  In this paper, we consider a molecular diffusion based communications link
that conveys information on the macro-scale (several metres). The motivation is
to apply molecular-based communications to challenging electromagnetic
environments. We first derive a novel capture probability expression of a
finite sized receiver. The paper then introduces the concept of time-aggregated
molecular noise at the receiver as a function of the rate at which the sensor
can self-cleanse. The resulting inter-symbol-interference is expressed as a
function of the sensor cleanse time, and the performance metrics of bit error
rate, throughput and round-trip-time are derived. The results show that the
performance is very sensitive to the sensor cleanse time and the drift
velocity. The paper concludes with recommendations on the design of a real
communication link based on these findings and applies the concepts to a
test-bed.
