Early users laud 802.11a LANs

The first class of 802.11a wireless LAN users say the technology lives up to its advanced billing as a much speedier alternative to its predecessors, although it is not without shortcomings.

The 802.11a radios and adapters, rated to run at up to 54Mbps in the unlicensed 5GHz band, have proven simple to install and are priced aggressively vs. 11Mbps 802.11b wireless LAN gear.

As with any new technology, some issues still need to be addressed. For instance, vendors just now are introducing authentication based on the IEEE 802.11X standard. And early adopters say management tools for 802.11a are fewer – and less sophisticated – than those for 802.11b.

But if bandwidth is what users crave, 802.11a products deliver.

“We tested products by using laptops, playing DVD movies on our LAN and walking 40 to 50 feet [from an 802.11a access point],” says John Bucek, executive director of IT at Mount Saint Mary College, a liberal arts college of about 2,500 students in Newburgh, N.Y. “The movies played without a glitch. We didn’t do complex calculations, but it was clearly several times faster [than our older, pre-802.11 wireless LAN].”

Mount Saint Mary will begin deploying this week a campuswide 802.11a wireless LAN that will use nearly 100 access points.

Moving pictures seem to be a real attention getter for early customers. “I saw the SMC Networks (Inc.) 802.11a product, and I realized it had all the available bandwidth we needed to do streaming video,” says Tim Meriwether, a volunteer engineer with KOCT, a community television broadcaster in Oceanside, Calif. “We have totally successfully demonstrated that this works. It’s just amazing.”

So are the potential savings. Meriwether says that by using 802.11a products, the station will save most of the estimated US$28,000 in high-end equipment that’s usually needed to tie mobile television camera feeds into a video studio at the station.

A number of wireless LAN vendors now offer 802.11a access points and interface cards, most of them designed for laptop or desktop PCs, although some are available for handheld computers. The vendors aiming at the enterprise network market with available products include Intel Corp., Proxim Corp., SMC and Symbol Technologies Inc. Others, notably Agere Systems Inc., Cisco Systems Inc. and Enterasys Networks Inc., are expected to roll out 802.11a products for enterprise networks in the next few weeks.

Prices run from just less than US$300 to just more than US$500 per node for enterprise gear. Premium vendors, such as Cisco, likely will charge more, based on advanced systems management, security and other features.

Thinking About Throughput

In wireless LANs, throughput is relative. Actual throughput hinges on many variables, such as distance, building materials, even the number of people walking through the area. But even under optimum conditions, 802.11a products typically offer much less than half of the theoretical radio speed.

The performance range that Mount Saint Mary and KOCT found varied widely. College network administrator Arthur Emerson found that radio link speed (the speed with no data being pushed over the air) was subject to all kinds of variables. Putting one Proxim Harmony 802.11a access point in the centre of one dormitory created a fairly robust 12Mbps to the furthest corners. But when he added a second and positioned the access points opposite each other on two sides of the building, throughput jumped to 35Mbps.

Although, Emerson confesses: “I’m not sure I believe some of this.”

Radio test tools for 802.11a are not as sophisticated as those for 802.11b, he adds.

Emerson expects actual throughput to be in the range of 8Mbps to 12Mbps to distances of up to 30 feet from the access point. That will still be two to three times the throughput of the Proxim RangeLAN2 wireless network that’s been a staple on the campus since 1995. The RangeLAN2 is a proprietary radio that has a bandwidth of 1.6Mbps in the 2.4GHz band.

At KOCT, Meriwether says he’s getting transport speeds of 36Mbps and sometimes higher. He says the result is “rock solid” video displays on a laptop screen, with full stereo sound, at distances of 50 to 75 feet.

Coverage and Distance

The higher frequency of 802.11a means that the radio waves travel shorter distances, and have more trouble penetrating walls and other obstructions than the 2.4GHz radio in 802.11b wireless LANs. In theory, this means that you’ll need more 802.11a access points to cover the same area as with 802.11b.

Early experience at Mount Saint Mary indicates that in practice this is sometimes true, and sometimes not.

“We thought we’d need about two times the number of access points at first,” Bucek says. That remains true where buildings are made of lumber and Sheetrock. But for steel and concrete structures, Bucek now estimates they’ll need about three times the number of 802.11b access points.

But some of the additional access points are because the college wants redundancy. “If one access point fails, there is at least one other close enough to give you your Internet access,” he says.

Fiddling Around

Emerson says his IT staff will have to learn afresh the idiosyncrasies of 5.4GHz radios. They’ve noticed that the Proxim access point is quite sensitive to how its two visible antennas are positioned. Moving one antenna from horizontal to vertical, for example, can affect signal strength and range. And that creates a new worry: The old RangeLAN2 access points were mounted out of sight. Some number of the Harmony access points will be in plain view.

“They’re just out there for people to see…and to fiddle with,” Emerson says.

In many cases, installation appears to only involve replacing the old access point with a new one. At Mount Saint Mary, some Ethernet cable will be pulled to new locations, but it’s part of a long-planned upgrade of the 10Mbps backbone to 100Mbps.

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