Telecommunication networks

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TEL 401

Telecommunication networks are one of the oldest and wide spread communication networks in the world. The main purpose of these networks was, and still is, to enable telephone conversation between various parties who would like to have a regular voice conversation. Over the years the telecom network evolved in order to support more and more telephone users and in the last few years to account for the exponential growth in demand for data traffic and communication. It is customary to divide the telecommunication network to three parts: The Access network, the Metro network and the Core network. The Access network is basically the link between the end user telephone and his provider. It is most commonly a line of twisted copper pairs that connects the telephone line at home to the nearest central office equipment. When ISDN and xDSL equipment are also supported this copper infrastructure is used in order to support these services simultaneously (mainly by allocating additional bandwidth and splitting the available frequency between the services) The Metro network starts where the analog voice, sent over the copper lines of the access network, is converted to a digital representation and then multiplexed with other voice conversations via an ADM (Add Drop Multiplexer). The transmission rates at this part of the network are much higher then the transmission over the access as the links now are transmitting traffic of thousands of users. The Core network is the heart of the system where all the metro network traffic that needs to go from one area to the next is transferred. The data rates in the core network are very high and are usually run over fiber optics infrastructure.

A simple phone call is constructed from two distinct kinds of operation the Signaling and the Traffic transmission. Signaling are the way of the end user to indicate to whom he would like to call and get a feedback if the user is available, if the line is busy etc. The traffic is where a phone call was established the network needs to take the content conveyed in one end and deliver it to the other hand.

Other related subjects • E1/T1 communication • xDSL • dialing • Signaling SS7 • SDH • WAN