Bluetooth Smart: An Agent of Change

Faster is Better

The updated standard boosts sensor connectivity in multiple ways, all of which give the designer greater flexibility. It introduces a data-rate option that more than doubles data transfer speeds to around 300 Kbps and provides a 10-fold increase in the packet size. Combined, these features will enable faster, more stable firmware updates and allow designers to reduce wearable energy consumption by shortening the time required to complete transmissions.

One of the factors contributing to this performance improvement can be found in better management of connection intervals—the time between two Bluetooth Smart connection events. The specification allows connection intervals ranging from 7.5 milliseconds to 4 seconds, and it allows a Bluetooth Smart peripheral to skip a number of connection events. In so doing, it enables the device to sleep longer.

This feature allows tradeoffs among latency, responsiveness and power consumption. For example, when developing a smartphone or wearable that tracks your movements using a variety of sensors, the design engineer will usually opt for shorter connection intervals, but when developing a battery-operated instrument, the engineer might use the feature to reduce power consumption with a longer connection interval.

Go the Extra Mile

Perhaps best of all, Bluetooth Smart 4.2 makes it possible for devices to connect directly to the internet over a Bluetooth connection via IPv6/6LoWPAN. This means that Bluetooth-enabled devices can communicate directly with one another, opening the door for the gathering and use of ambient intelligence (AmI). AmI seeks to broaden the interaction between people and digital information technology through the use of ubiquitous computing devices and sensors, with an eye on improving quality of life.

The ability to connect with the internet by way of 6LowPAN will also make wearable devices more autonomous, eliminating the need for a go-between device like a smartphone. Using this new connective tissue, Bluetooth-equipped devices will be able to access app content and services via 6LowPAN networks. This feature will also allow designers to make wearable control devices for such applications as smart home appliances.

Energy and Privacy Issues

In addition to connectivity, the IoT has ramped up pressure on engineers to achieve greater energy efficiency and provide better privacy in their designs, particularly for battery-operated devices. Bluetooth Smart 4.2 helps with both issues by changing the way it resolves addresses for private devices.

Under the specification, the Bluetooth controller resolves addresses for private devices, not the host CPU. Because the CPU no longer has to engage in this process, it does not have to wake up, so it consumes less power.

Moving the functionality to the Bluetooth controller also prevents “untrusted” devices from accessing too much information on the device. Under version 4.2, other devices can access additional data only if they have been granted “trusted” status by the discoverable device.

On the Right Track

As the IoT ecosystem continues to grow, the challenge for device designers is to facilitate mass production of smaller, energy-efficient devices that can leverage expanding connectivity. Given these market forces, Bluetooth Smart 4.2 seems to be a technology that has arrived at the right time, with the right feature set.