Transmitter Nanomachine Research Articles

Game-Theoretic Analysis of Fusion Rules Over Molecular Reporting Channels.

This work adopts a game theoretic approach to analyze the behavior of transmitter nanomachines (TNMs) in a diffusive 3-dimensional (3-D) channel. In order to communicate the local observations about the region of interest (RoI) to a common supervisor nanomachine (SNM), TNMs transmit information-carrying molecules to SNM. For the production of information-carrying molecules, all the TNMs share the common food molecular budget (CFMB). The TNMs apply cooperative and greedy strategic efforts to get their share from the CFMB. In the cooperative case, all the TNMs communicate to SNM as a group, therefore they cooperatively consume the CFMB to increase the group outcome, whereas, in the greedy scenario, all TNMs decide to perform alone and thus greedily consume the CFMB to increase their individual outcomes. The performance is evaluated in terms of the average rate of success, the average probability of error, and the receiver operating characteristic (ROC) of RoI detection. The derived results are verified through Monte-Carlo and particle-based simulations (PBS).

Joint Synchronization and Range Estimation With Correlated Arrival Times in Molecular Communication Networks

Time synchronization is needed in information exchange and collaboration among nanomachines for molecular communication networks. The time of arrival-based synchronization method requires the range information between the transmitter nanomachine (TN) and the receiver nanomachine (RN) in order to improve the accuracy of clock synchronization. The range information between the nanomachines helps to choose the optimal transmission rate. In contrast to the existing methods, this article proposes a joint clock offset and range estimation with correlated arrival times based on the maximum likelihood estimator. The RN uses the molecules' transmission and correlated arrival times to estimate the clock offset and range between the TN and RN. Even with correlated arrival times, the individual clock offset estimation performance is comparable to independent arrival times performance. Notably, the joint estimation problem with correlated arrival times is generic and realistic for molecular applications.

Molecule Harvesting Transmitter Model for Molecular Communication Systems

This paper develops mathematical models for molecule harvesting transmitters in diffusive molecular communication (MC) systems. In particular, we consider a communication link consisting of a spherical transmitter nano-machine and a spherical receiver nano-machine suspended in a fluid environment. The transmitter and the receiver exchange information via signaling molecules. The transmitter is equipped with molecule harvesting units on its surface. Signaling molecules which come into contact with the harvesting units may be re-captured by the transmitter. For this system, we derive closed-form expressions for the channel impulse response and harvesting impulse response. Furthermore, we extend the harvesting transmitter model to the case of continuous signaling molecule release. In particular, we derive closed-form expressions for the average received signal at the receiver and the average harvested signal at the transmitter for different temporal release rates namely, constant, linearly increasing, and linearly decreasing release rates. Finally, we validate the accuracy of the derived mathematical expressions via particle-based simulations.

Bacterial Receiver Prototype for Molecular Communication Using Rhamnose Operon in a Microfluidic Environment.

Bacterial populations are promising candidates for the development of the receiver and transmitter nanomachines for molecular communication (MC). A bacterial receiver is required to uptake the information molecules and produce the detectable molecules following a regulation mechanism. We have constructed a novel bacterial MC receiver using an inducible bacterial L-rhamnose-regulating operon. The proposed bacterial receiver produces green fluorescent protein (GFP) in response to the L-rhamnose information molecules following a quite fast regulation mechanism. To fabricate the receiver, the bacterial population has been transformed using a plasmid harboring L-rhamnose operon genes and gene expressing GFP in a microfluidic environment. We mathematically model the reception process of information molecules and characterize the model parameters by comparing the simulation results of the model in the employed microfluidic environment and the data obtained from the experimental setup. Based on the experimental results, the receiver is able to switch between different low and high concentrations. This work paves the way for the fabrication and modeling of any bacterial operon-based receiver with any proteins rather than GFP. Further, our experimental results indicate that the proposed bacterial receiver has a faster response to information molecules compared to the previous bacterial receiver based on the quorum sensing (QS) process.

TDMA-MTMR-Based Molecular Communication With Ligand-Binding Reception

Multiple access-based molecular communication (MC) is an important way to implement MC nanonetworks for the Internet of Bio-Nano Things. In this letter, we propose a framework for time division multiple access (TDMA)-based MC by considering multiple-type transmission multiple-type reception (MTMR) for a system with multiple transmitter nanomachines and one receiver nanomachine (RN) which is non-ideal and has a switching delay. The reception process is based on ligand-binding reception. We study the drug release management approaches by minimizing the error probability. Besides, we propose a metric to find signal-to-interference ratio based on the channel memory. Analytical results, which are verified by the simulation, show that the TDMA-MTMR MC outperforms the state-of-the-art TDMA framework.

