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IrDA™ and Bluetooth Wireless Communication Compared

IrDA is an infrared wireless communication technology developed by the Infrared Data Association. Here we compare and contrast specific features of these technologies.

IrDA is a specific use of infrared light as a communications medium; Bluetooth technology is a specific use of radio waves as a communications medium. Like the Bluetooth special interest group (SIG), the IrDA specifies hardware and software protocols for wireless communication intended to promote interoperable applications.

Although both technologies are wireless, they use different parts of the electromagnetic spectrum with quite different signal propagation characteristics. Because infrared uses the nonvisible infrared light spectrum, IrDA communication is blocked by obstacles that block light (such as walls, doors, briefcases, and people). The signal wavelength used with Bluetooth communication (about 12.5 cm, at its associated frequency of 2.4GHz) is three orders of magnitude greater than that of IrDA. At this wavelength, radio frequency (RF) communications can penetrate many of these sorts of obstacles. Recent advances in infrared technology have enabled more diffuse transmission patterns, although much of the IrDA equipment in use today uses a relatively narrowly focused beam, which usually requires that the two devices engaged in IrDA communication be aligned with (pointed at) each other. RF transmission patterns radiate in some pattern (ideally, spherical) around the radio antenna, so any two devices within range can communicate with each other, whether or not they are "pointed at" each other (in fact, the second device might not be visible at all to the user of the first device, as it could be in another room behind doors and walls or even on another floor of a building, for example).

The initial IrDA data rate of 115 kilobits per second (Kbps) has now been enhanced to 1 megabit per second (Mbps), comparable to that of the first Bluetooth radios. Today, IrDA can achieve data rates of up to 4Mbps, with even higher rates already specified and beginning to be implemented. Bluetooth wireless communication occurs at a raw data rate of 1Mbps, with higher speeds being investigated.

The effective range for Bluetooth wireless communication is about 10 meters using the standard 0 dBm radio. With optional power amplification of up to 20 dBm, range on the order of 100 meters can be achieved. IrDA range is about 1 meter and, as noted already, generally requires a line of sight to establish a connection.

Both Bluetooth wireless technology and IrDA communication are optimized for low power consumption and low cost. Compared to other RF communication technologies, Bluetooth communication consumes very little power and is projected to have very low module costs in the foreseeable future. However, IrDA consumes significantly less power than Bluetooth technology, because far less power is required for infrared transceivers than for RF transceivers. IrDA hardware also already is less expensive than Bluetooth radio modules, owing largely to the maturity and wide deployment of IrDA.

This brief discussion indicates that IrDA technology compares favorably to Bluetooth technology in the areas of cost, power, and data rate. However, Bluetooth technology can add convenience and user mobility by relaxing the device alignment and line of sight requirements of IrDA communications. This illustrates an additional design parameter for WPANs: enhanced device usability enabled by the unconscious application of communications technology. RF technologies are well suited for this aspect of WPANs, and Bluetooth wireless technology further emphasizes device usability characteristics in the profiles. All of these considerations, both objective and subjective, may influence the choice of a WPAN technology for a particular application.

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