Amplify-and-forward relaying in mobile multi-hop molecular communication via diffusion

In this paper, we investigate amplify-and-forward (AF) relaying scheme for mobile three-dimensional (3D) multi-hop molecular communication via diffusion (MCvD) in the stochastic channel by using different type of molecules (DTM) and same type of molecules (STM) in each hop, respectively. Under the DTM scheme, both the inter-symbol interference (ISI) and the noise of each link are taken into account Compared with the DTM scheme, an additional factor should be considered for the STM scheme, which is the self-interference (SI) effect. Under DTM and STM, we derive the mathematical expressions of optimal detection thresholds at receiver node in mobile two-hop MCvD system by using the maximum-a-posterior (MAP) decision method. Then we extend the analysis to mobile multi-hop MCvD system. Furthermore, the performances of bit error probability and mutual information are evaluated via particle-based simulation of the Brownian motion. The numerical and simulation results reveal that the performance under DTM outperforms that under STM, which indicates the potential of AF relaying scheme under DTM to improve the overall performance of this system. Besides, the comparison results between mobile and static multi-hop link under DTM and STM are given. The obtained results are expected to provide guidance significance for designing mobile multi-hop MCvD system with lower bit error probability and higher mutual information.