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Duocast for Wireless Industrial Networks: an Experimental Study

Many Internet of Things (IoT) applications have increasingly stringent requirements: messages have to be delivered to the destinations before a given deadline. Unfortunately, radio networks are known to be lossy, and retransmissions and acknowledgements help to improve the end-to-end reliability. To provide high-reliability, most wireless industrial networks schedule the transmissions to reduce the collisions, and to make the medium access deterministic. In these conditions, duocast helps to improve both the reliability and the fault-tolerance: two receivers are associated with one transmission, so that the transmission fails only if both receivers fail to decode the packet. While anycast has been widely used in simulations, we provide here a thorough experimental evaluation. Indeed, radio links present practically variations, may be asymmetrical, and the hidden receiver problem may practically reduce the gain of duocast. We demonstrate in our experimental evaluation that duocast is really efficient to provide high-reliability while limiting the number of (re)transmissions. It also helps the network to be fault-tolerant: even if a device crashes, or if a given link quality degrades, an alternative path exists to forward the packets, without any additional delay.