In this paper, we design a drug release mechanism for dynamic time division multiple access (TDMA)-based molecular communication via diffusion (MCvD). In the proposed scheme, the communication frame is divided into several time slots over each of which a transmitter nanomachine is scheduled to convey its information by releasing the molecules into the medium. To optimize the number of released molecules and the time duration of each time slot (symbol duration), we formulate a multi-objective optimization problem whose objective functions are the bit error rate (BER) of each transmitter nanomachine. Based on the number of released molecules and symbol durations, we consider four cases, namely: static-time static-number of molecules (STSN), static-time dynamic-number of molecules (STDN), dynamic-time static-number of molecules (DTSN), and dynamic-time dynamic-number of molecules (DTDN). We consider three types of medium in which the molecules are propagated, namely: mild diffusive environment (MDE), moderate diffusive environment (MODE), and severe diffusive environment (SDE). For the channel model, we consider a 3-dimensional (3D) diffusive environment, such as blood, with drift in three directions. Simulation results show that the STSN approach is the least complex one with BER around $text{10}^{text{-2}}$, but, the DTDN is the most complex scenario with the BER around $text{10}^{text{-8}}$.
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