6th Generation: Communication, Signal Processing, Advanced Infrastructure, Emerging Technologies and Challenges

In the very initial stage of fifth-generation (5G) com-mercialization, researchers, scientists, and engineers are realizing the need for further enhancement in 5G parameters and more intelligent techniques to fulfill the expected future requirements. Due to advancement in infrastructure and rapid increment in wireless communication users, after few years, 5G parameters will not be sufficient to fulfill the requirements. The enhanced data rate, data security, ultra-low latency, low computation complexity, ultra-high spectrum efficiency, and power-efficient techniques are the main requirements. Thus sixth-generation (6G) wireless communication is becoming a research hot-spot. The key enablers techniques for 6G communication are auto-pilot unmanned aerial vehicle communication, high mobility communication, satellite communication, advanced device-to-device communication, accurate positioning system, GPS de-nied positioning, free-space optics, energy harvesting, wireless power transfer, internet of everything, massive internet of thing, intelligent reflecting surfaces, and artificial intelligence-enabled transceivers. In this review article, the role of these techniques for future wireless communication enhancement is discussed. We have also discussed enhancement in existing wireless technology such as pilot-based estimation to blind estimation, advanced error controlling techniques, advanced channel coding, millimeter waves, hybrid non-orthogonal multiple access techniques, orthog-onal time-frequency, and space modulation.