  Molecular communication (MC) allows nanomachines to communicate and cooperate
with each other in a fluid environment. The diffusion-based MC is popular but
is easily constrained by the transmit distance due to the severe attenuation of
molecule concentrations. In this letter, we present a decode-and-forward (DF)
relay strategy for the reversible binding receptor in the diffusion-based MC
system. The time-varying spatial distribution of the information molecules
based on the reversible association and dissociation between ligand and
receptor at the surface of receiver is characterized. An analytical expression
for the evaluation of expected error probability is derived, and the key
factors impacting on the performance are exploited. Results show that with a
constant molecular budget, the proposal can improve the performance
significantly, and the performance gain can be enhanced by optimizing the
position of the relay node and the number of molecules assigned to the source
node.
