Highlights:

• Achieved the world's fastest real-time bidirectional wireless transmission at a total rate of 140 Gbps --- more than twice the speed of conventional technology --- using the millimeter-wave band between 71 GHz and 86 GHz, a frequency range already in practical use for wireless systems.
• Demonstrated that OAM (Orbital Angular Momentum) mode multiplexing technology increases wireless transmission capacity, while OAM-mode control technology extends transmission distances and enables the use of reflected paths.
• Enabled the construction of flexible backhaul networks using both optical fiber and wireless connections, contributing to the realization of future 6G and beyond services such as high-definition video transmission and temporary lines during disasters.

TOKYO, Mar 25, 2025 - (JCN Newswire) - NTT Corporation, NTT DOCOMO, INC. and NEC Corporation announced today that they demonstrated a real-time bidirectional wireless transmission in the millimeter wave band between 71 GHz and 86 GHz that achieved a bit rate of 140 Gbps --- unprecedented for sub-100 GHz frequencies. The test demonstrated that OAM (Orbital Angular Momentum) mode multiplexing transmission technology can increase the capacity of wireless transmission, and that OAM-mode control technology can increase wireless transmission distances by using reflected paths (Figure 1). The achievement is expected to help realize high-capacity wireless transmissions to meet future demand anticipated in the 2030s.

OAM-mode multiplexing technology increases the capacity of wireless transmissions between fixed stations by transmitting multiple radio waves, each carrying signals multiplexed with different OAM modes, at the same frequency and time. Transmissions exceeding 100 Gbps enable both optical-fiber and wireless connections for communication lines between fixed stations, facilitating the construction of flexible backhaul networks,*1 wireless connections with mobile base stations during events, and temporary lines during disasters. The research results are expected to contribute to the development of high-capacity wireless backhaul for future services such as virtual reality (VR), augmented reality (AR) and high-definition video transmission in 6G and beyond.

The results will be presented at the Wireless Communications and Networking Conference (WCNC)*2 starting March 24.

Research Background

In the 6G era, the demand for wireless communications will accelerate with the emergence of high-definition video transmission, autonomous driving, remote medical surgery, and advanced applications such as VR and AR, increasing the need for high-capacity wireless communication. NTT, DOCOMO and NEC are working to increase capacity using a novel spatial multiplexing method that uses OAM, a property of electromagnetic waves (Figure 2).

OAM, a physical quantity that describes certain properties of electromagnetic waves, is generated by adjusting the phase difference of signals from the transmitting antenna so that the same-phase trajectory spirals in the direction of propagation. On the receiving side, the phase of the received signal can be synthesized at the antenna by rotating in the opposite direction of transmission, so that radio signals corresponding to multiple OAM modes with different helix structures can be superimposed and separated without interfering with each other. Using this feature, OAM-mode multiplexing technology can transmit different data that has been spatially multiplexed, enabling large amounts of data to be sent over limited bandwidths. High-capacity wireless transmission is possible even in frequency bands below 100 GHz, where wide bandwidth is not readily available. While there is a report*3 of a successful real-time transmission test that achieved 14.7 Gbps over 40 meters in a single direction using OAM-mode multiplexing technology with digital signal processing circuits in the 71 GHz to 86 GHz band (E-band), which is used in existing wireless systems, real-time transmission capacity needs to be further increased for 6G and beyond wireless systems.

Real-time wireless transmission using OAM-mode multiplexing technology in high-frequency bands has now been demonstrated by NTT, DOCOMO and NEC, supported by research on the practical application of OAM-mode multiplexing transmission (Figure 3).

NEC has developed an OAM-mode multiplexing transmission system capable of real-time transmission at a maximum rate of 70 Gbps per direction, using a 1 GHz bandwidth signal in the E-band. This was achieved by extending conventional digital signal processing circuits*3 to increase the modulation rate by about 2.6 times to 300 Mbaud*4 while also enabling bidirectional communication in the E-band.

DOCOMO explored expanding the application scenarios of OAM-mode multiplexing transmission and conducted demonstration experiments on reflection-based transmissions, using OAM-mode inverse-reception technology for transmissions via reflections off surfaces such as walls.

NTT has devised a circuit that doubles the transmission bandwidth and an OAM-mode control technology to support long-distance transmission and reflection scenarios.

Leveraging these developments, the three companies conducted demonstrations based on three scenarios:

Bidirectional transmission over a distance of 22.5 metersBidirectional transmission over a distance of 45 metersBidirectional transmission over a distance of 22.5 meters using a reflector

The result was successful transmission of 139.2 Gbps, 104.0 Gbps and 139.2 Gbps, respectively (Figure 4).

