What’s in the works for 6G backhaul?

• NTT, NTT Docomo and NEC have collaborated on the development of a wireless technology that might meet 6G backhaul needs  
• The ultimate goal is to develop a flexible network infrastructure for future services, such as virtual/augmented reality, ultra-high-definition video transmission and, of course, connected vehicles
• The technology has been presented at the IEEE’s Wireless Communications and Networking Conference in Milan, Italy

Japan’s NTT, its mobile operator NTT Docomo and giant tech vendor NEC are working on a novel spatial multiplexing technology that, they claim, could play a key role in providing backhaul connectivity in 6G networks. 

The technology uses Orbital Angular Momentum (OAM), a property of electromagnetic waves that enables large amounts of data to be sent over limited bandwidths, even in frequency bands below 100 GHz, according to the R&D partners. As a result, the technology can achieve bi-directional wireless data transmission rates of up to 140Gbit/s on a single wavelength (twice the rate of current systems) in the millimetre-wave band between 71 GHz and 86 GHz, and can both increase transmission capacity and extend transmission distances.

All in all, claims NTT, it could play a valuable role in future for mobile operators as their data access volumes start to balloon with the introduction of 6G.

For a proof of concept, the companies conducted line-of-sight demonstrations based on three scenarios: Bidirectional transmission over a distance of 22.5 metres; bidirectional transmission over a distance of 45 metres; and bidirectional transmission over a distance of 22.5 meters using a reflector. The result was successful transmission of 139.2Gbit/s, 104GBit/s and 139.2Gbit/s, respectively. 

The latter test validated the potential of OAM-mode multiplexing technology to enable real-time bidirectional wireless transmission exceeding 100Gbit/s. NTT notes that, up until now, “OAM-mode multiplexed transmissions have focused on line-of-sight conditions that require precise alignment of transmitters and receivers” but “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 139.2Gbit/s transmissions at 22.5 metres,” stated the operator. 

The three companies say they 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 network connections. They will also seek to increase wireless transmission capacity and extend transmission distances in millimetre-wave and higher frequency bands.

They claim mobile operators could use the technology to expand backhaul infrastructure beyond traditional fibre-optic connections, enabling more flexible backhaul configurations, including applications such as wireless connectivity to mobile base stations during events and temporary backhaul lines during disasters, with a view to supporting wireless communication demands expected in the 6G era and beyond. 

Ultimately, they aim to establish flexible network infrastructure for future services, such as virtual reality (VR), augmented reality (AR), ultra-high-definition video transmission, connected vehicles and remote medical applications in the 6G era and beyond. 

The technology has been on display at this week’s IEEE Wireless Communications and Networking Conference (WCNC) held at the Mico Milano Congressi convention centre in Milan, Italy. 

– Ian Scales, Contributing Editor, TelecomTV