  In this paper, we consider the bacterial point-to-point and multiple-access
molecular communications with ligand-receptors. For the point-to-point
communication, we investigate common signaling methods, namely the Level
Scenario (LS), which uses one type of a molecule with different concentration
levels, and the Type Scenario (TS), which employs multiple types of molecules
with a single concentration level. We investigate the trade-offs between the
two scenarios from the capacity point of view. We derive an upper bound on the
capacity using a Binomial Channel (BIC) model and the symmetrized
Kullback-Leibler (KL) divergence. A lower bound is also derived when the
environment noise is negligible. For the TS, we also consider the effect of
blocking of a receptor by a different molecule type. Then, we consider
multiple-access communications, for which we investigate three scenarios based
on molecule and receptor types, i.e., same types of molecules with Different
Labeling and Same types of Receptors (DLSR), Different types of Molecules and
Receptors (DMDR), and Same types of Molecules and Receptors (SMSR). We
investigate the trade-offs among the three scenarios from the total capacity
point of view. We derive some inner bounds on the capacity region of these
scenarios when the environment noise is negligible.
