The communications landscape of the present is characterized by a broad diversity of highly varied services, beginning with the classic voice service and continuing via various types of data services on to triple play offers. The consequent increase in bandwidth requirements all the way to the end customer has led to new technical framework conditions for the access network. Fixed network operators must make greater use of active technology in this part of the network, while mobile network operators are focusing on raising the density of their base stations and expanding the connections among existing stations. At the same time, solutions which meet all of the technical framework conditions and can also be realized at low cost must be found, yet taking into account the specific properties of the existing networks. Scalability and flexibility with respect to the adaptation to new services are further important basic conditions.

For a long time, telecommunications networks were operated according to the pattern “A network for every service”. This development came about because of the varying requirements on the quality of service (QoS) which was to be realized by the transporting network. High-quality voice connections, for example, demand the lowest possible running time of the data so that communications free of disruptions can take place. In contrast, this requirement is less important during utilization of the Internet; in this case, the transmitted data must be free of error. Voice communications do not make such high demands in terms of error-free transmission. People are used to communicating via a disrupted channel and can compensate for transmission errors to a certain degree.


Many Services – Many Transport Technologies
The varying requirements for the quality of service led to the development and utilization of differing transport technologies for the transmission of voice and data traffic in the access network. The example of the development and implementation of the digital subscriber line (DSL) makes this clear in the case of the fixed network. This technology separates voice traffic from the packet-based Internet traffic in the frequency band. The two traffic flows are directed into different transport networks at the exchange via the appropriate hubs.


A similar structure can be discerned in mobile networks. Voice data are transmitted via channels especially set up for voice when the GSM standard is used. Data communication is handled primarily by technologies such as GPRS and EDGE, which for their part have been set up to satisfy the special conditions of data communications. When the wireless standard UMTS is used, voice and data share a common channel at the air interface, but at the base station (Node B) the two traffics are separated again and directed into different hubs in the core network via separate transport networks by RNC.
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