# 6G Wireless Communication Systems: Applications, Opportunities and Challenges
## 2 Contributions  
The different papers in this Special Issue have made specific contributions, which we summarise in this section. To start with, [3] concentrated on identifying the limitations of 5G and how the 6G standard could solve these problems. The authors in [3] criticised the 5G standard for more data-intensive, low-latency, and ultra-high reliability applications. It characterised the enabling technologies for a future 6G network in terms of social, economic, and technological requirements. Although not included in that discussion, a fourth requirement is cultural as several cultural barriers might hinder the acceptance of any new technology.  
The authors in [4] envisage the 6G network from the practical perspectives and implementation examples of the Internet of Things. Examples of sectors discussed include healthcare sectors, smart grid, transport, and Industry 4.0. These sectors can be said to follow from the six domains of a sustainable city, which were motivated by the emergence of IoT and Industry 4.0.  
As the IoT, Industry 4.0 and data intelligence through machine learning and artificial intelligent technologies have pioneered low-power smart devices, future, modern technologies, and businesses will proliferate data intelligence orchestrated by the huge amount of data created from enabling IoT, Industry 4.0, and artificial intelligence. Fuzzy logic and new biological-inspired technologies will be explored to play significant roles in meeting the requirements for 6G in the future internet. On this premise, the authors in [5] surveyed the characteristics, challenges, potential use cases, and market drivers of intelligent edge computing devices for 6G applications. The intelligent edge computing devices will form the backbone for future services and emerging wireless communication networks. They are an improvement of cloud computing technology deployed to simplify access of near-end users to the generic network.  
The emergence of 5G networks has been dominated by IoT edge devices, most of which are intelligent edge devices. Besides the problem of privacy and security in the IoT edge devices, the other worry is about the sustainable future of the batteries of the billions of the IoT edge devices. In building sustainable cities and communities in the 6G era, a circular economy business model requires that these devices and their batteries should be reused, recycled, or refurbished at the end of their 10-year average life span. To minimise these concerns in the 6G era, energy-neutral IoT edge devices are discussed in [2] for position finding application as an example. In particular, the energy-neutral devices, which may be active or passive, can harvest energy from nature and use such energy sources to operate. The energy that they harvest are usually more than or equal to the energy they use to operate.  
Finally, future internet technologies including the immediate forthcoming 6G network standard should explore the opportunities to cushion its emergence and the generic bias of causing pandemic or health problems, as was the case of COVID-19, to avoid slowing down the uptake (and/or destruction) of such technology infrastructure. It should consider how to sensitiise the community ahead of the installation and launch of the 6G technology network, especially if it coincides with an outbreak of a new pandemic.