5G Evolution and the Road to 6G – Insights from NTT DOCOMO

At the 6G Global Summit in Mobile Korea 2024, Takehiro Nakamura, Chief Standardisation Officer at NTT DOCOMO, shared his technical perspective on the evolution of 5G towards 6G. His talk focused on how existing technologies can be enhanced and extended while new ones are introduced to prepare for the next generation of mobile communication.

Nakamura-san emphasised that operators still face the challenge of monetising 5G, but work on 6G must progress in parallel. The development of 6G should not be seen as a replacement but rather as an evolution, building on the solid technical foundations laid by 5G.

A key theme in his presentation was the vision of cyber–physical fusion, where massive amounts of real-world data are continuously collected, processed in the cyber domain using AI, and acted upon instantly in the physical world. To enable this type of real-time, AI-driven loop, networks will need significant advances in throughput, latency, reliability, energy efficiency, and coverage.

Among the technologies central to this evolution is the extension of millimetre-wave (mmWave) coverage. Nakamura-san noted his enthusiasm for wider mmWave deployment in 5G to ensure it remains relevant and usable in the 6G era. NTT DOCOMO is exploring innovative approaches, including metasurface lenses, reconfigurable intelligent surfaces (RIS), and radio-over-fibre solutions to enhance coverage and performance. Trials have demonstrated how metasurface lens films applied to building windows can focus radio signals indoors, drastically improving indoor mmWave coverage when combined with repeaters. Similarly, RIS technology has shown strong potential to extend coverage in non-line-of-sight areas, although practical use cases and deployment models are still being studied.

Beyond terrestrial enhancements, NTT DOCOMO is also preparing for the integration of non-terrestrial networks (NTN). The operator sees value in a multi-layer NTN approach combining geostationary (GEO), low Earth orbit (LEO), and high-altitude platform systems (HAPS). Each layer offers different performance and coverage characteristics suited to specific use cases. DOCOMO has already upgraded its GEO services, started business collaborations with LEO operators, and plans to begin HAPS services in 2026 in partnership with Airbus and other companies. The shorter distance of HAPS systems makes them particularly attractive for high-performance connectivity in disaster zones, construction sites, remote islands, and even maritime or aeronautical use cases. Interworking between terrestrial and non-terrestrial systems will be essential to ensure seamless service continuity for users without manual intervention.

Nakamura-san also described DOCOMO’s 6G simulation work, which provides valuable insights into the potential performance gains of new technologies before physical trials are conducted. Using detailed 3D point cloud data from real environments such as factories and shopping malls, DOCOMO’s ray-tracing based simulator helps visualise coverage and capacity improvements under various configurations. This approach allows for flexible testing and supports collaboration with partners to optimise deployment strategies.

Artificial intelligence remains another major focus. DOCOMO is working on both AI for networks and networks for AI. The operator has been experimenting with AI-driven radio access network optimisation, including trials with Nokia and SK Telecom. These tests have shown promising improvements, such as reduced reference signal overhead and lower block error rates, leading to around 30% performance gains in some cases. DOCOMO’s findings suggest that AI-based solutions can adapt flexibly across different propagation environments, paving the way for more intelligent and efficient radio systems in 6G.

Taken together, these efforts highlight DOCOMO’s dual strategy of strengthening 5G while advancing towards 6G. The operator’s research into mmWave enhancement, non-terrestrial network integration, simulation-based evaluation, and AI-driven optimisation all form part of a continuous roadmap. Rather than a disruptive leap, 6G is being shaped as a natural evolution, an extension of 5G’s capabilities designed to enable the fully intelligent, cyber–physical future that lies ahead.

His talk is embedded below:

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