Key Research Achievements

- Broadband Real-Time OAM Mode Multiplexing Transmission Technology: Using eight orthogonal OAM-modes and high-order modulation up to 256QAM, the team achieved wireless transmissions with a bandwidth of 500 MHz in four frequencies—74.875 GHz and 75.375 GHz for the uplink and 84.875 GHz and 85.375 GHz for the downlink. The system achieved real-time bidirectional wireless transmission of 139.2 Gbps at a distance of 22.5 meters in a sub-100 GHz band.

- OAM Mode Control Technology: In OAM-mode multiplexing transmissions, the antenna size was optimized to maximize transmission capacity according to the transmission distance. However, when operating beyond designed distances, transmission capacity typically decreased. In response, an OAM-mode control technology was developed to automatically adjust transmission parameters such as transmission power, OAM mode and modulation method. As a result, the system successfully maintained 104.0 Gbps of real-time wireless transmission over a distance of 45 meters, twice the initially designed range.

- Expanded Application Scenarios: To date, OAM-mode multiplexed transmissions have focused on line-of-sight conditions that require precise alignment of transmitters and receivers. To support flexible backhaul solutions for 6G and beyond, non-line-of-sight communication using wall reflections was investigated. Using OAM-mode inverse-reception technology, the test demonstrated that wall reflections can achieve 139.2 Gbps transmissions at 22.5 meters.

Future Outlook

The demonstration validated real-time bidirectional wireless transmission exceeding 100 Gbps using OAM-mode multiplexing technology. Such high-capacity wireless transmission technology can expand backhaul infrastructure beyond traditional fiber-optic connections, enabling more flexible backhaul configurations. This includes applications such as wireless connectivity to mobile base stations during events and temporary backhaul lines during disasters, ultimately supporting wireless communication demands expected in the 6G era and beyond.

The three companies will explore applications such as relay transmission using real-time, high-capacity wireless communications and will apply OAM-mode multiplexing technology to wireless backhaul and fronthaul networks. They will also seek to increase wireless transmission capacity and extend transmission distances in millimeter-wave and higher frequency bands. Ultimately, they aim to establish flexible network infrastructure for future services such as VR, AR, ultra-high-definition video transmission, connected vehicles and remote medical applications in the 6G era and beyond (Figure 5).

(l) Relay network that connects base stations to core communication network. 
(2) T. Kageyama, T. Yamada, R. Kudo, M. Kawai, S. Morimoto, E. Sasaki, A. Fukuda, F, Hada, Y. Suzuki, “Demonstration of real-time OAM multiplexing over 100 Gb/s in E-band,” in Proc of IEEE Wireless Communications and Networking Conference (WCNC 2025), Mar. 2025.
(3) M. Hirabe, R. Zenkyu, H. Miyamoto, K. Ikuta, and E. Sasaki, “40 M Transmission of OAM Mode and Polarization Multiplexing in E-Band,” in Proc. of 2019 IEEE Globecom Workshops, Dec. 2019.
(4) Unit representing the number of modulation changes per second.

About NTT

NTT contributes to a sustainable society through the power of innovation. We are a leading global technology company providing services to consumers and business as a mobile operator, infrastructure, networks, applications, and consulting provider. Our offerings include digital business consulting, managed application services, workplace and cloud solutions, data center and edge computing, all supported by our deep global industry expertise. We are over $97B in revenue and 330,000 employees, with $3.6B in annual R&D investments. Our operations span across 80+ countries and regions, allowing us to serve clients in over 190 of them. We serve over 75% of Fortune Global 100 companies, thousands of other enterprise and government clients and millions of consumers.

About NTT DOCOMO

NTT DOCOMO, Japan's leading mobile operator with over 90 million subscribers, is one of the global leaders in 3G, 4G and 5G mobile network technologies.Under the slogan “Bridging Worlds for Wonder & Happiness,” DOCOMO is actively collaborating with global partners to expand its business scope from mobile services to comprehensive solutions, aiming to deliver unsurpassed value and drive innovation in technology and communications, ultimately to support positive change and advancement in global society.https://www.docomo.ne.jp/english/

About NEC

NEC Corporation has established itself as a leader in the integration of IT and network technologies while promoting the brand statement of “Orchestrating a brighter world.” NEC enables businesses and communities to adapt to rapid changes taking place in both society and the market as it provides for the social values of safety, security, fairness and efficiency to promote a more sustainable world where everyone has the chance to reach their full potential. For more information, visit NEC at https://www.nec.com.

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