Bluetooth will kill off wireless standard
Published: 18 May 1999 08:37 BST
The 802.11 standard uses the same radio frequency as Bluetooth, the license free ISM (Industrial, Scientific and Medical) Band at 2.45GHz. This Band is also used by the HomeRF group's SWAP technology, microwave ovens and automatic garage doors.
For radios to coexist at this Band, they have to frequency hop. This means the Band has to be divided into a number of 1MHz wide channels and the radio hops from channel to channel in a predefined sequence. If the transmission on any channel is corrupted by interference, the radio waits until it gets to the next channel and retransmits. The theory is there are enough channels and few enough transmitters for everything to work together.
"Older wireless standards like 802.11 hop quite slowly, only two and a half times each second, which was dictated by the availability of silicon to control 1W transmitters back when 802.11 was proposed," said Nick Hunn, TDK Systems' technical manager. "Low power newcomers like Bluetooth do it faster, at 1,600 times a second. As long as 802.11 and Bluetooth are kept apart, there's no problem. But put them in the same laptop and it all starts to fall apart. If the Bluetooth transmitter is close enough to the 802.11 receiver, it will trash every data packet of 802.11. And there's a chance that the 802.11 transmissions will overload the receiver stage of Bluetooth."
According to Hunn, the problem is that the laptop is the natural home of both Bluetooth and 802.11 and users won't turn off one or the other. "They'll expect both to work, which they won't," he said. "Here 802.11 starts to suffer, as it's a one solution product."
Hunn refers to the fact that Bluetooth has wider applicability when you're on the move as it can link to mobile phones, CD`s, radios, PCs, notebooks, modems and so on.
"It's also quite satisfactory for dedicated one-to-one wireless LAN connections, which means it's very likely to usurp 802.11. Privately the wireless LAN manufacturers have been getting worried. The upgrade of 802.11 to 11MHz has been poorly taken up and the talk is of a need to ditch 2.45GHz and migrate to a higher bandwidth solution anyway to cope with 100M networks."
The implications are that the 802.11 standard will be killed off by virtue of the fact that it cannot `hop' across channels quick enough and by the fact that Bluetooth -- it's immediate replacement -- can hop quickly and therefore communicate `cleanly' and it also had a broader support base.
Wireless leader Proxim has also come out and said that it can foresee the death of 802.11 and is staking its future on HiperLAN.
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