IrDA stands for the Infrared Data Association, which is a standard controlled by another of the previously mentioned groups. This organization is responsible for standardizing the hardware and software protocols that make up this wireless technology designed for the PAN (see Figure 2.6).
Figure 2.6. Personal area network.
IrDA is a wireless technology that facilitates the communication of devices that only need to transmit or receive small amounts of information. Because this technology is cheap, it is integrated into all sorts of personal devices, such as watches , PDAs, phones, laptops, and even wireless mice and keyboards. Although Bluetooth (discussed in the next section) threatens to take over the PAN market, IrDA will be around for some time to come.
IrDA's strength is its versatility. It is a standard all to itself, which makes it simple and cheap to integrate into almost anything. However, it has multiple weaknesses that are closely tied to its functionality.
IrDA uses timed pulses of light to transmit data using a simple light bulb wired into a circuit board (see Figure 2.7) ”in other words, a computerized version of a flashlight. By turning a light on and off at modulated times, it transmits data bit by bit up to 4Mbps. Although this is sufficient for many uses, such as a mouse or watch programming, a file over 1MB will take several minutes to transmit, and then only if the IrDA devices are right next to each other.
Figure 2.7. Close-up of an IrDA light source on a circuit board.
Because IrDA uses light as its data medium, it is subject to transmission problems in a lighted environment. For example, office room lights flicker at 60Hz because of the AC current modulation. You don't see this because your brain doesn't detect it, but electric lights and most other light emitting devices go on and off 60 times a second. If the light is too bright, it will scramble the data as it is being transmitted.
For those of you who like to design circuits, adding a 60Hz "spike" filter to your receiving device can minimize this interference.
In addition, distance becomes an issue for IrDA. Typically, an IrDA device will not work beyond one meter. Although slower pulse times can increase this distance, anything slower than a solid 4Mbps, at a realistic range of several meters is inefficient by modern standards.
Still, IrDA will be around for a while. However, it will probably remain exclusively in devices that can only be used within a few feet of each other.