L'objectif de cette thèse est l'étude de l'efficacité énergétique des communications D2D dans les réseaux hétérogènes. Nous proposons dans un premier temps d'analyser la consommation énergétique d'un réseau de trois appareils, puis introduisons une nouvelle topologie prenant en compte l'entropie de données, afin d'augmenter l'efficacité énergétique globale. Par la suite, nous étudions la consommation énergétique et l'influence des interférences sur une cellule dans le cas pratique d'une catastrophe naturelle. Nous introduisons alors un nouveau protocole d'allocation de ressources basé sur le clustering en Fuzzy C-Means. Nous utilisons ensuite des outils et métriques issus de la géométrie stochastique afin d'analyser et de comparer l'efficacité énergétique et spectrale au sein de plusieurs types de réseaux munis de communications D2D. Dans un deuxième temps, nous introduisons les notions d'antennes directionnelles avec des ondes millimétriques. Pour ce faire, nous évaluons l'influence du canal millimétrique et introduisons les concepts de blocage, et de modèles sectorisés d'antennes, à des fins mathématiques. L'utilisation d'ondes millimétriques, et plus particulièrement d'antennes directionnelles ULA, s'avère être un choix totalement opportun dans l'objectif premier de cette thèse qui est d'augmenter à la fois l'efficacité spectrale (donc le débit) et l'efficacité énergétique au sein d'un réseau hétérogène comprenant des communications D2D. / The objective of this thesis is the study of the energy efficiency of D2D communications in heterogeneous networks. We first propose to analyze the energy consumption of a three device, then introduce a new topology taking into account the data entropy, in order to increase the overall energy efficiency. Subsequently, we study the energy consumption and the influence of interference in a cell for the use case of a natural disaster. We then introduce a new resource allocation protocol based on Fuzzy C-Means clustering. We then use tools and metrics from stochastic geometry to analyze and compare energy and spectral efficiency among multiple types of networks comprising D2D communications. The first study is done on a network in which the cellular and WiFi resources are shared. In a second step, we introduce the notions of directional antennas with millimeter waves. To do this, we evaluate the influence of the mmWave channel and introduce the concepts of blocking, and sectored models of antennas, for mathematical purposes. The use of millimeter waves, and more particularly ULA directional antennas, proves to be a totally appropriate choice in the primary objective of this thesis, which is to increase both the spectral efficiency (therefore the bit rate) and the energy efficiency within a heterogeneous network including D2D communications.

The next generation wireless networks i.e. 5G aim to provide multi-Gbps data traffic, in order to satisfy the increasing demand for high-definition video, among other high data rate services, as well as the exponential growth in mobile subscribers. To achieve this dramatic increase in data rates, current research is focused on improving the capacity of current 4G network standards, based on Long Term Evolution (LTE), before radical changes are exploited which could include acquiring additional/new spectrum. The LTE network has a reuse factor of one; hence neighbouring cells/sectors use the same spectrum, therefore making the cell edge users vulnerable to inter-cell interference. In addition, wireless transmission is commonly hindered by fading and pathloss. In this direction, this thesis focuses on improving the performance of cell edge users in LTE and LTE-Advanced (LTE-A) networks by initially implementing a new Coordinated Multi-Point (CoMP) algorithm to mitigate cell edge user interference. Subsequently Device-to-Device (D2D) communication is investigated as the enabling technology for maximising Resource Block (RB) utilisation in current 4G and emerging 5G networks. It is demonstrated that the application, as an extension to the above, of novel power control algorithms, to reduce the required D2D TX power, and multihop transmission for relaying D2D traffic, can further enhance network performance. To be able to develop the aforementioned technologies and evaluate the performance of new algorithms in emerging network scenarios, a beyond-the-state-of-the-art LTE system-level simulator (SLS) was implemented. The new simulator includes Multiple-Input Multiple-Output (MIMO) antenna functionalities, comprehensive channel models (such as Wireless World initiative New Radio II i.e. WINNER II) and adaptive modulation and coding schemes to accurately emulate the LTE and LTE-A network standards. Additionally, a novel interference modelling scheme using the 'wrap around' technique was proposed and implemented that maintained the topology of flat surfaced maps, allowing for use with cell planning tools while obtaining accurate and timely results in the SLS compared to the few existing platforms. For the proposed CoMP algorithm, the adaptive beamforming technique was employed to reduce interference on the cell edge UEs by applying Coordinated Scheduling (CoSH) between cooperating cells. Simulation results show up to 2-fold improvement in terms of throughput, and also shows SINR gain for the cell edge UEs in the cooperating cells. Furthermore, D2D communication underlaying the LTE network (and future generation of wireless networks) was investigated. The technology exploits the proximity of users in a network to achieve higher data rates with maximum RB utilisation (as the technology reuses the cellular RB simultaneously), while taking some load off the Evolved Node B (eNB) i.e. by direct communication between User Equipment (UE). Simulation results show that the proximity and transmission power of D2D transmission yields high performance gains for a D2D receiver, which was demonstrated to be better than that of cellular UEs with better channel conditions or in close proximity to the eNB in the network. The impact of interference from the simultaneous transmission however impedes the achievable data rates of cellular UEs in the network, especially at the cell edge. Thus, a power control algorithm was proposed to mitigate the impact of interference in the hybrid network (network consisting of both cellular and D2D UEs). It was implemented by setting a minimum SINR threshold so that the cellular UEs achieve a minimum performance, and equally a maximum SINR threshold to establish fairness for the D2D transmission as well. Simulation results show an increase in the cell edge throughput and notable improvement in the overall SINR distribution of UEs in the hybrid network. Additionally, multihop transmission for D2D UEs was investigated in the hybrid network: traditionally, the scheme is implemented to relay cellular traffic in a homogenous network. Contrary to most current studies where D2D UEs are employed to relay cellular traffic, the use of idle nodes to relay D2D traffic was implemented uniquely in this thesis. Simulation results show improvement in D2D receiver throughput with multihop transmission, which was significantly better than that of the same UEs performance with equivalent distance between the D2D pair when using single hop transmission.