6G Networks: Is This an Evolution or a Revolution? [From the Guest Editors]

The lessons learned from the third industrial revolution taught us that the transformation from mechanical and analog technology to digital electronics have changed the world once and forever. While computers and communication networks have become the new oil that defines the wealth of countries, research and industrial communities have been the driving forces that have made this transition possible. In the future, the same communities and stakeholders are required to enable the transition to net-zero communication networks. With reference to mobile communications, 5G is an evolution from all previous networks with the adoption of new radio access technologies, multisliced architecture, cloud-native and automation, and so on. By definition, 5G is a network that adapts to user needs and dynamic changes in traffic, designed to serve a new class of users: “machines.” Therefore, latency has become a critical metric in 5G. Looking forward, 6G shall employ cell-less access networks, integrated nonterrestrial networks, joint sensing and communications, new spectrums such as terahertz (THz) communications, switching from traditional channel-based design paradigms to designing channels through novel technologies such as intelligent reconfigurable surfaces, open interfaces that interconnect all network functions, end-to-end orchestrators, and, most noticeably, artificial intelligence (AI) machines that govern all functional modules and operational services. The various network functions generate traces of various operations that are ingested into databases; then AI will leverage this data for optimized decisions that are reflected into network status transitions, resource utilization, service enhancement, and ultimately lead to self-synthesizing networks. Built upon commercial clouds, 6G will have the flexibility to scale and restructure for more resilient response to traffic fluctuations and user requirements. To this end, cybersecurity features will become an embedded part of network functions to shield the network services not only from external threats but also from hosting domains. From an air interface perspective, 6G will integrate nonterrestrial (space, air, drone, and ocean) communications technologies to connect and route new users such as drones and coastal trading vessels. Furthermore, future wireless networks need to make use of a spectrum that extends into the optical spectrum and includes the THz range. The channel becomes a critical component due to the impact of blockages and random orientations at these frequencies. Active and passive intelligent reflecting surfaces (IRSs) will become a new wireless system element that will help overcome new challenges related to coverage and the propagation channel.