cteristics The Infrared Data Association (IrDA) began life in 1993 as a non-profit organisation with the aim of promoting the use of infrared communication links between PCs and other devices by developing and supporting standards to ensure hardware and software interoperability. The group Wireless PAN Standards published its first standard in June 1994, including the specification of the Serial Ir Link (SIR) which uses infrared to replace the serial interface cable. Since then IrDA has grown to be the most widespread wireless connection technology, with over 250 million IrDA compliant interfaces shipped in 2004. IrDA is a low-cost, low-power, serial data connection standard that supports a half-duplex, point-to-point connections with a range of at least one metre and a data rate of up to 115 kbps (SIR and standard power mode). IrDA operates at a wavelength of roughly 1 um compared to 12.5 cm for Bluetooth at 2.4 GHz. Unlike the omnidirectional coverage achievable with RF transmitters, IrDA's point-to-point connection model requires the Ir transceivers to be aligned within +30° in order for the receiver to be illuminated with the required minimum power density (Figure 10-10). This physical requirement makes IrDA well suited for some applications, like secure simple object exchange, but not SO well suited for others, such as ad-hoc networking or supporting audio or telephony headsets. IrDA has also been successful in developing generic protocols, such as the OBEX (object exchange) protocol, which allows devices to exchange objects such as business cards, files, pictures and calendar items. This was introduced by IrDA in 1997, and has been broadly adopted as a simple solution for object exchange over various transport options, including TCP/IP and Bluetooth. Half angle 15° OK; angular misalignment but within beamwidth enabled device Not OK; angular alignment but outside beam width Figure 10-10: IrDA Device Alignment Chapter Ten Protocol Stack The IrDA protocol stack supports data link initialisation and shutdown, c