Impacts of Unintended Nanomachine in Diffusion-Based Molecular Communication System

The effect of unintended nanomachine (UN) on the performance of a 3-dimensional (3-D) diffusive point-to-point molecular communication system is investigated in this article. To analyze the impacts of the presence of UN, two different scenarios are considered. In the first scenario, UN is considered as an unintended transmitter nanomachine (UTN). The expression for arrival probability of molecules received at the spherical absorbing receiver, considering exponential molecular degradation, is obtained. Moreover, this scenario is analyzed in terms of average probability of error (APoE) and maximum achievable rate (MAR), with and without Genie-aided assumptions. Further, in the second scenario, wherein we consider UN as a unintended receiver nanomachine (URN), the system is analyzed in terms of information leakage and maximum achievable secrecy rate (MASR). In second scenario, we consider two different models to find the arrival probability of molecules at the intended receiver nanomachine (IRN). In the first model, independence of the particle death in URN and IRN is assumed, and in second model, mutual influences of URN and IRN on each other are assumed. Moreover, in both the scenarios, to optimize the system performance, an optimal detector is used. In the end, the derived analytical expressions are verified through particle-based and Monte-Carlo simulations.

Energy efficiency analysis of multi-hop mobile diffusive molecular communication

Diffusive molecular communication (DMC), in which molecules are used to deliver information in diffusion channel, is one of the most prominent systems in nanonetworks. In particular, the research on end-to-end mobile DMC system is even more challenging. In this paper, we investigate the energy efficiency of multi-hop mobile DMC system. First, the energy model for this system is proposed based on the mobilities of transmitter nanomachine (TN), relays and receiver nanomachine (RN). Then the mathematical expressions of total energy consumption and throughput are derived. Furthermore, the energy efficiency which is defined as the throughput per unit energy consumption is analyzed. Finally, the numerical results show that the parameters including the diffusion coefficients and velocities of mobile TN, relays and RN, the initial distance of each hop, the number of molecules emitted in each time slot by TN and relays, and each time slot duration have different impacts on the energy efficiency. How to set these system parameters can be used to provide guidelines for designing energy efficient multi-hop mobile DMC system.

Sum capacity analysis of mobile broadcast diffusive molecular communication

In this paper, we study the mobile broadcast diffusive molecular communication (DMC) system which is composed of one mobile transmitter nanomachine (TN) and multiple mobile receiver nanomachines (RNs). Considering that the reception event at each RN is different due to the time-varying impulse response of the mobile diffusion channel, in order to ensure that RNs can share the common information from TN with lower bit error probability (BEP), we add two fusion centers (FCs) in this system which are used to gather the information from RNs to make global decisions by using an N-out-of-K fusion rule. We propose three reporting schemes for the transmission between RNs and FCs including perfect reporting, different type of molecules and same type of molecules. Then the mathematical expressions of the optimal decision thresholds at RNs and FCs by using maximum-a-posterior detection method are obtained. On this basis, the BEP and sum capacity under the three reporting schemes are analyzed. Furthermore, the impacts of different parameters and reporting schemes on the performance of this system are evaluated and discussed by the numerical results. The setting of these parameters and reporting schemes can be used to provide the guideline for designing the mobile broadcast DMC system with lower BEP and higher sum capacity.

Spatial Nanomechanical Communications Based on State Transitions.

In this paper, we present a novel framework of a nanomechanical communication (NMC) system where nanomechanical (NM) systems can communicate using mechanical movements to encode and transfer information between a transmitter (TX) nanomachine and a receiver (RX) nanomachine. First, some unique features of the envisioned NMC system have been presented in contrast to traditional communications systems. It is demonstrated that the encoding of distinct repeatable movements or motions is the key to information transfer in an NMC system. Using a state transition framework, we identify rest states (RSs) and motional degrees of freedom (MDoF) as the two essential concepts that determine the transmission rate of an NMC system in the spatial domain in two different modes, namely, synchronous and asynchronous transmissions. While the synchronous transmission is found to achieve much higher transmission rate compared to the asynchronous transmission in the noise-free case, the asynchronous mode is less restrictive and may have wider applicability. A stochastic model is considered to incorporate the influence of thermal noise in the system. A closed-form expression of the symbol error rate (SER) and its bounds have been derived for a particular symbol of a synchronous sliding motion NMC system with MDoF = 2. Numerical results show a promising SER performance in support of developing an NMC system model for nanoscale communications networks.

