# 6G Mobile Networks: Key Technologies, Directions, and Advances
## 4 6G Technologies
### Terahertz-Communication
In contrast to the direct modulation THz system, which permits high-power THz sources to be input for the purpose of authorising relatively long-distance dispatches, the solid-state THz system transforms intermediate frequency (IF) modulated signals to THz frequency. Finally, we explore a number of implicit operation scripts as well as some crucial technical difficulties that will be faced in upcoming THz dispatches. In [42], it has summarised the state of THz dispatches investigation, spectrum management, and standardised conditioning at the moment. In all three sectors, encouraging progress has recently been made on the route to 100 Gbit/ s of wireless transmission. These discoveries will serve as the foundation for the creation, standardisation, and ultimately the use of ultra-rapid THz communication networks. According to recent developments, the business launch of THz dispatches may be anticipated in the near future and will assist in handling the continuous demand for cellular data rates is rising. In [43], it is summed up that:  
* The bit rate may be raised by using high frequency carriers like millimetre and terahertz waves. * Perfect connectivity between wired and wireless networks is made possible by the grounded signal generation and modulation techniques of photonics. * The wireless connection in the 300 GHz band using the direct discovery approach has attained 30 Gbit/s error-free. The 600 GHz band guarantees advanced. * Coherent discovery strategy has been investigated in order to boost bit rate and receiver perceptibility; a proof-of-concept experiment has been shown in the 100 GHz range. * The usage of RTDs in 300 GHz band, in addition to Si grounded Tx/Rx, has been shown. Electronics grounded technique is crucial for low cost and/or consumer operations. In [44], the current state of the development of upcoming THz broadcasts have been examined and presented. The initial propagation properties of the most probable operations and scripts in this frequency range are well known. Modern semiconductor technology advancements have made it possible to build up demos that indicate the possibility of achieving data speeds of several hundred Gbit/s. One of the most important challenges for unborn tasks is the development of intelligent antenna generalities to overcome the high path loss in confluence with dynamic shadowing events caused, for illustration, by moving humans. In order to enable the operation of several knockouts of GHz, diapason sharing generalities with unresistant services will have to be developed. In [45], The frequency band between 0.1 and 30 THz is practically uncharted territory, it dispatches. This terahertz gap has recently received the most attention from researchers since the high carrier frequency suggests unknown channel capacities1. In fact, predictions for 2015 were for data speeds of 100 Gbit/s. Then, we provide a single-input, single-output, 100 Gbit/s wireless communication system operating at 237.5 GHz for the first time, capable of sending data over a distance of 20 m. A narrow-band terahertz carrier is photonically created by merging the comb lines of a mode-locked ray in an unravelling-carrier photodiode in this development, which combines terahertz photonics with electronics. Additionally, the single-traveling-carrier photodiode system is transmitted through a ray-fastening antenna. A millimeter-surge monolithic interwoven circuit with new terahertz mixers and amplifiers enters the signal. This method, in our opinion, offers a way to assess wireless dispatches to Tbit/s rates across distances greater than 1 km.