## 1 Introduction
### Review of Related Works
#### 1.1.1 Transport Solutions  
The increasing demand for broadband services has instigated an unprecedented deployment in different wireless technologies. The resulting wireless technologies have different capacities, and the appropriate application of each technology depends on a specific deployment scenario. Consequently, wireless systems have to be well-classified for effective application and performance. In [15; 16; 17; 18; 19; 20; 21; 22], wireless systems were classified, and the state of wireless access was discussed. Moreover, how future wireless technologies can support broadband wireless access services was considered. Note that, for ubiquitous and flexible connections, there should be a seamless convergence of wireless and high-speed fiber networks. Therefore, a wide variety of optical transport schemes that can support 5G FWA use cases was considered in [5; 8; 11; 23; 24; 25; 26; 27]. A review of the key attributes of the evolving passive optical network (PON) and the fourth-generation (4G) mobile broadband technologies were presented in [28]. Besides, viable ways to leverage both access schemes in order to achieve a hybrid fiber-wireless network were discussed. Furthermore, in [29], a unified cable and wireless cellular access network was proposed by employing the infrastructure of hybrid fiber-coax (HFC) cable network as the fiber fronthaul network for the cellular wireless services. Furthermore, to facilitate the efficient operation of the unified network, a remote fast Fourier transform (R-FFT) node was presented. This performs physical (PHY) layer processing and helps in ensuring that the LTE and the DOCSIS are based on a shared FFT module. Furthermore, means of reducing the fronthaul bitrate requirements and supporting statistical multiplexing through the caching of repetitive quadrature amplitude modulation (QAM) symbols in the R-FFT node were proposed. The Remote PHY (R-PHY) and Remote MACPHY (R-MACPHY) modular cable access network architectures were compared in [30]. In the former architecture, the PHY layer processing is implemented in the remote node (RN) that is close to the cable modems (CMs), and for the upstream transmissions, the medium access control (MAC) layer processing is handled in the headend, while for the latter architecture, both PHY and MAC layers are processed in the RN. Besides, analytical delay models were developed for polling-based MAC with gated bandwidth allocation in both architectures. Likewise, it has been identified that seamless convergence of optical and wireless access technologies, termed hybrid fiber-wireless (FiWi) access networks, has the potential of supporting a plethora of emerging and future broadband services and applications on the same infrastructure. Consequently, the main enabling optical and wireless technologies along with their corresponding responsibilities in the emerging FiWi access networks were explained in [31]. Moreover, the need for effective design of the future FiWi network architectures and protocols were examined. Besides, the radio-over-fiber (RoF) and radio-and-fiber (R&F) testbeds were highlighted. Furthermore, the future opportunities and challenges regarding integrated path selection, hybrid MAC protocols, bandwidth allocation, integrated channel assignment, wireless frame aggregation, optical burst assembly, and flow and congestion control were outlined. Besides, a concept that focuses on the realization of a unified Internet protocol/digital video broadcasting (IP/DVB) networking platform for always-on connectivity and triple-play services was presented in [32]. In this, by exploiting the advances of DVB and the synergy with wireless/wired telecommunication technologies such as xDSL and WLAN, a common networking infrastructure was realized. Moreover, an architecture and optimization framework that enables the detection of optimum operating conditions in a converged 5G infrastructure was presented in [33].