Upgrading access networks involves numerous devices because service to each
telephone company and cable TV customer as well as equipment in neighborhood
locations must often be changed. This is a challenge for both traditional telephone
companies and cable TV Multiple System Operators ( MSOs). However, cable TV providers
have newer voice infrastructure than traditional telephone companies because
the cable TV providers only started delivering these services around 2004. Thus, their
voice switches don’t require upgrades at this time. However, upgrading cabling and
electronics connected to them for higher capacity is costly and complex.
The driving force behind upgraded access networks is the need to support more
channels of high-definition television (HDTV) and Video-on-Demand (VOD) so that
individuals are able to select from a menu of movies and premium television. In addition,
customers are requesting HDTV, which requires more bandwidth and complex
electronics than standard definition. Three-dimensional television (3D-TV) will also
require upgrades as subscribers purchase 3D-compatible televisions and as content in
3D becomes available.
Improved compression and other techniques such as rate shaping provide the
capability to carry additional video traffic. Rate shaping adds capacity by using a form
of over-subscription. It’s analogous to pouring one-and-a-quarter quarts of water into a
pail that holds only a single quart. Rate shaping equipment discards bits in real time so
that adding eight megabits of traffic to a six-megabit channel does not impact quality.
