Experimental Analysis of a Wireless Sensor Network in a Multi-Chamber Metal Environment

Wireless sensor networks (WSN) are finding increasing use in all-metal marine environments such as ships, oil and gas rigs, freight container terminals, and marine energy platforms. However, wireless propagation in an all-metal environment is difficult to model and the use of sealed doors between compartments further complicates wireless network planning. This makes it necessary to characterise the physical wireless links performance in real environments to support the design and deployment of the network. In this paper, we report on the deployment of a 2.4 GHz network of 18 nodes distributed in three freight containers, with various obstacles inside and between them. Input variables included the placement of the nodes, antenna orientation, transmission power, and door openings while output variables included the key link quality indicators of packet delivery ratio (PDR), RSSI, and LQI for every possible link, as well as the performance of every node. We believe that this is the first time that this full range of physical link quality indicators has been measured in this type of application environment. We found that, even with apparently fully sealed containers, sufficient propagation occurred through micro-openings to allow an 80.65% PDR sink connectivity. Providing as little as a 5 cm door opening increased sink connectivity to 96.92%. Average PDR sink connectivity over all the experiments was 91.97%, indicating that a WSN could operate in a multi-chamber metal structure under different conditions, and can be a viable alternative to reduce cost and complexity in these environments.