14.5.1 Irda (Historical)

Prior to the widespread adoption of short-range radio technologies, personal area networking was commonly implemented using infrared (IR) light under standards defined by the Infrared Data Association (IrDA). Devices exchanged modulated infrared pulses over distances typically less than 1 m, requiring an unobstructed line-of-sight path and close alignment.

Most IrDA implementations operate in half-duplex, simplifying the optical front-end and avoiding self-interference from a device’s own transmitter. Data rates evolved from 9.6 kbit/s in early implementations to several megabits per second in later variants, but the strict line-of-sight requirement and limited range constrained usability.

By the mid-2000s, infrared networking was largely superseded by radio-based technologies. Infrared communication remains in use primarily in simple Consumer IR (CIR) applications such as remote controls, where one-way command signaling is sufficient.

The practical limitations of infrared—particularly the requirement for line-of-sight alignment and very short range—highlighted the need for a more flexible short-range networking solution. This led to the development of low-power radio-based personal area networks capable of automatic device discovery, non-line-of-sight operation, and robust performance in multipath indoor environments. Bluetooth emerged as the first widely adopted technology to satisfy these requirements.