Progress on FMC Network Architectures. Functional Convergence Sharing the infrastructure of an access/aggregation network implies that the control functions responsible for this infrastructure take into account both mobile and fixed traffics. In other words, the control planes of the fixed and mobile networks have to converge, at least partially, in order to efficiently allocate resources. This convergence can be achieved at different levels, depending on how the infrastructure sharing is performed. For example, if the sharing is limited to the allocation of different wavelengths channels on WDM links, the control plane has only to ensure that a given wavelength channel is just allocated once, either to fixed or to mobile traffic. A more complex set of networking functions has to be designed for a more complete convergence with finer granularity, e.g. the sharing of a common new MAC (called here a Meta-MAC) in the aggregation network. Ethernet-based architectures, and in particular those considered for delivering Carrier-Ethernet, are likely candidates for the Meta-MAC, as they are currently used both for backhauling mobile traffic and for operating fixed metro networks. COMBO shall also specifically consider Meta-MACs designed for transparent optical transport (such as OBS and OPS) in order to take advantage of their energy-friendly potential. Specification of a M eta-M AC: The set of networking function to be designed to facilitate functional convergence would potentially include the specification of filtering and marking rules, used to classify fixed and mobile traffic into Meta-MAC SDUs, prior to encapsulation into Meta-MAC PDUs. Meta-MAC scheduling and forwarding principles should be defined (i.e. functions belonging to the data plane of the converged network), together with control plane functions such as routing. The following major points shall be addressed:
Progress on FMC Network Architectures. Structural Convergence Once specified, functions have to be distributed over network equipment. At the level of fixed-mobile convergence in the sense of equipment and infrastructure mutualization (which we call structural convergence), some work has been done in the context of the European FP7 ALPHA project on Analogue Radio over Fibre technologies [31], [32] (see Section 1.2.4 for more details). In COMBO, Digital Radio over Fibre (D-RoF) is of higher interest because it has no linearity constraints, an advanced standardization and it is widely implemented by mobile station vendors. Moreover, D-RoF opens the way to BBU hotelling and C- RAN [33]. COMBO will contribute to the progress of the state-of-the-art of current separated fixed and mobile access/aggregation networks with a set of innovative architectural concepts: - Sharing of equipment supporting both fixed (OLT) and mobile (BBU) interfaces: The advantages and feasibility of shared equipment supporting both fixed (OLT) and mobile (BBU) interfaces will be investigated. As an example, consider the problem of mobile backhauling. Nowadays mobile traffic is gathered from distributed sets of base stations typically with a dedicated backhaul. COMBO proposes to enable new backhaul architectures that allow moving the mobile- traffic processing (which takes place in the so called Base Band Unit, or BBU) in a separated and possibly distant location, which can be far from the antenna location (reduced to a Remote Radio Header or RRH). This kind of approach is usually referred to as BBU hotelling. - Node consolidation in a fixed mobile converged network: Up to now, the availability of locations for mobile base station sites and for fixed network central offices are not re-considered by each other for new deployments. This leads to contradicting evolution paths. While the fixed networks access considers a node consolidation by reducing the number of central offices with pure passive long reach access up to 100 km, in mobile networks, a strongly increasing number of new active sites are expected. COMBO will provide new use cases and assessment tools for node consolidation in a fixed-mobile converged network.
