Performance Limits of Spatially Distributed Molecular Communications With Receiver Saturation

Molecular via diffusion are affected by unreliability and inter symbol interference in case of single transmitter. A promising solution to these issues appears to be the adoption of a swarm of randomly distributed transmitting nano-devices and a single spherical receiver. However, such a perspective assumes the receiver as fully absorbing (i.e., able to absorb an unlimited number of molecules per second). In this letter, we show that, if this assumption is relaxed, increasing the number of point transmitters leads to a saturation effect which makes communication impossible when digital transmission is considered. By means of a first and second order spatio-temporal stochastic model, we analytically derive the maximum allowed point transmitters density before saturation arises, as a function of parameters such as the diffusion coefficient, the maximum number of absorbed molecules, and the number of previously transmitted symbols. The analysis is validated via Monte Carlo simulation.