If I did my calculations right, you're at about 30 meters per half bit. Not sure about your environment, but it would seem like 30m isn't far enough especially considering possible strong ir reflective surfaces. My guess is that you'd end up with at least some dead areas, possibly a lot of dead areas, where a simple on off bitstream couldn't be recovered. This is even more true if you are relying on reflections to get the ir signal through. If you decide to try this, please report back with your findings as I'm kinda curious. It would be interesting to investigate whether one of the rf digital modulation methods (ofdm/qam, psk, etc) could be applied. Some of these are multipath sensitive, some are not so much. One possible ic resource is the power line modems such as the max2990. These are generally ofdm modems in various frequency bands. On Dec 26, 2017 12:26 PM, "Harold Hallikainen" wrote: Several years ago I designed a system that transmits audio and data over IR. The audio is transmitted as frequency modulated RF over IR. The data is transmitted is frequency shift keyed RF over IR. I've been thinking about direct digital modulation of the IR. The IR LEDs would be pulsed. The bit rate to carry the audio and digital would need to be in the area of 5 Mbps. Does anyone have experience, thoughts, or references on this? The IR is transmitted in a large room (movie theater auditorium). I'm concerned about reflections causing intersymbol interference. What do people think would be a good method of encoding the data (async, biphase, etc.)? Are such systems existing? Are there any chip sets? Thanks! Harold -- FCC Rules Updated Daily at http://www.hallikainen.com Not sent from an iPhone. -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .