## 1 Introduction
### Review of Related Works
#### 1.1.2 Enabling Technologies
Similarly, in [57], a unified SDN was presented as a common control scheme for end-to-end optical circuit switching (OCS)/optical packet switching (OPS) networks, with the introduction of OpenFlow agent. The SDN control plane was employed in the OPS network to offer advantages such as optimal network organization, simplified data plane design, improved control flexibility, contention alleviation, and advanced handling of network dynamics. Furthermore, leveraging the SDON platform, a service design idea for an enhanced network abstraction was introduced. Besides, for efficient fault-tolerant control and effective detection of attacks in the SDON, a distributed control architecture for SDON based on the blockchain concept was proposed in [58]. In [59], a service-variable optical equipment that is capable of supporting several services is presented. Furthermore, a multi-layer restoration system in a service-oriented SDON was proposed and the feasibility of the scheme was experimentally validated. Furthermore, a control architecture that is based on an SDON for optical transport networks was presentedin [60]. The proposed architecture can support control layer artificial intelligence (AI) as well as onboard AI. Furthermore, experimental results were presented to demonstrate the viability of the cross-layer optimization and coordination between the onboard and control layer AIs. In addition, an Internet of Things (IoT)-aware multi-layer transport SDN and cloud/edge orchestration architecture were presented and experimentally validated in [61]. This helps in the deployment of IoT flow monitors as well as traffic congestion avoidance algorithms integration into the control and orchestration platform. Similarly, it facilitates the dynamic and effective distribution of IoT processing from the core data centers to the network edge based on the actual network resource state. This enables efficient offload of the packet and optical transport networks at the infrastructure layer. Furthermore, an SDN-enabled container-based edge node was presented and integrated into the SDN control architecture. This is in an effort to reduce network bandwidth utilization. Moreover, a hybrid SDN network with a combination of SDN and legacy network devices was comprehensively surveyed in [62]. In an effort to meet diverse application requirements, an integrated heterogeneous networking scheme was proposed in [63] for fiber-wireless access network and multi-access edge computing network. In the paper, network virtualization was exploited for the dynamic orchestration of computing resources and network storage. Similarly, resource allocation methods that enable frequency reuse and interference avoidance for the BFWA system were investigated in [64; 65; 66; 67] to improve the system performance. Furthermore, to ensure effective implementation of beamforming in the open RAN (O-RAN), the main research challenges are presented in [68]. In this regard, different beamforming techniques in O-RAN were analyzed for ultra-reliable low-latency communications. Based on this, a zero-forcing equalizer was recommended as a precoding vector for the beamforming method that leverages the channel information.