The commercial fifth-generation (5G) wireless communications networks have already been deployed with the aim of providing high data rates. However, the rapid growth in the number of smart devices and the emergence of the Internet of Everything (IoE) applications, which require an ultra-reliable and low-latency communication, will result in a substantial burden on the 5G wireless networks. As such, the data rate that could be supplied by 5G networks will unlikely sustain the enormous ongoing data traffic explosion. This has motivated research into continuing to advance the existing wireless networks toward the future generation of cellular systems, known as sixth generation (6G). Therefore, it is essential to provide a prospective vision of the 6G and the key enabling technologies for realizing future networks. To this end, this paper presents a comprehensive review/survey of the future evolution of 6G networks. Specifically, the objective of the paper is to provide a comprehensive review/survey about the key enabling technologies for 6G networks, which include a discussion about the main operation principles of each technology, envisioned potential applications, current state-of-the-art research, and the related technical challenges. Overall, this paper provides useful information for industries and academic researchers and discusses the potentials for opening up new research directions.

Cooperative communication (CC) has been introduced as an effective technique to combat the detrimental effects of channel fading by exploiting spatial diversity gain, resulting in improved throughput and network performance. CC provides an opportunity for single antenna nodes to share their resources and construct a virtual antenna array at a lower cost. As a result, CC is considered an efficient solution for mobile nodes where some difficulties in terms of physical size and energy consumption arise from implanting multiple antennas. However, since CC is a new technology it brings new challenges that should be adequately addressed to render it a viable solution for wireless communication. Parameters such as link reliability, energy efficiency, overall throughput, and network performance are all affected by cooperative transmission. Besides, nodes' operation in physical layer should be coordinated with higher layers, especially with medium access control (MAC), for reliable operation in time varying channels. Accordingly, designing a cooperative MAC protocol that supports node coordination, error recovery and dynamic link optimization is important. In this paper, the most well-known cooperative MAC protocols are classified based on their channel access strategy into two groups: 1) contention-based and 2) contention-free schemes. At first, the preliminaries, constraints, and requirements for designing effective cooperative MAC protocols are illustrated. Then the current state-of-the-art cooperative MAC protocols are surveyed by benchmarking their scheduling schemes, characteristics, benefits, and drawbacks, in line with the suggested taxonomy. The cooperative MAC protocols are classified and analyzed based on their application and network utilized into five subsections, including vehicular networks, cognitive networks, multi-hop protocols, cross-layer protocols, and network coding-based protocols. Finally, challenges, open issues, and solutions are considered, which may be used in improving the available schemes or designing more reliable and effective cooperative MAC protocols in the future.

This paper proposed and implemented an energy-aware routing multi-level and mapping problem (EARMLP) algorithm to minimize the overall power consumption in Software-Defined Networking (SDN)-based core networks. To enforce network utilization toward green policies design for Data Centers (DCs), SDN leverages protocol configurations for routing available in the infrastructure. Therefore, the proposed mechanism aimed to design an optimal routing strategy that considers system configuration and traffic demand between the data and control planes in networks. The problem is then addressed from the perspective of the policy-based EARMLP technique, which is used to carefully determine the optimal assignment between controllers and their switches to optimize network energy savings. Hence, a controller placement problem (CPP) is established to select the optimal locations and number of controllers in core networks and create an optimal mapping and resource allocation between switches and controllers. Since the formulated energy-aware routing algorithm is designed as a multi-objective NP-hardness of the problem, a heuristic approach is developed to find optimal solutions for traffic routing between inter-controllers and controller-switch in terms of energy-aware consumption strategies. Consequently, the proposed optimal routing mechanism can rearrange traffic to meet provisioning criteria by utilizing the capacity-aware design. Remarkably, the energy saved in networks by our suggested method can approach up to 70% of the energy saved in SDN-based networks compared to other methods.

Passive radars utilising illuminators of opportunity are being actively studied in the field of radar. In the last few years, many illuminator sources have been employed for passive radar applications. However, there have been no published results on the use of the long‐term evolution (LTE) signal as a novel source for passive radar applications. For the first time an experimental investigation into the feasibility of LTE‐based passive radars for detecting a moving target is presented. A theoretical analysis was conducted on a captured LTE signal in the atmosphere. This was then followed by a field experiment. The preliminary results show that the LTE signal is capable of being an illuminator for passive radars.

The passive bistatic radar (PBR) system can utilize the illuminator of opportunity to enhance radar capability. By utilizing the forward scattering technique and procedure into the specific mode of PBR can provide an improvement in target detection and classification. The system is known as passive Forward Scattering Radar (FSR). The passive FSR system can exploit the peculiar advantage of the enhancement in forward scatter radar cross section (FSRCS) for target detection. Thus, the aim of this paper is to show the feasibility of passive FSR for moving target detection and classification by experimental analysis and results. The signal source is coming from the latest technology of 4G Long-Term Evolution (LTE) base station. A detailed explanation on the passive FSR receiver circuit, the detection scheme and the classification algorithm are given. In addition, the proposed passive FSR circuit employs the self-mixing technique at the receiver; hence the synchronization signal from the transmitter is not required. The experimental results confirm the passive FSR system’s capability for ground target detection and classification. Furthermore, this paper illustrates the first classification result in the passive FSR system. The great potential in the passive FSR system provides a new research area in passive radar that can be used for diverse remote monitoring applications.

The unmanned aerial vehicles (UAVs) in military and civilian systems access sensitive data via cellular networks and are ubiquitous. Therefore, the number of handovers may increase, and the process of sharing authentication keys between drones to new drones may be vulnerable to eavesdropping due to the wireless connectivity. For example, a UAV initially served by cell A may be handed over to cell B after a certain point. Therefore, Security and privacy concerns raise if there is a change in the flight path of the UAV due to wide-area connectivity traffic management, including authentication threats as well as the leakage of identity, location, and flying routes. Also, drones are resource-constrained devices that cannot perform extensive operations, leading to the inability to resist drone capture attacks and impersonation attacks. Therefore, this paper presents a high-performance and efficient anonymous handover authentication protocol to secure the drone traveling path. The protocol utilizes the advantages of the AES-RSA algorithm to provide efficient and secure key management and a fast verification and signature generation that speeds up drone authentication. The protocol's security was proved using the formal verification ROR model and automated security verifier ProVerif tool to validate the protocol resistance against various attacks and provided forward secrecy. In addition, the performance of the proposed protocol is evaluated using the OMNeT++ simulator in terms of communication, computation cost, energy consumption, packet drop ratio, end-to-end delay, and throughput. The results showed that the protocol achieves better security, efficiency, and performance than other protocols.