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IrDA is an acronym for the Infrared Data Association, an organization which sets communications standards for infrared over small distances. IrDA has been around since 1993, as an overseeing body for a wide group of infrared technologies. Traditionally, infrared devices, such as old television remote controls, use a one-way beam. They send information out, but aren't capable of receiving information back. Bi-directional infrared devices are substantially more complicated than one-way emitters, and so IrDA formed to help maintain a set of standards everyone could stick to.
IrDA devices include printers, cameras, handheld portables, smart remotes with display screens, cell phones, and even new smart bank cards. IrDA devices are quite cheap, with the parts that make them up costing only pennies, making them attractive for use in a wide range of devices. Because IrDA beams are directional, they are relatively secure from eavesdropping and other unauthorized forms of access to information sent over their channel.
The range on IrDA devices is intended to be approximately 3 feet (1m), but in practice some devices have smaller ranges than this, while others may have ranges near 10 feet (3m). Current bandwidth can reach up to 16Mbps (megabytes per second), though technology in development may propel that maximum speed to in excess of 100Mbps. Even mid-level speeds will usually reach the 1-4Mbps range, which is on a par with the parallel ports traditionally used with devices such as printers and cameras.
The specifications of IrDA are given as different levels, with higher levels stacking on top of lower ones. The basic level of IrDA specs is the Infrared Physical Layer Specification (IrPHY), which is necessary in all IrDA devices. This spec lays out the angle limits, speed range, distance range, and modulation for an IrDA device.
The second and third layers of the IrDA specification, which are both also required, are the Infrared Link Access Protocol (IrLAP) and Infrared Link Management Protocol (IrLMP). The IrLAP outlines the ways in which an IrDA device finds and connects with another IrDA device. The IrLMP outlines how service provider lists can be made available, as well as how different data channels are found.
Some of the optional protocols an IrDA device might employ are the IrLAN, Tiny TP, and IrFM. The IrLAN specification gives guidelines for how to allow an IrDA device to connect to a traditional local-area network. The Tiny TP specification has methodologies for transmitting large messages easily and with little data interference. The IrFM specification is relatively new, and intended to allow devices such as PDAs or cell phones to act as wireless sources of funds. These devices can be pointed at IrFM-enabled devices such as next-generation subway terminals or soda machines to deduct money from an account and handle the transaction automatically.