Once upon a time, Bluetooth was a quaint low-speed, low-bandwidth networking technology that appeared to be destined for the obsolescence pile. Several competing standards with broadcast industry support arose to challenge it with lower-power requirements, higher throughput, or both.
Bluetooth took heed of the motto of the Round Table (no, not that round table): "adopt, adapt, improve," and won out by extending what it does and co-opting what others attempted to provide (and failed to do).
But this may be confusing when you're not using a Bluetooth peripheral, like a headset, headphones, or mouse, and wonder why iOS, your Mac, or your Apple Watch is complaining about its absence or not functioning as expected.
Answers to that and other networking questions in this week's Mac 911.
Is that you, Harald?
Reader and colleague Scholle wrote in wondering what had happened with AirDrop between Mavericks and Yosemite: why was Bluetooth suddenly required? Other readers (and your correspondent) regularly see problems with AirDrop, too.
The reason that the iOS and OS X versions of AirDrop lacked compatibility until Yosemite is that Apple used a special Wi-Fi mode in OS X, but opted for a different approach that combined Bluetooth and Wi-Fi in iOS. Yosemite switched to that version, though a backward-compatible option remains.
Bluetooth is used for signaling, or sending information related to forming a connection, passing control data (like performing an action), and the like between the same kind of devices and different ones. The Apple Watch uses Bluetooth 4.0, which has an extremely efficient low-energy mode, to communicate with an iPhone.
That limits the range the watch and an iPhone can be apart, but it also essentially makes the watch's battery life feasible at its current weight. Continuity in OS X and iOS also relies on Bluetooth to send tiny bits of detail. All of these devices switch to Wi-Fi for high-speed bulk data transfer using a Personal Area Networking (PAN) mode that allows an iOS or OS X device to remain connected to the Internet and transfer data with other Apple hardware.
If you're having trouble with getting AirDrop, Continuity features like Handoff, or your Apple Watch to work, you can try toggling Bluetooth and Wi-Fi on and off, and Airplane mode on a Watch or iOS device. In a house, one intervening wall made of signal-blocking material, like plaster over wire or brick, can also block Bluetooth's effectiveness even while Wi-Fi can still blast through it.
Roam if you want to, roam around your house
I'm repeating here in brief some hard-won advice I mentioned in passing a few weeks ago relating to Wi-Fi. Apple's base stations (and all current base stations I'm aware of from other makers) allow roaming by default. Choose a network name from any device, and all base stations with the same parameters and same network name will let you roam about.
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