  Exact analytical channel models for molecular communication via diffusion
(MCvD) systems involving multiple fully absorbing receivers (FARs) in a
three-dimensional (3- D) medium are hard to obtain due to the mathematical
intractability of corresponding diffusion equations. This work, therefore,
consider an MCvD system with two spherical FARs in a 3-D diffusion-limited
medium and develop several insights using an approximate analytical expression
for the hitting probability of information molecule (IM). Further, based on the
hitting probability, a novel approximate closed-form analytical expression for
the area under the receiver operating characteristic curve (AUC) is derived to
analyze the detection performance at each FAR in the presence of other FAR.
Finally, simulation results are presented to validate the analytical results
using the particle-based and Monte-Carlo simulations and to yield important
insights into the MCvD system performance with two FARs
