Desenvolvimento de sistemas de comunicações codificados por wavelets e baseados no padrão IEEE 802.15.4 para sistemas de controle por redes de sensores sem fio industrial

Abstract

With the advent of Industry 4.0, wireless communication has become a trend towards transmitting signals in industrial environments, saving resources and enabling new applications when compared to wired communication systems. In this context, data transmission between sensor and controller within control loops that use nodes interconnected by wireless link is susceptible to the degenerative effects produced by multiple propagation paths. However, most industrial wireless sensor network standards do not provide any error correction control, which would be useful to improve reliability and efficiency. In order to minimize these destructive effects characteristic of wireless channels, several techniques have been investigated recently. In order to minimize these destructive effects characteristic of wireless channels, several techniques have been investigated recently. Among them, wavelet coding is a good alternative for nodes interconnected by wireless link, due to its robustness to the effects of the wireless channel and its low computational complexity. This work is based on an approach that explores wavelets matrices for the design of finite impulse response filters used in encoding the complex signals generated by the physical layer of the IEEE 802.15.4 protocol. With this, a new transmission system is proposed that is still based on the IEEE 802.15.4 protocol, which allows maintaining the interoperability with legacy systems and still achieving superior performance regarding the necessary requirements for the establishment of control systems over networks wireless. Specifically, the proposed system increases communication reliability and decreases retransmission events caused by errors caused by the wireless channel on the transmitted data packets. In particular, the communication delays derived from these retransmission events seriously interfere with the control system, as they do not guarantee the temporal restrictions of the control signal. Furthermore, an important point regarding the performance of the proposed system is the possibility of improving communication reliability without decreasing spectral efficiency. Allied to this, the proposed system also allows an adaptive performance in terms of the encoding rate and parameters of the wavelet matrix, without a significant increase in implementation complexity. The proposed communication system was implemented using the concept of radio defined by software in the GNU Radio development environment, in order to demonstrate the feasibility of implementing the proposed system in a real communication system. The performance of the communication system was evaluated in terms of bit error rate versus Eb/N0 and spectral efficiency, considering a time-varying channel model with flat Rayleigh fading. Furthermore, the effects of the transmission system were considered in the controllability analysis of a control system.