Per Laukemann’s research while affiliated with Esslingen University of Applied Sciences and other places

The application of the "Parallel Redundancy Protocol" (PRP) according to IEC 62439-3 with two diverse redundant wireless channels achieves an improved overall wireless communication channel. Performance parameter like jitter and reliability increase significantly compared to the single wireless channels. In this work, a series of measurements on a redundant setup with two parallel WLANs according to IEEE 802.11n in diverse configuration settings is conducted and the results presented. A Markov model for the parallel redundant system is developed and the analytical results compared against the measurements.

WLAN according to standard IEEE 802.11 is widely regarded unsuitable as communication channel for real-time and safety applications. Non-determinism and interference liability leads to packet loss, exceeded and variable latency times due to retransmissions. This work proposes a method that compensates such consequences of stochastic channel fading by the parallel operation of diverse wireless channels, applying frequency and space diversity techniques. A fault-tolerant wireless “black channel” is achieved that is able to fulfill soft real-time availability plus providing redundancy. This is realized with standard WLAN components and the “Parallel Redundancy Protocol” (PRP) according to IEC 62439-3. Reliability and performance characteristics are derived from measurements on an experimental setup with SafetyNET p nodes.