## 3 6G State-of-the-Art
### Evolution of 6G
#### 3.2.3 HCSs  
A new level of physical experience may be delivered with the use of 6G technology, which enables the provision of HCS services that can be tightly tied with human users. As an excellent example of HCS, wireless brain computing interfaces are particularly well-suited since network performance is determined by the physiology and behaviour of human users. The major needs for 6G systems are high efficiency, smooth integration, innovative technologies, accurate indoor location, high density, advanced connectivity, and healthy communication. 6G systems must also meet the following characteristics. These more advanced requirements necessitate the provision of technical help that is more innovative in nature. Following is a breakdown of the existing techniques in this field into four (4) groups, as seen in the table below. (1) Offloading energy-conscious tasks the majority of IoT devices are battery-powered and have limited computing and communication capabilities. As a result, these gadgets can only perform a limited number of functions at a slow rate. On the other side, applications are becoming more computationally intensive, necessitating reduced latencies and real-time answers. These apps might quickly consume the devices' power resources, making them unavailable for usage in the network. Extending the lifetime of IoT devices by conserving/boosting device energy to make full use of their finite energy supplies is still a major challenge [379]. (2) Massive IoT: this term refers to the connectivity of a large number of devices, sensors, and equipment on a big scale [380,381]. The Internet of Things is classified according to the number of connected devices and the volume of traffic generated by such devices. The number of devices linked to the Internet has expanded dramatically during the last decade. This number will more than double in the next several years, necessitating the establishment of a robust network to enable their connectivity [382]. The network density in huge IoT is extraordinarily high, reaching roughly 1 million devices per square kilometre [383]. This will result in a significant amount of data being distributed between devices, a large number of tasks being performed, and massive volumes of data being saved and analyzed [384]. As a result, 6G and fog computing will be critical facilitators of huge IoT applications. (3) High Efficiency: refers to a broad issue that incorporates high data transmission rates, high capacity, large-scale data processing capability, exact research and conclusions, and more. Dynamic Spectrum Allocation: High flexibility is required for 6G networks to achieve significant efficiency. When it comes to dynamic spectrum allocation, the flexible use of perceptual context information, the rapid allocation of spectrum resources in a matter of seconds, and the intensive use of valuable spectrum resources as a final goal are all possible requirements. Optimisation of the supply of any service to a varied variety of users, automobiles, equipment, and industries is made possible through the use of dynamic network slicing technologies by network operators. (4) Energy-Efficient Communication: 6G will meet and exceed a number of requirements, including the delivery of high-energy performance, most notably in the context of widespread IoT use and an eco-system of numerous minute sensors. Additionally, extending the battery life of smartphones is necessary, in accordance with the assumption that their skills and abilities to deal with complex multimedia signal processing improve exponentially as their power consumption increases [385]. Thus, low energy consumption and extended battery charge life length are two study areas in 6G that aim to address the daily recharging challenges faced by the majority of communication equipment and to meet communication objectives. As a result, 6G must elicit a complete plan for energy-efficient wireless communication.