Performance of amplitude modulation schemes for molecular communication over a fluid medium

In this paper, we consider three different amplitude modulation schemes for molecular communication through a fluid medium with a positive drift velocity. The channel is divided into time slots of equal duration and transmission is done at the beginning of every slot. The molecules, transmitted by a nanomachine, propagate via Brownian motion and reach the receiver nanomachine. The amplitude levels are represented by the number of molecules transmitted. The communication is corrupted by randomness due to diffusion as well as interference from the previous slots. Considering maximum likelihood detection at the receiver, the probability of error is analyzed for all the three schemes, and its variation with the parameters involved is studied. The results are also compared with previously proposed time modulation schemes, where the information is encoded as the transmit time of molecules.