From Microwave to Free Space Optical Communication
RoLa communications technology, millimetre wave transmission revolution cracks 5G networking challenges. 5G network construction faces a core contradiction: sub-6GHz band resource depletion and millimetre wave (24-100GHz) transmission distance limitation. RoLa (Radio over Laser) technology modulates RF signals with laser carriers and realises millimetre-wave band transmission over line-of-sight in free space. The measured single-hop distance is up to 3.2 kilometres (data from Fraunhofer Institute, Germany). It is more than 5 times higher than the traditional microwave relay. Its technological breakthrough is reflected in the dual-band fusion architecture – a 1550nm laser carrier carrying 28GHz/60GHz millimetre-wave signals. It circumvents spectrum licensing restrictions while maintaining a peak rate of 1.2Gbps (Tokyo Institute of Technology 2023 road test data).
The technology is reconfiguring base station deployment logic—Telefónica in Madrid pilot. By replacing 73% of fibre backhaul nodes with RoLa, the cost of building 5G base stations has been reduced by 41%, while enabling dynamic capacity provisioning in hotspot areas. This “wireless fibre” feature is especially suitable for sea islands, mountainous areas and other traditional infrastructure difficult to cover the scene.
Chemical bonding for low-power wide-area connectivity
The value of RoLa for IoT lies not only in transmission efficiency, but also in its heterogeneous network convergence capability. By relaying protocols such as LoRaWAN/ZigBee through laser links (analysis of LoRa and RoLa), IoT terminals can be directly connected to the 5G core network. Break through the protocol conversion bottleneck of traditional gateways. In the Eindhoven smart agriculture project in the Netherlands, soil sensors equipped with RoLa modules reduce the latency of data directly to the cloud to 8ms. This is a 90% improvement over the NB-IoT solution, and the life of the device is extended to 3 years.
The physical layer characteristics of the technology revolutionise security. The extremely narrow divergence angle of the laser beam of 0.5 degrees, together with quantum key distribution (QKD) technology, enables the success rate of eavesdropping to be less than 10^-9 (results of the 2024 experiments by the University of Science and Technology of China). It provides a natural protective barrier for sensitive scenarios such as industrial control and smart healthcare. Huawei’s AirPON 2.0 solution has integrated the RoLa-QKD module to realise anti-jamming control of driverless shuttle buses at Shenzhen’s Bao’an Airport.
From lab protocols to industrial consensus
The biggest challenge to RoLa industrialisation is protocol fragmentation. Currently, there are three main technology routes:
1. Direct modulation type (led by NTT in Japan): using electrical absorption modulator to achieve RF-optical signal conversion. The advantage lies in the low cost of equipment (single module <$500), but the transmission distance is limited to 1 km. 2;
2. differential mixing type (Germany HHI advance): through the optical differential receiver to enhance the sensitivity. In the haze weather still maintains more than 95% link stability, but requires precision temperature control system;
3. All-photon processing type (supported by US DARPA): adopts optical beamforming technology. Supports multi-user MIMO with air-port efficiency up to 38.9 bit/s/Hz, but the equipment complexity is extremely high.
In June 2024, ETSI established the ISG RoLa Working Group . Pushing for unified physical layer interface (ROLa-PHY 1.0) and management plane standards. The first certified products will be available in 2025Q2, and Ericsson and Nokia have announced compatibility roadmaps.
From alternative to enabling technology
RoLa is undergoing a qualitative change in its value proposition:
– Alternative value: Indonesian operator XL Axiata replaces submarine fibre optic cables with it. Cost of inter-island transmission reduced from 32k/km to 32k/km to 4800;
– Enhanced value: Tesla Berlin Superfactory deploys RoLa-Mesh network. Enabling microsecond synchronisation accuracy for AGV cluster control;
– Innovation value: SpaceX Starlink V3 satellite carrying RoLa payload. Completed the test of 100Gbps laser link from LEO satellite to ground station.
Capital market heat confirms its potential: global RoLa-related financing reaches $1.7bn in 2024. Startup Aryze Technologies’ Phased Array Laser Terminal (PAT) technology is valued at over $820 million. The device achieves beam tracking accuracy of ±0.01 degrees and supports uninterrupted connectivity in mobile scenarios.
Breaking the “weather dependent” curse
The shortcomings of traditional free-space optical (FSO) communications, which are greatly affected by weather, have been systematically improved in RoLa technology:
1. Multi-wavelength redundancy: Adoption of 1550nm/850nm dual band adaptive switching. Rain and fog attenuation is reduced to 0.8dB/km;
2. Adaptive coding: Dynamically adjusts the LDPC coding rate (from 1/2 to 9/10) according to the channel state, ensuring that the BER is always below 10^-12;
3. MIMO enhancement: 8×8 optical phased array to achieve spatial diversity. Maintains 78% transmission efficiency in sandstorm environments (UAE Etisalat incumbent network data).
Reliability verified by NEOM smart city project in Saudi Arabia: 128 RoLa nodes with an average annual failure rate of 0.2 failures/node in an environment with an average annual temperature of 46°C and 37% dusty weather. Significantly better than traditional microwave relay system.
Strategic positioning in 6G pre-research
In the 6G terahertz communication blueprint, RoLa plays a bridge role. Japan’s NICT has achieved 0.3 THz signal transmission experiments on the RoLa link, path loss than free-space propagation reduced by 24dB. This “light-carrying terahertz” technology may reshape the base station architecture – the future of the 6G small base station may be simplified as follows In the future, small 6G base stations may be reduced to optical-to-electrical converter modules, with core signal processing shifted to a centralised optical switching centre.
Even more far-reaching implications lie in the integration of air and space. The HydRON project of the European Space Agency (ESA) plans to launch a high-orbit RoLa relay satellite in 2026 to build an Earth-Moon space laser communication backbone network. When the satellite Internet converges with the terrestrial RoLa network, IoT devices may realise truly seamless global roaming. This heralds a paradigm shift in connectivity technology from “global coverage” to “smart interstellar connection”.
