  A key challenge in Molecular Communications (MC) is low data transmission
rates, which can be addressed by channel multiplexing techniques. One way to
achieve channel multiplexing in MC is to leverage the diversity of different
molecule types with respect to their receptor binding characteristics, such as
affinity and kinetic binding/unbinding rates. In this study, we propose a
practical multiplexing scheme for MC, which is based on the diversity of
ligand-receptor binding affinities. This method requires only a single type of
promiscuous receptor on the receiver side, capable of interacting with multiple
ligand types. We analytically derive the mean Bit Error Probability (BEP) over
all multiplexed MC channels as a function of similarity among ligands in terms
of their receptor affinities, the number of receptors, the number of
multiplexed channels, and the ratio of concentrations encoding bit-1 and bit-0.
We investigate the impact of each design parameter on the performance of
multiplexed MC system.
