  Molecular communication is a biologically-inspired method of communication
with attractive properties for microscale and nanoscale devices. In molecular
communication, messages are transmitted by releasing a pattern of molecules at
a transmitter, which propagate through a fluid medium towards a receiver. In
this paper, molecular communication is formulated as a mathematical
communication problem in an information-theoretic context. Physically realistic
models are obtained, with sufficient abstraction to allow manipulation by
communication and information theorists. Although mutual information in these
channels is intractable, we give sequences of upper and lower bounds on the
mutual information which trade off complexity and performance, and present
results to illustrate the feasibility of these bounds in estimating the true
mutual information.
