needed to deploy the new network cannot be made available in a short time. The convergence of all the telecommunication services toward the Internet paradigm opens the possibility of unifying data transport on the same infrastructure and collect- ing traditional wireline residential and business users, together with mobile users. Such a convergence is possible to connect the access points of the mobile network (the base stations) to the infrastructure of the wireline. This requires a further penetration to the fiber infrastructure, besides the capability of supporting a large variety of termination equipment. From the bandwidth management point of view, the copper network assures physical separation among signals belonging to different users in the whole access segment: each user has his own twisted pair. This is a good situation from several points of view. The pri- vacy of the user signal is completely guaranteed because it is impossible to detect the sig- nal belonging to a user from another user terminal. Moreover, the concept of unbundling is strictly related to this characteristic of the copper network, assuring, in this case, perfect separation among signals belonging to different carriers. For these reasons, it would be desirable to reproduce this situation as much as possible in the next generation access network. 11.2 TDMA and TDM Overlay Passive Optical Network As we have seen in Chapter 3, both due to the need of a careful use of already deployed fibers and tubes and to reflect the broadcast nature of a few key services like IP-TV, passive optical network (PON) is an almost universal choice for the deployment of the fiber access infrastructure. Using a PON means that the fiber is deployed in a tree topology, often called the optical distribution network (ODN). Since part of this medium is shared among the different channels, a shared medium access strategy is needed. While almost all the possible strategies have been proposed, TDMA is by far the most used and all the PON products on the market are bas