Dear Colleagues,

The future digital society, in the scope of increasing automation, namely the digital society of 2030 and beyond, comprises more and more connected devices (IoT), including sensors, vehicles, aerial drones, data, etc. While 5G supports autonomous vehicles, the increasing number of sensors per vehicle requires higher-speed communications and lower latencies. Society and organizations demand new services to be included in 6G, including the following:

• Augmented reality and extended reality;
• Artificial-intelligence-infused applications;
• Wireless brain-computer interactions;
• Holographic services;
• The integration of communications with localization, mapping, and remote control;
• Emerging eHealth applications;
• Improved autonomous vehicles;
• More efficient support of IoT, namely smart cities and smart houses, supporting an extremely high number of low-power devices;
• Support of flying vehicles and increased mobility speed.

In addition, 6G aims to have higher energy efficiency and more efficient strategies of energy-harvesting so that the autonomy of user equipment can be increased despite its demanding applications.

These new services and capabilities to be supported by 6G continue to require more efficient networks, such as increased data rate, lower latency, more efficient spectral efficiency, increased energy efficiency, and improved network capacity. Some of the foreseen requirements for 6G include the following:

• Nomadic peak data rate of at least 1 Tbps (100 times higher than 5G);
• Mobile data rate of 1 Gbps (10 times higher than 5G);
• Energy efficiency 10 to 100 times better than 5G;
• Spectral efficiency 5 to 10 times better than 5G.

While 5G requirements are achieved based on mm-Wave and m-MIMO, 6G must incorporate new concepts such as passive antennas, namely reconfigurable intelligent surfaces (RIS). In order to achieve potential gains (coverage, interference cancellation, secrecy, spectral efficiency, etc.), there is a need to estimate the channel characteristics, and this is difficult to achieve with passive elements. Recently, active antennas, such as large intelligent antenna systems (LIS), also referred to as ultra massive MIMO (UL-MIMO) or extremely large antenna arrays (ELAA), have been employed to achieve such gain desiderates; however, the complexity also increases with the employment of these processes. In terms of frequency bands, 6G is revolutionary, as it includes visible light communications (VLC) and terahertz bands (100 GHz–10 THz), enabling data rates in the order of hundreds of Gbps. VLC is a mature communication technique well suited for short-range coverage, though susceptible to interferences, such as from the sun.

This Special Issue aims to provide an overview of 6G communications and beyond, in terms of network, services, and requirements, while describing advances in networks, services and transmission techniques foreseen for future versions. All new ideas about how to improve performance, capacity, and/or spectrum efficiency of transmission techniques for 6G and beyond, while keeping computational cost at an acceptable level, are most welcome. Contributions to this Special Issue should provide an overview of how the proposed schemes bring added value to the advances in cellular communications in terms of performance, services and/or advanced requirements.

Dr. Mário Marques da Silva
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• 6G and beyond
• advances in cellular communications
• LIS antenna systems
• RIS antenna systems
• terahertz bands