Living Without Wires: A Bluetooth Primer
By Darryl Wilkinson
I hate cords, cables, and wires. Wires and cables collect dust, trip you, are never long enough (or are way too long), and in general make living with electronics a tangled mess. If you’ve ever had headphones wrenched from your ears when the cord got snagged on something, you’ll understand why I have a particularly intense loathing of headphone cords. Fortunately wireless pioneers such as Tesla and Marconi sought to cut our electronic chains. For well over a hundred years, others have amplified their efforts, to the point where new wireless technologies are developed with such frequency that it is tough to keep track of them all. Life without wires doesn’t have to be an endless cycle of confusion, though. In this series, we’ll peek at one wireless technology at a time so you can wave your wire troubles goodbye.
Bluetooth: Here’s What It Is - and What It Isn’t.
According to the Bluetooth Special Interest Group (SIG), “Bluetooth technology is the global wireless standard enabling, convenient, secure connectivity for an expanding range of devices… Created by Ericsson in 1994, Bluetooth wireless technology was originally conceived as a wireless alternative to RS-232 data cables. Bluetooth technology exchanges data over short distances using radio transmissions. Bluetooth technology operates in the unlicensed industrial, scientific and medical (ISM) band at 2.4 to 2.485 GHz, using a spread spectrum, frequency hopping, full-duplex signal at a nominal rate of 1600 hops/sec. The 2.4 GHz ISM band is available and unlicensed in most countries.” (Aren’t you glad you asked?)
Unless you’re planning on developing products that incorporate Bluetooth technology, there’s not much in the above technical description that you need to remember. You just need to be aware of two main facts about Bluetooth.
To begin with: “Bluetooth technology exchanges data over short distances using radio transmissions.” In other words, Bluetooth is primarily about enabling electronic devices to communicate - as long as they’re located relatively close together. Most commonly, that means they need to be within 10 meters (33 feet) of one another. The hitch here, however, is that we’re talking about line-of-sight distance. The range of typical Class 2 Bluetooth device inside your home or office will almost always be less than 10 meters due to walls and other obstructions. Of course, just to confuse things, there are also wimpy Class 3 devices with about 1 meter (3 feet) of range and over-achieving, primarily industrial Class 1 devices that spec out with ranges as far as 100 meters. If you currently have a Bluetooth-enabled smartphone, wireless headset, or other such consumer electronics gadget, it’s most likely a Class 2 device.
The other thing to bear in mind is that Bluetooth technology uses radio transmissions and “operates in the unlicensed industrial, scientific and medical (ISM) band at 2.4 to 2.485 GHz…” Calling it an “unlicensed” band doesn’t imply that Bluetooth operates in a Wild, Wild West of the electromagnetic spectrum; on the other hand, it does mean that Bluetooth uses a frequency range that lots of other electronic gear - handy things, such as some types of cordless phones and routers with Wi-Fi - are designed to use, too. Even though microwave ovens don’t include radio transmitters, they often flood the 2.4 GHz band with waves of static. To get around all this interference, Bluetooth uses a sophisticated technology called adaptive frequency hopping (AFH). But hopping, skipping, and jumping across frequencies can’t perform miracles. The result is that excessive amounts of interference can limit your Bluetooth device’s effective range.
You Want Music With That?
Bluetooth is rapidly becoming ubiquitous in personal and portable electronics, such as powered portable speakers, smartphones, hands-free headsets, and wireless headphones. Since so many people use smartphones and tablets to listen to music, more and more home audio devices - including AV receivers, portable speakers, desktop audio systems, and soundbars - come with Bluetooth built-in. A number of companies now make standalone Bluetooth receivers with stereo audio outputs, which means they can be used with older analog audio components; and a few Bluetooth receivers also include better-sounding digital audio outputs.
While using Bluetooth to send music from your smartphone to a separate audio device is incredibly convenient, there are a couple of potential downsides to using a Bluetooth connection for musical entertainment. The first is the limited range of most Bluetooth devices. If you and a couple of friends are sitting in the living room listening to music coming from your smartphone paired with, let’s say, a soundbar, you’ll have a great time until you get up to go to the bathroom. If your phone happens to be in your pocket when you walk out of the room, it won’t be long before the music begins to breakup and, eventually, quit playing altogether as the devices become too far away from one another - or have too many obstructions between them - for the Bluetooth connection to be maintained.
The fact that so many devices use Bluetooth technology for audio purposes is rather amazing considering the fact that when Bluetooth was first developed back in 1994, it was intended to be a wireless replacement for computer data cables. Multiple enhancements to the format’s features and specifications over the past 20 years have allowed Bluetooth to be used for a wide variety of applications that I’m sure its developers never dreamed would be the case. Those changes have led to a bewildering alphabet soup of Bluetooth “profiles”, such as Health Device Profile (HDP), Human Interface Device Profile (HID), Audio/Video Remote Control Profile (AVRCP), and Advanced Audio Distribution Profile (A2DP), as well as a jam-packed warehouse of others. Don’t despair, though. In terms of multimedia audio - in other words, music - there are only a couple that you’ll want to be aware of.
AVRCP gives a Bluetooth device - a pair of wireless headphones, for example - limited ability to control some functions (volume and transport controls, in some cases) of the transmitting device, most commonly a smartphone. AVRCP is most often used in conjunction with A2DP, which is what makes listenable multimedia audio via Bluetooth possible.
Just because it’s “listenable,” however, doesn’t make it “high fidelity.” In its basic form, A2DP compresses the audio signal using (another acronym you can immediately forget) Low Complexity Subband Coding (SBC). “Low Complexity” is your clue that you’ll hear sound, but it won’t be as good as the original. Fortunately, A2DP allows for the optional use of alternate codecs (the software that compresses and then decompresses the audio signal), such as AAC and aptX. AAC is what Apple uses. Other companies incorporate aptX, which claims to provide near-CD-quality audio. “Optional” is the operative word here. Devices with Bluetooth don’t have to include aptX, for instance; and to get the sonic benefit aptX provides, both the transmitting and the receiving devices have to support aptX. The good news is that Bluetooth-enabled gear with aptX will most likely be prominently labeled as such. So, if audio quality is important, look for the aptX logo.
Here, There, Bluetooth is Everywhere!
Bluetooth is definitely the jack-of-all-trades when it comes to wireless technology. Thanks to all of its different profiles, Bluetooth is used in a laundry list of applications that already or will soon include:
- For hands-free calling and smart interaction with various features of your automobile
- 3D glasses, remote controls, soundbars, AV receivers, and speaker systems
- Interface devices, such as keyboards and mice
- Personal Health & Wellbeing
- Smart scales, activity trackers, heart rate sensors, and sleep pattern monitors
- Wireless stethoscopes and blood glucose monitors
- Bluetooth-enabled “smart watches”
- Home Automation
- Motorized door locks, automated lighting, shading, thermostats and temperature sensors
Despite a limited range of barely 33 feet in most consumer implementations, Bluetooth technology can be adapted to a nearly limitless number of applications. In the unlikely event that you don’t already own at least one device with Bluetooth capabilities, you will own one in the near future - and most likely, many more than just one device. Like all technologies, Bluetooth has its flaws; but for specific applications and circumstances, Bluetooth may be your best option.