  In this paper, a diffusion-based molecular communication channel is modeled
in presence of a probabilistic absorber. The probabilistic absorber is an
absorber which absorbs molecules upon collision with probability q. With random
walk analysis, the discrete probability function of particle location in the
presence of a probabilistic absorber can be found. Then, a continuous
probability function is fitted to this Markov-based results with introducing
several fitting parameters to the known probability function of particle
location in an unbounded environment without an absorbing barrier. With this
approach, a single receptor is modeled as an M/M/1/1 queue in which q
represents the complementary blocking probability and the mean service time is
the mean trafficking time. Therefore, we are able to model the stochastic
nature of ligand-receptor binding, which comes from the incapability of a
receptor to receive all molecules in its space; and also known as receptor
occupancy. The proper consideration of the absorption effect leads to the
accurate calculation of the concentration at the desired site, which is
definitely less than the concentration obtained when neglecting it. These
findings can have a crucial role in designing drug delivery systems in which
determining the optimal rate of the drug transmitting nanomachines is critical
to avoid toxicity while maintaining effectiveness.
