Synchronization Error Robust Transceivers for Molecular Communication

Molecular communication has been proposed as a signaling mechanism to enable communication between nano-machines via molecular diffusion. Precise synchronization of transmitters and receivers is particularly challenging in diffusive molecular communication environments due to the propagation characteristics. To mitigate sensitivity to synchronization errors, a decision feedback equalizer, sequential probability ratio test (DFE-SPRT) based receiver and an approximate maximum-likelihood delay estimator are derived. The performance of the delay estimator is shown to be close to a Cramér-Rao bound at low transmission rates. Numerical results show that the DFE-SPRT makes a decision well before the full symbol interval is exhausted; the desirability of this effect is theoretically justified through the adaptation of the analysis of the log-loss function for mismatched Poisson random variables. Performance bounds on the DFE-SPRT are employed to design optimized modulation for the mis-synchronized communication channel. The proposed receiver and modulation designs achieve strongly improved asynchronous detection performance for the same data rate relative to recently proposed receiver designs that also exploit decision feedback.