Basic Communication System

A basic communications system consists of end user equipment, network access connections, network interconnection devices (e.g. switches) and a control system that coordinates the network. A carrier or service provider is company that is engaged in transferring electrical signals or messages for hire through one or more telecommunications systems.

Customers (users) request and may receive telecommunications services from the telecommunications network. Because customers request and receive services, a customer is sometimes called a service subscriber or end user. A telecommunications service provider offers communications for a fee directly to the public, or to such classes of users as to be effectively available directly to the public, regardless of the facilities used.

A network operator is a provider of telecommunication services. A network operator manages the network equipment parts of a communications system to allow authorized customers to transfer and/or process information via the network. The network operator may provide services directly to end customers or may only manage network equipment and another company (service provider) may manage the provision of services to customers.

End-user equipment converts various types of information from a user (such as audio or computer data) into a signal that can be transferred via a communications system. Since the late 1800’s, different types of systems had very specific types of end user devices. For example, public telephone systems have a telephone, data communication systems have a channel service unit (CSU), and wireless systems have a mobile telephone. As technology has evolved, end user equipment devices began to combine functionality. This can be found in voice telephone systems that can transfer digital data by using a modulator/demodulator (modem).

Access connections are the link between the end user equipment and the wide area network, WAN, owned by the service provider. Access connections can be provided via pairs of copper wires, radio links, or fiber connections. Twisted pairs of copper wires can carry low frequency audio signals such as voice and high-speed digital signals (e.g., 11 Mbps DSL). Radio access can carry low speed information signals (such as wide area cellular) or can be high-speed data transmission (such as microwave directional signals). Each strand of fiberoptic cable (and there may be several hundred fibers per cable) can carry more than 1 Terabit per second of data (1,000,000 million bits per second).

Interconnection systems connect of all the various types of equipment. Interconnection systems may include signal taps, splitters, bridges, gateways, switches, and routers to move the information from one part of the network to another along its path between originating and destination points. The interconnection can be completely dumb such as the form of signal taps and splitters that only direct part of the signal energy to multiple points. Some interconnection devices such as bridges and gateways adapt the format of the information to another form (e.g., different packet length or type of packet) between dissimilar networks. Active devices such as switches and routers can direct signals from one source to various other paths depending on call setup information (e.g., telephone number) or an address contained in a data packet (such as a signal router that transfers Internet packets of data).

System control and coordination functions ensure that the various resources of the network are coordinated in their actions by detecting equipment and network status. Commands are issued to direct the various network elements in order to configure the network parts and to maintain a high level of network service. .Network operators can centrally coordinate system control or multiple network operators can independently and dynamically control it. An example of a centrally managed control system is the signaling system number 7 (SS7) packet control system that coordinates the public telephone network. The SS7 network contains packet switching points and databases that are controlled by the public telephone network operators. Distributed network control is demonstrated by how the Internet is dynamically managed. The Internet is composed of thousands of independent networks that use intelligent routing devices within each network to forward packets throughout the Internet.

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