[RIIM] Does RIIM use FEC (forward error correction)? If not, why?

RIIM does not use FEC.

RIIM uses short packets, so if anything happens on the channel, much of the packet will be lost, so a re-transmission is smarter than trying to re-build a packet which we lost most of. FEC is used more when you have long packets because damage is done to a small part of the packet, then re-construction is feasible, and a re-transmission is a waste of time and bandwidth.