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).<>