Weekly Update

Bluetooth 4, the internet of things, and low power communcations

Ever since Bluetooth 4 rolled out in the iPhone 4S in October of 2011, I’ve wondered whether the low energy iteration of the network technology could reinvigorate a communications tech that many, including myself, often saw as irritating to pair and having high energy requirements that could drain battery life. But as the internet of things continues its growth trajectory and more devices want connectivity at low power, there could be an opportunity here for a renaissance of the decade old tech.

The focus historically for Bluetooth had been on increasing the amount of data it could transmit, from 720 kbps to 3Mbps with Bluetoth 2 (2004) to 24 Mbps with Bluetooth 3 (2009).  The 24 Mbps was impressive as a high speed data capability that could communicate over an 802.11 link. The downside with all of these leaps in data transfer rates was that energy requirements kept moving up just as we were evolving toward a more mobile world.

To be clear what was added with Bluetooth 4 was Bluetooth Low Energy, which was hoped could allow short range wireless communication on a single coin battery for months or years. In terms of Bluetooth 4 and Bluetooth Low Energy, we’re seeing dual mode chips which can provide functionality with both Bluetooth versions as well as backwards compatibility.

I wrote recently about Bitlock, a startup that is pioneering a bike lock that can be wirelessly locked and unlocked from your phone. It also uses the GPS on your phone to locate bikes on a map, opening the door to sharing within closed networks. I spoke with founder Mehrdad Majzoobi, who is very bullish on the technology. He noted to me:

The difference between Bluetooth 4 and classic Bluetooth is that it’s very easy to connect with other devices. If you remember, if you had a hands free device, you had to pair it and enter a pin number. But the Bluetooth 4 connectivity is very fluid. As soon as the device comes in range it can connect. Also the power consumption for Bluetooth 4 is designed for low power devices. That’s why we can run on batteries for such a long time. The radio power consumption is negligible compared to classic Bluetooth.

John Donovan provided a comprehensive look at why Bluetooth 4 has low power designed into.  He writes:

One of the ways Bluetooth Low Energy manages to minimize power consumption is to switch the radio on for only very brief periods of time. Bluetooth Low Energy radios only need to scan three advertising channels to search for other devices – which they can do in 0.6 to 1.2 ms – while Classic Bluetooth radios must constantly scan 32 channels, which require 22.5 ms each time. This trick alone enables low-energy devices to consume 10 to 20 times less power than Classic Bluetooth ones.

This overall strategy of powering down the radio as much as possible is reminiscent of some of the strategies used at low power server makers. Built into those low power server architectures is energy management software that powers down cores whenever they’re not in use to reduce idle power consumption.

So what does this all mean for the internet of things? Well there are many players in the short range wireless market, ranging from ZigBee to 6LoWPAN, but Bluetooth’s big advantage is its compatibility with a couple billion devices. In particular, as consumer devices ranging from bike locks to fitness trackers require connectivity and control from a smartphone, Bluetooth 4 looks like an intriguing option. I could see it finding a place in mobile health, with data collection devices linked to the body.

Perhaps most importantly, the final message here is just how important power issues have become for any communications protocol where mobility is involved. Add Bluetooth’s innovations in terms of passive connectivity, and a better power envelope might just find lead to the classic network technology finding new applications.