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May 17, 2023

Bluetooth The King
Ragnar Lodbrok was a legendary Norse king, conquering parts of Denmark and Sweden. And if we’re to believe the songs, he led some of the best raids against the Franks and the the loose patchwork of nations Charlemagne put together called the Holy Roman Empire. 

We use the term legendary as the stories of Ragnar were passed down orally and don’t necessarily reconcile with other written events. In other words, it’s likely that the man in the songs sung by the bards of old are likely in fact a composite of deeds from many a different hero of the norse.
Ragnar supposedly died in a pit of snakes at the hands of the Northumbrian king and his six sons formed a Great Heathen Army to avenge their father. His sons ravaged modern England int he wake of their fathers death before becoming leaders of various lands they either inherited or conquered. One of those sons, Sigurd Snake-in-the-Eye, returned home to rule his lands and had children, including Harthacnut. He in turn had a son named Gorm. 

Gorm the Old was a Danish king who lived to be nearly 60 in a time when life expectancy for most was about half that. Gorm raised a Jelling stone in honor of his wife Thyra. As did his son, in the honor of his wife. That stone is carved with runes that say:

“King Haraldr ordered this monument made in memory of Gormr, his father, and in memory of Thyrvé, his mother; that Haraldr who won for himself all of Denmark and Norway and made the Danes Christian.”

That stone was erected by a Danish king named Herald Gormsson. He converted to Christianity as part of a treaty with the Holy Roman Emperor of the day. He united the tribes of Denmark into a kingdom. One that would go on to expand the reach and reign of the line. Just as Bluetooth would unite devices. Even the logo is a combination of runes that make up his initials HB. Once united, their descendants would go on to rule Denmark, Norway, and England. For a time. Just as Bluetooth would go on to be an important wireless protocol. For a time. 

Personal Area Networks
Many early devices shipped with infrared so people could use a mouse or keyboard. But those never seemed to work so great. And computers with a mouse and keyboard and drawing pad and camera and Zip drive and everything else meant that not only did devices have to be connected to sync but they also had to pull a lot of power and create an even bigger mess on our desks. 

What the world needed instead was an inexpensive chip that could communicate wirelessly and not pull a massive amount of power since some would be in constant communication. And if we needed a power cord then might as well just use USB or those RS-232 interfaces (serial ports) that were initially developed in 1960 - that were slow and cumbersome. And we could call this a Personal Area Network, or PAN. 

The Palm Pilot was popular, but docking and pluging in that serial port was not exactly optimal. Yet every ATX motherboard had a port or two. So a Bluetooth Special Interest Group was formed to conceive and manage the standard in 1988 and while initially had half a dozen companies now has over 30,000. The initial development started in the late 1990s with Ericcson. It would use short-range UHF radio waves in the 2.402 GHz and 2.48 GHz bands to exchange data with computers and cell phones, which were evolving into mobile devices at the time.

The technology was initially showcased at COMDEX in 1999. Within a couple of years there were phones that could sync, kits for cars, headsets, and chips that could be put into devices - or cards or USB adapters, to get a device to sync 721 Kbps. We could add 2 to 8 Bluetooth secondary devices that paired to our primary. They then frequency hopped using their Bluetooth device address provided by the primary, which sends a radio signal to secondaries with a range of addresses to use. The secondaries then respond with the frequency and clock state. And unlike a lot of other wireless technologies, it just kinda’ worked.

And life seemed good. Bluetooth went to the IEEE, which had assigned networking the 802 standard with Ethernet being 802.3 and Wi-Fi being 802.11. So Personal Area Networks became 802.15, with Bluetooth 1.1 becoming 802.15.1. And the first phone shipped in 2001, the Sony Ericsson T39. 

Bluetooth 2 came in 2005 and gave us 2.1 Mbps speeds and increased the range from 10 to 30 meters. By then, over 5 million devices were shipping every week. More devices mean we have a larger attack surface space. And security researchers were certainly knocking at the door. Bluetooth 2.1 added secure simple pairing. Then Bluetooth 3 in 2009 bringing those speeds up to 24 Mbps and once connected allowing Wi-Fi to pick up connections once established. But we were trading speed for energy and this wasn’t really the direction Bluetooth needed to go. Even if a billion devices had shipped by the end of 2006.

Bluetooth 4
The mobility era was upon us and it was increasingly important, not just for the ARM chips, but also for the rest of the increasing number of devices, to use less power. Bluetooth 4 came along in 2010 and was slower at 1 Mbps, but used less energy. This is when the iPhone 4S line fully embraced the technology, helping make it a standard. 

While not directly responsible for the fitness tracker craze, it certainly paved the way for a small coin cell battery to run these types of devices for long periods of time. And it allowed for connecting devices 100 meters, or well over 300 feet away. So leave the laptop in one room and those headphones should be fine in the next. 

And while we’re at it, maybe we want those headphones to work on two different devices. This is where Multipoint comes into play. That’s the feature of Bluetooth 4 that allows those devices to pass seamlessly between the phone and the laptop, maintaining a connection to each. Apple calls their implementation of this feature Handoff. 

Bluetooth 5 came in 2016, allowing for connections up to 240 meters, or around 800 feet. Well, according to what’s between us and our devices, as with other protocols. We also got up to 2 Mbps, which dropped as we moved further away from devices. Thus we might get buffering issues or slower transfers with weaker connections. But not outright dropping the connection.

Bluetooth Evolves
Bluetooth was in large part developed to allow our phones to sync to our computers. Most don’t do that any more. And the developers wanted to pave the way for wireless headsets. But it also allowed us to get smart scales, smart bulbs, wearables like smart watches and glasses, Bluetooth printers, webcams, keyboards, mice, GPS devices, thermostats, and even a little device that tells me when I need to water the plants. Many home automation devices, or IoT as we seem to call them these days began as Bluetooth but given that we want them to work when we take all our mostly mobile computing devices out of the home, many of those have moved over to Wi-Fi these days.

Bluetooth was initially conceived as a replacement for the serial port. Higher throughput needs moved to USB and USB-C. Lower throughput has largely moved to Bluetooth, with the protocol split between Low Energy and higher bandwidth application which with high definition audio now includes headphones. Once the higher throughput needs went to parallel and SCSI but now there are so many other options. 

And the line is blurred between what goes where. Billions of routers and switches have been sold, billions of wireless access points. Systems on a Chip now include Wi-Fi and Bluetooth together on the same chip. The programming languages for native apps have also given us frameworks and APIs where we can establish a connection over 5G, Wi-Fi, or Bluetooth, and then hand them off where the needs diverge. Seamless to those who use our software and elegant when done right.

Today over four billion bluetooth devices ship per year, growing at about 10 percent a year. The original needs that various aspects of Bluetooth was designed for have moved to other protocols and the future of the Personal Area Network may be at least in part moved to Wi-Fi or 5G. But for now it’s a standard that has aged well and continues to make life easier for those who use it.