> I often wonder if there is even one ham working on adapting > the existing > ham DRM type protocol to a pipelined ARQ connected mode that has > adaptability to conditions.
I think no. The main problem of arq-drm is the very long turnaround time. It's in the 20sec range. This makes "normal" arq like in pskmail or packet a very lame thing. The only work-around is the thing digital sstv does. keep the number of arq cycles as low as possible. This is done by sending out all data at once (20kb or more), and then getting the not-ack's (there are no ack's) for all the lost segments (packets, 400ms data chunks) at once. This does work very well for large amounts of data, but is not good for small (less 5k) data transfers.
