Using infrared impulses to transmit data asynchronously

This paper presents a data transmission technique using infrared pulse modulation which differs from usual schemes such as FSK or bi-phase PPM. It is based on HDLC-like frames including the `bit stuffing´ mechanism. HDLC is basically a synchronous transmission oriented protocol, used here however to transmit an asynchronous flow of characters. The automatically inserted `flags´ maintain a `data carrier´ when no data character is pending for transmission. The modem described has been primarily designed for providing a low-cost, low-energy, continuous high-speed data communication channel between moving automatic vehicles (AGV´s) and static infrastructures (AGV traffic control)