On the Capacity of Point-to-Point and Multiple-Access Molecular Communications With Ligand-Receptors

In this paper, we consider bacterial point-to-point and multiple-access molecular communications with ligand-receptors. For point-to-point communication, we investigate common signaling methods, namely, the level scenario, in which the information is encoded into multiple concentration levels of a single molecule type, and the type scenario, in which the information bits are encoded in multiple molecule types each with a single concentration level. We investigate the tradeoffs in the two scenarios in terms of the capacity. We derive an upper bound on the capacity using a Binomial channel model and the symmetrized Kullback-Leibler divergence. A lower bound is also derived when the environmental noise is negligible. We also consider the blocking effect of a receptor by a different molecule type. Finally, we study multiple-access communications, for which we investigate three scenarios based on molecule and receptor types: 1) same molecule types with different labeling and the same receptor types; 2) different molecule types with different receptor types; and 3) the same molecule types with the same receptor types. We investigate the tradeoffs in the three scenarios in terms of the total capacity. We derive inner bounds on the capacity region of these scenarios when the environmental noise is negligible.