Laws bite at Bluetooth

With the recent introduction of many new products using 802.11b wireless local area network (Wlan) technology and the Bluetooth short-range wireless standard, the chance of both technologies being used at any given site are increasing. Because both operate in the 2.4GHz region of the electromagnetic spectrum, this could cause problems, but perhaps not for the reasons most people expect.

Let's forget for a moment about the safety aspects of employing radio technology with a similar frequency to that of microwave ovens, and just concentrate on the issues of interoperability. As a Lan standard, 802.11b has a much higher data transfer rate, but Bluetooth has found a niche that may enable it to supplant infrared as a means of linking peripheral devices.

Recently, notebook PCs fitted with both wireless technologies have fallen foul of US Federal Communications Commission (FCC) regulations regarding electromagnetic emissions. In order to comply with the US regulations, Toshiba had to implement a Bios firmware switch in its Tecra 9000 and Portege 4000 notebooks that switches 802.11b off if Bluetooth is used, and vice versa. However, Wlan and Bluetooth technologies can still be used in the same office space.

Most concerns over 802.11b and Bluetooth have focused on the potential for the two standards to interfere with each other because their frequency ranges overlap. But Toshiba has said that its tests show only about a 15 per cent hit on Bluetooth performance when the two are used side by side.

Our own tests have shown that operating a Bluetooth PC Card next to an 802.11b access point results in a drop in Bluetooth performance by a third, but the signal still gets through. However, that's beside the point. To pass the FCC regulations, a device must not exceed a certain level of electromagnetic radiation, and it appears that putting Bluetooth and Wlan together in the same unit breaks that rule.

This could be a stumbling block for wireless integration, at least in the near future. Large vendors such as Toshiba will probably find a way around the problem - perhaps with a Bios update for European buyers that allows both to operate ? but, for the present, you can't use the two standards at the same time.

Another mainstream vendor, Dell, has said that it won't fit Bluetooth into its products until the standard is sufficiently mature, to avoid compatibility problems with different vendors' kit. It also intends to offer Bluetooth as an optional mini PCI card, which is how Wlan functions are currently supported, so buyers may be forced into choosing between the two standards.

The problems of interference could be removed by the introduction of the proposed 802.11h Wlan standard, if it ever gets off the ground. This uses the 5GHz frequency range, and is based on the US-only 802.11a.

It can push the maximum network data rate up to 54Mbit/s, and would clear the 2.4GHz band for Bluetooth. That may not solve the FCC problem, of course, as devices would still have to meet emissions standards.

Bluetooth may yet fail to catch on, not because it is a bad standard but because notebook buyers will be forced to choose between it and having a Wlan connection. It just goes to show that good ideas aren't always defeated for technological reasons.