Enzymatic cycle-based receivers with high input impedance for approximate maximum a posteriori demodulation of concentration modulated signals

Molecular communication is a bio-inspired communication paradigm where molecules are used as the information carrier. This paper considers a molecular communication network where the transmitter uses concentration modulated signals for communication. Our focus is to design receivers that can demodulate these signals. We impose three features on our receivers. We want the receivers to use enzymatic cycles as their building blocks, have high input impedance and can work approximately as a maximum a posteriori (MAP) demodulator. No receivers with all these three features exist in the current molecular communication literature. We consider enzymatic cycles because they are a very common class of chemical reactions that are found in living cells. Since a receiver is to be placed in the communication environment, it should ideally have a high input impedance so that it has minimal impact on the environment and on other receivers. Lastly, a MAP receiver has good statistical performance. In this paper, we show how we can use time-scale separation to make an enzymatic cycle to have high input impedance and how the parameters of the enzymatic cycles can be chosen so that the receiver can approximately implement a MAP demodulator. We use simulation to study the performance of this receiver. In particular, we consider an environment with multiple receivers and show that a receiver has little impact on the bit error ratio of a nearby receiver because they have high input impedance.