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Tremendous strides have been made on
wired networks. Copper and fiber networks dominate the Layer 1
space. The transmission capacity of wired networks is virtually
limitless as carriers can arbitrarily add bandwidth as demand
increases.
Despite the capacity of wired
networks, wireless networks have had the greatest success among
consumers. Broadcast television, cellular telephone, paging, and
direct broadcast satellite are all wireless services that have met
with commercial success-despite the fact that wireless networks
typically carry lower bit rates and higher costs than wired
networking.
When installing cables underground,
you may be forced to obtain permission from residents. Product managers who roll out wired services struggle with marketing
and demographic studies to determine the best neighborhoods in which
to introduce services.
Even if the right neighborhoods are
identified, it is expensive and time-consuming to dig or install
overhead cables. Furthermore, permits and easements must be
obtained. To some observers, the fixed networks of wired systems
look like vulnerable high-capital assets in a world of fast-changing
technologies.
Numerous wireless access network
technologies are intended by their proponents to serve the consumer
market. These are direct broadcast satellite (DBS), Multichannel
Multipoint Distribution Services (MMDS), and Local Multipoint
Distribution Services (LMDS). The Figure illustrates the network
architecture of a typical wireless network The return-path flows, if
any, travel through wired networks or, in the case of LMDS, through
wireless networks.
The content provider forwards content
through the core network and to the wireless access node. This
access node reformats data and modulates it for satellite or
land-based microwave transmission. A receiving antenna at the home
end forwards traffic through the home network to the terminal
equipment, which is either a TV set-top box or a PC.
In the return path, the consumer uses
either the same network used for the forward transmission or another
access network. Another access network is needed when using DBS or
MMDS services, which are one-way networks. The return-path network
could be telephone return, xDSL, or another wireless service, such
as digital personal communications services (PCS). PCS service
includes wireless voice, a digital form of cellular telephony, as
well as wireless data.
Because forward- and return-path
traffic can use different physical media, traffic sources must be
matched so that a single bidirectional session exists between the
content provider and the terminal equipment. This matching can be performed by the
wireless access node or another switching/routing device inside the
core network.
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