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Broadband Wireless: Not More Of The Same
By Karen J. Bannan, Inter@ctive Week
August 9, 1999 5:09 AM PT
URL: http://www.zdnet.com/intweek/stories/news/0,4164,2310908,00.html

Even though they are now lumped together under the wireless broadband banner, the technologies
underlying Multichannel Multipoint Distribution Service and Local Multipoint Distribution Service
have some significant differences that ultimately will affect the way they are deployed and the
services they will deliver.

The differences start with the radio components used in the two flavors of broadband wireless,
says George Harter, chief technology officer at Harden & Associates, a wireless technology and
engineering consultancy.

"LMDS [Local Multipoint Distribution Service] uses a higher frequency, and it is being set up in a
point-to-point fashion, so each customer link has its own radio transmitter," Harter says. "MMDS
[Multichannel Multipoint Distribution Service] installations have a single transmitter serving multiple
subscribers."

The differences in radio frequencies translate directly into a stark contrast in operating
characteristics. With a maximum operating range of about three miles, LMDS has a smaller signal
footprint than MMDS, which has a signal that can carry up to 35 miles. But LMDS packs more of
a bandwidth punch, maxing out at up to 2.2 gigabits per second, compared with 1.2 Gbps for
MMDS, Harter says.

To make more efficient use of spectrum, MMDS operators can segment their networks into
smaller areas to reuse bandwidth. This can cause interference problems for some signals.

Siting by sight

Both technologies require a direct line of sight between the network and end-user antennas to get
the most efficiency out of bandwidth, but MMDS typically is characterized as a
"near-line-of-sight" technology because current versions penetrate foliage and suffer less from
environmental factors.

"LMDS makes more sense in an urban area because there are more customers and the antennas
are higher up on buildings," Harter says.

Deployment costs for both MMDS and LMDS are still up in the air, analysts say, since demand
for equipment is only in its nascent stages. Costs will drop as more installations actually roll out.
Although the number of installations will be limited, operators will be able to achieve economies of
scale depending on how many cell sites they set up and how extensive their coverage areas will
be.

Equipment costs aren't the only expenses to consider when deploying broadband wireless
technology. Wireless companies have to factor in installation costs, which can differ widely.

"Installing the equipment could cost $500 or it could cost $30,000," says John Skoro, a marketing
director at Nortel Networks. "It's almost impossible to price an installation until you actually get
into the system."

Bunker mentalities

Although wireless carriers don't face right-of-way issues as complex as those for wireline carriers,
they still need to negotiate with localities and building owners for permission to use a building as a
hub. Wireless carriers must buy or lease enough property for cell tower rights of way, and pay to
construct "bunkers," or places to house all the equipment, says Ray Jodin, a senior analyst at
Cahners In-Stat Group.

The promise of intensive growth in broadband wireless is spurring some makers of wireline access
equipment to move into the wireless market. Cable modem manufacturers including 3Com,
Com21, General Instrument, Scientific-Atlanta, and Toshiba are watching the technology. Several
have completed beta tests using MMDS, and Com21 has started making wireless cable modems.
Since the equipment is so similar to that of cable modems, the companies expect a short learning
curve.

"We did MMDS trials over a year ago," says Bill Wall, technical director for subscriber networks
at Scientific-Atlanta. "MMDS equipment is something we could do very quickly if the industry
continues to ramp."

Com21 has been running trials of MMDS gear for the past six months, according to John
Wattsman, the company's director of wireless business development. "It's cheaper to install
wireless than it is to deploy fiber or Hybrid Fiber-Coaxial cable," he says. "We think wireless
technology is going to be used to round out carriers' portfolios."
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