Forward error correction in wireless communication systems for industrial applications

Abstract

Industrial manufacturing is more and more based groups of robots in production cells. The robots consist of moving, bending and rotating arms with multiple joints. Cables that connect sections of robots undergo heavy stress from stretching and twisting, resulting in wear-out and failure. Replacing cables on robots by wireless communication therefore is an alternative that has been investigated for some time. Unfortunately, communication channels in industrial environments suffer from some adversary effect. First, standard industrial communication networks work on rigid time frames which limit allowed latencies in communication systems considerably. Second, multiple path propagation and destructive interferences make such communication channels sensitive to fading problems. Therefore forward error correction (FEC) that can compensate massive variations of signal strength becomes a must. On the other hand, forward error correction using known methods such as BCH codes, Reed-Solomon codes, turbo codes and low-density parity checks (LDPC) is not very fast by nature. Codes for single effort correction and double error detection (SEC-DED-codes) such as Hamming code and Hsiao code are fast, but they are not powerful enough to correct multiple bit errors or restore missing symbols, unless they are applied in a step-wise approximation. PENCA (programmable encoding architecture) is a new approach in multiple error detection and correction which is, at present based on BCH codes, reasonably fast by parallel hardware. Furthermore, it allows for adaptive error correction, based on the quality of the channel, therefore providing a better overhead / performance ratio than methods that are based on a fixed number of allowed error bits in a symbol, tailored to handle worst-case conditions. PENCA is currently becoming part of an industrial communication systems developed in the ParSeC project, which is a cooperative effort of industries, universities and research institutes, funded by the German Ministry of Research and Education (BMBF).