Today's
users of mobile devices depend on wireless connections
for their voice, data and even video communications.
Even homes and businesses may depend on wireless,
especially those who are not in urban or suburban areas
served by FTTH (fiber to the home) or FTTC (fiber to the
curb.) Some of us in the business now use the term FTTW
for fiber to wireless, since wireless depends on fiber
for the communications backbone and increasingly the
connection to the wireless antennas, no matter what
kinds of wireless we use.
Wireless
is not entirely wireless. The easiest way to understand
wireless is to
think of it as a link that replaces the cable that
connects your
cellular or wireless phone to the phone system or
the patchcord
that connects your computer or other portable Internet
device to the
network. To understand wireless, it is necessary to look
at several
different and unique types of wireless systems,
including cellular
wireless phones, wireless in premises cabling, municipal
or private wireless links
and even some of the short distance links used for
computer peripheral
connections.
Cellular Wireless
Cellular phone systems have grown to dominate the
telecommunications
marketplace. Countries that have had extensive landline
phone systems
for a century now already have more cell phones than
land lines.
Countries that had not developed landline-based phone
networks skipped
them entirely and went directly to cellular wireless
where the adoption
rates have been extremely high.
While cellular wireless started out as
a voice network, text messaging became very popular,
eclipsing voice
for most users. Smart phones brought the Internet to the
phone, and
soon data became the largest traffic generator for
cellular networks.
In the first 3-1/2 years of the iPhone, AT&T claimed
their data
traffic grew 8000% - 80 times! Now video is coming to
these same
devices, creating an even faster growth rate for
cellular network
traffic.
To accomodate this traffic level, wireless needs new
systems with more
radio frequency
spectrum. Current systems (CDMA for some systems, in the
US, GSM for
the rest of the US and the world) are evolving into new
generations of
systems (4G, LTE) that have more data bandwidth.
Almost from the
beginning, cellular towers were connected to
the telco networks over fiber optics, just like any
other
connection.
Wireless towers have small huts at the base that connect
to fiber
backbones that connect towers to the various phone
companies. As
traffic grows, towers need more antennas. Instead of 3-4
antennas on a
tower, now one sees dozens, so towers and buildings now
look like this:
or on buildings
All these antennas on a tower or the side of a building
have created
another problem. In the past, each antenna has been
connected by a
large (2", 50mm) coax cable that carries both signal and
power to the
antenna. But with all these antennas, the size, weight
and even wind
resistance of these cables has become a big problem.
These towers which
have been upgraded to add many antennas show the problem
with these
large coax cables.
This
is another application where copper cable is being
replaced by optical
fiber. One small fiber cable can replace all those coax
cables and a
separate power cable is used for the drivers on the
antennas. These
applications use mostly prefab
cable assemblies
since making
terminations on top of the tower is difficult to say the
least. Some
applications use prefab at the top of the tower and
conventional
termination at the base. Many of
these systems use multimode fiber because the distances
are so short
and the transceivers are much less expensive for MM
fiber.
Below
are photos from Corning showing a remote antenna head
end
and antenna and the fiber terminal serving the antennas.
Note the use
of a prefab cable system at the top of the tower, making
installation
much easier. Some installations use a composite cable
that includes
both fiber and power conductors so only one cable need
be installed up
the tower.
 
Photos courtesy of Corning.
Many cell towers are independently owned and
space for antennas
is rented to the service providers. Installation of
fiber to the towers
and fiber up to the antennas is generally done by
independent
contractors who specialize in this kind of work.
Wireless
In Premises Networks
Wireless in the corporate premises network is WiFi (IEEE
802.11), the common network
built into most laptop or netbook computers, tablets,
VoIP phones, many
cellular phones and other portable devices. The
wireless
“antenna” in the network, called an "access point," is a
lot
more than that. It’s a radio transceiver and network
adapter that
connects to your laptop to allow access to the network,
with some logic
that implements part of the network protocols allowing
access to the
network. The transceiver in the antenna has limited
power as does the
transceiver in the portable device, so the distance from
the antenna to
your laptop is limited. Connection between devices and
antennas can be
affected by metal in a building that reflects or
attenuates signals.
Signals can even be absorbed by people in the building.
A typical
office building may need 4-8 antennas per floor to get
consistent
connections throughout the area.
The antenna is connected to the network just like
a PC, using
UTP or fiber optic cable to a local switch which
connects it into the
network backbone. Not only does the wireless antenna
require a network
cable to connect to the network, but it needs power –
uninterruptible
power, just like any network hub or switch – to operate.
So replacing a wired network with a wireless one doesn’t
mean you don’t
need cabling; you may in fact need more when you
consider the power
needs of the antennas. Any advantage of a wireless
network is not
in the installation, it’s in the flexibility of users
roaming but
maintaining connections.
Bluetooth (IEEE 802.15) is a limited
distance network
mainly used for consumer devices. It has been used to
connect a
wireless printer or mouse to a PC, wireless headsets to
cell phones and
stereos, cell phones to cars for hands-free operation,
digital cameras
to printers, etc. In terms of installation, Bluetooth is
built-in to
many devices and adapters can be plugged into USB ports
or added as
cards to PCs, not installed as access points like WiFi,
so it is not
generally of interest for cabling installers.
More
on wireless in premises systems including wireless
network standards.
Metropolitan Wireless
Metropolitan wireless systems have had a rocky road.
Initially, they
were proposed as an inexpensive way of offering
broadband to everyone,
but providing support and competitive issues with other
broadband
suppliers ended most of these early trials. Now cities
often install
WiFi for public service use and free Internet access in
parks and
plazas, like these examples. The distances these access
points are from
the network connections require fiber, usually SM fiber
available in
the metro fiber network used for other communications.
Downtown
Santa Monica California, where you can see two separate
systems, one
public, one private for city services, on one pole.
Istanbul, Turkey installed metro WiFi for visitors as
the European City of the Year.
WiMAX is a further development of wireless
network technology
that expands the data capacity of wireless to ~ 100 Mb/s
and it’s
distance capability to several miles. Unlike WiFi which
was primarily a
short distance network aimed at private networks, WiMAX
appears aimed
at communications carriers who could use it in place of
landline
networks, substituting WiMAX, for example, for Fiber To
The Home, in
areas needing upgrades of their networks or using it to
allow notebook
PC or PDA roaming in a metropolitan area.
"Super WiFi" On Fiber
Bringing broadband to
the rural areas of the US or any large country with
sparse population
can be very expensive. The US has a plan, however, that
may make it
more affordable. "Super WiFi" is not your usual WiFi. It
is using WiFi
protocols but broadcasting on frequencies of unused TV
channels, called "white space." The
FCC is ready to open up new frequencies to broadband to
allow
delivering broadband Internet and phone to rural areas
where cabling is
too expensive.
An example of a super Wi-Fi antenna: Altai
Super
WiFi works at a lower frequency than either regular WiFi
or cellular
systems so it has more reach into areas that are too
rugged for most
wireless systems. Usage in more urban areas may be a
problem however,
if there are too many broadcast TV stations which can
interfere with
Super WiFi signals (and vice versa.) These antennas will
also require fiber to connect into the network.
More
in MIT Technology Review And
the US Government Announcement.
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