NTT Corporation, NTT DOCOMO, INC., and NEC Corporation successfully demonstrated real-time, bidirectional wireless transmission in the 71 GHz-to-86 GHz millimeter wave band, reaching a record-breaking bit rate of 140 Gbps (an unprecedented bit rate for sub-100 GHz frequencies).
To do so, the companies utilized orbital angular momentum (OAM) mode multiplexing transmission technology. This technology enhances wireless transmission capacity by simultaneously sending multiple radio waves, each carrying distinct signals using different OAM modes. Additionally, OAM-mode control technology extends transmission distances by leveraging reflected paths. By adjusting the phase difference of signals from the transmitting antenna, OAM creates spiraling wave patterns that can be separated at the receiving end using inverse-reception technology.
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NEC developed a real-time, OAM-mode multiplexing system capable of transmitting signals at a maximum rate of 70 Gbps per direction using a 1 GHz bandwidth in the E-band (71 GHz to 86 GHz). By enhancing digital signal processing circuits, NEC achieved a 2.6x increase in modulation rate to 300 Mbaud, supporting bidirectional communication. DOCOMO expanded the application scenarios by conducting reflection-based transmission experiments using OAM-mode inverse-reception technology. NTT further contributed by devising a circuit that doubles transmission bandwidth and implementing OAM-mode control for long-distance and reflection-based transmission.
Using eight orthogonal OAM modes and high-order 256QAM modulation, the companies achieved wireless transmission with a bandwidth of 500 MHz, attaining 139.2 Gbps over a 22.5-meter distance, 139.2 Gbps over 22.5 meters, 104.0 Gbps over 45 meters, and 139.2 Gbps over 22.5 meters. This achievement marks a significant step toward the realization of high-capacity wireless communications for 6G and beyond.
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With bit rates exceeding 100 Gbps, this advancement paves the way for the integration of both optical-fiber and wireless communication lines between fixed stations. Such high-speed, wireless connections could support flexible backhaul networks, improve connectivity at large-scale events, and provide temporary network solutions during natural disasters. These advancements are set to play a critical role in future applications such as high-definition (HD) video streaming, augmented and virtual reality (AR/VR) experiences, autonomous driving systems, and remote medical procedures.
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