Health monitoring scheme‐based Forster resonance energy transfer nanocommunications in the Internet of Biological Nanothings

SummaryIn this paper, a health monitoring approach for a targeted drug delivery (TDD) system taking into consideration the binding of drug to a target cell is proposed. The proposed scheme is mainly based on Forster resonance energy transfer (FRET) nanocommunications and the physical phenomenon such as protein–protein interactions in biological systems, in order to propose a molecular communication system with various forms for single and/or multiple ligand–receptor binding. Inspired by classical wireless communication system, the analysis of proposed scheme in terms of bit error rate (BER) and mutual information between the transmitter nanomachine (TN) and receiver nanomachine (RN) is presented. Subsequently, we are able to obtain a closed‐form expression for BER for the proposed scheme. The proposed scheme can be employed in the promising Internet of Biological Nanothings (IoBNT) paradigm. The numerical results reveal that the proposed scheme with multiple donors multiple acceptors system analogous to multiple input multiple output (MIMO) communication system is a superior scheme for transmission therapeutic drug information with achievable BER.

Nanomachine Localization in a Diffusive Molecular Communication System

The information-bearing molecules are used for communication among nanomachines in a diffusion-based molecular communication (DMC) system. The location of the nanomachine is needed for improving the performance of a DMC system. In the literature, only the distance between a transmitter nanomachine (TN) and a receiver nanomachine is estimated. In contrast, an iterative maximum likelihood estimate of the nanomachine location is computed herein. Notably, both the signal-dependent noise and intersymbol interference (ISI) effects are considered for nanomachine localization. Further, the nanomachine localization is performed, when the locations of the receiver nanomachine are both known and unknown. Additionally, the condition for the unique localizability of the TN and the bound of the proposed estimator are obtained. The results illustrate the effectiveness of the proposed method.

Drug Release Management for Dynamic TDMA-Based Molecular Communication

In this paper, we design a drug release mechanism for dynamic time division multiple access (TDMA)-based molecular communication via diffusion (MCvD) in case of having multiple transmitter units and a single receiver. In the proposed scheme, the communication frame is divided into several time slots in 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 multi-objective optimization problems 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: “fixed-time fixed-number of molecules” (FTFN), “fixed-time varying-number of molecules” (FTVN), “varying-time fixed-number of molecules” (VTFN), and “varying-time varying-number of molecules” (VTVN). For the channel model, we consider a 3-dimensional diffusive environment with drift in three directions. Simulation results show that the FTFN approach is the least complex one with BER around ${10}^{-2}$ , but, the VTVN is the most complex scenario with the BER around ${10}^{-8}$ .

Signal reconstruction in diffusion‐based molecular communication

AbstractMolecular communication (MC) is an important nanoscale communication paradigm, which is employed for the interconnection of the nanomachines (NMs) to form nanonetworks. A transmitter NM (TN) sends the information symbols by emitting molecules into the transmission medium and a receiver NM (RN) receives the information symbols by sensing the molecule concentration. In this paper, a model of how an RN measures and reconstructs the molecular signal is proposed. The signal around the RN is assumed to be a Gaussian random process instead of the less realistic deterministic approach. After the reconstructed signal is derived as a doubly stochastic poisson process, the distortion between the signal around the RN and the reconstructed signal is derived as a new performance parameter in MC systems. The derived distortion, which is a function of system parameters such as RN radius, sampling period, and the diffusion coefficient of the channel, is shown to be valid by employing random walk simulations. Then, it is shown that the original signal can be satisfactorily reconstructed with a sufficiently low level of distortion. Finally, optimum RN design parameters, namely, RN radius, sampling period, and sampling frequency, are derived by minimizing the signal distortion. The simulation results reveal that there is a trade‐off among the RN design parameters which can be jointly set for a desired signal distortion.

Spatial Modulation for Molecular Communication.

In this paper, we propose an energy-efficient spatial modulation-based molecular communication (SM-MC) scheme, in which a transmitted symbol is composed of two parts, i.e., a space derived symbol and a concentration derived symbol. The space symbol is transmitted by embedding the information into the index of a single activated transmitter nanomachine. The concentration symbol is drawn according to the conventional concentration shift keying (CSK) constellation. Benefiting from a single active transmitter during each symbol period, SM-MC can avoid the inter-link interference problem existing in the current multiple-input multiple-output (MIMO) based MC schemes, which hence enables low-complexity symbol detection and performance improvement. Correspondingly, we propose a low-complexity scheme, which first detects the space symbol by energy comparison, and then detects the concentration symbol by the maximum ratio combining assisted CSK demodulation. In this paper, we analyze the symbol error rate (SER) of the SM-MC and of its special case, namely the space shift keying-based MC (SSK-MC), where only space symbol is transmitted and no CSK modulation is invoked. Finally, the analytical results are validated by computer simulations. Our studies demonstrate that both the SSK-MC and SM-MC are capable of achieving better SER performance than the conventional MIMO-MC and single-input single-output-based MC, when given the same symbol rate.

