5G heterojen bulut radyo erişim ağlarında enerji verimli kullanıcı birliği ve aktarımı

5G wireless networks are expected provide data rate improvement, low-latency, ultra-reliable and energy-efficient communication. Heterogeneous Cloud Radio Access Network (HCRAN) has been proposed to meet the aforementioned goals in 5G through the combination of Macro Base Stations (MBS)s, which operate at LTE cellular frequencies, and Small Base Stations (SBS)s, which operate at mmWave frequencies, with cloud infrastructures. For the provision of high data rates in 5G HCRANs, dense deployment of SBSs is necessary because high bandwidth available in millimeter wave spectrum enables to meet the data rate demands. On the other hand, for ultra-reliable and low-latency communication, special techniques are used to overcome high pathloss since mmWave signals are very susceptible to physical blockage. However, dense deployment of SBSs leads to a rise in power consumption and carbon emission, whereas techniques proposed for ultra-reliable and low-latency communication cause increase in signaling overhead and decrease in achievable rate and latency performances. This, in result, drives research efforts to find more energy efficient and reliable user association approaches. To that end, this thesis mainly focuses on the development of novel energy efficient user association methods and a handover algorithm in 5G HCRANs. First, based on the realistic power consumption model proposed for 5G, an energy-efficient user association approach is proposed in Uplink/Downlink Decoupled HCRANs and improvements of the proposed model in power consumption, delay and fairness have been examined. In addition, to enhance the robustness of mmWave signals to blockages in a mobile scenario, a User-Base Station association method, which is based on multi-connectivity technique, is proposed and the effects of the proposed User-Base Station association method on the power consumption, achievable rate, delay and reliability have been investigated. Last, to increase achievable rate, latency and reliability performances of Multi-Connectivity based Uplink/Downlink Decoupled HCRANs in case of high mobility, an Energy constrained Handover policy has been proposed to minimize the number of handovers. The supremacy of the proposed algorithms over existing methods are demonstrated by simulations in terms of closeness to the optimal for different networks sizes and various data rate requirements.