Telecommunications

D

Performance

A circuit-switched network, such as the PSTN, provides end-to-end connections on demand, as long as the necessary network resources are available. The connection’s end-to-end delay is usually small and always constant, and other users cannot interfere with the quality of communication.

In contrast, in a packet-switched network, packets queue for transmission at each switch. The cross-network delay is therefore variable as it depends on the volume of traffic encountered en route and if it exceeds a certain level, system performance can be badly impaired.

V

The Internet

It is evident from the recent growth in data communications that the telephone network is far from exhausted. The Internet—an expanded group of computer networks that shares a common set of protocols and address space—has grown over the past 25 years and now links around 40 million people worldwide.

Originally conceived by the United States military as a means of removing reliance on central computers, the Internet has grown into a global community of users who use the facility to send and receive mail messages, to exchange files, and to access shared data. This has been enabled by the adoption of a family of protocols (known as TCP/IP), which allow most users to communicate with most remote services, irrespective of local equipment type.

The Internet provides a means for any computer to communicate with any other. The World Wide Web is an Internet-based application that exploits this capability to provide a global information service. It enhances the mail and file transfer features of the Internet in that it can support multimedia—that is, allow a user to access pages containing pictures, video clips, and sounds, as well as text. It also provides connections that allow users to navigate between information held on different computers, simply by clicking on hypertext links displayed on the computer screen. Many companies, organizations, interest groups, and individuals now have Web pages, mostly for promoting their services or offering information of general interest.

The basic tool for reading Web pages is called a browser (Netscape Navigator, Internet Explorer, and the older Mosaic are the most common examples). The browser is packaged as part of the software given when users register with an Internet service provider.

VI

Convergence

Convergence of computing and communications, with the widespread use of Internet Protocol (IP) data format for all kinds of information transmission, has created an IP-centric world in which the distinction between speech, data, and video has been eliminated, at least as regards the way these types of traffic are conveyed across the networks. The opportunity for reducing costs means that many major telecoms carriers are now re-equipping their networks to provide edge-to-edge IP technology across an all-broadband network. However, even though the new 21st-century networks under construction are nothing like the networks of before, the user interfaces will not appear to change. You will still be able to use your existing telephone but the way the network carries calls is changing completely. There will be no telephone exchanges as such. Instead, multimedia “softswitches” supporting a range of broadband and narrowband access technologies will connect calls, which will be delivered to subscribers through multi-service access nodes.

Many companies already channel inter-site telephone and data calls across the Internet using a technique known as VoIP (Voice over Internet Protocol). To avoid the risks of hacking and denial of service attacks, these communications are starting to employ individual virtual private networks that offer supervised and controlled communication running through secure “tunnels” running across the Internet. VoIP also enables home users and small businesses to make PSTN calls using their broadband line and a telephony service provider hosted on the Internet. The cost of these calls is low because the service provider buys calls at wholesale rates, undercutting conventional PSTN call charges.

VII

The Future

No one can predict with certainty exactly how telecommunications will develop, but certain trends can be noted. The cost of communication is falling in real terms, making advanced applications more affordable and, in the case of some Internet service providers, free. Broader competition in the marketplace will reduce prices further. Telephone companies (telcos) recognize their revenues from carrying calls will decline and are encouraging, successfully, many new valued-added services that combine communication with the supply of information or services. Most of these have yet to evolve, but electronic commerce, mobile commerce, and various information-on-demand services are already being developed.

Some communication services currently provided by wire are migrating to radio means for greater convenience and flexibility; this includes not just cordless telephones (see Cellular Radio) in the home and the workplace but also connecting these telephones to the network. The short-range radio standard (known as Bluetooth) will be used to connect a range of devices into a fixed network. Conversely, radio and television programmes, traditionally broadcast over the airwaves, are also carried on cable networks (see Cable Television) and in an increasing number of areas, as multimedia services on broadband.

New “disruptive” technologies, the unexpected new processes that can knock industry predictions for six, may offer alternative access methods between users and the fixed telecoms network. Powerline technology (using electric power cables) is one potential option and UWB (ultra-wideband radio) is another.

Fixed-mobile convergence is another trend, in which the distinction between conventional telephones and mobile networks will dwindle. Predictions that many people will carry a single “personal communicator” that functions as a cordless phone within the home, as their business extension in the workplace, as a remote phone in Wi-Fi hotspots, and as a pocket mobile telephone elsewhere are becoming a reality with new-breed multifunction videotelephone and pocket computer devices coming on the market now (early 2005). These third generation mobile phones enable the user to see video images of the person they are talking to, send e-mails, and surf the Internet.