## 2 Vision and Key Features for Future 6G Networks  
Given the massive capabilities of 5G cellular mobile wireless communications networks and their likely evolution, is there any tangible rationale for 6G networks? If yes, then, what are the missing units from LTE and 5G that 6G must integrate? Academicians, industries, and research communities have set out research modalities on the formulation, definition, design, and identification of important core-enabling technologies driving the initiation toward a \"beyond 5G\" or 6G system [15; 16]. This section will cover a large range of topics discussed in recently published works about the vision and key features of 6G communications. First, this section starts with a brief view of the expected applications that will be supported by 6G communications and which will lead to identifying the key features that are required in such communications. The following are five expected scenarios of applications that will be supported by 6G communications:  
* eMBB-Plus eMBB-Plus [17; 18] in 6G will replace its 5G counterpart of eMBB and provide a high-quality experience (QoE) in data utilization and standards. Notably, other integral components of the wireless communication of network optimization, handover, and interference should be able to exploit the concepts of big data to facilitate these operations. Providing other add-ons such as accurate indoor positioning and a globally compatible connection among diverse mobile operating networks is expected, at an affordable rate for network subscribers. A strategy should be designed for eMBB-Plus communication services without compromising the security, secrecy, and privacy of network subscribers;
* Big communications (BigCom) BigCom [19] in 6G aims to provide a large coverage of urban and remote areas by maintaining resource balance, thereby allowing subscribers to communicate with one another everywhere with a high data rate speed due to the unconventional technologies adopted by 6G communication systems, such as an extremely large bandwidth (THz waves) and a high AI that will include operational and environmental aspects as well as the services of the networks;
* Secure ultra-reliable low-latency communications (SURLLC) Vehicular communications in 6G could also largely benefit from SURLLC [19; 20]. SURLLC in 6G is an advancement of the URLLC and the mMTC in 5G and has more stringent demands on reliability (higher than 99.9999999%) and latency (less than 0.1 ms) coupled in a security framework;
* Three-dimensional integrated communications (3D-InteCom) Before the evolution of 6G networks, device communication heights were inconsequential, as could be seen from the established propagation empirical models. This situation anticipates change in the 6G 3D-InteCom model [19; 20; 21; 22], which highlights the need for a radical change from two to three dimensions, through which the heights of communications nodes must be considered. Some of the notable technologies that have already incorporated this dimension are satellite, unmanned aerial vehicle (UAV), and underwater communications. Thus, the analytical framework designed for 2D wireless communications that stemmed from stochastic geometry and graph theory needs re-adjustment in the 6G environment. Considering the device height leads to the actualization of elevation beamforming with full dimensional MIMO architectures, thereby preventing the need for a different approach for attaining network optimization;
* Unconventional data communications (UCDC) Currently, the actual meaning and composition of UCDC [19] lack proper definition. Nevertheless, some of the following facets should be addressed: holographic, tactile, and human-bond communications. * _Holographic communications:_ Holographic communications are one aspect that will add glamor to the 6G era. A hologram is a 3D technology that manipulates light rays beamed to an object and subsequently captures the resulting interference pattern using a recording device.