Access network

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Structure of the “classic” access network based on copper wires

The access network in telecommunications , engl. access network , developed as a separate network from the telephone network . In the past, every telephone was connected to an exchange via a copper wire pair ; there were no controlling elements between the two. However, this required a large number of exchanges in order to achieve area coverage with the limited range of the subscriber line (TAL). With the digitization of the telephone network in the course of the expansion of the ISDN , the access network was also increasingly digitized. ISDN connections are digital concentrators and multiplexers in PCM connected to the central office technique. In order to save costs, attempts have been made in countries with a high connection density to reduce the number of exchanges. In order not to have to expand the existing cabling, reinforcing and controlling network elements had to be inserted between the telephone and the exchange. These network elements are called "access nodes" in the technical language of the access networks, while the switching centers are called "service nodes". Access nodes often use fiber optics in the access area in order to transmit the telephone channels in a multiplexed manner. Usually, to synchronous digital hierarchy technology (SDH) used, as well as passive optical networks (PON) are installed (especially in Japan). Depending on how far the glass fiber extends into the access network, one speaks of "Fiber to the Curb" ( FTTC ), "Fiber to the Building" ( FTTB ), "Fiber to the Home" ( FTTH ), "Fiber to the Desk" ( FTTD ).

Broadband access network

In generalized linguistic usage, not only is the voice telephony access network called this, but the “broadband” access network is also used. This is understood to mean the classic access network, upgraded with fiber optic and DSL technology. With outdoor DSLAMs and VDSL , data transmission rates of up to 200 Mbit / s can be provided for one subscriber. The mobile radio networks and the cable television network now also use this term for the part of their networks that includes the subscriber connections and offers access to higher network levels .

V interfaces

The interface between "Access Nodes" and "Service Nodes" has been standardized: ITU-T calls it the V-Interface. Concentrators and multiplexers are connected to the exchange via so-called V1 and V2 interfaces. Larger connection networks are connected via a V5 interface .

In Germany, almost all new network operators who have their own subscriber lines and access nodes but do not have a comprehensive network of switching centers are now connecting their access nodes to DTAG's switching systems via V5 interfaces. Commercial and technical conditions for this connection via V5 are regulated by the Federal Network Agency in Germany , as is the collocation .

The V5 interface is a 2 Mbit / s interface (E1). From a functional point of view, the V5 interface is similar to that between an exchange of the EWSD and an APE .

See also