The Effects of Channel Characteristics on Relay Behavior and Position in Wireless Industrial Networks

In wireless industrial networks consisting of distributed sensors and actuators, the problem of providing reliable and timely communication is still one of the key challenges. Previous research has proved that relaying or socalled cooperative communications can be fruitfully deployed in wireless industrial networks. The goal of the present work is to investigate how different types of channels encountered in industrial environments affect the benefits, the behavior and the position of a relay node. We consider two types of behavior: either the relay node only retransmits a packet if it has obtained a correct copy of it, or it always retransmits the packet even if the CRC check has failed. We conduct simulations for different positions of the relay node and for two types of channels: a channel with a strong line-of-sight (LOS) represented by AWGN and one with no LOS, represented by Rayleigh fading. The results clearly show that the benefit of using relay nodes depends on the wireless channel. The best behavior of a relay node depends on if bit errors appear randomly or in bursts, whereas the best position of a relay node depends on the fading characteristics but also on the overall distance between the source and the final destination.