It’s generally acknowledged these days that Bluetooth and Wi-Fi can live together in harmony as standards, but it’s another matter to get them to work together while residing in the same device. Interference problems from collisions — since both use the same radio frequency (RF) band — causes dropped packets, which only cascades into other problems. However, Texas Instruments (TI)
believes it has the answer.
The director of advanced technology in TI’s WLAN Business Unit, Matthew Shoemake, says the company has been working on this problem for a while — in fact, its solutions already built into the company’s WANDA reference design for a PDA that would have Wi-Fi, Bluetooth, and cellular all in one PocketPC.
“Our customers need [Bluetooth and Wi-Fi] in products they’re bringing to market, say a PDA which wants to use both simultaneously, doing data download while talking on a Bluetooth headset,” says Shoemake.
The TI Bluetooth/802.11 coexistence package is specifically focused on makers of mobile devices like PDAs and handsets, as the problem of coexistence is magnified the closer together the chips for each are placed. The design criteria therefore was that that no RF radio isolation should be required. Instead, the chips use “time domain coordination,” not RF isolation, to get simultaneous use.
TI has made the solution modular and flexible enough to support both Bluetooth 1.1 or 1.2 (via the BRF6100, which measures only 6×6 millimeters) or 802.11a, b, or g (with the 12×12 mm TNETW1100b for 802.11b or the slightly larger 16×16 mm TNETW1130 for 11a/b/g). All of TI’s chips are designed to use as little power as possible, particularly when in standby mode.
The design features a coexistence bus that runs between the WLAN and Bluetooth chips, running in real time on the MAC Layer, which dynamically adjusts to the traffic patterns on the devices.
“If they’ve both got traffic, it makes smart and optimal decisions on which needs to get the most traffic,” says Shoemake.
The design can be implemented with from one to three antennas, with two being the optimal number since there’s no performance degradation, lower cost, and no additional switch needed if the two chips share a single antenna.
The company is offering the Bluetooth/802.11 coexistence package as part of the embedded station development kit, which won’t have general availability until the fourth quarter. Shoemake says customers are already lined up and that one product using this solution might even ship in September.
Later versions of this package are expected to support Voice over IP (VoIP) on wireless LANs.
What else can impact your WLAN hardware?
Join us at the 802.11 Planet Conference
& Expo, June 25 – 27, 2003 at the World Trade Center Boston in Boston, MA.
TI’s own WLAN Product Technologist will be on hand for the panel
Balancing Act: Hardware Performance vs Equipment Cost.