Intelligent Control and Automation, 2016, 7, 25-38 Published Online May 2016 in SciRes. http://www.scirp.org/journal/ica http://dx.doi.org/10.4236/ica.2016.72004 How to cite this paper: Abou Eita, M.N., Hussein, M.W., Ibrahim, A.A., Abouelazayem, S.S., Morsi, M.A., Moustafa, E.A., Halawa, H.H., Daoud, R.M., Amer, H.H. and ElSayed, H.M. (2016) Multi-Node Fault-Tolerant Two-Cell Real-Time S2A Net- work. Intelligent Control and Automation, 7, 25-38. http://dx.doi.org/10.4236/ica.2016.72004 Multi-Node Fault-Tolerant Two-Cell Real-Time S2A Network Merna N. Abou Eita 1 , Mostafa W. Hussein 1 , Ahmed A. Ibrahim 1 , Shereen S. Abouelazayem 1 , Mennatallah A. Morsi 1 , Eslam A. Moustafa 1 , Hassan H. Halawa 1 , Ramez M. Daoud 1 , Hassanein H. Amer 1 , Hany M. ElSayed 2 1 Electronics and Communications Engineering Department, The American University in Cairo, New Cairo, Egypt 2 Electronics and Communications Engineering Department, Cairo University, Giza, Egypt Received 2 March 2016; accepted 8 May 2016; published 11 May 2016 Copyright © 2016 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ Abstract This paper presents a novel fault-tolerant networked control system architecture consisting of two cells working in-line. This architecture is fault-tolerant at the level of the controllers as well as the sensors. Each cell is based on the sensor-to-actuator approach and has an additional supervi- sor node. It is proven, via analysis as well as OMNeT++ simulations that the production line suc- ceeds in meeting all control system requirements with no dropped or over-delayed packets. A re- liability analysis is then undertaken to quantitatively estimate the increase in reliability due to the introduction of fault-tolerance. Keywords Fault-Tolerance, NCS, S2A, In-Line, TMR, Ethernet, OMNeT++, Reliability 1. Introduction Traditional point-to-point control systems are currently being replaced by networks in modern manufacturing systems. These networks reduce cost by decreasing the amount of electrical wiring and also decrease mainten- ance costs. These Networked Control Systems (NCSs) transmit packets that have real-time constraints. These packets are small and frequent. They originate from a Sensor node (S) that samples a physical phenomenon, such as temperature, either regularly (in clock-driven systems) or when there is a system change (in event-driven systems). A packet is then sent to a controller (K) that decapsulates it, calculates the control decision, encapsu-