2.4. Wireless Technology Suitability

When we think about the hospital setting and its unique requirements as a use case, there are several wireless technologies which could be applied for the bed connectivity system. Displayed in Table 1 is a comparison table showing the typical range, power, and bit rate trade-offs between different wireless technologies.

Wireless technology comparison of key features. Adapted from: Security and Privacy Issues in IOT Things [13].

The more typical and popular wireless technologies, i.e Bluetooth and WiFi, are less than ideal in a hospital setting. Bluetooth is more suited to low range communication at a distance of several meters [12], and WiFi requires extensive infrastructure investment to allow connectivity throughout an entire building. While most hospitals already have this WiFi connectivity, it is heavily used for normal internet traffic and data transfer. Burdening this system with hundreds, if not thousands, of IoT enabled beds would reduce speed and reliability of the system [14]. In the event of a power outage or internet connectivity dropout, the units would be rendered non-operational.

The mesh network protocols such as Z-Wave and Zigbee show promise for the hospital setting, which usually has beds in close proximity. However, they cannot be engineered as a solution in the same way. As the beds are mobile and often moved, the mesh network will only remain operational as long as a the maximum transmission distance is kept below the minimum distance to the next node (i.e., 30 m for Z-Wave). A potential situation could arise in which relocating of beds dynamically breaks the mesh network by exceeding this distance. If this was to occur, any beds past the break would be rendered unconnected. This risk was considered too high for these technologies without significant infrastructure investment such as multiple repeaters and gateways around the hospital. To engineer the system as a standalone unit, it was decided to use LoRaWAN as the base wireless transmission protocol. This was due to the extremely long-distance capabilities of the technology and low power consumption. Using LoRaWAN, it is reasonable to expect that a single commercial gateway, well placed in the hospital, could provide connectivity to several thousand beds and the system could be adapted to new environments very quickly. Saban et al. performed thorough testing on the indoor and outdoor transmission quality that can be expected with LoRa modulation. Their experiments showed that, in outdoor urban environments, a distance of 400 m could be achieved with no packet loss. Indoors, a large series of buildings up to four levels was tested with no packet loss [8].