The Infrared Data Association (IrDA) defines physical specifications communications protocol

Communications protocol

A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...

 standard

Standardization

Standardization is the process of developing and implementing technical standards.The goals of standardization can be to help with independence of single suppliers , compatibility, interoperability, safety, repeatability, or quality....

s for the short-range exchange of data

Data

The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...

 over infrared

Infrared

Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

 light, for uses such as personal area network

Personal area network

A personal area network is a computer network used for communication among computer devices, including telephones and personal digital assistants, in proximity to an individual's body. The devices may or may not belong to the person in question. The reach of a PAN is typically a few meters...

s (PANs).

• IrDA is a very short-range example of free space optical communication.
• IrDA interface
  Network interface device
  In telecommunications, a Network Interface Device is a device that serves as the demarcation point between the carrier's local loop and the customer's premises wiring....
  
  s are used in medical instrumentation, test and measurement equipment, palmtop computers, mobile phone
  Mobile phone
  A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
  
  s, and laptop
  Laptop
  A laptop, also called a notebook, is a personal computer for mobile use. A laptop integrates most of the typical components of a desktop computer, including a display, a keyboard, a pointing device and speakers into a single unit...
  
   computers (most laptops and phones also offer Bluetooth
  Bluetooth
  Bluetooth is a proprietary open wireless technology standard for exchanging data over short distances from fixed and mobile devices, creating personal area networks with high levels of security...
  
   but it is now becoming more common for Bluetooth to simply replace IrDA in new versions of products).
• IrDA specifications include IrPHY, IrLAP, IrLMP, IrCOMM, Tiny TP, IrOBEX, IrLAN and IrSimple. IrDA has now produced another standard, IrFM
  IrFM
  Infrared Financial Messaging is a wireless payment standard developed by the Infrared Data Association.-External links:**...
  
  , for Infrared financial messaging
  IrFM
  Infrared Financial Messaging is a wireless payment standard developed by the Infrared Data Association.-External links:**...
  
   (i.e., for making payments) also known as "Point & Pay".

For the devices to communicate via IrDA, they must have a direct line of sight similar to a TV remote control.

IrPHY

The mandatory IrPHY (Infrared Physical Layer Specification) is the first (lowest) layer of the IrDA specifications.
The most important specifications are:

• Range: standard: 1 m; low power to low power: 0.2 m; standard to low power: 0.3 m
• Angle: minimum cone ±15°
• Speed: 2.4 kbit/s to 1 Gbit/s
• Modulation: baseband
  Baseband
  In telecommunications and signal processing, baseband is an adjective that describes signals and systems whose range of frequencies is measured from close to 0 hertz to a cut-off frequency, a maximum bandwidth or highest signal frequency; it is sometimes used as a noun for a band of frequencies...
  
  , no carrier
• Infrared window
• Wavelength: 875 ± 30 nm

IrDA transceivers communicate with infrared pulses (samples) in a cone that extends minimum 15 degrees half angle off center. The IrDA physical specifications require that a minimum irradiance

Irradiance

Irradiance is the power of electromagnetic radiation per unit area incident on a surface. Radiant emittance or radiant exitance is the power per unit area radiated by a surface. The SI units for all of these quantities are watts per square meter , while the cgs units are ergs per square centimeter...

 be maintained so that a signal is visible up to a meter away. Similarly, the specifications require that a maximum irradiance not be exceeded so that a receiver is not overwhelmed with brightness when a device comes close. In practice, there are some devices on the market that do not reach one meter, while other devices may reach up to several meters. There are also devices that do not tolerate extreme closeness. The typical sweet spot for IrDA communications is from 5 centimetre away from a transceiver, in the center of the cone. IrDA data communications operate in half-duplex mode because while transmitting, a device’s receiver is blinded by the light of its own transmitter, and thus, full-duplex communication is not feasible. The two devices that communicate simulate full duplex communication by quickly turning the link around. The primary device controls the timing of the link, but both sides are bound to certain hard constraints and are encouraged to turn the link around as fast as possible.

Transmission rates fall into various categories: SIR, MIR, FIR, VFIR, UFIR, and Giga-IR. Serial Infrared (SIR) speeds cover those transmission speeds normally supported by an RS-232

RS-232

In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...

 port (9600 bit/s, 19.2 kbit/s, 38.4 kbit/s, 57.6 kbit/s, 115.2 kbit/s). Since the lowest common denominator for all devices is 9600 bit/s, all discovery and negotiation is performed at this baud rate. MIR (Medium Infrared) is not an official term, but is sometimes used to refer to speeds of 0.576 Mbit/s and 1.152 Mbit/s. Fast Infrared (FIR) is deemed an obsolete term by the IrDA physical specification, but is nonetheless in common usage to denote transmission at 4 Mbit/s. FIR is sometimes used to refer to all speeds above SIR. However, different encoding approaches are used by MIR and FIR, and different approaches frame MIR and FIR packets. For that reason, these unofficial terms have sprung up to differentiate these two approaches. The future holds faster transmission speeds (currently referred to as Very Fast Infrared, or VFIR) which supports a speed of 16 Mbit/s. There are (VFIR) infrared transceivers available such as the TFDU8108 operating from 9.6 kbit/s to 16 Mbit/s. The UFIR (Ultra Fast Infrared) protocol supports a speed of 96 Mbit/s. There, 8B10B coding is used. The Giga-IR protocol supports transmission speeds of 512 Mbit/s (64MB/s) and 1 Gbit/s (125 MB/s) and uses 2-ASK and 4-ASK modulation.

