One has to admire the flexibility exhibited by the custodians of Bluetooth, the popular short-range 2.4-GHz wireless technology. Enhancements to the standard’s specification sanctioned by the Bluetooth Special Interest Group (SIG) have allowed it to evolve in directions that the inventors can scarcely have imagined. This combination of foresight—and a little luck—have brought considerable commercial success for the technology and could see it expand to northwards of three billion annual shipments as early as next year, according to analyst IHS.
The latest incarnation, Bluetooth 5, (which has dropped the geeky “x.y” naming of previous versions in favor of a catchy label appealing to consumers) was adopted in a blaze of marketing hype in December. The changes continue the SIG’s recent trend to entrench Bluetooth as a vital component of the Internet of Things (IoT). That’s not an unreasonable strategy considering that wireless will be the primary way the 80 billion connected “things” will be busily gathering and sending data across the network by 2025, according to International Data Corporation (IDC).
Things were very different back in the mid 90s when Ericsson engineers Sven Mattisson and Jaap Haartsen looked at the tangle of wires linking electronic devices and wondered if there was a better way. This was at a time when the phrase “Internet of Things” was still several years away from being coined by British engineer Kevin Ashton and from when NCR and AT&T had only recently come up with IEEE 802.11, the precursor of Wi-Fi.
Mattisson and Haartsen were tasked with using low-throughput, short-range radio links to exchange information between handsets without resorting to plugging in a cable. Ericsson encouraged other companies, including Nokia, IBM, and Toshiba, to join the initiative, which by then had become an open standard operating in the unlicensed 2.4-GHz band (freed-up courtesy of a far-sighted decision by the Federal Communication Commission (FCC) in 1985).
The standard, now called Bluetooth—a name harking back to an ancient Scandinavian king—was adopted in 1998. Those early expectations were perhaps a little too high. The performance of Bluetooth Version 1.0 was a little underwhelming. In ideal conditions, throughput was around 700 Kbps, but in practical circumstances, it was often considerably less, and it didn’t help that manufacturers had various problems getting their equipment to interoperate.
But focusing on these early teething problems misses the point. Establishing an open standard for a 2.4-GHz short-range wireless technology was no mean feat, and it blazed a trail that many have since trod. Subsequent iterations added bandwidth and, crucially, Adaptive Frequency Hopping (AFH), which allowed the radios to continuously and randomly hop around 79 1-MHz wide channels to avoid RF interference from a growing band of other devices using the license-free 2.4-GHz band.
Through subsequent iterations, Bluetooth enjoyed a degree of success built mainly on its incorporation into cellphones. Much of this development was targeted at making the handset the center of so-called Personal Area Networks linking phones to hands-free headsets, Personal Digital Assistants (before smartphones wiped out that product category), and … well, perhaps not as many personal devices as were originally envisaged.
But a bit more tinkering with the firmware stack to optimize performance to suit specific applications eventually saw Bluetooth find its way into cars, PCs, printers and speakers. Such progress was helped in part by the introduction of Bluetooth 3.0 + HS. Introduced in 2009, this upgrade provided a Bluetooth bandwidth of up to 3 Mbps and, by employing a co-located 802.11 channel, enabled Bluetooth to boost speeds up to a Wi Fi-competing 24 Mbps.
Bluetooth’s biggest breakthrough came with Bluetooth 4.0. In a break with previous versions, this version introduced a second radio with a lightweight stack that was interoperable with its bigger brother. Dubbed Bluetooth low energy, the technology targeted compact wireless devices designed to send a small amount of data in a rapid burst and then return to an ultra-low power consumption “sleep” state, thus running from small-capacity batteries for long periods.
Bluetooth low energy was able to build on handset interoperability to leverage smartphone app software and access to the Cloud. This uploaded data could be analyzed and transmitted wirelessly across bidirectional links in sensors used in a wide range of consumer products, medical devices, security devices, and more. So much so that Bluetooth low energy is growing at a compound annual growth rate of 35 percent and will represent some 25 percent of those three billion chips shipped next year, according to analyst ABI Research.
Following the success of Bluetooth 4.0, the SIG realized they had a technology on their hands that just might be applicable for a swathe of IoT applications beyond its consumer foundation. Key to realizing this potential was the addition of a channel in 4.1 that could be used for IPv6 communications—endowing sensors with a unique IP address and Internet connectivity without piggy-backing a smartphone. Then 4.2 added the Internet Protocol Support Profile to the stack allowing devices to discover and communicate with others using IPv6 packets.
Bluetooth 4.2 also featured an increase in packet capacity by almost ten times and boosted the range of Bluetooth low energy devices up to 2.5 times. And it bought some overdue security improvements that attempted to allay fears that IoT-connected devices could be used as a backdoor to hijack the owner’s Wi-Fi network and (presumably) then to drain their bank account.
Bluetooth 5 now adds higher speed (2 Mbps) to Bluetooth low energy which, apart from pleasing consumers by making things run more smoothly, is handy for accelerating the over-the-air updates that IoT sensors routinely need to keep them humming nicely and protected from hackers. Bluetooth 5 also offers up to four times the range of 4.2 (at the cost of a serious hit to throughput which drops to 125 kbps when range is extended), increasing its viability for “whole-of-house” applications such as smart lights in sprawling homes.
Bluetooth 5 also now incorporates the “0.9” Mesh Networking standard to compete with other smart home and industrial networking technologies such as Thread, zigbee and Z-Wave. Mesh passes packets from node to node until they reach their intended destination, endowing a system with “self-healing” properties and range extension. Bluetooth 5’s long-range feature eliminates the need for mesh in some smart home applications, but mesh’s other advantages will see it used in many more.
For example, Bluetooth mesh will allow a smartphone or PC to communicate with everything on the network without having to deal with a hub, saving cost and complexity. (Competing technologies often require a hub to control network activity, introducing a potential weak link.) A second example is called a “scene” by the SIG and refers to instances whereby one user action automatically triggers others via communication over the mesh—e.g., when a consumer arrives home and activates a smart door lock, Bluetooth mesh could automatically activate lights, thermostats, and music player.
It’s a nice example, but where Bluetooth mesh (and Bluetooth 5) will really prove its usefulness is in Industrial IoT (IIoT) applications. While still in its infancy, IIoT will dwarf smart home technology; such is the flexibility of Bluetooth mesh that in addition to controlling lighting, HVAC, and security, the same mesh will be able to facilitate machine-to-machine (M2M) communication, machine health monitoring, asset tracking, energy use, and much more. Providing Bluetooth mesh proves as robust as its consumer counterpart, we’ll see widespread industrial and commercial implementations comprising hundreds of sensors deployed in retail premises, offices, and manufacturing campuses.
And next…well, apart from a few well-placed insiders, no one knows. But it’s a fair bet that the SIG will continue down the path of evolving the core specification to suit new trends and applications as they appear. The day when everything, literally everything, no matter how inexpensive and disposable—think band aid, plastic coffee cup, socks and nuts & bolts—is wirelessly connected by Bluetooth low energy is not so far away.
Steven Keeping gained a BEng (Hons.) degree at Brighton University, U.K., before working in the electronics divisions of Eurotherm and BOC for seven years. He then joined Electronic Production magazine and subsequently spent 13 years in senior editorial and publishing roles on electronics manufacturing, test, and design titles including What’s New in Electronics and Australian Electronics Engineering for Trinity Mirror, CMP and RBI in the U.K. and Australia. In 2006, Steven became a freelance journalist specializing in electronics. He is based in Sydney.
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