Researchers at Tokyo Polytechnic University have presented a simple and cost-effective wireless data transmission system using LEDs. The project boasts stable outdoor operation, even in bright sunlight, and could form the basis for future solutions in intelligent transportation systems.
The technology is based on data transmission via visible light, a method increasingly considered an alternative to radio communications, especially in conditions of congestion, interference, or regulatory restrictions. LEDs integrated into streetlights and traffic lights can be used not only for lighting but also for information exchange. However, in practice, such systems often face challenges such as pulse distortion and interference from external light.
The proposed solution is based on the novel 8B13B encoding scheme, developed specifically for such applications. It is implemented on a field-programmable logic gate array ( FPGA ) connected to a Raspberry Pi microcomputer via a standard SPI interface. The system uses exclusively commercially available components.
The encoding uses a zero-return format, maintaining a balance between ones and zeros, eliminating flicker and ensuring stable synchronization . The primary objective is to capture the rising edge of the light pulse, compensating for pulse width variations caused by the LED response characteristics. This design ensures stable data transmission even in bright light conditions , including direct sunlight with an intensity exceeding 90,000 lux.
In experiments, the system demonstrated data transmission rates of up to 3.48 Mbps over a distance of approximately three meters. To improve the receiver’s accuracy, the team used multiple photodiodes and a narrowband optical filter to reduce the effects of background light.
The new development can be used to transmit video signals from road infrastructure to vehicles, for example from intersections or blind spots. This could improve road safety, including in autonomous driving. Furthermore, the developed platform can be used for educational purposes, combining analog electronics, digital logic, and software in a single system.
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