Future of Physical Layer Technologies for 6G Wireless Communication Networks

Dear Colleagues,

The conceptualization of sixth-generation (6G) networks has begun to sustain the competitive edge of wireless communication networks. The initial research schedule of 6G was released in February 2020, and the vision, and the technical study of 6G will be completed by 2023. Compared to 5G (IMT-2020), 6G networks will achieve superior performance and introduce new performance metrics. Additionally, 6G networks will be the solution to the bandwidth demands of the post-2030 world and will provide advanced functions, such as ultra‑high throughput, ultra‑high reliability, ultra‑low latency, massive connectivity, global coverage, better intelligence and security levels, etc. The key features of 6G networks will be a transmission data rate up to 1 Tbps, a spectral efficiency up to 1000 bps/Hz/m², reliability up to a 10⁹ frame error rate, mobility support up to 1000 km/h, a C-plane latency of less than 1 ms, a processing delay of 10 ns, traffic capacity up to 1–10 Gbps/m², connectivity up to 10⁷ devices/km², and full integration of artificial intelligence (AI). New air interface and transmission technologies, including new waveforms, multiple access schemes, channel coding methods, multi-antenna technologies, dynamic spectrum sharing, multi-connectivity/radio resource management techniques for uRLLC, and AI-based wireless accessing and networking will be required for 6G. The novel network architectures of 6G include softwarization, virtualization, slicing, cloudification/fog/edge, and Intelligence. In addition, 6G networks will enable extensive spectrum exploration in the mmWave, sub-6 GHz, terahertz, optical bands, non-terrestrial/terrestrial/maritime communications for cost-effective/seamless/ubiquitous services, AI/ML integration for better network management/automation/dynamic network orchestration, and endogenous network security from the network to physical layers. Consequently, 6G will improve network performance in all aspects, including quality of service, quality of experience, security, fault management, and spectral/energy/cost efficiency, and will handle the big datasets generated by extremely heterogeneous networks in diverse communication scenarios. Key enabling technologies/approaches for 6G include massive multi-antenna technologies, coexistence of variable radio access technologies, tactile internet, blockchain, free duplexing and spectrum sharing, e‑health/bio sensing, photonics defined radio, quantum communications, and robotics and automated vehicles for beyond the Industry 4.0 era.

The modification and exploitation of promising physical layer technologies and fundamental topics (e.g., complex signal processing, channel modeling, coding techniques, and transceiver design and hardware implementations) are required to be implemented in the 6G era. This Special Issue aims to cover a wide range of research in the broader domain of physical layer technologies for 6G and solicits high-quality original research papers that identify and discuss novel techniques, concepts, innovations, potential use cases, open research problems, technical challenges, and promising solution methods from the perspective of the physical layer. Prospective authors are invited to submit original manuscripts on topics including but not limited to:

• Massive MIMO systems (e.g., cell-free massive MIMO, beamspace massive MIMO, holographic beamforming, and orbital angular momentum‑aided MIMO);
• Adaptive signal processing and analytical modeling and design;
• Novel modulation and coding techniques (e.g., channel modeling and propagation);
• Transceiver and antenna designs (e.g., metasurface-based transceivers for high frequency bands);
• Radio resource and interference management;
• Communications over terahertz (i.e., 0.1–10 THz) and mmWave (i.e., 30–300 GHz) bands;
• Emerging networks such as wireless powered networks, aerial/terrestrial networks (e.g., UAV, satellite), vehicular ad hoc networks (e.g., V2V, V2X, and V2I), and cooperative relaying networks;
• Advanced solutions such as NOMA, reconfigurable intelligent surfaces, joint sensing and communication, small cells, and full-duplex communications;
• Spectrum inter-operability and dynamic spectrum allocation (e.g., cognitive radio);
• Requirements/solutions for 6G physical layer;
• Testbeds/experimentation for the prototyping of physical layer in 6G systems;
• Energy-efficient operations (e.g., wireless power transfer, energy harvesting);
• Network security (e.g., physical layer security techniques);
• Physical layer technologies to support 6G massive IoT;
• Mobile edge/fog computing;
• AI techniques and ML/deep learning algorithms for the physical layer design and optimization (e.g., MIMO signal detection, real-time channel estimation, multi-user detection).

Dr. Waqas Khalid
Dr. Heejung Yu
Dr. Song Noh
Dr. Rashid Ali
Guest Editors

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• 6G
• Physical layer
• MIMO
• Channel modeling
• Artificial intelligence