# Revolution or Evolution? Technical Requirements and Considerations towards 6G Mobile Communications
## 4 Requirements of 6G  
To compare 6G with 5G, the focus of 5G is more on speed, mass connectivity, reliability, and latency, while the suggested focus directions for 6G are sustainability, coverage connectivity, synchronization, geo-location, and trustworthiness [37]. Fifth generation is capable of a low latency of one millisecond, while it was not designed with guaranteed time synchronization. Therefore, there is a time difference between different flows or different sessions generated by different objects that need interactions with each other. In 6G, multiple objects will integrate with each other, either in virtual or physical worlds. Therefore, the time differences between all objects and the communication links need to be within a certain limit to provide natural reaction and interaction between them. On the other hand, time jitter is also highly important for future communications which are beyond 5G capability. As the objects' interaction in 6G is essential, the need for high-quality and high-resolution geo-location plays a vital role in realizing 6G. Connectivity is another critical problem of 6G that should be addressed properly. The future network not only needs ultra-high-speed connectivity but also needs resilience and adaptive and customizable connectivity. For example, for 4D video transmission, a large amount of data needs to be transferred, in the range of terabits per second; therefore, along with a high bandwidth, smart algorithms are required to compress data, for example, with the help of AI to predict the next posture of a face. On the other hand, such exhaustive data transmission needs massive backhaul with low latency. In addition, 6G requires flexible spectrum access, high-resolution channel state information (CSI), and precoding for distributed mMIMO, high-capacity uplink, higher network capacity and quality for mobile cloud XR, and low-power, high-precision positioning [42; 43; 44]. Another connectivity target of 6G is to overcome the digital divides, where everybody, irrespective of their location, has decent access to the network services. On another extreme, massive low-powered devices or \"things\" communication requires resource utilization for high connection density but which also supports a timely, efficient, and reliable mechanism to deliver data. The 6G network would provide a very high peak transmission rate, up to 1-10 Tbps, with very low latency, as low as 10-100 us, but all of this needs to be achieved while having much lower energy consumption not only per unit data but also as overall power consumption [45]. Overall, 6G offers remarkable network capabilities that are imperative for realizing the 2030 intelligent information society. Figure 2 presents the technical requirements of 6G, compared with 4G and 5G requirements, which include the following elements of 6G [28]:  
1. Spectrum efficiencies 5 to 10 times higher than those of 5G;
2. Peak data rate of at least 1 Tbps or up to 10 Tbps in some instances that involve THz wireless backhaul and fronthaul (x-haul) [46];
3. User experienced data rate of 1 Gbps or even up to 10 Gbps in certain cases (e.g., indoor hotspot);
4. Ten times higher connectivity density than that of 5G which can sustain up to 107 devices per area (in km\({}^{2}\)) and area traffic capacity of up to 1 Gbps per area (in m\({}^{2}\)) for hotspot;
5. A wireless network that can support various (or at times, conflicting) requirements [47];
6. High mobility (\(\geq\)1000 km/h) and over-the-air latency of 10-100 us for acceptable quality of experience (QoE) in cases that involve hyper-HSR and airline systems;
7. Huge connection density up to 107 devices/km\({}^{2}\), which means 10 times the connectivity density of 5G; in addition, area traffic capacity of up to 1 Gbps/m\({}^{2}\) for scenarios such as hotspots;
8. 10-100 times higher energy efficiency than in 5G;(9) 5-10 times greater spectrum efficiency than in 5G. Table 1 summarizes the differences between 5G and 6G. It shows that 6G will make dramatic changes in mobile communications.