Analytical characterization of inband and outband D2D Communications for network access

Mención Internacional en el título de doctorCooperative short-range communication schemes provide powerful tools to solve interference and resource shortage problems in wireless access networks. With such schemes, a mobile node with excellent cellular connectivity can momentarily accept to relay traffic for its neighbors experiencing poor radio conditions and use Device-to-Device (D2D) communications to accomplish the task. This thesis provides a novel and comprehensive analytical framework that allows evaluating the effects of D2D communications in access networks in terms of spectrum and energy efficiency. The analysis covers the cases in which D2D communications use the same bandwidth of legacy cellular users (in-band D2D) or a different one (out-band D2D) and leverages on the characterization of underlying queueing systems and protocols to capture the complex intertwining of short-range and legacy WiFi and cellular communications. The analysis also unveils how D2D affects the use and scope of other optimization techniques used for, e.g., interference coordination and fairness in resource distribution. Indeed, characterizing the performance of D2D-enabled wireless access networks plays an essential role in the optimization of system operation and, as a consequence, permits to assess the general applicability of D2D solutions. With such characterization, we were able to design several mechanisms that improve system capabilities. Specifically, we propose bandwidth resource management techniques for controlling interference when cellular users and D2D pairs share the same spectrum, we design advanced and energy-aware access selection mechanisms, we show how to adopt D2D communications in conjunction with interference coordination schemes to achieve high and fair throughputs, and we discuss on end-to-end fairness—beyond the use of access network resources—when D2D communications is adopted in C-RAN. The results reported in this thesis show that identifying performance bottlenecks is key to properly control network operation, and, interestingly, bottlenecks may not be represented just by wireless resources when end-to-end fairness is of concern.Programa Oficial de Doctorado en Ingeniería TelemáticaPresidente: Marco Ajmone Marsan.- Secretario: Miquel Payaró Llisterri.- Vocal: Omer Gurewit

Design of a High Capacity, Scalable, and Green Wireless Communication System Leveraging the Unlicensed Spectrum

The stunning demand for mobile wireless data that has been recently growing at an exponential rate requires a several fold increase in spectrum. The use of unlicensed spectrum is thus critically needed to aid the existing licensed spectrum to meet such a huge mobile wireless data traffic growth demand in a cost effective manner. The deployment of Long Term Evolution (LTE) in the unlicensed spectrum (LTE-U) has recently been gaining significant industry momentum. The lower transmit power regulation of the unlicensed spectrum makes LTE deployment in the unlicensed spectrum suitable only for a small cell. A small cell utilizing LTE-L (LTE in licensed spectrum), and LTE-U (LTE in unlicensed spectrum) will therefore significantly reduce the total cost of ownership (TCO) of a small cell, while providing the additional mobile wireless data offload capacity from Macro Cell to small cell in LTE Heterogeneous Networks (HetNet), to meet such an increase in wireless data demand. The U.S. 5 GHz Unlicensed National Information Infrastructure (U-NII) bands that are currently under consideration for LTE deployment in the unlicensed spectrum contain only a limited number of 20 MHZ channels. Thus in a dense multi-operator deployment scenario, one or more LTE-U small cells have to co-exist and share the same 20 MHz unlicensed channel with each other and with the incumbent Wi-Fi. This dissertation presents a proactive small cell interference mitigation strategy for improving the spectral efficiency of LTE networks in the unlicensed spectrum. It describes the scenario and demonstrate via simulation results, that in the absence of an explicit interference mitigation mechanism, there will be a significant degradation in the overall LTE-U system performance for LTE-U co-channel co-existence in countries such as U.S. that do not mandate Listen-Before-Talk (LBT) regulations. An unlicensed spectrum Inter Cell Interference Coordination (usICIC) mechanism is then presented as a time-domain multiplexing technique for interference mitigation for the sharing of an unlicensed channel by multi-operator LTE-U small cells. Through extensive simulation results, it is demonstrated that the proposed usICIC mechanism will result in 40% or more improvement in the overall LTE-U system performance (throughput) leading to increased wireless communication system capacity. The ever increasing demand for mobile wireless data is also resulting in a dramatic expansion of wireless network infrastructure by all service providers resulting in significant escalation in energy consumption by the wireless networks. This not only has an impact on the recurring operational expanse (OPEX) for the service providers, but importantly the resulting increase in greenhouse gas emission is not good for the environment. Energy efficiency has thus become one of the critical tenets in the design and deployment of Green wireless communication systems. Consequently the market trend for next-generation communication systems has been towards miniaturization to meet this stunning ever increasing demand for mobile wireless data, leading towards the need for scalable distributed and parallel processing system architecture that is energy efficient, and high capacity. Reducing cost and size while increasing capacity, ensuring scalability, and achieving energy efficiency requires several design paradigm shifts. This dissertation presents the design for a next generation wireless communication system that employs new energy efficient distributed and parallel processing system architecture to achieve these goals while leveraging the unlicensed spectrum to significantly increase (by a factor of two) the capacity of the wireless communication system. This design not only significantly reduces the upfront CAPEX, but also the recurring OPEX for the service providers to maintain their next generation wireless communication networks

Development and Performance Evaluation of Urban Mobility Applications and Services

L'abstract è presente nell'allegato / the abstract is in the attachmen

Softair: Software-defined networking and network function virtualization solutions for 5g cellular systems

One of the main building blocks and major challenges for 5G cellular systems is the design of flexible network architectures, which can be realized by the paradigm of software-defined networking (SDN) and network function virtualization (NFV). Existing commercial cellular systems rely on closed and inflexible hardware-based architectures both at the radio frontend and in the core network. These problems significantly delay the adoption and deployment of new standards, impose great challenges in implementing new techniques to maximize the network capacity and coverage, and prevent provisioning of truly-differentiated services for highly variable traffic patterns. The objective of this thesis is to introduce an innovative software-defined architecture for 5G cellular systems, called SoftAir. First, a detailed overview is provided for priori wireless SDN architecture solutions. Second, the SoftAir architecture is introduced with key design elements. Third, four essential management tools for SoftAir are developed. Last, novel software-defined traffic engineering, enabled by SoftAir, are proposed. Through the synergy of SDN and NFV, SoftAir enables the next-generation cellular networks with the needed flexibility for evolving and adapting to the ever-changing network context, and lays out the foundation for 5G wireless software-defined cellular systems.Ph.D.Ph.D