Dual protocol performance using WiFi and Zigbee for industrial WLAN

Abstract

This paper evaluates the performance of an industrial Wireless Networked Control System (WNCS) that is based on utilizing two parallel protocols for communication namely Zigbee and WiFi. The proposed WNCS demonstrates the combined advantages of both the IEEE 802.15.4 protocol (which ZigBee is based on) without modifications being low cost and low power compared to other wireless technologies as well the advantages of WiFi being increased bit rate and higher immunity to noise. OMNeT++ simulations are used to measure the end-to-end delay and packet loss from the sensors to the controller and from the controller to the actuators. It demonstrates that the measured delay of the proposed WNCS including all types of transmission, encapsulation, de-capsulation, queuing and propagation, meet real-time control network requirements while guaranteeing correct packet reception with no packet loss. Moreover, it shows that the demonstrated performance of the proposed WNCS operating redundantly with WiFi and Zigbee networks in parallel is significantly superior to a WNCS operating on either a totally wireless Zigbee or WiFi network individually in terms of measured delay and interference tolerance. All results presented in this study were based on a 95% confidence analysis.