|Thesis abstract: |
Nowadays customers can access telecom services via fixed-line networks or via mobile networks. Fixed-line broadband networks in Europe are currently dominated by ADSL technologies which provide up to 16 Mbit/s. Other solutions like Fiber to the Curb (FTTC) with VDSL are widely used with access speeds up to 50 Mbit/s. The technologies which will deliver fiber access directly to the home, referred to as Fiber to the Home (FTTH) solutions, are the next step and first deployments have been started. If the implementation of FTTH is based on a Passive Optical Network (PON) instead of a point-to-point solution, it is possible to reduce the network cost by eliminating the power supply through the installation of passive network elements, and by sharing a significant portion of the network cost among multiple users, while still enabling data rates of hundreds of Mbit/s.
For the mobile area, different network technologies are available and widely used. 2G (e.g., GSM, GPRS) and 3G (e.g., UMTS, HSPA) networks have been already installed and in some countries the deployment of the 4G LTE technology (with data rates up to 100 Mbit/s) has been started. Future step is the LTE advanced (LTE-A) technology which can provide data rates up to 1 Gbit/s. With regard to wireless technologies, systems like Wi-Fi (standard IEEE 802.11) or WiMax (standard IEEE 802.16) are also widely used.
So far fixed and mobile access networks have been optimised and evolved independently, with some contradicting trends. In fact there is a tendency to centralize fixed networks and to decentralize mobile networks.
A certain degree of convergence among the two network domains, typically referred as Fixed Mobile Convergence (FMC), has only been achieved at the service level with the introduction of all IP services (e.g., a practical case of FMC at service level can be found in smartphones and tablets which can access the same services through Wi-Fi and/or the cellular network).
It is widely agreed that the development of a single convergent infrastructure for fixed and mobile networks would enable relevant savings in terms of Capex and Opex and would provide converged services to customers at reasonable costs in the years. The development of this FMC access network is driven by the requirement to combine optimal seamless quality of experience for end-users together with an optimised network infrastructure. Moreover, another motivation to merge together in a single and optimized structure both fixed and mobile traffic is related to the energy consumption of the current access network. In fact the access is the part of the network which is consuming the highest amount of energy. The convergence of fixed and mobile access networks in a single structure can help saving energy. In this sense, we can classify fixed mobile convergence referring to two aspects: functional convergence and the structural convergence. The functional convergence refers to the convergence of fixed and mobile network functions, while the structural convergence is the convergence of fixed and mobile infrastructures and equipment. The integration of functionalities and equipment are expected to enable relevant energy saving, e.g, lowering the number of nodes of the access network.
One of the most promising network solutions to develop such FMC access networks are Next-Generation Passive Optical Network (NG-PONs). In particular, Long-Reach PONs which use both time-domain and wavelength-domain multiplexing, referred as LR WDM/TDM PON, are a suitable candidate to support a large number of different services (with different QoS requirements) originating from both fixed and mobile users.
The aim of this work is to propose, define and technically assess candidate FMC network solutions by comparing them through different parameters such as, packet delay, energy consumption, Capex, Opex...
Moreover, since FMC networks must efficiently manage traffic with different QoS requirements in terms of delay and also bitrate, algorithms to administrate the diverse kinds of traffic, such as Dynamic Bandwidth and Wavelength Allocation (DBA) algorithms, can be sought during this research.
The research is organized as follows. First of all, various FMC architectures will be quantitatively evaluated using different key performance indicators, such as average and maximum packet delay, energy consumption, Capex, Opex. Particular attention will be devoted to the investigation of possible innovative network architectures and control strategies that maximize network energy efficiency by leveraging the mutualisation of network functionalities and equipment enabled by fixed-mobile convergence.
Besides this, different DBAs will be proposed to allocate transmissions over the access/aggregation network which must be able to minimize the traffic delay/latency and guarantee the targeted QoS, as required by different types of users. Moreover, such DBAs will be required to allocate bandwidth taking in account that different access technologies, connected to the same FMC network, might have different requirements, in terms, e.g, of latency, and so they should be served in a differentiated manner (e.g., exploiting different multiplexing techniques).
The results of this research will be of impact for the future generations of high-speed broadband and mobile network infrastructure. An FMC access network will lead to significant network cost and energy-consumption reductions which will be key to address the profound transformations needed to face data traffic explosion in the medium to long term.