WIRELESS NETWORKS
Make 4G wireless a reality
By Tony Lefebvre
ADC
The industry is buzzing about
such next-generation wireless
services as WiMAX and Long
Term Evolution (LTE), but these
services will require significant
changes to the underlying
wireless infrastructure. Carriers
face several important issues in
choosing the right migration
path. In this article, we’ll examine key infrastructure changes
that will be required for 4G services, and look at some of the
considerations in making those
changes.
What’s 4G?
The term “4G wireless” generally describes the next evolution
of wireless communications.
While such 3G systems as EVDO,
HSPA, and UMTS are delivering
sufficient data bandwidth for
some applications, the goal of
4G systems is to support voice,
data and streamed multimedia
for all users, in all locations. This
means that 4G systems must
be capable of delivering from
100Mbps to 1Gbps of bandwidth
to each subscriber, indoors and
out. The central technologies
under development for 4G services are WiMAX and 3GPP LTE
with additional interest in WiBro,
iBurst, and 3GPP2 Ultra Mobile
Broadband (UMB).
Naturally, carriers want to
expand to 4G services without
disrupting service to existing
subscribers. In order to provide
backward compatibility for users
of legacy services, a variety of
groups developing 4G standards
are aiming to support most of
the standards used by 2G, 2.5G,
and 3G services today. However,
4G infrastructure will be completely based on IP technology,
so new infrastructure must be
integrated carefully. This has
several implications for carriers
planning to upgrade their networks to support 4G services.
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Coverage
4G services will require higherquality coverage in more places.
Earlier wireless networks were
based on the idea of blanketing
an outdoor area with frequency
from cell towers and rooftops,
but 4G services will often use frequencies of 2 GHz and higher, and
these will attenuate more quickly.
This means that more antennas
will be required, and that wireless
signals will have to be boosted inside buildings, in urban canyons,
in underground facilities, and
other locations where traditional
macro coverage won’t reach.
At the same time, interference
will be an even greater issue than
it is today. Even in areas with
an abundant supply of rooftop
cell towers, users today often
find that signal strength tails off
towards the lower floors of tall
buildings, while on the upper
floors of buildings, subscribers
can experience poor service because signals from multiple towers may be visible and the phone
constantly hunts from one signal
to another.
Assuming that 4G services will
require more antennas in more
locations, carriers will have to
engineer systems more carefully
to minimise interference from the
multiple antennas that any given
device may be able to “see” at a
time.
Capacity
Macro networks that were
designed to support an average user base five or ten years
ago can’t support current call
volumes or the need for higherspeed data support. Many users
have experienced an inability to
make or sustain calls in stadiums,
on bridges, or even on crowded
highways or urban sidewalks
simply because the nearest
macro towers are overloaded.
4G wireless cells will be much
smaller than today’s cell areas
not only because of the need for
better coverage (due to signal
attenuation) but also the need
for higher per-user capacity.
Backhaul
costs,
options
4G networks delivering from 100
to 1000 times as much bandwidth
per user will require much larger
and more cost-effective backhaul
networks. Most of today’s macro
cellular networks still rely on
1.5Mbps E1 lines, which will be rapidly swamped by users exchanging photos, videos, and data files.
3G data services are further straining existing backhaul networks.
Carriers implementing new 4G
architectures will need even larger
backhaul pipes, while controlling
costs at the same time.
Apply infrastructure choices
to business needs
There are dozens of vendors offering hundreds of products to
meet the challenges outlined
above, but it’s difficult to develop
a strategy without a list of business priorities. The key to successful 4G deployment will be
to align infrastructure migration
with business needs.
Maintain subscriber revenue
While the goal of 4G services is to
increase ARPU with new services,
carriers must first ensure that existing subscriber services are not
disrupted. Early adopters will be
willing to pay for new advanced
services but carriers must continue
to provide service to the majority
of subscribers who are not willing
to pay and want purchase only
basic services. As a result, new
4G equipment must integrate
with the network separately, or it
must offer backward support for
services previously offered.
To ensure effective rollouts of
new services, carriers will need a
range of specific equipment options to address the coverage and
capacity needs of many different
environments. For cost control,
carriers will also need solutions
that can cost-effectively distribute
new 4G services to low-capacity environments while providing
options to cover existing services.
For example, using distributed
antenna systems (DAS) allows
carriers to deploy a single base
station and distribute the signal
over an urban or enterprise location with low-cost radios.
New 4G solutions should be
added incrementally to a network on a build-as-you-go basis,
to minimise upfront investment
by carriers and shorten the return
on investment.
Right changes at the right
time
If 4G services require changes
for coverage, capacity, and backhaul, which changes come first?
The first challenge is coverage. There are few subscribers
for a new service at the outset,
but these subscribers will still
demand ubiquitous coverage.
Carriers must find ways to deploy
coverage in the most cost-effective manner while allowing easy
scaling to support additional
coverage as the user base grows.
In the old macro network model,
extending coverage required
installation of new base stations,
yet newer solutions allow carriers
to expand coverage via remote
radios so that coverage can be
expanded independently of more
expensive base station gear.
As the subscriber count
ramps up, capacity issues arise,
and more base station and
switching capacity is necessary.
Even though more base stations
are required, it is more cost-effective to use distributed radios
to deliver the signal while maintaining base stations in a central
location. With base stations consolidated in one location, they
are easier to maintain. Moreover,
the facilities costs of distributing
radios are far lower, as these can
be mounted on utility poles or
overhead lines.
As network capacity grows
along with subscriber counts
and service demands, carriers will
next have to address the backhaul
problem. Here again, base station
consolidation makes sense, since it
allows carriers to aggregate backhaul capacity in a single location
rather than paying for individual
connections throughout a geographically-dispersed
network
of base stations. IP technologies
such as Ethernet will give carriers
maximum transport efficiency at
the lowest cost, with easy scaling
to support bandwidth growth.
In addition, fibre or microwave
backhaul technologies offer the
ability to transport multiple bands
of traffic, thereby increasing flexibility and capacity.
Improve efficiency
Operating efficiency is always an
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important goal. By centralizing
base stations and distributing
signals with DAS solutions, carriers can make more efficient
use of scarce wireless spectrum.
Distributing coverage over a larger
number of smaller cells enables
carriers to maximise frequency
re-use, thus making the most of
the limited spectrum. Carriers can
maximise capacity within the cell
for 4G services while reusing this
limited commodity over multiple
non-adjacent cells. And as we
have seen, centralizing base stations also enables better use of
backhaul resources.
Throughout their networks,
carriers will leverage IP-based
technology, either via metro
Ethernet or customer-owned DSL
connections. IP transport allows
carriers to precisely match the
bandwidth being used with the
service level desired, it eliminates
the need to lease backhaul circuits
from potential competitors, and it
offers easier maintenance with
lower costs.
Minimise management costs
Finally, the 4G wireless infrastructure will benefit from a unified
management system that enables
monitoring and configuration of
radios, base stations, network links,
and switching systems. IP-based
technology allows for carriers to
accomplish such management
with standard SNMP-based network management tools, bringing an end-to-end control never
before possible.
Conclusion
As wireless carriers explore the
most efficient ways to deploy 4G
services, they will face numerous
challenges. However, with the
range of solutions that will be
available at their disposal, they will
also have to opportunity to shorten their return on investment,
improve operating efficiency,
and increase revenues. The key is
to align business challenges with
infrastructure choices.