Transmitter Nanomachine Research Articles

Comprehensive Reactive Receiver Modeling for Diffusive Molecular Communication Systems: Reversible Binding, Molecule Degradation, and Finite Number of Receptors.

This paper studies the problem of receiver modeling in molecular communication systems. We consider the diffusive molecular communication channel between a transmitter nano-machine and a receiver nano-machine in a fluid environment. The information molecules released by the transmitter nano-machine into the environment can degrade in the channel via a first-order degradation reaction and those that reach the receiver nano-machine can participate in a reversible bimolecular reaction with receiver receptor proteins. Thereby, we distinguish between two scenarios. In the first scenario, we assume that the entire surface of the receiver is covered by receptor molecules. We derive a closed-form analytical expression for the expected received signal at the receiver, i.e., the expected number of activated receptors on the surface of the receiver. Then, in the second scenario, we consider the case where the number of receptor molecules is finite and the uniformly distributed receptor molecules cover the receiver surface only partially. We show that the expected received signal for this scenario can be accurately approximated by the expected received signal for the first scenario after appropriately modifying the forward reaction rate constant. The accuracy of the derived analytical results is verified by Brownian motion particle-based simulations of the considered environment, where we also show the impact of the effect of receptor occupancy on the derived analytical results.

Ion Channel Based Bio-Synthetic Modulator for Diffusive Molecular Communication.

In diffusion-based molecular communication (DMC), a transmitter nanomachine is responsible for signal modulation. Thereby, the transmitter has to be able to control the release of the signaling molecules employed for representing the transmitted information. In nature, an important class of control mechanisms for releasing molecules from cells utilizes ion channels which are pore-forming proteins across the cell membrane. The opening and closing of the ion channels is controlled by a gating parameter. In this paper, an ion channel based modulator for DMC is proposed which controls the rate of molecule release from the transmitter by modulating a gating parameter signal. Exploiting the capabilities of the proposed modulator, an on-off keying modulation technique is introduced and the corresponding average modulated signal, i.e., the average release rate of the molecules from the transmitter, is analyzed. However, since the modulated signal is random in nature, it may deviate from its average. Therefore, the concept of modulator noise is introduced and the statistics of the modulated signal are investigated. Finally, by assuming a simple transparent receiver, the performance of the proposed on-off keying modulation format is studied. The derived analytical expressions for the average modulated signal are confirmed with particle based simulations. Our numerical results reveal that performance estimates of DMC systems obtained based on the assumption of instantaneous molecule release at the transmitter may substantially deviate from the performance achieved with practical modulators.

A Novel Electrical Model for Advection-Diffusion-Based Molecular Communication in Nanonetworks.

In this paper, we propose an end-to-end electrical model to characterize the communication between two nanomachines via advection-diffusion motion along the conventional pipe medium. For this modeling, we consider three modules consisting of transmitter, advection-diffusion propagation and receiver. The modulation scheme and releasing molecules through the conventional pipe medium from the transmitter nanomachine is represented in the transmitter module. The advection-diffusion propagation of molecules along the flow-induced path is shown in advection-diffusion propagation module, and the demodulation scheme of bounded particles at the receiver nanomachine is characterized in the receiver module. Our objective is to find an electrical model of each module under the zero initial condition which enables us to represent the electrical circuit related to each module. The transmitter and the signal propagation models are built on the basis of the molecular advection-diffusion physics, whereas the receiver model is interpreted by stemming from the theory of the ligand-receptor binding chemical process. In addition, we employ the transfer function of modules to derive the normalized gain and the delay of each module. Supported by numerical results, we analyze the effect of physical parameters of the pipe medium on the total normalized gain and delay of molecular communications.

Diffusion-Based Clock Synchronization for Molecular Communication Under Inverse Gaussian Distribution

Nanonetworks are expected to expand the capabilities of individual nanomachines by allowing them to cooperate and share information by molecular communication. The information molecules are released by the transmitter nanomachine and diffuse across the aqueous channel as a Brownian motion holding the feature of a strong random movement with a large propagation delay. In order to ensure an effective real-time cooperation, it is necessary to keep the clock synchronized among the nanomachines in the nanonetwork. This paper proposes a model on a two-way message exchange mechanism with the molecular propagation delay based on the inverse Gaussian distribution. The clock offset and clock skew are estimated by the maximum-likelihood estimation. Simulation results by MATLAB show that the mean square errors of the estimated clock offsets and clock skews can be reduced and converge with a number of rounds of message exchanges. The comparison of the proposed scheme with a clock synchronization method based on symmetrical propagation delay demonstrates that our proposed scheme can achieve better performance in terms of accuracy.

