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Molecular communication via diffusion (MCvD) is one of the paradigms in nanonetworks. Finding an approximation or analytical solution for the fraction of the received molecules to analyze the channel behavior is essential in molecular communication. Current studies propose approximations to model simple channel topologies, i.e. topologies with few nodes. To model complex channel topologies, time-consuming particle-based Monte Carlo simulations are used. We propose MCvD-Transformer to avoid the time-consuming simulations and estimate the fraction of the received molecules for complex topologies. MCvD-Transformer is trained via instances containing various topologies and time-dependent estimations for a fraction of received molecules estimated by particle-based Monte Carlo simulations. Finally, MCvD-Transformer is compared with both the studies in the literature and the simulations. As a result, MCvD-Transformer performs better than literature studies in terms of root mean squared error and maximum normalized absolute error metrics on our test dataset. Therefore, the proposed model is more accurate in modeling complex MCvD topologies than the current state of the art without time-consuming simulations. Additionally, it is expected to be a benchmark for the works that focus on complex MCvD topologies. [Display omitted] • Estimation of the expected fraction of the received molecules until time t for complex and generic 3D MCvD channel topologies using ANN. • Elimination of time-consuming simulations. • Being a benchmark for future studies focusing on complex topologies. [ABSTRACT FROM AUTHOR]

We investigate mobile multiple-input multiple-output (MIMO) molecular communication via diffusion (MCvD) system which is consisted of two source nodes, two destination nodes and one relay node in the mobile three-dimensional channel. First, the combinations of decode-and-forward (DF) relaying protocol and network coding (NC) scheme are implemented at relay node. The adaptive thresholds at relay node and destination nodes can be obtained by maximum a posteriori (MAP) probability detection method. Then the mathematical expressions of the average bit error probability (BEP) of this mobile MIMO MCvD system based on DF and NC scheme are derived. Furthermore, in order to minimize the average BEP, we establish the optimization problem with optimization variables which include the ratio of the number of emitted molecules at two source nodes and the initial position of relay node. We put forward an iterative scheme based on block coordinate descent algorithm which can be used to solve the optimization problem and get optimal values of the optimization variables simultaneously. Finally, the numerical results reveal that the proposed iterative method has good convergence behavior. The average BEP performance of this system can be improved by performing the joint optimizations. [ABSTRACT FROM AUTHOR]

Mobile molecular communication via diffusion (MCvD) has attracted lots of attentions due to its time-varying channels. In this paper, we investigate a mobile two-way MCvD model, which consists of two mobile source nanomachines and a mobile relay nanomachine. The amplify-and-forward (AF) relaying and analog network coding (ANC) are utilized to implement the exchange of information between two source nanomachines in this model. To explore the performance of the mobile two-way MCvD system, we first adopt the depleted molecule shift keying (D-MoSK) modulation, and then the mathematical expressions of symbol error probability (SEP) and mutual information are derived by using AF and ANC scheme on the basis of maximum a posteriori (MAP) probability detection. Finally, we present the numerical and simulation results. Compared with the AF-No-ANC scheme which is without use of ANC scheme, the scheme of combining AF and ANC can significantly improve the performance of SEP and mutual information. Moreover, the D-MoSK modulation outperforms the molecule shift keying (MoSK) modulation for this mobile two-way MCvD system. In addition, we propose the evaluation and discussion about the impacts of several important parameters on the performance of this system. These results can be used to design mobile two-way MCvD system with lower SEP and higher mutual information. [ABSTRACT FROM AUTHOR]

In this letter, we consider a 3D molecular communication via diffusion system (MCvDS) with a single point transmitter and multiple fully-absorbing spherical receivers whose centers are distributed as a Poisson point process (PPP) in the medium. We derive the probability that a transmitted molecule hits any of the receivers within time $t $. We consider both degradable and non-degradable molecules. We verify the analysis using particle-based simulation. The framework can be used for various applications, e.g., to derive event detection probability for systems where the IMs are transmitted to convey the occurrence of a particular event to trigger reactions at receivers or can be used as channel models for such systems. [ABSTRACT FROM AUTHOR]

Molecular communication via diffusion (MCvD) is a method of achieving nano- and micro-scale connectivity by utilizing the free diffusion mechanism of information molecules. The randomness in diffusive propagation is the main cause of inter-symbol interfe-rence (ISI) and the limiting factor of high data rate MCvD applications. In this paper, an apertured plane is considered between the transmitter and the receiver of an MCvD link. Either after being artificially placed or occurring naturally, surfaces or volumes that resemble an apertured plane only allow a fraction of the molecules to pass. Contrary to intuition, it is observed that such topology may improve communication performance, given the molecules that can pass through the aperture are the ones that take more directed paths towards the receiver. Furthermore, through both computer simulations and a theoretical signal evaluation metric named signal-to-interference and noise amplitude ratio (SINAR), it is found that the size of the aperture imposes a trade-off between the received signal power and the ISI combating capability of an MCvD system, hinting to an optimal aperture size that minimizes the bit error rate (BER). It is observed that the trend of BER is accurately mirrored by SINAR, suggesting the proposed metric’s applicability to optimization tasks in MCvD systems, including finding the optimal aperture size of an apertured plane. In addition, computer simulations and SINAR show that said optimal aperture size is affected by the location of the aperture and the bit rate. Lastly, the paper analyzes the effects of radial and angular offsets in the placement of the apertured plane, and finds that a reduction in BER is still in effect up to certain offset values. Overall, our results imply that apertured plane-like surfaces may actually help communication efficiency, even though they reduce the received signal power. [ABSTRACT FROM AUTHOR]

