Bluetooth Low Energy Explained

Bluetooth 4.0 [6] is going to lead to some pretty cool medical devices, such as wireless thermometer and heart rate products [7]. One of its key features, Bluetooth low energy [8], will allow devices equipped with the wireless technology to consume far less power than before. MED asked Tim Whittaker, a system architect in the wireless division of product development firm Cambridge Consultants [9], what Bluetooth low energy means for medical electronics designers.

MED: How is Bluetooth low energy different from previous versions of Bluetooth? What can it do that other versions could not?

TW: Bluetooth low energy devices can operate with a battery that is a fraction of the size of existing Bluetooth devices, and with standby times in months or years.  These tiny ‘low-energy only’ chips cost under a dollar. Bluetooth low energy is not a substitute for standard Bluetooth, but it has been purposefully designed so that it can be added on to a standard Bluetooth chip for almost no additional cost. Bluetooth low energy chips are designed to turn themselves off completely for long periods of time, waking up and connecting very efficiently, only when there is data to be sent.  This allows operation over many years even with a very small battery.
 
MED: What type of applications will Bluetooth low energy enable? How do they differ from traditional Bluetooth applications?

TW: The Bluetooth low energy capability is perfect for transmitting small amounts of data you might want to show on a watch or collect from an exercise machine, for example.  Bluetooth low energy chips are already being built into watches, exercise machines, remote controls and medical devices.  For example, I could wear a watch with an electronic display, and it’s connected via Bluetooth low energy to my mobile phone. When my phone rings, the caller’s name and number appear on my watch, and I answer by pressing a button on the watch. Bluetooth low energy is also very well-suited for the remote control of home lighting, security and entertainment.  I could operate these applications from another of my smartphone apps.
 
MED: What does Bluetooth low energy mean for medical electronics devices? What aspects of the technology are particularly suited to healthcare applications?

TW:Low-cost Bluetooth low energy enabled drug delivery devices could log vital health information as well as dosage stats, reliably. Transforming what is usually a disparate and complicated calculus into an automatically self-updating database, a device could alert you or be alerted about any irregularities in your dosage intake or health status.

MED: What type of healthcare applications will Bluetooth low energy enable?

TW: For people with chronic medical conditions, like diabetes, it’s very important to take regular blood glucose readings, and keep accurate notes. Patients must log what their blood sugar level is, when they take insulin and the amount. Low-cost Bluetooth low energy devices in this dosing device and in the instrument will do all this logging for the patient, and, with consent, share this information with the doctor. This could revolutionize the quality of such a patient’s healthcare management. Another example, can be found in logging one’s exercise regime and weight. Bluetooth low energy devices are cheap enough to put in exercise bicycles, treadmills, pedometers, weight scales, etc. So an individual can run an application on their smartphone that collects this data and tells them how they are doing.
 
Wireless data transfer is great, but it also raises security issues. Does Bluetooth low energy have any features to lessen security risks? Should medical device designers be concerned about security when incorporating Bluetooth low energy into devices?

This was addressed by the designers of Bluetooth low energy, and a strong security mechanism based on AES-128 encryption is included as a feature. To put this in context, it is the same encryption used by military and financial organisations, well-tested and proven.

MED: One of the biggest benefits of Bluetooth low energy is extended battery life. What possibilities does this open up for medical device designers?

TW: What this means is connectivity with 'no new batteries' in many cases. For example, a glucometer with reporting capability could use the same, or a very slightly larger, battery than the one used for its core function. For a non-electronic instrument (like many spirometers), its data collection could be improved considerably by adding at low cost a Bluetooth low energy chip, with a small battery that could easily last for several years.

MED: Does Bluetooth low energy present any other challenges for medical device designers?

TW: We have talked mostly about adding Bluetooth low energy to a medical device, but we also need to think about the other end of the link. This could be an app on a smartphone, in which case this needs to be developed too. There may also be a medical service provided as part of the package, so the smartphone app must talk to the back-office systems, which will also need development. For users that don't want smartphones, there will be a demand for easy-to-use home hubs, and the process of linking (pairing) your medical devices to the hub and to the service provider must be quick, easy and transparent—all big challenges!

MED: Do any Bluetooth low energy healthcare applications already exist? If not, where might we see Bluetooth low energy first?

TW: Makers of glucometers for diabetes are already designing Bluetooth low energy into their devices, and other home instruments like blood pressure monitors and weight scales will follow soon. There will also be cellphone apps and home hubs, providing a gateway between the medical device and the IT system of a provider of medical or care services.

MED: When will Bluetooth low energy reach a critical mass?

TW: Smartphones with Bluetooth low energy will be shipping this year. As what happened with standard Bluetooth, success will depend on a large existing base of devices than can make the other end of a connection, and we expect this to happen over the next 18–24 months.

MED: How can designers get a jumpstart on incorporating Bluetooth low energy into their medical devices?

TW: Development kits with demonstration software are available now from all the Bluetooth low energy chip vendors: CSR, TI, Nordic. These will allow designers to start experimenting with BLE, measuring its performance and assessing the size of the radio. Chips are also available now, so design-in of Bluetooth low energy can start as soon as you wish.

MED: What's next for Bluetooth low energy?

TW: Over the last decade or two, the experience has been that each time the cost of a radio system drops by a factor, the market for it multiplies by a considerably greater amount. Bluetooth low energy is on course to have a radio unit cost of less than a dollar, which means that it will be possible almost to add connectivity by default, not only to medical devices, but also assisted living, entertainment, home monitoring and security. It's predicted that there will be 50 billion connected devices in the world by the end of the decade.

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