This paper presents a methodology to evaluate the safety performance in wideband wireless systems through frequency-selective channels. We propose a methodology based on the error distribution along an Orthognal Frequency Division Multiplexing (OFDM) symbol for a given channel situation. From there, a mathematical method that considers the benefits of channel coding is derived to characterize the performance of safety communication layer tools as defined by the regulatory framework. This process is illustrated using an example with industry-specific data. It is shown that the effect of fading variability benefits the safety performance of the wireless system. The analytical model shows that variability reduces the probability of events with many errored subcarriers. This reduction facilitates the identification of a higher number of situations that put the safety function at risk. The possibilities of reaching some SIL limits within the proposed scenario are also explored.

Presents corrections to the paper, On the Feasibility of Wireless Communications for Safety Applications in Industry.

This article presents a methodology to characterize the reliability and safety capabilities of redundant wireless systems planned for an industrial application. The equations that describe the residual error are presented and studied in situations that model an industrial wireless scenario. We propose different voting systems and their performance is evaluated analytically and by simulations. Likewise, a voting system based on a combination of filtering and cross-checking techniques is proposed. This solution significantly reduces the probability of undetected dangerous events while maintaining availability under control. Moreover, an improved version with triple redundancy is also presented. The results demonstrate that it is possible to fulfill the requirements of standard IEC 61508 without compromising system availability statistics. The solutions have been implemented on hardware wireless prototypes to illustrate the effectiveness of the proposed voting systems.

This paper presents a method to evaluate the feasibility of using wireless links as part of functional safety systems. We present an analytical model to describe the wireless safety links' performance operating in fading industrial environments. The work considers integrity failures, wrong addressing, message sequence errors, and masquerade events. The contributions of each perturbation to the overall system residual error are modeled with equations. Moreover, a MAC scheme based on the tools suggested in IEC 61784–3 is proposed and validated under industry-recommended use case parameters. The results show that the variation of the frame structure and application-specific parameters impact the overall residual error. The work concludes that the residual error probability of the CRC dominates residual error performance, but it may be reduced using consistent countermeasures against other possible sources of error.

This paper presents a methodology to characterize the impact of deep fading in wireless links related to safety functions for industrial applications. We analyze the different methods available to describe the residual error probability and discuss their application to practical wireless systems, where fading is a key propagation impairment. An analytical method to derive the residual error probability in fading channels is proposed, and calculated curves are compared to empirical results obtained by system simulations. The procedure is illustrated using two well known CRC polynomials with codeword lengths and appropriate safety data rates for industry cases. The system residual error probabilities are compared with those associated to SIL targets. Moreover, an erroneous packet filtering technique is proposed to approach IEC 61508 specifications. Results show that the choice of a proper CRC is critical in safety wireless and demonstrate that CRCs, combined with filtering techniques, can achieve performance values in the range of SIL targets.