Spectrum resources have become increasingly scarce and valued for future mobile information systems, due to the increasing number of wireless devices and the high demand for communication quality. Dynamic spectrum access has promise in tackling this issue, as it enables unlicensed users to dynamically access the spectrum band of licensed users under the condition that the interference caused to licensed users is tolerable. To strengthen the performance of dynamic spectrum access, passive communication (PaC), including backscatter communication and intelligent reflecting surface, have recently attracted significant attention from academia and industry. By compromising a set of passive phase shifters, PaC is able to reflect the incident signals with desired phase shifts so as to combine the reflected signals with non-reflected signals in a destructive or constructive manner and inhibit detrimental interference. This can help enhance the performance of mobile information systems significantly.

However, some major challenges still exist in intelligent spectrum access in passive communication for mobile information systems. One major challenge is complicated performance analysis, where many practical applications, such as unmanned aerial vehicle-assisted three-dimensional spectrum sharing and multi-PaC enhanced cooperative spectrum sharing, need to be investigated and analyzed. A second challenge is intelligent system optimization, where multi-objective strategies based on intelligent algorithms need to be devised to achieve a good tradeoff between conflicting objectives. Another challenge is the application of intelligent non-orthogonal multiple access techniques into PaC enhanced spectrum dynamic access, as non-orthogonal multiple access techniques have advantages in spectrum efficiency and massive connectivity.

To address the above major challenges in mobile information systems, this Special Issue is to provide a new comprehensive overview on PaC and create more ideas on PaC enhanced spectrum dynamic access. This Special Issue will bring together researchers from academia, industry, and governmental agencies to promote the research and development that pertain to this cutting-edge research topic. Original research and review articles are welcome.

Potential topics include but are not limited to the following:

• Intelligent algorithm design for spectrum access
• Performance evaluation of PaC communication
• Performance evaluation of spectrum access
• Backscatter communication with spectrum access
• Intelligent reflecting surface with spectrum access
• Deep learning for PaC communication
• Federated learning for PaC communication
• Physical-layer security for PaC communication
• Unmanned aerial vehicle assisted communication
• Intelligent computing for spectrum access
• Cross-layer design for spectrum access