The trouble with mesh WiFi and why WiMax is the better bet for today's citywide wireless networks.
Slowly but surely, cities have begun to roll out municipal wireless
networks to improve communications with public safety officials such as
police and firefighters, to make Internet access more accessible to
their citizenry, or both. Riverside, Calif., Anaheim, Calif., and
Toronto are just some such wireless pioneers, with Philadelphia nearing
the end of its test phase and poised for a formal rollout this year.
Related Articles:
Thee early pioneers use a technology called mesh WiFi,
which connects hundreds or even thousand of wireless access points to
create a web of radio signals throughout a community, using public
airwaves as the medium. It’s essentially the same technology as used in
residential and business wireless LANs, so people with recent computers
are likely to have the ability to connect.
But mesh WiFi may be
nothing more than an interim step in municipal wireless networks. The
city of Grand Rapids, Mich., has decided to forgo WiFi and instead use WiMax,
a long-touted alternative whose mobile variation was finally
standardized in December 2005 and for which commercial products are
supposed to be available by 2008. Although WiMax has been promised for
close to a decade, it seems as if it is finally becoming real enough to
plan a municipal network around.
Pros and Cons
WiMax
has several factors in its favor, notes Karl Edwards, principal of the
Excelsio consultancy that advises cities on wireless strategies:
- You
need only a few radio towers to cover a 10-square-mile area, versus 300
to 400 WiFi access points to get the same coverage at the same traffic
levels — this significantly lowers both deployments and maintenance
costs. (Getting access to — never mind reliable power — to all the
utility poles and other structures needed to place the WiFi access
points on is painstaking work.)
- Users won’t need to buy a
radio amplifier in their homes to capture the signal, as they typically
need to use a mesh WiFi service, since the WiMax signal is stronger and
less likely to be blocked by walls or trees.
- The 2.5GHz
spectrum assigned to mobile WiMax is licensed, so there aren’t the
interference issues that the 2.4Ghz spectrum has for WiFi. These were
all reasons that Grand Rapids selected WiMax, says Sally Wesorick, the
city’s wireless project manager. The top requirement was supporting
public safety needs, and Wesorick was not happy about the many dead
spots and difficulty of getting signals inside buildings when she
tested WiFi service in other cities. By contrast, she was very happy
with the signal reach and quality when testing a pre-approval version
of WiMax in Greensboro, N.C.
But WiMax has some disadvantages as well:
- The
mobile version that supports police and firefighters on the go — the
primary reason many cities bother to support a municipal wireless plan
— runs only on licensed spectrum, which is held primarily by two
companies: Clearwire (which recently obtained AT&T’s spectrum in addition to its own) and Sprint Nextel.
So cities have to trust they can get a favorable deal with the local
spectrum monopoly owner. (As an example of that concern, several years
ago, the District of Columbia decided to deploy and manage its own
public safety network using 700MHz spectrum and technology from what is
now Qualcomm’s Flarion division rather than hire Verizon
as its public safety wireless network provider. Suzanne Peck, the
district’s CTO, said at the time that Verizon’s pricing was much too
high and its service level commitments much too low.)
- WiMax
service tends to cost more than WiFi service — 50 percent to 100
percent more — which makes it hard for cities to bridge the so-called
digital divide and bring affordable access to poor citizens, as many
cities do as part of their municipal wireless efforts. Although WiMax
costs less to deploy in terms of radios, the carriers have spectrum
costs that they include in their usage prices.
- Unlike WiMax,
WiFi has significant consumer adoption, making it easier for a
municipal service to get users quickly, notes Ina Mari Sebastian, an
analyst at Jupiter Research. That company’s surveys show that in 2006,
32 percent of broadband users had home WiFi networking gear and 31
percent of online consumers had used a public WiFi location in the last
12 months. And users of a mesh WiFi municipal network keep the
convenience of being able to use the same equipment for their home and
business wireless LANs as well as at public hot spots throughout the
country.
Although mesh WiFi may require users to buy a
radio booster, WiMax requires them to buy a WiMax card, so the two
technologies tie when it comes to user hardware costs.
Consultant
Edwards says he expects cities whose primary wireless goal is for
public safety and mobile government worker use will prefer WiMax
networks, while those who are deploying municipal wireless for
near-universal Internet access will favor mesh WiFi.
Cities that
start with WiFi may shift to WiMax in the future. The city of
Riverside, for example, plans to assess the technology every five years
to see what makes the most sense at the time. “You have to make your
decisions based on what is available today and tested,” says CIO Steve
Reneker. When Riverside began its wireless municipal effort a few years
ago, “we preferred to go WiMax, but products that support both 2.4GHz
and 4.9GHz for public safety were not available at the time of award of
our project.” The 4.9GHz public-safety spectrum was key, since that
supports the mobile technology that police, firefighters, and others
need.
And many will likely use both technologies. WiMax is a
natural for the backhaul connections that link the WiFi access points
to the Internet, so the access points aren’t wasting bandwidth passing
traffic from one to the other before finally reaching a fiber or other
direct connection to the Internet, notes Carl Reinwand, VP of product
strategy and marketing at EarthLink
Municipal Networks, which is managing several cities’ mesh WiFi
networks. But he notes that WiMax has just 70 percent the backhaul
capacity of other options, such as Motorola’s
proprietary Canopy wireless system. With a WiMax backhaul, the user
traffic goes straight from the access point to a WiMax tower, which has
a fiber connection to the Internet.
The Other WiMax Options
There
is another option that cities can consider if their goal is to provide
universal service rather than develop a strong public safety network:
fixed WiMax, which can be run over licensed spectrum or unlicensed
spectrum. Fixed WiMax over unlicensed spectrum would ensure that the
city is not beholden to a specific carrier, just as a mesh WiFi city
can fire its provider and choose another without losing access to the
spectrum. “If 2.4GHz — for 802.11b/g/n users — is all you need, WiMax
is the way to go,” says Riverside’s Reneker. While interference is
still an issue, it’s no different than interference in a mesh WiFi
network. And fixed WiMax gets around the deployment and management
hassles of all those access points. But it doesn’t satisfy public
safety’s mobility needs.
Some cities may have a third option if
they like the idea of WiMax but not being beholden to a carrier. In
many areas, there is local “education” 2.5GHz spectrum, notes Edwards,
typically owned by hospitals and universities. Cities might be able to
work out access to that bandwidth, so cities would have the deployment
and uncrowded spectrum advantages of WiMax for both public safety and
universal Internet purposes.
