Transcending the LAN

Wireless networking based on the 802.11 standard - or Wi-Fi as its proponents prefer to call it - is a dark horse technology that's becoming increasingly common thanks to unorthodox usage and its innate flexibility reports Juha Saarinen.

Wireless networking based on the 802.11 standard — or Wi-Fi as its proponents prefer to call it — is a dark horse technology that’s becoming increasingly common thanks to unorthodox usage and its innate flexibility.

Originally intended for local area network use, the various 802.11 implementations — the letterless, a, b and g varieties already — are seeing use outside the office as well.

One popular application for 802.11 is bridging inter-building networks. It’s often much more cost-effective to set up a point-to-point 802.11b bridge between two adjacent office buildings than to lease fixed data connections, or even to lay your own cable. The wireless bridge can be set up in a few hours, and it avoids permit hassles and exorbitant one time and ongoing charges such as the “ground lease” levied by Auckland City Council.

So-called hotspots are also starting to appear: these are areas saturated with wireless signal, allowing users in the vicinity easy network access. Wellington has some 11 hotspots around the city centre, operated by CafeNET, while Walker Wireless has deployed an 802.11b network at Auckland airport. Elsewhere, large telcos BT and NTT are deploying saturation networks in UK and Japan respectively. (Telecom New Zealand has no such plans.)

Big name vendors are jumping on to the wireless bandwagon: Microsoft New Zealand Windows platform product manager Jay Templeton says Wi-Fi hardware is planned, noting that Windows XP is the first commercial OS to support the 802.1X security and authentication method. Templeton says 802.1X will be implemented in Windows 2000 later, depending on customer demand. He believes wireless LANs and public hotspots will “dramatically increase” the freedom of mobile users by providing flexible access to remote data and systems.

Together with Intel, Microsoft is looking at incorporating a small base station into Wi-Fi adapters. The idea is that mobile users should be able to set up an ad hoc peer-to-peer wireless network without additional gear. The initiative has been dubbed “Soft-Fi”, and if the security concerns are solved is likely to become a must-have for mobile business computing.

Network giant Cisco naturally enough also sees Wi-Fi networks as a major opportunity: Roger de Salis of Cisco New Zealand says the company is looking at releasing 802.11b VoIP handsets, offering the intriguing prospect of wireless being used to bypass the New Zealand local telephone loop.

Early market entrants are taking the technology even further: Auckland company Technautics, a marine computer systems integrator, is putting 802.11b networks into yachts and harbour facilities.

Community wireless networks, meanwhile, offer opportunities for internet broadcasters, once cheap access to saturation networks becomes available. Far East electronics vendors are already pondering low-cost wireless media devices.

Wireless headaches

As deployment of wireless networking increases, so do the problems. Security is one issue; interference is another. All 802.11 transmitters share the same 2.4GHz frequency band, which is divided into 70 1MHz channels.

Cordless phones, microwave ovens and Bluetooth devices also use the 2.4GHz spectrum with 802.11b devices, and can cause interference with data transmissions.

Wireless performance angst is another problem. While 802.11 and 802.11b hit 11Mbit/s (10% faster than standard ethernet), this is shared bandwidth. Furthermore, you only get 11Mbit/s under ideal conditions, close to the access point. Move away from the access point, or place a solid object in between (the more moisture, the more of the signal is absorbed), and speed can drop considerably, down to 1Mbit/s. With many users, an 802.11b solution will choke.

Vendors like Intel and Netgear have released 802.11a products which could help solve the interference and performance problems, at least to a degree. Intel’s Pro Wireless 5000 promises a throughput of 54Mbit/s under ideal conditions. This is matched by Netgear’s HE102, though a “turbo” mode boosts speed to 72Mbit/s — at the cost of 30% reduction in range. Furthermore, 802.11a offers eight channels for an aggregate bandwidth of 432Mbit/s; 802.11b only has three channels, maxing out at 33Mbit/s aggregate bandwidth.

Another advantage of 802.11a is that it uses the less congested 5.8GHz spectrum and thus should be less affected by interference. However, the shorter wavelength means 802.11a signals are more affected by physical obstructions and their range is shorter: Intel claims 54Mbit/s is possible within 12m indoors/30m outdoors of the base station.

Speed drops to 6Mbit/s when the distance increases to 30m indoors/300m outdoors, giving a considerably shorter range than 802.11b.

While 802.11g products are still being readied, offering 54Mbit/s maximum speed when operating in the 2.4GHz spectrum, existing 802.11b technology has received a performance boost: Texas Instruments’ ACX100 chip uses a new modulation scheme that bumps up the maximum speed to 22Mbit/s and makes the signal less susceptible to interference. US Robotics has already released cards and access points built with the TI chip.

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