Safety Related Systems Design Methodology for Wireless Time-Varying Channels

摘要

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.