As explained by Jim Lansford of Mobilian Corp. (Hillsboro, OR), wireless personal-area networking (WPAN) and wireless local-area networking (WLAN) are two technologies headed for significant growth. WPAN applications primarily include Bluetooth devices such as wireless headsets, wireless synchronization with PDAs, and other wireless peripherals such as printers. WLAN applications will likely focus on using Wi-Fi (IEEE 802.11b) for Internet access, e-mail, and file sharing with speeds of 11 Mb/sec up to 100 m.

"Coexistence has become a significant topic of analysis and discussion throughout the industry," says Lansford. "WPAN and WLAN are complementary rather than competing technologies. With both of them expecting rapid growth, collocation of Bluetooth and Wi-Fi devices will become increasingly likely. But, because both technologies occupy the 2.4-GHz frequency band, there is potential for interference between the them."

Lansford presented techniques for enabling the two technologies to successfully operate in the same place at the same time. "They create in-band colored noise for one another. Neither Bluetooth nor Wi-Fi was designed with specific mechanisms to combat the interference that each creates for the other. Bluetooth assumes it will hop away from bad channels. The 802.11b media access layer assumes that if it fails, two Wi-Fi stations tried to transmit at the same time."

One solution, he says, is to convince FCC to modify its rules such that Bluetooth could legally hop over a smaller portion of the band. It is currently required to hop over a minimum of 75 of the 83.5-MHz available in the 2.4-GHz band. Lansford also presented some practical solutions, including a ban on 802.11b in environments where Bluetooth is considered mission critical. General system approaches, as well as the driver layer, MAC layer, and physical layer were discussed.

"Some in the industry have positioned coexistence in the 2.4-GHz frequency band as motivation to hasten the migration to 5-GHz WLAN standards such as 802.11a or HiperLan2," he says. "Coexistence, and ultimately simultaneous operation between 802.11b and Bluetooth is a highly desirable goal." Lansford suggests that rather than just focusing on a regulatory solution or instituting restrictive practices, the indsutry will be best served through a systems-oriented approach that allows users to take full advantage of both technologies.