Effects of Framing Errors on the Performance of Molecular Communications With Memory

In conventional digital communication systems, synchronous transmission is achieved by embedding the clocking information into the data signal. However, the implementation of this technique in molecular communication systems, which rely on the diffusion of molecules as information carriers, becomes very complex due to the randomness of the diffusion process. Hence, in this paper we consider the molecular communication between two nanoscale devices with no exchange of any clock signal. To initiate the communication, the transmitter sends a special molecular symbol called beacon in order to trigger the detection process in the receiver. Therefore, this beacon symbol is equivalent to the start bit used for framing in asynchronous serial communication systems. We assume that both transmitter and receiver clocks are perfect, but not synchronized. Accordingly, the analysis focuses on the effects of framing errors on the performance of the molecular channel, measured via the symbol error probability. These errors are inherent to the random nature of the beacon arrival instant, which tends to degrade the alignment between the transmitter and receiver frames. We also assume a molecular channel with any level of inter-symbol interference and the use of different types of molecules to encode information symbols. We validate the derived SEP expression by means of extensive simulation experiments, and finally we develop a design scheme for the beacon symbol that satisfactorily mitigates the effects of framing errors.