In the A5 algorithms, after generating 114 bits each for down and upstream, does the pseudo random number generator get set to 0000 at the end of each frame? So it is reinitialized at the next frame with 64-Bit-Kc, 22-Bit-Frame-COUNT and then the 100 cycles, whose output is discarded, before finally producing output again? Or is the generator simply paused and continues from the saved state at the next burst?
Yes, it is reinitialized in each frame, with a new COUNT (derived from the frame number) as the input. However, a mobile subscriber might even be assigned multiple timeslots on one frame, in which case there is a different calculation for COUNT. but the re-initialization happens at every time slot, regardless of how COUNT is calculated. For further info see Barkan et al. Instant Cyphertext-only ... 2003