Influence of multipath fading on the implementation of a radio sensor as an isolated station on a Web CAN-based control systems

Abstract

Industrial Computing Networks based on CAN terrain bus (Controller Area Network) are used in the framework of real time distributed applications. They support the CSMA/CA access technique (Carrier multiple Sense Access/ Collision Avoidance) and can work on several kilometers. Such applications cover the driving of drinking water, the transportation and the distribution of electricity, purification stations systems the oil field or gas exploitation, and multi-agent robot systems. Unshielded Twisted Pair are generally used for the binary signal transmission, nevertheless, when the terrain is injured or the system spreads on great rays, one uses modems of the series V and radios. ASK and FSK Modulations are the better adapted for this access type. The carrier detection allows an easy arbitration of the CAN bus. Codes and modulations, having an important spectral efficiency (PSK and Trellis QAM coding) are to several states and necessitate voluminous processing and are maladjusted to the arbitration of the CAN bus. Nevertheless, normalized modems have too weak debits (300 BPS in Full Duplex to 1200 BPS in Half Duplex) and do not allow possible debits on CAN networks (5 KBPS to 1.6 MBPS). We plan in this contribution to show the influence of the presence of MultiPath Fading (MPF) on the propagation segment and consequently on the real debit of CAN networks. We will give also details of the implementation of emission and reception chains of a sensor modem -radio, as entire unit, to basis of the signal processor TMS320C5XX the micro controller 16 bits Full-CAN Siemens SAB-C167CR-LM and the current generator circuit 4 -20 mA INA105.