Performance Analysis of Diffusive Mobile Multiuser Molecular Communication With Drift

Diffusive molecular communication (DMC), in which molecules are used to deliver information, is one of the most prominent systems in nanonetworks. In this paper, we consider the mobile multiuser DMC system with drift which is composed of multiple mobile transmitter nanomachines and one mobile receiver nanomachine. In this system, both the inter-symbol interference (ISI) and multi-user interference (MUI) unavoidably exit in the same fluid medium. In order to evaluate the performance of this system, the mathematical expressions of ISI and MUI are first obtained. Then the mutual information, channel capacity and the bit error rate (BER) based on the derivation of optimal decision threshold are analyzed. Furthermore, the impacts of different parameters on the performance of this system are evaluated and discussed by the numerical results. The setting of these parameters can be used to provide a guideline for designing the mobile multiuser DMC system with higher channel capacity and lower BER.

Lifetime Improvement of a Multiple Transmitter Local Drug Delivery System Based on Diffusive Molecular Communication.

In this paper, a multiple transmitter local drug delivery system associated with encapsulated drug transmitters is investigated. One of the limitations of drug delivery systems is the reservoir capacity. In order to improve the lifetime of drug transmitting nanomachines, and, hence, the longevity of drug delivery scenario, the system is associated with encapsulated drug transmitters. Encapsulated drugs are incapable of reaction with the environment unless they are unpacked in a drug transmitter nanomachine. Therefore, far-reaching transmitters do not have harmful effects on the healthy parts of the body. The advantage of this protocol is to increase the time interval between consecutive administrations without increased toxicity. As a result, it improves the mental health of patients and reduces the costs of treatment. The lifetime of this drug delivery system depends on the distribution and topology of encapsulated drug transmitters rather than their rates. Finally, a lower bound is derived on the expected lifetime of a Poisson distributed random network of nanomachines.

Time Synchronization for Molecular Communication With Drift

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.

Diffusive Mobile Molecular Communications Over Time-Variant Channels

This letter introduces a formalism for modeling time-variant channels for diffusive molecular communication systems. In particular, we consider a fluid environment where one transmitter nano-machine and one receiver nano-machine are subjected to Brownian motion in addition to the diffusive motion of the information molecules used for communication. Due to the stochastic movements of the transmitter and receiver nano-machines, the statistics of the channel impulse response change over time. We show that the time-variant behaviour of the channel can be accurately captured by appropriately modifying the diffusion coefficient of the information molecules. Furthermore, we derive an analytical expression for evaluation of the expected error probability of a simple detector for the considered system. The accuracy of the proposed analytical expression is verified via particle-based simulation of the Brownian motion.

Capacity and Delay Spread in Multilayer Diffusion-Based Molecular Communication (DBMC) Channel.

In nanoscale communication, diffusion-based molecular communication (DBMC) in which information is encoded into molecule patterns by a transmitter nanomachine, has emerged as a promising communication system, particularly for biomedical and healthcare applications. Although, numerous studies have been conducted to evaluate and analyze DBMC systems, investigation on DBMC system through a multilayer channel has received less attention. The aims of this paper are to formulate channel characteristics and to evaluate the performance of multilayer DBMC channel in terms of delay spread and capacity. In this paper, the propagation of molecules over an n- layer channel is assumed to follow the Brownian motion and subjected to Fick's law of diffusion. Fourier transform is used to convert time to frequency domain functions. Besides, the multilayer channel is considered as a linear and deterministic channel. For the performance evaluation, the air-water-blood plasma medium representing the simplified multilayer diffusion model in the respiratory system was chosen. It was found that a high channel capacity can be achieved with wide transmission bandwidth, short transmission distance, and high averaged transmitted power. In addition, the findings showed that channel delay spread increases as both the transmission distance, and the pulse duration increased. By setting the symbol duration greater than the pulse duration or delay spread, an inter-symbol interference problem due to previous molecules transmission can be mitigated. These findings can be used as a guide in the development and fabrication of future artificial nanocommunication and nanonetworks systems involving multilayer transmission medium.

Reliability and delay analysis of multicast in binary molecular communication

Molecular communication is a new and promising communication technology. However, we consider that molecular communication easily suffers from high unreliability and long delay due to the stochastic behavior of the molecules in a biological environment, thus it is essential to investigate the characteristics of reliability and delay in molecular communication. In this paper, we analyze the reliability and delay in multicast topology based on binary molecular communication model. First, we give the mathematical expressions of reliability and delay in different scenarios including a single link, a single path and multicast topology, respectively. In particular, we use retransmission mechanism for transmission failure. Then the numerical results derived from the simulation performances show how the parameters including diffusion coefficient, the distance between transmitter nanomachine and receiver nanomachine, the number of molecules emitted in each time slot, the number of slots and each time slot duration have impacts on reliability and delay. More importantly, under the same reliability, lower delay can be theoretically realized by binary molecular communication model compared to the concentration model of virus-based nanonetworks.