Wireless Wans may soon be the answer for companies looking for a
cheap, fast and easy solution to setting up their own
communications networks.
Wireless local area networks have been around for some time, but
opportunities for creating wireless wide area networks, operating
over distances of more than a few dozen metres, are only just
beginning to arise.
A WWan can be defined as a network allowing data transmission by
satellite or radio between different buildings situated hundreds of
metres or more apart. The sites connect with each other or through
a central network through antennae installed on the buildings.
WWans can be much cheaper than traditional networks, more flexible
and easier to install.
WWans have been in use for some time among very large companies
such as IBM and communications carriers, but they have recently
become an option for mainstream commercial organisations.
"We rarely get asked about WWans," said Ian Keene, an analyst at
Gartner.
"It is only in the past six months that people have been exploring
the concept," said Dave Swift, solutions marketing director at
Alcatel.
Wide area wireless transmissions can be implemented on a
point-to-point basis or in a networked many-point-to-many-point
environment. The term WWan is used to describe both types of
infrastructure.
WWans can be implemented by adapting a wireless Lan; using
unlicensed radio frequencies; using more powerful licensed radio
frequencies; through satellite transmissions or through a
combination of these technologies with traditional wired
technologies.
"Many of our customers move seamlessly from Wi-Fi to WWan and back
to the corporate networks via a VPN channel," said Shelly Julien,
vice-president of Netmotion Wireless. Three years ago, Netmotion
introduced software called Mobility, which is designed to provide
transparency of operation to the user.
For wireless data transmissions over a greater range than the few
metres covered by wireless Lans, "The main option is in the 2.4GHz
or 5GHz ranges, which are based on 802 standards," said Maurice
Philpott, an analyst at Ovum. Transmissions taking place at 2.4GHz
or 5GHz radio frequency provide data throughputs of a maximum
11mbps and 54mbps respectively.
This is much faster than the services offered by the cellular radio
companies using 2.5G (GPRS) or 3G (UTMS) mobile phone networks.
With these, the maximum available speed is 144kbps, and the user
typically gets a lot less. And it is more than 10 times faster than
the services possible with 2G (GSM) mobile phone networks, which
are essentially restricted to niche applications such as SMS.
The 2.4GHz and 5GHz transmissions are made according to standards
set by the IEEE. The standard governing 2.4GHz transmissions is
802.11b, which is widely promoted under the name Wi-Fi. The
standard governing 5GHz transmissions, which has only just come
into use, is 802.11g.
You do not need a licence to create a network using these
standards. "The technology is relatively standardised so you can
get economies of scale. Suppliers are making equipment with prices
comparable to DSL products," said Philpott.
Theoretically, point-to-point 802.11 connections can cover
distances of up to 25 miles, but the power needed to span that
range is outside statutory electromagnetic radiation limits.
Typically, said Ged Fitton, systems engineering manager at Cisco,
802.11b wireless bridges span a range of between two and five
miles. With 802.11g transmissions, "You could probably do a
point-to-point connection over seven to 12 miles."
You can also create networks using IEEE 802.11 technology. "This is
attractive for organisations such as councils that own a lot of
buildings," said Swift.
"You give your employees 802.11b phones and you have a solution
that bypasses traditional carriers." "I know about half a dozen
councils doing that," said Alan Wright, wireless technology
consultant at Cable & Wireless subsidiary ALLnet.
However, the 802.11 transmissions are unlicensed so potentially,
you could get interference from another device. Another problem is
that the throughput provided may not be sufficient.
If a company needs either more bandwidth than provided by Wi-Fi, or
transmissions over a greater distance than a few miles, another
option is to use licensed microwave radio frequencies.
These frequencies start at just above the unlicensed range at
7.5GHz, and go upwards: typical frequencies are 11GHz or 13GHz.
This gives transmission rates of 100mbps and upwards - well above
those provided by 802.11.
Microwave transmissions are regulated by the Radiocommunications
Authority, a government body that deals with the radio spectrum and
has responsibility for assigning fixed terrestrial point-to-point
links. Constitutionally it is an executive agency of the DTI and
one of the bodies scheduled to become part of industry watchdog
Ofcom, probably at the end of 2003.
Wright sees microwave as a cost-effective alternative to
cable-based transmissions using dial-up, ISDN or leased lines.
"They are quicker than leased lines and more cost-effective than
Lan extension services. The outlay is up-front and the customer
then owns the bandwidth. The revenue costs are basically what the
Radiocommunications Authority charges."
Cable & Wireless was the contractor for the Lancashire Police
WWan as reported in Computer Weekly (19 September 2002). This
network replaced an ISDN network, and connects 55 police sites
using a 155mbps backbone. The annual licence fee charged by the
Radiocommunications Authority for this network is £55,000.
Kep Simcox, project manager, said, "We anticipate a 5% to 10%
saving over a 10-year period when compared with the alternatives.
We will also save on infrastructure costs as the only changes will
be the replacement of radio links between stations."
An even more powerful network implemented by Cheshire County
Council was reported in the 8 April issue of Computer Weekly. It
provided up to 620 mbps using microwave frequencies ranging up to
38GHz.
"Even though the start-up costs were higher, we have gone for radio
technology as it will be much cheaper over five years," said Mike
Tuck, head of ICT planning at Cheshire County Council.