  We consider nanonodes randomly distributed in a circular area and
characterize the received signal strength when a pair of these nodes employ
molecular communication. Two communication methods are investigated, namely
free diffusion and diffusion with drift. Since the nodes are randomly
distributed, the distance between them can be represented as a random variable,
which results in a stochastic process representation of the received signal
strength. We derive the probability density function of this process for both
molecular communication methods. Specifically for the case of free diffusion we
also derive the cumulative distribution function, which can be used to derive
transmission success probabilities. The presented work constitutes a first step
towards the characterization of the signal to noise ratio in the considered
setting for a number of molecular communication methods.