These are distinguished from other similar infrared communications systems that operate outside IrDA specifications. PDA communications formats such as HPSIR and ASKIR are such. This also includes CIR (Consumer IR

Consumer IR

Consumer IR, consumer infrared, or CIR, refers to a wide variety of devices employing the infrared electromagnetic spectrum for wireless communications. Most commonly found in television remote controls, infrared ports are equally ubiquitous in consumer electronics, such as PDAs, laptops, and...

), commonly used in remote control

Remote control

A remote control is a component of an electronics device, most commonly a television set, used for operating the television device wirelessly from a short line-of-sight distance.The remote control is usually contracted to remote...

s, based on a raw protocol which uses sequences of pulse and space. It's possible to manage CIR via software like Lirc

LIRC

LIRC is an open source package that allows users to receive and send infrared signals with a Linux-based computer system.There is a Microsoft Windows equivalent of LIRC called WinLIRC....

.

IrLAP

The mandatory IrLAP (Infrared Link Access Protocol) is the second layer of the IrDA specifications. It lies on top of the IrPHY layer and below the IrLMP layer. It represents the Data Link Layer

Data link layer

The data link layer is layer 2 of the seven-layer OSI model of computer networking. It corresponds to, or is part of the link layer of the TCP/IP reference model....

 of the OSI model

OSI model

The Open Systems Interconnection model is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar...

.
The most important specifications are:

• Access control
• Discovery of potential communication partners
• Establishing of a reliable bidirectional connection
• Distribution of the Primary/Secondary device roles
• Negotiation of QoS Parameters

On the IrLAP layer the communicating devices are divided into a Primary Device and one or more Secondary Devices. The Primary Device controls the Secondary Devices. Only if the Primary Device requests a Secondary Device to send is it allowed to do so.

IrLMP

The mandatory IrLMP (Infrared Link Management Protocol) is the third layer of the IrDA specifications. It can be broken down into two parts.
First, the LM-MUX (Link Management Multiplexer) which lies on top of the IrLAP layer. Its most important achievements are:

• Provides multiple logical channels
• Allows change of Primary/Secondary devices

Second, the LM-IAS (Link Management Information Access Service), which provides a list, where service providers can register their services so other devices can
access these services via querying the LM-IAS.

Tiny TP

The optional Tiny TP (Tiny Transport Protocol) lies on top of the IrLMP layer. It provides:

• Transportation of large messages by SAR (Segmentation and Reassembly)
• Flow control by giving credits to every logical channel

IrCOMM

The optional IrCOMM (Infrared Communications Protocol) lets the infrared device act like either a serial

Serial port

In computing, a serial port is a serial communication physical interface through which information transfers in or out one bit at a time...

 or parallel port

Parallel port

A parallel port is a type of interface found on computers for connecting various peripherals. In computing, a parallel port is a parallel communication physical interface. It is also known as a printer port or Centronics port...

. It lies on top of the IrLMP layer.

OBEX

The optional OBEX

OBEX

OBEX is a communications protocol that facilitates the exchange of binary objects between devices. It is maintained by the Infrared Data Association but has also been adopted by the Bluetooth Special Interest Group and the SyncML wing of the Open Mobile Alliance...

(Object Exchange) provides the exchange of arbitrary data objects (e.g., vCard

VCard

vCard is a file format standard for electronic business cards. vCards are often attached to e-mail messages, but can be exchanged in other ways, such as on the World Wide Web or Instant Messaging...

, vCalendar or even applications) between infrared devices. It lies on top of the Tiny TP protocol, so Tiny TP is mandatory for OBEX to work.

IrLAN

The optional IrLAN (Infrared Local Area Network) provides the possibility to connect an infrared device to a local area network. There are three possible methods:

• Access Point
• Peer to Peer
  Peer-to-peer
  Peer-to-peer computing or networking is a distributed application architecture that partitions tasks or workloads among peers. Peers are equally privileged, equipotent participants in the application...
  
  
• Hosted

As IrLAN lies on top of the Tiny TP protocol, the Tiny TP protocol must be implemented for IrLAN to work.

IrSimple

IrSimple achieves at least 4 to 10 times faster data transmission speeds by improving the efficiency of the infrared IrDA protocol. A 500 KB normal picture from a cell phone can be transferred within 1 second.

IrSimpleShot

One of the primary targets of IrSimpleShot (IrSS) is to allow the millions of IrDA-enabled camera phones to wirelessly transfer pictures to printers, printer kiosks, flat panel TV's.

Popularity

IrDA was popular on PDA's, laptops and some desktops during the late 90s through the early 2000s. However, it has been displaced by other wireless technologies such as WiFi

WIFI

WIFI is a radio station broadcasting a brokered format. Licensed to Florence, New Jersey, USA, the station is currently operated by Florence Broadcasting Partners, LLC.This station was previously owned by Real Life Broadcasting...

 and Bluetooth

Bluetooth

Bluetooth is a proprietary open wireless technology standard for exchanging data over short distances from fixed and mobile devices, creating personal area networks with high levels of security...

, favored because they don't need a direct line of sight, and can therefore support hardware such as mice and keyboards. It is still used in some environments where interference makes radio

Radio

Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

-based wireless technologies unusable. IrDA popularity is making a comeback with its highly efficient IrSimple protocols by providing sub 1 second transfers of pictures between cell phones, printers, and display devices. IrDA hardware is still less expensive and doesn't share the same security problems encountered with wireless technologies such as Bluetooth.
In addition, some Pentax DSLRs (K-x, K-r) use IRsimple for image transfer and gaming.

External links

• Infrared Data Association website
• IrPro IrDA Protocol Stacks
• ZMD IRDA
• Linux Infrared HOWTO
• Linux Infrared Remote Control
• Linux status of infrared devices (IrDA, ConsumerIR, Remote Control)
• Latest IRDA developments including IrSimple, VFIR and UFIR (2005)
• IrDA project of Universidad Nacional de Colombia SIE board