A Time-Slotted Molecular Communication (TS-MOC): Framework and Time-Slot Errors

Abstract

Synchronization is a critical issue in molecular communications (MC). Additionally, the lack of an appropriate time-slotted framework for MC systems hinders the in-depth analysis of desynchronization. Therefore, this paper addresses both issues. First, taking inspiration from oscillators found in nature, we propose a time-slotted framework suitable for MC systems where the time instances of the oscillations demarcate the time-slot boundaries. The use of biological oscillators readily satisfies biocompatibility requirements. We name such system as a time-slotted molecular communication-based (TS-MOC) system. A TS-MOC system will be beneficial to many MC applications, such as when multiple nanomachines have to transmit data simultaneously to a control/sink node or share the channel in a time-division multiplexing manner. Second, oscillation perturbations induce desynchronization - the misalignment of time-slots. Desynchronization combined with large propagation delay results in a time difference between the arrival of a signal and the beginning of a time-slot. This phenomenon is called time-slot error, and it can degrade a system's performance. Therefore, the immediate goal is to mitigate time-slot errors. Depending on the initiation type, we propose two synchronization schemes: sender-initiated time-slot alignment and receiver-initiated time-slot alignment. An analytical model for time-slot error is also derived. Our analysis demonstrates that the proposed schemes are robust and energy-efficient - they achieve relatively low errors indicating robustness and relatively less synthesizing energy costs indicating energy efficiency. Our analysis also highlights the good agreement between the simulations and the analytical model. Finally, in conclusion, we provide brief insights into key open research challenges.