Multilayer diffusion‐based molecular communication

AbstractDiffusion‐based molecular communication (DBMC) has emerged as a promising communication option, particularly for biomedical and healthcare applications. Although, numerous studies have been conducted to evaluate and analyse DBMC system, investigation on DBMC through multilayer channels has had less attention. In this paper, a closed‐form expression is derived for the mean molecular concentration over an n‐layer channel. An averaged diffusion coefficient for thin, dissimilar and multilayer propagation channels is determined through the addition of a diffusion resistance for each medium analogously to the sum of series resistors in circuit theory. The channel characteristics such as impulse response, time delay and attenuation are analytically obtained using amplitude detection technique. The effects of layer thickness and the distance between a transmitter nanomachine and a receiver nanomachine on the channel time delay and channel attenuation under the pulse modulation scheme are evaluated and discussed. The results show that increasing the diffusion coefficient leads to time delay decrements; however, the channel attenuation remains unchanged. Moreover, lengthening the transmission distance increases the time delay and decreases the channel attenuation. Copyright © 2015 John Wiley & Sons, Ltd.

Distance Estimation Schemes for Diffusion Based Molecular Communication Systems

Molecule concentration is often used as the information carrier to accomplish diffusion-based molecular communications (DMC) among nano-machines. To achieve the optimal functionality, knowing the distance between the transmitter nano-machine (TN) and the receiver nano-machine (RN) is of high importance. In this paper, two distance estimation schemes are proposed based upon the RN-sensed concentration which changes with regards to the time and distance. The RN estimates the distance by means of measuring either the concentration-peak time or received concentration energy. Simulations are performed to compare the accuracy of each scheme and to discover how the diffusion channel and noise may influence the accuracy. Results show that both schemes will provide a beneficial enhancement to molecular communication systems.

Channel capacity analysis of a diffusion‐based molecular communication system with ligand receptors

SummaryDiffusion‐based communication is one of the most dominating forms in the micrometer and nanoscale communications. Generally, information is coded in molecules that are released by a transmitter nanomachine, propagated via a diffusion‐based channel, and then received by a receiving nanomachine (called receiver). The receiver considered in this paper is equipped with multiple ligand receptors. The molecular communication system in this paper is single hop and SISO. Namely, there is only a channel connecting a pair of transmitter and receiver. While most literature considers either the channel or the receptors, this paper proposes a channel model that takes into account both the diffusion‐based channel and the ligand‐based receiver. The channel capacity under such model is analyzed, which studies the impact of different parameters at both channel and the receiver on the performance of the molecular communication system. We establish a digital channel model based on the on–off keying and time slot scheme. A capacity expression is derived with consideration of the effects of the channel memory and ligand‐receptor binding mechanisms. The numerical results show that the overall channel capacity is restricted by the physical parameters of diffusion channel and ligand receptors. Copyright © 2014 John Wiley & Sons, Ltd.

Channel Model and Capacity Analysis of Molecular Communication with Brownian Motion

In this paper, we analyze the capacity of a molecular communication channel in a one dimensional environment where information is represented with molecules that are released by a transmitter nanomachine, propagate via Brownian motion, degrade over time, and stochastically reach the receiver nanomachine. The channel is modeled as a time slotted binary channel, and two modulation schemes are proposed: a naive modulation scheme and an extended modulation scheme with a redundant number of molecules. Our analysis demonstrates that the channel capacity is largely affected by the life expectancy of molecules. Our analysis also indicates that the extended modulation scheme can achieve nearly one bit per slot at the expense of extra molecules under optimal conditions.

Nanoscale Communication With Molecular Arrays in Nanonetworks

Molecular communication is a promising nanoscale communication paradigm that enables nanomachines to exchange information by using molecules as communication carrier. Up to now, the molecular communication channel between a transmitter nanomachine (TN) and a receiver nanomachine (RN) has been modeled as either concentration channel or timing channel. However, these channel models necessitate exact time synchronization of the nanomachines and provide a relatively low communication bandwidth. In this paper, the Molecular ARray-based COmmunication (MARCO) scheme is proposed, in which the transmission order of different molecules is used to convey molecular information without any need for time synchronization. The MARCO channel model is first theoretically derived, and the intersymbol interference and error probabilities are obtained. Based on the error probability, achievable communication rates are analytically obtained. Numerical results and performance comparisons reveal that MARCO provides significantly higher communication rate, i.e., on the scale of 100 Kbps, than the previously proposed molecular communication models without any need for synchronization. More specifically, MARCO can provide more than 250 Kbps of molecular communication rate if intersymbol time and internode distance are set to 2 μs and 2 nm, respectively.

Addressing by beacon distances using molecular communication

A transmitter nanomachine performs molecular communication to transmit information to a receiver nanomachine by modulating the concentration of molecules over time (e.g., concentration of ions, peptides, or DNA). In many designs for molecular communication systems, a transmitter selects a receiver nanomachine by using a predetermined type of molecule (e.g., type of ion, type of peptide, or specific sequence of DNA). The type of molecule represents the address of the receiver. In the proposed system, a transmitter addresses receivers by location. Molecular beacons use molecular communication to provide distance measurements and establish a coordinate system. The address of a receiver is the set of distances to molecular beacons at the location of the receiver. The transmitter is assumed to have the address of the receiver. A transmitter communicates to a receiver by encapsulating information into a carrier. The carrier uses distances to molecular beacons and applies a movement technique similar to bacterial chemotaxis to move to the location matching the address. The proposed system is simulated and evaluated in terms of probability of successfully contacting the receiver and propagation delay to arrive at the receiver.