Wireless specs are on collision course

When a Bluetooth connection collides with a wireless LAN connection, either or both connections can jam, resulting in a transmission error

Bluetooth may be a boon to mobile devices, but to wireless LANs, it's a bully.

At Comdex in Las Vegas, an entire pavilion of vendors will be showing products based on Bluetooth, the code name of an emerging specification for low-cost, short-range radio links among mobile PCs, phones and other portable devices. Actual products based on the specification are not likely to show until the second half of next year.

Bluetooth's main benefit: providing persistent, wireless connections between different kinds of devices.

Its main problem: It uses the 2.4GHz radio frequency, the same used by wireless LANs based on the 802.11 standard. When a Bluetooth connection collides with a wireless LAN connection, either or both connections can jam, resulting in a transmission error.

"There can be some interference between the two," said Skip Bryan, director of technology market development at Ericsson which is building Bluetooth chip sets for wireless phones. "While we're a shorter-range link than they are, we can get into the same space."

The two specs have different functions. Bluetooth requires little power and is meant for transmitting small amounts of data (at 1M bps) over short distances (up to 10 meters); 802.11 connections can range in transmission rates from 2M to 11M bps and at distances from 50 to several hundred feet.

The potential for colliding connections is more of a problem for the LAN radio than for Bluetooth devices. Because Bluetooth can hop frequencies faster than 802.11, it's likely to catch a wave first, analysts said.

"The trick with Bluetooth is that it's seamless and always connecting," said Jill House, an analyst at International Data Corporation. "But that means it can always be jamming the network, too."

Several members of the Wireless LAN Alliance are also members of the Bluetooth Special Interest Group, but none of them has solved the problem -- yet. "They'll probably figure out how to pause one network while the other network does its thing," Bryan said. "There should be some solution; there just isn't one yet."

Hundreds of companies have Bluetooth products in the works, many of which will be on display at Comdex.

Ericsson, Intel, Motorola and Silicon Wave are building chip sets for manufacturers. Xircom is developing Bluetooth PC Cards for notebook computers as well as a Bluetooth-enabled version of the Rex, a personal digital assistant that fits into a PC Card slot for synchronisation.

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