Edge-position modulation for high-speed wireless infrared communications

Driven by the Infrared Data Association (IrDA), wireless infrared communication has become a very popular and widely used method for short-range data transmission between mobile devices such as laptops, PDAs and mobile phones. The quality and speed of infrared communications are mainly limited by the bandwidth of the infrared transceivers. Therefore, it is important to use a modulation technique with a high bandwidth efficiency, while simultaneously maintaining a low bit-error rate and high power efficiency. Consequently, the IrDA has continuously improved the modulation techniques of its standards by introducing return to zero (inverted), RZ(I), for the serial infrared (SIR) mode, 4-pulse position modulation (4-PPM) for the fast infrared (FIR) mode and HHH(1,13) for the latest very fast infrared (VFIR) mode (serial infrared physical layer specification, version 1.4, May 2001). This article presents a new modulation scheme called edge position modulation (EPM) with run-length-limited (RLL) coding, which offers an increased bandwidth efficiency over the previous methods and an attractive power efficiency. Since the novel modulation technique can be optimised to the characteristics of the wireless infrared channel, it also maintains low bit-error rates.