New standards are faster, for a price
- By Paul Korzeniowski
- Jun 03, 2002
When representatives of the Institute of Electrical and Electronics Engineers Inc. began crafting new wireless local-area network standards, the group understood that no matter how much bandwidth a network offers, users always want more. So in examining ways to boost network transmission speeds, which were 2 megabits/sec at the time, the group developed two specifications.
The 802.11a standard, which has a top speed of 54 megabits/sec, was completed first, but because it relies on complex emerging technology, vendors put development plans on the back burner. The 802.11b standard was wrapped up a few months later, but it was easier to deploy and therefore the first one to reach the market.
The 802.11b standard operates in the 2.4 GHz radio frequency band and uses
direct-sequence spread spectrum technology to move data from sending to receiving stations. In theory, this places a premium on security and reliability while sacrificing efficient use of available bandwidth.
However, other wireless technologies also use this frequency range. Consequently, cordless telephones and Bluetooth devices, which laptops and personal digital assistants use to exchange information with desktop machines, can interfere with wireless LAN transmissions.
The 802.11a standard operates in the 5 GHz band. This option uses a modulation technique called Orthogonal Frequency Division Multiplexing, which increases bandwidth efficiency and supports several data rates. Because this frequency has been allocated only to wireless LANs, there is no risk of interference from other devices.
That standard is expected to support more sophisticated applications, such as streaming video, but vendors must address a few issues before users adopt the technology.
The 802.11a specification operates in a more complex frequency band — and the higher the band, the more complex the underlying technology. So the transmission range it supports will be narrower than what 802.11b systems support.
A general guideline used by vendors is that an 802.11b access point has a range of about 250 feet to 300 feet, while an 802.11a access point will cover only about 90 feet. That means customers will have to deploy more access points, and it will be more difficult for transmissions to
travel through walls, floors, furniture and other obstructions on the faster LANs.
Because it operates in a different frequency range, 802.11a systems will be incompatible with 802.11b devices. Management software will operate with the new specification, but administrators will have to replace the underlying hardware, such as adapters and access points.
"Vendors are working on ways to run both protocols on one chipset," said Anthony Armenta, executive director of the Wireless LAN Association, a nonprofit group that acts as an information clearinghouse about wireless LAN technology.
At this stage, 802.11a is a U.S.-only standard. The European Telecommunications Standards Institute has developed yet another high-speed wireless LAN option: HiperLAN/2. Like 802.11a, it promises data rates of up to 54 megabits/sec and operates in the 5 GHz frequency band.
Despite those issues, vendors have begun releasing the first round of 802.11a products. "Customers are now definitely at the kick-the-tires stage of interest with regard to 802.11a," said Dan Shell, a consulting engineer at Cisco Systems Inc., "but we expect deployment to ramp up later this year."