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]] Siemens CXT70 ]] The Infrared Data Association ('''IrDA''') defines physical specifications Communications Protocol Standard s for the short-range exchange of Data over Infrared light, for uses such as Personal Area Network s (PANs).
For the devices to communicate via IrDA they must have a direct line of sight. SPECIFICATIONS IrPHY The mandatory IrPHY ('''Infrared Physical Layer Specification''') is the lowest layer of the IrDA specifications. The most important specifications are:
IrDA transceivers communicate with infrared pulses in a cone that extends minimum 15 degrees half angle off center. The IrDA physical specifications require that a minimum 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 will support speeds up to 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 is also in development. It will support speeds up to 100 Mbit/s. 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 of the OSI Model . The most important specifications are:
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 it is 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:
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:
IrCOMM The optional IrCOMM ('''Infrared Communications Protocol''') lets the infrared device act like either a Serial or Parallel Port . It lies on top of the IrLMP layer. IrOBEX The optional IrOBEX ('''Infrared Object Exchange''') provides the exchange of arbitrary data objects (e.g. VCard , VCalendar or even applications) between infrared devices. It lies on top of the Tiny TP protocol, so Tiny TP is mandatory for IrOBEX 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:
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. IrSimple protocol maintains backward compatibility with the existing IrDA protocols. 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 and printer kiosks. SEE ALSO EXTERNAL LINKS
LITERATURE Charles D. Knutson with Jeffrey M. Brown, IrDA Principles and Protocols, 2004, ISBN 0-9753892-0-3 |
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