Charting The Course To 3G
BY PEGGY ALBRIGHT
MONDAY, JANUARY 8, 2001
WIRELESS WEEK
Building a third-generation wireless network is somewhat akin to creating a living,
breathing thing.
The systems, which will be known as IMT-2000 technologies, will share certain
characteristics: They will allow voice and high-speed data along with multimedia
services and international roaming. But, like living beings, no two networks will
really look or behave exactly alike. In the United States, most will be configured
around a current second-generation system and built to deliver a very precise
blend of services that will meet both global and local voice and data needs.
Even after the new networks come online, operators will find they continually need
to tweak their systems to meet ever-changing market dynamics and traffic
patterns. The 3G network will grow gradually, while the 2G network gradually
recedes. And if managed well, the new system will generate revenue
immediately–paying for itself as it grows.
So just how can operators plan these systems strategically so that buildouts will be
smooth for customers and cost-effective for the operators? "I think every carrier is
struggling with this to a certain extent," says Jim Grams, vice president for the
technology development group at AT & T Wireless Services.
Fundamentally, each company's approach depends on its current business
environment. For those that are upgrading existing networks, the migration path
depends on whether the company is using CDMA, GSM or TDMA 2G technologies.
A CDMA Scenario
CDMA operators believe they'll have the easiest migration path. The current
standard, cdmaOne, also known as Interim Standard-95, was invented from the
get-go to allow easy upgrades in a system's existing 1.25-megahertz channel.
Because of that, a CDMA operator installing the first phase of a 3G system, called
cdma2000 1XRTT, can look forward to a relatively graceful process.
A CDMA operator can keep its existing base stations and core network equipment,
and add the upgrade technology by simply adding 1XRTT channel cards at their
base stations. The process is the same whether they're adding 1X or IS-95 voice
capacity cards. The company will have to add some software upgrades at the base
station controller and mobile switching center, and it will have to add a packet
data switching node in the network, but the latter will be needed only in certain
switching offices, not all.
"This is relatively easy and graceful to roll out," says Bill Stone, executive director
for network planning at Verizon Wireless. "I can leverage existing infrastructure
and go from ground zero to nationwide deployment pretty quickly."
One advantage that CDMA offers, Stone says, is that operators should not face
resource limitations. Channel cards are relatively easy to manufacture in volume;
the vendors simply will have to ramp up supply. Installing the cards is business as
usual. Best of all, Stone says, Verizon can do it all within its existing budget
allocation for capacity expansion.
Verizon is conducting two 1X trials: with Nortel in Columbus, Ohio, and with Lucent
in Mapleshade, N.J. Stone expects 1XRTT to be available on a mass-market basis
by the second half of next year.
The GSM And TDMA Process
GSM and TDMA networks will both migrate to a series of modulation technologies,
called enhanced data rate for global evolution, or EDGE. The first step begins with
installing the general packet radio services core.
The process involves several more steps. At its simplest, an operator needs to
install a "serving GPRS service node," a bridge between the radio network and the
core network. They also must put in a "gateway GPRS service node," a bridge
between the core network and the Internet, and a "border gateway," which
functions as an interface between roaming partners.
Nokia offers an additional element, a "charging gateway" that gathers call data
records, filters them and sends the output to operators for use in billing and
customer care, says Mike Walters, marketing manager at Nokia. Such capabilities
will identify customer charges in a packet data environment, whether or not they're
using the network.
While building a GPRS core is not all that expensive in the grand scheme of
things, Walters says, those at Wireless Facilities Inc. caution that it is not entirely
cheap because of the number of routers required. In some ways, WFI says, it is
easier to migrate from a GSM system to GPRS and EDGE than it is from TDMA. And
regardless of the starting point, if a company does not change the air interconnect
to accommodate the high data rate air interfaces, the GPRS core can't be used
properly.
Costs increase when the operators install EDGE, which requires installation of EDGE
radios and new software in the rest of the network. But most vendors are
designing those to fit into existing base stations to ameliorate costs, Walters
says. And the new equipment can be installed over the original footprint.
AWS will add the GPRS overlay to its cell sites while leaving the existing IS-136
and CDPD networks alone. It will begin offering EDGE in part of its network by the
end of 2001, while continuing to offer its legacy services. As customers migrate to
the new technology, it will adjust the network accordingly.
But AWS is taking an additional, parallel path now that Japan's NTT DoCoMo has
invested in the company. The operator now plans to add GPRS as a consumer
service offered separately from its other options, which will require adding a new
GSM 1900 MHz radio network.
Then, AWS will top everything off with a wideband-CDMA network, which it hopes to
have up in 70 markets by 2003 or 2004.
AWS is maximizing its available spectrum by applying capacity enhancements
such as smart antennas and tightening its frequency reuse plans.
Ultimately, for any of this to be cost efficient for a company, carriers will observe a
rule of thumb: Migration to 3G will be modular, not a wholesale change-out, says
George Wozencraft, vice president for telecom strategy group at WFI.
For operators, he says, the biggest challenge is modeling voice and various kinds
of data traffic to develop the right mix of services, technical designs and business
models so that the business, once activated, will generate revenue from day one.
Each operator will have to figure out that path on their own, and then bite the
bullet to implement and pay for it. |
