Development of the access network

In upgrading the access network to be broadband capable, re-use of existing infrastructure is essential to manage this risk. FTTCab (fibre to the cabinet) has been proposed as an architecture that can make the development to broadband economic. The FTTCab architecture uses optical fibre to an active node sited at the primary cross-connect point (PCP) in the copper access network. The existing copper pair from the PCP to the customer is used to transport the VDSL (very high speed digital subscriber loop) modulation transparently to the existing POTS (plain old telephony service) and ISDN (integrated services digital network) service. Two VDSL delivery options in the FTTCab architecture are considered: the VDSL modem is sited in the PCP to deliver the broadband service; and the VDSL modem is back-hauled higher in the network to reduce the cost of the PCP node. Both methods may satisfy the requirement for between 6 to 25 Mbit/s downstream, to the customer. However, the use of back-hauling makes the upstream requirement for about 2 Mbit/s very difficult to meet. The preferred way forward is therefore to use a VDSL modem at the PCP and a corresponding unit in the customer premises.