  This work considers the problem of flow-induced diffusive molecular
communication under various mobility conditions such as (i) both transmitter
(TX) and receiver (RX) nanomachines are mobile, (ii) TX is mobile and RX is
fixed, and (iii) TX is fixed and RX is mobile. Closed-form expressions for the
probability density function (PDF) of the first hitting time under the
aforementioned mobile scenarios are derived, by characterizing the movement of
the nanomachines and information molecules using Brownian motion with positive
drift. The derived PDF expressions are validated through particle-based
simulations. Based on these results, the performance of molecular communication
with on-off keying (OOK) modulation in flow-induced diffusive channels is
investigated. In particular, closed-form expressions for the probabilities of
detection and false alarm with optimal Likelihood ratio test (LRT) based
decision rule, probability of error, and the capacity in the presence of
inter-symbol interference, counting errors, and noise from the other sources
are derived. Simulation results are presented to verify the theoretical results
and to yield insights into the system performance for different mobility
conditions.
