Selecting your connectivity technology
Visilion: Why BLE works best for tracking and analytics systems in hospitals
Are you about to pick a tracking system for your hospital? Read here about the pros & cons of the different connectivity technologies available today.
Visilion’s RTLS (real-time location system) is an end-to-end tracking service adapted for use in hospitals. It was developed by Sony with input from Dräger, international leaders in medical and safety technology.
In the system, tags are attached to essential pieces of equipment, and wi-fi-based devices called ‘observers’ are installed at key locations in the hospital. The position of the tagged equipment is picked up by the observers and displayed on digital maps so hospital staff can easily find what they need on a computer, tablet, smartphone or dedicated wall-mounted screen. The hospital’s on-site Wi-Fi network is used for access to the service, while tags and observers communicate via BLE.
“There is no such thing as the ‘perfect’ technology,” says Fredrik Wendel, technology leader on the Visilion team at Sony. “Ultimately it’s about choosing the technology that most closely aligns to the needs of the application and user environment.”
The Sony development team looked at several connectivity options such as passive RFID, Wi-Fi, GPS, UWB and BLE before settling on the latter. Their selection criteria included energy-efficiency, accuracy, latency, robustness, range, price of tags and suitability for indoor positioning.
At first glance, Wi-Fi tags deliver on the main criteria. They take advantage of existing wireless infrastructure and actively report their location to back-end databases to provide continuous updates. But the downside of Wi-Fi is that it was designed for high throughput of data, so it is both costly and power hungry. Batteries need replacing frequently which, in a facility with hundreds of tagged assets, would mean a lot of maintenance time. And, while using the ‘existing wi-fi infrastructure’ sounds good in theory, in practice existing systems do not always achieve the required positioning precision without additional access points and/or other technologies such as IR or ultrasound.
RFID (radio-frequency identification) is great for some applications since the tags are inexpensive and don’t require batteries. However, the team ruled it out for use in Visilion for two reasons. First, the tags do not transmit by themselves. A reader picks up a signal from a tagged object when it passes within approx. 2-3 meters. This is adequate for applications like inventory and process control, where readers are positioned on either side of an entrance to e.g. a warehouse or lab, but not for real time location in hospitals. Second, the cost savings on tags and batteries are more than off-set by the costs of infrastructure (readers) and installation.
GPS transmits continuously and has no range limitations. But this option was also ruled out by the Visilion team because GPS is simply not suitable for indoor use. Construction materials cause signal attenuation. Moreover, GPS chips are less energy-efficient than BLE and relatively expensive to buy.
“Bearing all these things in mind, we found that BLE hit the sweet spot for the Visilion application we’ve developed for Dräger’s customers,” says Fredrik. Designed for smaller data loads, BLE is an energy-efficient technology. It gives you continuous position updates (every 2 seconds) and a long battery life (up to 7 years).
The only potential issue the team identified with BLE is that its low energy consumption is achieved at the cost of shorter range (max 30 meters). But this is easily solved by placing Visilion observers in electrical sockets at strategic points around the hospital, in such a way as to reach all tagged equipment.
“BLE combines a high update rate with long battery life,” concludes Fredrik. “In the end this clinched it. No other only connectivity technology gives you both.”