Molecular communications has recently emerged as a new form of information transfer that uses chemical signals as information carriers. Alongside their novel applications in communications theory, chemical signals may also be utilized for various other applications, such as abnormality detection, direction finding, and entity localization. Among localization tasks, current literature mainly focuses on locating active entities that emanate chemicals, whereas the localization of a silent entity (e.g., an eavesdropper) is rarely considered. Exploiting the fact that different positions of a silent entity yields different received signals at the sensing device, this letter introduces a machine learning-based approach to detect the presence of a silent entity and localize it. Overall, the study shows that such a localization task is also achievable in cases where a clear analytical formula characterizing the received signal is not available, and provides a framework for further research on silent entity localization approaches. [ABSTRACT FROM AUTHOR]

In this paper, spatial transmission techniques in the area of multiple-input multipleoutput (MIMO) diffusion-based molecular communications (DBMC) are investigated. For transmitter-side spatial coding, Alamouti-type coding and repetition MIMO coding are analyzed. At the receiver-side, selection diversity and equal-gain combining are studied as combining strategies. Throughout the numerical analysis, a symmetrical 2 × 2 MIMO-DBMC system is assumed. Furthermore, a trained artificial neural network is utilized to acquire the channel impulse responses. The numerical analysis demonstrates that there is no spatial diversity gain in the DBMC system under investigation, but that it is possible to achieve an array gain instead. In addition, it is shown that for MIMO-DBMC systems repetition MIMO coding is superior to Alamouti-type coding.

In emerging Internet-of-Nano-Things (IoNT) and molecular communication (MC), digital information will be embedded in chemical molecules in order to propagate through complex and absorbing media. However, two main challenges in signal detection are the intensive inter-symbol-interference (ISI) and the severe background noise, which may heavily deteriorate the reliability of molecular communications. This may be even worse when facing unknown channel impulse response (CIR), which is common in the industrial practice of MCs, rendering most of coherent signal detection schemes in traditional wireless communications less attractive. In this paper, we propose an improved non-coherent signal detection scheme, aiming at addressing ISI and noise contamination in the absence of CIR. Specifically, we utilized three non-coherent metrics to characterize transient features of received signals, and furthermore, designed an optimized combination scheme for more reliable signal detections. Given that the significance of each non-coherent metric remains unknown, we devise a self-adaption method premised on the concept of deflection coefficient, which can recursively determine the optimal combination weights. Numerical simulations demonstrate that our proposed scheme significantly improves the detection performance in terms of bit error rate (BER), and outperforms the adaptive threshold detection (ATD) method over 7 dB. [ABSTRACT FROM AUTHOR]

Benefiting by the fast development of nanotechnology, molecular communication (MC) has received great attention in recent years. In many potential applications of MC, such as drug delivery and pollution prevention, it is essential to locate or trace the target. In this paper, we consider a 3D diffusive MC environment consisting of several obstacles, a molecule-releasing source (RS) and a mobile molecule sensor (MS) which aims to find the RS within a time constraint. The problem is reformulated using Markov Decision Process (MDP) and an adaptive multi-layer reward based Q-Learning (AMR-Q Learning) approach is proposed. By exploiting information from the number of received molecules and adaptively setting multi-layer rewards, MS with AMR-Q Learning can find the RS efficiently, unlike the gradient based method which is usually trapped in locally optimal points. Numerical results demonstrate that the proposed AMR-Q Learning approach outperforms existing path-planning schemes with significantly reduced training overhead. [ABSTRACT FROM AUTHOR]

Molecular communication via diffusion in vessel-like environment targets critical applications such as the detection of abnormal and unhealthy cells. In this letter, we derive the analytical formulation of the channel model for diffusion dominated movement, considering ring-shaped (i.e., patch) observing receivers, and Poiseuille flow with the aim of localization of the transmitter cell. Then, we derive formulations using this channel model for two different application scenarios. We assume that the emission start time is known in the first scenario and unknown in the second one. We successfully localize the transmitter cell using a single receiver for the first scenario, whereas two receivers are used to localize the transmitter cell in the second scenario. At last, the devised analytical framework is validated with simulations. [ABSTRACT FROM AUTHOR]

Analyzing the achievable rate of molecular communication via diffusion (MCvD) inherits intricacies due to its nature: MCvD channel has memory, and the heavy tail of the signal causes inter-symbol interference (ISI). Therefore, using Shannon’s channel capacity formulation for memoryless channel is not appropriate for the MCvD channel. Instead, a more general achievable rate formulation and system model must be considered to make this analysis accurately. In this letter, we propose an effective ISI-aware MCvD modeling technique in 3-D medium and properly analyze the achievable rate. [ABSTRACT FROM PUBLISHER]

In diffusion-based molecular communication, information transport is governed by diffusion through a fluid medium. The achievable data rates for these channels are very low compared to the radio-based communication system, since diffusion can be a slow process. To improve the data rate, a novel multiple-input multiple-output (MIMO) design for molecular communication is proposed that utilizes multiple molecular emitters at the transmitter and multiple molecular detectors at the receiver (in RF communication these all correspond to antennas). Using particle-based simulators, the channel’s impulse response is obtained and mathematically modeled. These models are then used to determine interlink interference (ILI) and intersymbol interference (ISI). It is assumed that when the receiver has incomplete information regarding the system and the channel state, low complexity symbol detection methods are preferred since the receiver is small and simple. Thus, four detection algorithms are proposed—adaptive thresholding, practical zero forcing with channel models excluding/including the ILI and ISI, and Genie-aided zero forcing. The proposed algorithms are evaluated extensively using numerical and analytical evaluations. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]