IrDA
If you have a laptop or a PDA, you probably have an infrared port. Named after the Infrared Data Association, which oversees the system, IrDA is supposed to be a simple way to replace cables when printing or sending data to another PC. Millions of them are installed worldwide, theoretically making it one of the world's most popular standards. Of all wireless data technologies, its installed base is second only to SMS.
But despite its ubiquity, IrDA is hardly ever used. This is partly because at first it didn't work very well; different companies implemented the system in different ways. Although these early problems have been ironed out, the perception has stopped people from using it, which in turn has stopped vendors from implementing it on more devices. This creates a vicious circle—users won't ask for IrDA unless it's fully supported, and it won't be fully supported until users ask for it.
IrDA's creators envisaged a world where people would print simply by pointing their computers at a printer, or link up to a network by pointing it at an access point. The problem is that few manufacturers have developed these, meaning that the only thing many laptops get the chance to connect to is another laptop.
Few people have two laptops, but most laptop users do have a desktop PC. The most practical application for many users would be to synchronize the two, but so far this has been impossible. Although an infrared transceiver costs less than a dollar, almost no companies build them into desktops. A notable exception is Apple, one of IrDA's first adopters. It has been promoting infrared data since the 1980s, using a proprietary system before the standard was defined.
Types of IrDA
Over the years, IrDA has progressed almost unnoticed to increasingly faster speeds. There are now four different versions of it, with no obvious way to tell which is built into a given device. One laptop may be able to send and receive infrared more than a hundred times faster than another, even if they were built at the same time, cost the same, and had similar processor, display, and memory configurations.
Infrared is almost never an issue for people buying a laptop, so manufacturers have no incentive to fit the latest version, even if it would cost no more. Some high-speed transcribers are wrongly configured to run at the lower speeds, meaning that they can often be upgraded with software alone.
The other good news is that the different versions of IrDA differ only in their data rate and are entirely backward-compatible. A new device ought to be able to work with an older one, albeit at the slower speed.
SIR (Serial Infrared) was the original standard and ran at 115 kbps. This is the same speed as a standard serial port, on which the IrDA protocol was based.
MIR (Medium Infrared) runs at 1.152 Mbps, fast enough to transmit or receive television-quality video. It is not widely implemented, with most systems choosing either the serial or fast versions.
FIR (Fast Infrared) offers speeds of up to 4 Mbps. This is built into most new computers and is the standard setting on Windows 98 and 2000.
VFIR (Very Fast Infrared) goes up to 16 Mbps, and is not yet widely implemented. Undeterred, the Infrared Data Association is working on even further upgrades, and claims it can push the ports up to a blistering 50 Mbps.
Such high data rates may seem like overkill for simple file transfer between computers, but the plan is for IrDA to be incorporated into other devices, such as digital cameras and mp3 players. At the current 4 Mbps, a full CD's worth of music in mp3 format would take longer than six minutes to transfer to a player, compared to less than 30 seconds at 50 Mbps.
Infrared LANs
Although designed only to connect two points together, IrDA can also be used to form complex networks. The principle is the same as for most Ethernet LANS—every computer is connected separately to a central switch through which all data passes.
An IrDA-based LAN isn't as useful as a radio-based wireless LAN, because the range is usually shorter and it requires a line of sight between the switch and the terminal. But it has one enormous advantage—the infrared port is already built into many laptops. It consumes much less power than a separate plug-in card, and people can't lose it or forget it (unless they lose the entire computer).
Because the data rates available from IrDA vary so much, nearly all these systems are switched. An ordinary hub would try to transmit all data to every computer, which would limit PCs equipped with 16 Mbps VFIR to the 0.1 Mbps of SIR.