Dear Colleagues,

While terrestrial networks have achieved great success in the 3G/4G eras, there are still 750 million people who lack mobile Internet coverage, and half of the world's population lacks Internet access, according to GSMA. Providing Internet access from space is not a new idea for connecting the unconnected, but it was proven unsuccessful in the 1990s via the Iridium bankruptcy. For 6G and beyond, large low Earth orbit (LEO) satellite constellations are proposed to provide global broadband access with digital communication payloads, advanced modulation schemes, multi-beam antennas, more sophisticated frequency reuse schemes, cost reductions from advanced manufacturing processes, and reduced launch costs. Some famous LEO satellite constellations include SpaceX’s Starlink, OneWeb, and Telesat, and Starlink has planned a mega-constellation consisting of 42,000 satellites.

Concerns arise about the sustainability of these fast-growing mega-constellations. The first concern is economic sustainability, as the revenue from the satellite Internet services may not cover the launch and maintenance costs, especially when an LEO satellite has an average lifespan of 5 years. Satellite Internet connectivity is less expensive than laying millions of miles of fiber optic cable for rural and hard-to-reach areas but is more expensive than cellular networks in densely populated metropolitan areas.

The second concern is space sustainability, as the spectrum-orbit resource is valuable and indispensable. It has been reported that the first batch of Starlink satellites has a failure ratio of at least five percent, highlighting the growing concerns that satellite mega-constellations could litter the low Earth orbit with hundreds of dead satellites.

The third concern is environmental sustainability, as the likelihood of collisions grows proportionately with mega-constellation size. Space debris may pose a hazard to Earth's atmosphere, with unexpected environmental problems. The disruptive light streaks from the Starlink satellite constellation have already affected astronomical observations, and this problem will expand with the launch of more satellites.

In this Special Issue, we invite you to submit high-quality papers on the "Sustainability of Future Satellite Communications: Opportunities and Challenges for 6G and beyond". The scope of this Special Issue is a broad and cross-disciplinary analysis of the sustainability and symmetry techniques in future satellite communications, which is aligned with the scope of the journals Sustainability and Symmetry. This Special Issue aims to draw attention to related research topics from various research communities, e.g., from the engineering, environment, and economic communities, and to help build a sustainable solution together for the unconnected in the 6G eras with symmetry techniques. To our knowledge, this research theme has not been fully discussed in the literature. The following is a (non-exhaustive) list of topics of interest:

• Information and communication engineering with satellite communications;
• Techno-economic analysis of satellite communications;
• Sustainability issues of satellite communications;
• Economic, space, and environmental sustainability of satellite communications;
• Symmetry techniques for satellite communications;
• Technological development for satellite communications;
• Novel network management schemes for satellite communications;
• Artificial intelligence techniques for satellite communications;
• Big data techniques for satellite communications;
• Sustainable infrastructures for satellite communications;
• Challenges and opportunities to develop sustainable satellite communication systems.

You may choose our Joint Special Issue in Symmetry.

Prof. Dr. Ray E. Sheriff
Dr. Ayman Radwan
Dr. Weiwei Jiang
Guest Editors

Manuscript Submission Information

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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. Sustainability 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.

• satellite communication
• communication engineering
• technical sustainability
• network management
• resource allocation
• artificial intelligence
• big data
• 6G communication