14.2: Duration and Extent of Tele-communications Infrastructure
Figure 14.1.1 showed the rapid growth in the number of users of telecommunications services. In addition, new applications require large amounts of information to be available rapidly. Figure 14.2.1 shows some of the demands for applications such as videoconferencing and entertainment (such as movies on demand).
A variety of media are used for telecommunications, including copper wires, fiber optic cables and wireless transmission. Even power wires can be used for communication. As an indication of the extent of this infrastructure, Figure 14.2.2 shows a map of submarine communications cable as of 2015. In addition to these undersea cables, roughly 1,000 communications satellites are in orbit around the earth. Internet services also make use of high speed, high capacity connections such as fiber optic cables and satellite communications.
The duration and extent of telecommunications infrastructure depend in large part on how the infrastructure is defined. For example, radio and television transmission towers are often classified as entertainment rather than telecommunications (and are omitted from the statistics shown in Figure 14.1.1). Nevertheless, radio and television now may be broadcast or provided over the Internet.
Wireless communications, particularly with mobile telephones and personal digital assistants (PDAs) have also seen notable growth Clarke, 2014). These services typically connect through cell sites to the regular telecommunications network; with some 300,000 such cell sites existing in the US in 2012 (See Figure 14.2.3).
With rapid expansion of use and growing speed and capacity, many parts of the telecommunications infrastructure have relatively short lifetimes. Smartphones and computers may become functionally obsolete within five years. In contrast, some parts of the infrastructure may have relatively long lifetimes. Fiber optics
Interdependence between telecommunications and other
infrastructure systems is apparent. For example, telecommunications
is needed to manage the electric power grid, while electricity is
needed for telecommunications. Back-up power by means such as
batteries is provided to ensure continuing telephone service in
case of power interruptions.
The growth of the internet has increased the complexity of the
telecommunications network and the extent of infrastructure
interdependencies. As an illustration, Figure 14.2.4 shows a
partial map of the internet, where nodes are internet protocol (IP)
addresses and the length of links shows the typical delay between
two IP addresses.