Point-and-see picture transfer requires no setup, employs IrDA
By Graham Prophet, EDN Europe -- EDN, January 4, 2007
As a long-term supplier of transceivers to the IrDA (Infrared Data Association) market, Sharp Microelectronics is promoting the IrSimple "special case" of that standard for sending pictures from camera phones to televisions. Sharp expects that this task—informal sharing of pictures among family or colleagues—will be an attractive feature for camera-phone makers to offer. IrSimple allows fast picture transfer with virtually no setup procedure. Compared with the original IrDA specification—possibly one of the most widely deployed yet least-used interfaces—IrSimple increases transfer speed by stripping off most of the preamble and postdata "wrapping" that IrDA uses to ensure correct transmission and to facilitate retransmission of data blocks if any data is missing or corrupted. According to Sharp, the rationale is that, in the case of sending a picture for immediate display, users have equally immediate feedback if the transmission has failed; they see a poor picture or no picture at all. In that case, they can retransmit the picture themselves without the overhead of a protocol to do it for them.
The raw data rate remains the same as with IrDA 1.3: 4 Mbps. With the "reduced" protocol, the connection-setup time is 0.2 seconds as opposed to 3 seconds, and almost all the 4-Mbps data rate is available to deliver the payload, as opposed to an effective rate of approximately 500 kbps with IrDA. The overall effect, Sharp says, is that a typical JPEG of 150 kbytes takes 0.5 seconds in IrSimple versus 5 seconds in IrDA. The company contends that the usage model—point the phone at the television from approximately 1m away and see the picture almost instantly—is an intuitive process that suits the task and may do the same for other informal, "closed-system" data transfers at lower cost than alternatives, such as Bluetooth or Wi-Fi. Bluetooth Version 1.1, Sharp points out, would take more than 30 seconds to transfer the same picture.
