Current studies on modulation and detection schemes in molecular communication mainly focus on the scenarios with static transmitters and receivers. However, mobile molecular communication is needed in many envisioned applications, such as target tracking and drug delivery. Until now, investigations about mobile molecular communication have been limited. In this paper, a static transmitter and a mobile bacteriumbased receiver performing random walk are considered. In this mobile scenario, the channel impulse response changes due to the dynamic change of the distance between the transmitter and the receiver. Detection schemes based on fixed distance fail in signal detection in such a scenario. Furthermore, the intersymbol interference (ISI) effect becomes more complex due to the dynamic character of the signal which makes the estimation and mitigation of the ISI even more difficult. In this paper, an adaptive ISI mitigation method and two adaptive detection schemes are proposed for this mobile scenario. In the proposed scheme, adaptive ISI mitigation, estimation of dynamic distance and the corresponding impulse response reconstruction are performed in each symbol interval. Based on the dynamic channel impulse response in each interval, two adaptive detection schemes, concentration-based adaptive threshold detection (CATD) and peak-time-based adaptive detection (PAD), are proposed for signal detection. Simulations demonstrate that, the ISI effect is significantly reduced and the adaptive detection schemes are reliable and robust for mobile molecular communication.

Molecular communication is a promising communication paradigm which enables information exchange by emitting and sensing molecules at a micro- or nano-scale. Time synchronization is a basic but important issue for molecular communication. This letter proposes a maximum likelihood estimator for the clock offset between two nanomachines in a molecular communication system with drift. In a directional fluid medium, the transmitter nanomachine records the message sending time instant and passes it to the receiver. The receiver uses this information to estimate the clock offset. Newton-Raphson method is used to approximate the maximum likelihood estimator. The conditions of the channel parameters, such as the flow velocity, the distance between the transmitter and the receiver, and the diffusion coefficient, are discussed. The simulation results validate the effectiveness of the proposed estimator.

Molecular communication (MC) enables conveying information at nano- to micro- scales via molecules or nanoscale particles. MC systems for fixed transmitter and receiver nanomachines have been extensively investigated. However, the scenarios for mobile MC are seldomly studied. In the paper, the mutual information and achievable rate in the presence of inter-symbol interference (ISI) and noise for the mobile MC is investigated. The scenario that both the transmitter and the receiver are in independent random motions is considered. Due to the mobility, the channel impulse response (CIR) varies and results in a varying received signal with varying signal-dependent noise. This further leads to the random variation of the probability density functions of received concentration for symbols which further generates varying error probability and therefore varying mutual information and maximum achievable rate. In this work, the mutual information and maximum achievable rate for mobile MC scenario are derived and analyzed. The impacts of different parameters such as the initial transmitter-receiver distance, number of released molecules, symbol interval, the mobility of nanomachine, and priori probabilities of transmitted symbol on the mutual information and maximum achievable rate in mobile MC scenario are studied by simulation investigations.

Molecular communication offers new possibilities in the micro-and nano-scale application environments. Similar to other communication paradigms, molecular communication also requires clock synchronization between the transmitter and the receiver nanomachine in many time-and control-sensitive applications. This letter presents a novel high-efficiency blind clock synchronization mechanism. Without knowing the channel parameters of the diffusion coefficient and the transmitter-receiver distance, the receiver only requires one symbol to achieve synchronization. The samples are used to estimate the propagation delay by least square method and achieve clock synchronization. Single-input multiple-output (SIMO) diversity design is then proposed to mitigate channel noise and therefore to improve the synchronization accuracy. The simulation results show that the proposed clock synchronization mechanism has a good performance and may help chronopharmaceutical drug delivery applications.

Targeted drug delivery system is believed as one of the most promising solutions for cancer treatment due to its low-dose requirement and less side effects. However, both passive targeting and active targeting rely on systemic blood circulation and diffusion, which is actually not the real “active” drug delivery. In this paper, an ant-behavior inspired nanonetwork composing of intelligent nanomachines is proposed. A big intelligent nanomachine take small intelligent nanomachines and drugs to the vicinity of of the tumor area. The small intelligent nanomachines can coordinate with each other to find the most effective path to the tumor cell for drug transportation. The framework and mechanism of this cooperative network are proposed. The route finding algorithm is presented. The convergence performance is analytically analyzed where the influence of the factors such as molecule degradation rate, home-destination distance, number of small nanomachines to the convergence is presented. Finally the simulation results validate the effectiveness of the proposed mechanism and analytical analysis.

Molecular communication (MC) is a promising paradigm, which conveys messages at the nano- or micro- scale for information exchange by using molecules or particles as signal carriers. Clock synchronization between transmitters and receivers in MC systems plays an important role in information exchange and nanodevices’ collaboration. The current research about the synchronization mainly focuses on fixed MC systems. However, the movements of transmitters and receivers commonly exist in MC systems. In this paper, two clock synchronization schemes, the least square method and the peak time method, are proposed to estimate the clock offset between a mobile transmitter and a mobile receiver in mobile MC systems. The synthesis time of information molecules is also taken into consideration in the proposed schemes, and by using different types of molecules, the influence of the synthesis time of molecules can be solved. The effects of the movement of receiver on the received signal are discussed. The performance of the proposed schemes is evaluated by simulations and discussed.