The power that deep space probes have allows an RF communication capacity of a few kbps from a range like Pluto-Earth. If we go into optics, the range will be better. But, of course, we want to send scouts (small probes) to far away galaxies. This would potentially require having a chain of communication relays (or repeaters, let's say).
How can we send these repeaters, and at what periods, so that they always keep moving like a train, and so that we keep communications with the probe?
(irrelevant, but, the repeaters would probably be smaller, but they should be able to travel the same speeds as the probe, and should have one beam towards the probe (or the forward Repeater), and another beam towards the behind repeater)