Merged Bluetooth

By Mark Hachman  |  Posted 2002-12-12 Print this article Print

/WiFi chips, or not?"> "I dont see a merge here. Youll continue to see what we have right now – device to device connectivity with each device choosing the technology to use depending on what it needs," Graham said.The problem is that many communications chip manufacturers do see a design path toward a merged Bluetooth/802.11 capable chip. While there are several potential design methods, all assume Bluetooth and 802.11 antennae will be in close proximity, almost assuring interference. Furthermore, upon encountering interference, an 802.11 transceiver lowers its data rate to ensure fidelity; "exactly the wrong thing to do, as it increases the problem of interference," said Tim Godfrey, strategic marketing manager at Intersil.
The 1.2 version of the Bluetooth specification, due next year, will support adaptive frequency hopping. Bluetooth radios with AFH will survey the frequency band for potential sources of interference, such as a channel on which an 802.11b wireless network is operating, and exclude the channel from its pseudo-random hopping pattern.
"Once 802.11b is switched on, Bluetooth can be smart enough to figure that out and hop out of the bandwidth," Godfrey said. "This opens up a new world of coexistence with a bunch of products buying out of the same band."The spec will account for a mix of AFH-less 1.1 Bluetooth devices and the newer 1.2 products, potentially leading to a complicated mix of hopping patterns and timings, said Joel Linsky, a senior Bluetooth design architect for Silicon Wave and a member of the 802.11 Coexistence working group.Silicon Wave has worked with Intersil and Intel to address the coexistence issue with Blue802 – an example of proprietary coexistence technology, that enables Bluetooth applications such as mouse, keyboard, printing and file transfer to take place at the same time the user is connected to the network over 802.11b. While other proposed solutions, such as Alternating Wireless Mechanism Access (AWMA) and Packet Traffic Arbitration either multiplex the Bluetooth and 802.11 signals or ask the Media Access Controller to act as a "traffic cop" between the two, Blue802 simply uses the 802.11 chips power-saving mode to switch the 802.11 portion on and off. Blue802 effectively shares bandwidth by only having one component in operation at one time, Intersils Godfrey said. While the technology has been out since April, the chipset is not yet available in full production.


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