KDDI, KDDI Research, and Samsung Research have achieved a peak downlink speed of 3.6 Gbps in an outdoor field trial using the 7 GHz band, highlighting the potential of higher-frequency spectrum and advanced antenna technologies for future 6G networks.
The companies conducted the trial from August 18 to 20 at Samsung Electronics’s Seoul R&D Campus. The test used a base station equipped with eXtreme multiple-input multiple-output (X-MIMO) technology and 1024 quadrature amplitude modulation (1024 QAM) across a 100 MHz bandwidth.
KDDI said the trial achieved a peak downlink data rate of 3.6 Gbps, which it described as the world’s highest speed per unit in a 100 MHz bandwidth.
The result was achieved by combining X-MIMO‘s directional transmission capabilities with 1024 QAM. Higher-order modulation can transmit more data using the same bandwidth, but it requires sufficiently high signal quality.
In the same test environment, the companies achieved 3.0 Gbps using 256 QAM, a modulation scheme used in current 5G systems. Moving to 1024 QAM increased the measured data rate to 3.6 Gbps, representing a 20% improvement.
The trial also examined a key challenge associated with using spectrum around 7 GHz: propagation loss. Signals at these frequencies generally travel shorter distances and experience greater propagation loss than signals in lower-frequency Sub-6GHz bands.
KDDI and Samsung used multiple antenna elements to improve signal transmission and found that the 7 GHz system achieved coverage comparable to Sub-6 GHz base stations at the same location within the measured test area.
The coverage result is significant because the availability of additional mid-band spectrum could give future mobile networks more capacity, while advanced antenna techniques could help mitigate some of the coverage limitations associated with higher frequencies. However, the field test result does not establish that 7 GHz can universally match Sub-6 GHz coverage; the comparison was limited to the test environment and measured area.
The 7 GHz range is being considered as potential spectrum for future IMT/6G services. Spectrum in the broader 7 GHz-to-8 GHz range is among the frequencies being considered in the international regulatory process, with relevant discussions scheduled for the ITU World Radiocommunication Conference 2027 (WRC-27). The outcome of those discussions will help determine the future regulatory framework for the use of these frequencies for mobile services.
KDDI said the trial forms part of its broader work on high-capacity, low-latency networks to support growing traffic associated with AI and other data-intensive services. The operator is also pursuing its Digital Belt Initiative, which aims to connect communications networks with AI computing infrastructure.
For the wider 6G industry, the trial provides another demonstration of how higher-frequency spectrum, large-scale antenna arrays, and higher-order modulation could work together to increase wireless capacity. Commercial 6G networks, however, will depend on future spectrum decisions, standardization, equipment development, and further testing under a broader range of deployment conditions.
KDDI and KDDI Research said they will continue research and development into wireless technologies designed to deliver higher speeds and greater network capacity.