As wireless devices have proliferated in number in recent years, wireless communication networks have become an important information infrastructure for connecting people and objects. Enormous amounts of data are being exchanged through wireless communication networks in order to perform everyday tasks such as downloading files, making online transactions, monitoring health and environments, and storing information in the Cloud.

Communication networks keep evolving to accommodate ever-increasing amounts of mobile traffic and to respond to the communication needs of various services. However, as the capacity and coverage of communication networks increase, the system’s energy consumption also increases. From an environmental perspective, the communications industry currently consumes between 2-3% of global energy and produces 2% of global CO₂ emissions, among which wireless networks account for 57% of this energy consumption. Moreover, the high energy consumption of communication networks leads to high heat dissipation and electronic pollution, while the huge number of disposed batteries for wireless devices cause many serious environmental issues. Many nations mandate that businesses, including the communications industry, adhere to global energy reforms which seek to reduce greenhouse gas emissions by 50% by 2030. As a result, 3GPP 5G specifications call for a 90% reduction in energy use. High energy consumption has been a significant concern of network operators because it accounts for approximately 20-40% of their network operational costs. From a user’s perspective, it has been shown that 60% of users complain about their limited battery capacity, even though the capacity of batteries has steadily increased over recent years.

Considering the importance of green communications and networks, this Special Issue seeks to collect relevant original research and review articles, particularly those that consider energy efficiency in 5G systems, discuss comprehensive solutions and crystalize future research directions. We invite contributions from academia and industry on recent developments that can help tackle the challenges associated with green communications and networks.

Potential topics include but are not limited to the following:

• Energy efficiency issues in 5G networks
• Energy consumption model for network nodes as well as wireless devices
• Conflict management between energy efficiency and other performance metrics
• Energy efficient device-to-device networks
• Energy efficient ultra-dense networks
• Energy efficient Internet of Things systems
• Energy efficient secure networks
• Energy efficient spectrum efficiency
• Energy efficient transmission control
• Energy efficient network resource management
• Energy efficient quality of service provisioning
• Energy harvesting and transfer
• Energy efficient network nodes and wireless devices