Engineering an Interstellar Communications Network by Deploying Relay
  Probes
  We develop a model for an interstellar communication network that is composed
of relay nodes that transmit diffraction-limited beams of photons. We provide a
multi-dimensional rationale for such a network of communication in lieu of
interstellar beacons. We derive a theoretical expression for the bit rate of
communication based on fundamental physics, constrained by the energy available
for photons and the diffraction of the beam that dilutes the information by the
inverse square law. We find that meter-scale probes are severely limited in
their bit rate, under 1 Gbps, over distances of a light year. However, that bit
rate is proportional to the 4th power of the size of the optics that transmit
and receive the photons, and inversely proportional to the square of the
distance between them, thus favoring large optics and short separations between
nodes. The optimized architecture of interstellar communication consists of a
network of nodes separated by sub-light-year distances and strung out between
neighboring stars.
