How Bluetooth Got As Fast As Wi-Fi
Bluetooth last week stopped being chained to the low-power, low-throughput radio that has been both its strength and its weakness. New code lets Bluetooth applications now run over 802.11g wireless connections in the 2.4GHz, with a throughput jump to 20M to 24Mbps, from 1M to 3Mbps.
Mon, April 27, 2009
Network World — Bluetooth last week stopped being chained to the low-power, low-throughput radio that has been both its strength and its weakness. New code lets Bluetooth applications now run over 802.11g wireless connections in the 2.4GHz, with a throughput jump to 20M to 24Mbps, from 1M to 3Mbps.
We talked to one of the key creators of this bit of wizardy: Kevin Hayes, a technical fellow with Atheros Communications, who has worked in m ore than a dozen task groups around the IEEE 802.11 wireless LAN standard, and in Wi-Fi Alliance projects such as Wi-Fi Protected Access.
Hayes was the technical editor for the 802.11 Protocol Adaption Layer (PAL), one of the big changes in the just-announced Bluetooth 3.0 specification, a two-year project. PAL, together with the 802.11 media access control (MAC) and 802.11 physical (PHY) layers constitute the Alternate MAC/PHY or AMP, enabling a Bluetooth profile (such as file transfer) to run over a Wi-Fi link. It's the beginning of "Bluetooth everywhere," according to Network World blogger Craig Mathias.
But make sure you look for the full formal designation: Bluetooth 3.0 + High Speed (or HS). (For some uses, vendors can deploy 3.0 without the ability to use a Wi-Fi connection but they can't use "high spped" in labeling it).
So, is this a big change?
It's a generational change. The Bluetooth SIG wanted something what would deliver five to ten times the performance of current Bluetooth; they wanted something that would be available to customers in a short timeframe; and they wanted something that was proven technology.
[Gartner analysts picked Bluetooth 3.0 as one of eight mobile technologies to watch.
With 3.0, the Bluetooth stack opportunistically exploits whichever radio link is best, right?
First, it would only be used if both sides support it, in silicon and software. Some of the classic Bluetooth profiles, such as the headset profile or the hands-free profile for a car kit, will never use high-speed [Wi-Fi] silicon.
But there are many object and file transfer protocols and profiles that would. Things like file transfer, object push, printing, imaging: all these would involve taking some object or file from one device to another. The new standard is appropriate for almost all of these.
What happens when the new Bluetooth code is deployed on gadgets with a Wi-Fi radio?
There's a generic Bluetooth framework, that rides over the classic Bluetooth radio. There are a set of protocols for doing things like discover and negotiation and so on. Some configuration variables [now] are handed over to the new software module, called the 802.11 PAL, which translates those variables from the Bluetooth domain to the .11 domain. It translates the data packets [sent] from the Bluetooth stack, and sends these [out] over 802.11.
