Evaluating the Maturity of 5G and the Rise of Optical/THz Architectures for 6G

Abstract

5G was developed to address growing mobile traffic demands with higher spectral efficiency, multi-gigabit data rates, and low-latency access. While 5G delivers improvements over LTE, realworld performance falls short of early projections due to spectrum scarcity, RF propagation loss at higher frequencies, and the cost of network densification. These constraints are structural and limit the scalability of radio-only architecture. As global data consumption continues to accelerate, future networks are expected to transition toward optical wireless communication (OWC) and terahertz (THz) bands, which provide orders of magnitude more bandwidth and
enable tightly directional links to reduce interference. Moreover, integrated sensing and communication (ISAC) architectures are emerging as a necessary enabler for device awareness, mobility robustness, and resource-efficient 6G operation. This paper evaluates the current maturity of 5G within its physical and infrastructural limitations and analyzes the role of optical and THz systems as foundational spectrum domains for functional 6G networks.