Wireless LANs: Good Show
Stable, flexible and relatively fast, wireless networking has matured to the state where administrators can look ahead to the next big wireless LAN thing. The number of wireless LAN vendors is growing, and the technology keeps getting better, smaller and less expensive. Organizations are benefiting from increased interoperability among the access points that connect to a wired Ethernet LAN and the PC Cards that give notebooks and handheld computers their wireless capabilities.
By now, the advantages and, to a lesser extent, disadvantages of wireless LANs are well-known. Operating in the 2.4GHz band, 802.11b-based wireless LAN equipment delivers data at a nominal 11M bpsslower than the 100M bps generally found on wired LANs but fast enough for most applications and acceptable when a traditional network would be difficult or impossible to set up.
However, network administrators should expect to fine-tune their wireless LAN through trial and error. Effective wireless LANs are deployed with extensive site surveys, not general equations based on range. During an eWeek eValuation of wireless LANs at Corporate Partner site Cornell Universitys S.C. Johnson School of Management, eWeek Labs conducted a site survey to determine where access points should be placed for optimal use in a common area of the school. (The full eVal can be found at www. eweek. com/ links.)
After the eVal, a more extensive site survey performed by Corporate Partner Kevin Baradet, the schools university network systems director, found that the school library would be a wireless LAN sticking point: The moisture in the books absorbed the radio signal, requiring that more access points be set up.
The 802.11b protocol competes at some levels with the HomeRF specification, geared toward home networking, and Bluetooth, which enables wireless personal area networks and ad hoc networking.
Geared for business use, IEEE (Institute of Electrical and Electronics Engineers) 802.11b and Bluetooth share the 2.4GHz bandas do microwave ovens, portable phones, and some scientific and medical equipment.
All roads lead to wireless
Because they share the same frequency band, interference between Bluetooth- and 802.11b-based equipment is a concern. Howeverjudging from a number of tests conducted by eWeek Labs, wireless LAN vendors, and independent bodies such as the IEEE and the Wireless Ethernet Compatibility Allianceit appears that both technologies will coexist and perform well with the number of access points and devices most organizations would use.
On the horizon, another IEEE standard promises to compete for, if not usurp, 802.11bs dominance in the wireless LAN arena. Equipment based on 802.11a will operate in the cleaner 5GHz band at nominal data rates of 54M bpsabout five times the throughput allowed by 802.11b. Chip sets based on 802.11a are already in production, and prototype equipment is expected this summer, with volume production by the first quarter of next year.
The 802.11a protocol faces some competition of its own: the HiperLAN2 standard. Developed in Europe, HiperLAN2 is an interoperable standard intended for next-generation wireless and mobile communications. Like 802.11a, HiperLAN2 can operate at up to 54M bps in the 5GHz band. Unlike 802.11a, which supports only IP over Ethernet, HiperLAN2 supports several core networks, including IP over Ethernet, Point-to-Point Protocol, asynchronous transfer mode and IEEE 1394.
HiperLAN2 also provides support for quality-of-service control, allowing multimedia traffic, for example, to be given priority across the network. The core technical specifications for the standard were approved by the European Telecommunications Standards Institute in February, and HiperLAN2 equipment is expected to ship on the heels of 802.11a-based equipment.
The impact of these competing standards will be felt especially in global organizations, where mobile workers may have to carry two PC Cardsone for 802.11a environments and one for HiperLAN2 environments. Eventually, however, equipment vendors may push for a unified standard to simplify 5GHz wireless LAN equipment.
Beyond the LAN
Once a wireless LAN is set up and functional, the next logical step is to connect LANs, either from building to building (forming a MAN, or metropolitan area network) or into a WAN.
While a WAN spans multiple, geographically dispersed sites using local and long-distance carrier facilities, a MAN generally uses public transmission facilities. Wireless avenues for connecting buildings generally fall into the microwave and optical laser link categories, called FSO (free space optics).
Although there is great potential for high data throughput using FSO, the technology must overcome many hurdles before it will be deployed widely. These hurdles include line-of-sight requirements and degradation because of weather.
Vendors such as AirFiber Inc., LightPointe Communications Inc. and Terabeam Corp. are addressing these problems by moving transmitters closer together and, when necessary, repeating links. However, practical FSO equipment is still three to five years away.