Demodulation of Reaction Shift Keying Signals in Molecular Communication Network with Protein Kinase Receiver Circuit

This paper is concerned with the performance of diffusion-based molecular communication when both the transmitter and receiver are molecular circuit based or chemical reaction based. On the transmitter side, we use Reaction Shift Keying (RSK) which is a recently proposed modulation scheme. RSK uses different chemical reactions to generate different emission patterns for different transmission symbols. On the receiver side, we use a molecular circuit found in living organisms. This circuit uses multiple intermediate chemical species and negative feedback. The information on the transmitted symbol is contained in the time series of the counts of the intermediate species. If the receiver measures the counts of some of these intermediate species, it can use these counts to infer the symbol sent by the transmitter. We are interested to study how the choice of measurements and negative feedback affect the communication performance in terms of symbol error rate. We address these questions by first deriving the optimal demodulator using the maximum a posteriori framework and Bayesian filtering. We learnt two lessons from this study. First, there is a pattern in the form of the optimal demodulation filters where the rates of reactions leading to the production or consumption of the measured chemical species play a strong role. Second, negative feedback can impact on the communication performance in different ways depending on which chemical species are measured.