Issue 55 Uncrewed Systems Technology Apr/May 2024 Sellafield’s UAV equipment l Applied EV Blanc Robot l Battery tech l Robotican’s Goshawk l UGVs l UAVHE RW1 rotary l Roboat UVD l Autopilots l Arkeocean UVD l UMEX 2024 l CycloTech UVD

Platform one Researchers in China have created an alllight real-time communications network to enable seamless connectivity across space, in air and underwater (writes Nick Flaherty). Different light sources are combined to provide connectivity, initially to and from fixed nodes. It can support wired and wireless device access simultaneously, and carry out bidirectional data transmission between network nodes. “This wireless network enables uninterrupted connectivity across environments for two-way, real-time data transmission between the network nodes carrying out communication and data exchange within and between networks,” said research team leader Yongjin Wang of Nanjing University of Posts and Telecommunications. The network uses blue light for underwater communication as seawater has a reduced absorption window for blue-green light, allowing it to travel farther underwater than other wavelengths. So the system can be used to control uncrewed underwater vehicles or establish communications between underwater devices and buoys. White LEDs are used to transmit information between objects such as buoys or ships that are above water. For connections with airborne devices, such as UAVs, deep ultraviolet light is used as this avoids interference from sunlight. bandpass filter isolates the desired light signals from those in the other spectra.” The researchers showed the all-light network could accomplish full-duplex real-time video communication and transmission of sensor data, images and audio files via wired and wireless access. When 2560 x 1440-pixel and 1920 x 1080-pixel real-time videos at 22 frames per second were fed into the network, they remained clear with little lag. A network packet analysis tool showed a maximum packet loss ratio of 5.80% and a transmission delay of less than 74 ms. “The all-light communication could be used in oceans and lakes, where sensors gather ecological data and communicate with surface buoys,” said Wang. Light Space-air-sea connectivity Finally, for point-to-point communications in free space, near-infrared laser diodes are applied because they emit directional light with high optical power. The researchers designed the network so that it allows wireless or wired access to the internet, based on the TCP/IP scheme, making it useful for real-time connections. “It was important to establish a unified transmission mode from communication with blue light, white light, deep UV wavelengths and laser diodes, so we can integrate them using Ethernet switches,” said Wang. “The LEDs and modulation schemes determine network throughput, while the avalanche photodiode limits the transmission range, and an optical Is your job search lacking focus? Frustrated at looking for autonomous and robotics related engineering vacancies on generic job boards? Visit for a clearer view of what’s on offer. Different light sources are combined to provide connectivity