay bounds, and simulations in OPNET have been done afterwards in order to validate the theoretical results, taking into account several industrial environments (e.g. lognormal shadowing, Rice and Rayleigh fading and interference). Furthermore, the proposed communication system, based on the IEEE 802.11a/g physical layer, has been implemented in a FPGA, and simulations in OPNET network simulator and measurements on real hardware have been carried out in order to characterize its performance. The obtained results prove the capability of the proposed spectrum handoff mechanism to guarantee bounded delays and reliable operation in harsh propagation environments with interference, what makes it a suitable candidate for replacing wired communication systems in industrial environments.