  In this paper, we consider a mobile molecular communication (MC) system
consisting of two mobile nanomachines, a transmitter and a receiver, propelled
by a positive drift velocity and Brownian motion in a realistic
blood-vessel-type flow regime. Considering the nonlinear movement of the
nanomachines, an extended Kalman filter is employed to estimate the distance
from the transmitter. Furthermore, based on the predicted distance, to keep the
number of received molecules for bit 1 at a stable level, we employ power
control on the number of transmitted molecules based on the distance between
the transmitter and the receiver and the residual molecules in the channel from
the previous transmission. Finally, the optimal detection threshold is obtained
by minimizing the error probability. It is verified that a fixed optimal
detection threshold can be effective for the power control scheme in the mobile
MC. The bit error rate (BER) performance of our scheme is verified via
simulation results.
