Flow control by giving credits to every logical channel.
Transportation of large messages by SAR (Segmentation and Reassembly).The optional Tiny TP ( Tiny Transport Protocol) lies on top of the IrLMP layer. 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 by querying the LM-IAS. Allows change of primary/secondary devices.It can be broken down into two parts.įirst, the LM-MUX (Link Management Multiplexer), which lies on top of the IrLAP layer. The mandatory IrLMP ( Infrared Link Management Protocol) is the third layer of the IrDA specifications. Only if the primary device requests a secondary device to send, is it allowed to do so. The primary device controls the secondary devices. On the IrLAP layer the communicating devices are divided into a "primary device" and one or more "secondary devices". Distribution of the primary/secondary device roles.Establishing of a reliable bidirectional connection.Discovery of potential communication partners.It represents the data link layer of the OSI model. It lies on top of the IrPHY layer and below the IrLMP layer. The mandatory IrLAP ( Infrared Link Access Protocol) is the second layer of the IrDA specifications. 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.
The two devices that communicate simulate full-duplex communication by quickly turning the link around. 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 typical sweet spot for IrDA communications is from 5 to 60 cm (2.0 to 23.6 in) away from a transceiver, in the center of the cone. There are also devices that do not tolerate extreme closeness. In practice, there are some devices on the market that do not reach one meter, while other devices may reach up to several meters. The IrDA physical specifications require the lower and upper limits of irradiance such that a signal is visible up to one meter away, but a receiver is not overwhelmed with brightness when a device comes close. IrDA transceivers communicate with infrared pulses (samples) in a cone that extends at least 15 degrees half angle off center. Combined with a low bit error rate of generally <10 −9, that communication could be very efficient compared to other wireless solutions. Finally, data blocks up to 8 MB can be sent at once. This can be adjusted with a parameter called "window size" (1–127). Additionally, bigger blocks of data can be transferred by sending multiple frames consecutively. The frame size depends on the data rate mostly and varies between 64 B and 64 kB.
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