Radio Resource Management in 5G Cellular Networks

The fifth generation (5G) of cellular networks aims at providing connectivity for a large number of applications. To achieve this goal, 5G has been designed considering three generic services with vastly heterogeneous requirements: enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable low-latency communications (URLLC). To accommodate these wide range of services, a key role is played by scheduling and radio resource allocation, whose aim is allowing efficient sharing of the limited radio spectrum among different services. The aim of this Dissertation is to investigate and to design Radio Resource Management (RRM) techniques and scheduling strategies that are suitable to meet the heterogeneous requirements of eMBB and mMTC usage scenarios. For this reason, the analysis provided considers different frequency band, like the mmWave transmissions and the sub-6GHz transmissions, different access techniques, like Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA) and the novel Sparse Code Multiple Access (SCMA), the support of advanced radio access technologies, such as beamforming technique and device-to-device (D2D) communications, the definition of very simple random access procedure to meet the requirements of low-complexity connected devices, and various network architectures, like Millimeter-Wave Mobile Broadband (MMB) and single-cell. In the context of radio resource allocation, we present four research activity. First, we provide an OFDMA-based Quality-of-Service (QoS) aware scheduling framework to allocate radio resources among Guaranteed Bit Rate (GBR) and non-GBR services. Second, we consider a D2D-enabled MMB and propose a TDMA-based centralized access control scheme which jointly manages D2D communications and transmissions in both the access and the backhaul networks. Third, we propose a new access control scheme tailored for mMTC scenarios, where radio resources are allocated in the Physical Uplink Shared Channel (PUSCH) by means of the SCMA technique to properly multiplex a large number of small-sized date. Fourth, in order to reduce jointly the transmission energy consumption and the signaling overhead from the prospective of the MTC devices, we present the strategy of transmitting tagged preambles in the Physical Random Access Channel (PRACH) and present a rigorous analytical model to analyze the correct detection of both the preamble and the tag at the receiver next Generation NodeB (gNB), considering the presence of interference, noise, and multi-path fading.