Molecular Communication: Modeling Noise Effects on Information Rate

Molecular communication is a new paradigm for communication between biological nanomachines over a nano- and microscale range. As biological nanomachines (or nanomachines in short) are too small and simple to communicate through traditional communication mechanisms (e.g., through sending and receiving of radio or infrared signals), molecular communication provides a mechanism for a nanomachine (i.e., a sender) to communicate information by propagating molecules (i.e., information molecules) that represent the information to a nanomachine (i.e., a receiver). This paper describes the design of an in vitro molecular communication system and evaluates various approaches to maximize the probability of information molecules reaching a receiver(s) and the rate of information reaching the receiver(s). The approaches considered in this paper include propagating information molecules (diffusion or directional transport along protein filaments), removing excessive information molecules (natural decay or receiver removal of excessive information molecules), and encoding and decoding approaches (redundant information molecules to represent information and to decode information). Two types of molecular communication systems are considered: a unicast system in which a sender communicates with a single receiver and a broadcast system in which a sender communicates with multiple receivers. Through exploring tradeoffs among the various approaches on the two types of molecular communication systems, this paper identifies promising approaches and shows the feasibility of an in vitro molecular communication system.      

Embedded Coded Relay System for Molecular Communications

With the emergence of the COVID-19 pandemic, the World Health Organization (WHO) has urged scientists and industrialists to explore modern information and communication technology (ICT) as a means to reduce or even eliminate it. The World Health Organization recently reported that the virus may infect the organism through any organ in the living body, such as the respiratory, the immunity, the nervous, the digestive, or the cardiovascular system. Targeting the abovementioned goal, we envision an implanted nanosystem embedded in the intra living-body network. The main function of the nanosystem is either to perform diagnosis and mitigation of infectious diseases or to implement a targeted drug delivery system (i.e., delivery of the therapeutic drug to the diseased tissue or targeted cell). The communication among the nanomachines is accomplished via communication-based molecular diffusion. The control/interconnection of the nanosystem is accomplished through the utilization of Internet of bio-nano things (IoBNT). The proposed nanosystem is designed to employ a coded relay nanomachine disciplined by the decode and forward (DF) principle to ensure reliable drug delivery to the targeted cell. Notably, both the sensitivity of the drug dose and the phenomenon of drug molecules loss before delivery to the target cell site in long-distance due to the molecules diffusion process are taken into account. In this paper, a coded relay NM with conventional coding techniques such as RS and Turbo codes is selected to achieve minimum bit error rate (BER) performance and high signal-to-noise ratio (SNR), while the detection process is based on maximum likelihood (ML) probability and minimum error probability (MEP). The performance analysis of the proposed scheme is evaluated in terms of channel capacity and bit error rate by varying system parameters such as relay position, number of released molecules, relay and receiver size. Analysis results are validated through simulation and demonstrate that the proposed scheme can significantly improve delivery performance of the desirable drugs in the molecular communication system.     

Molecular communication and networking: opportunities and challenges

The ability of engineered biological nanomachines to communicate with biological systems at the molecular level is anticipated to enable future applications such as monitoring the condition of a human body, regenerating biological tissues and organs, and interfacing artificial devices with neural systems. From the viewpoint of communication theory and engineering, molecular communication is proposed as a new paradigm for engineered biological nanomachines to communicate with the natural biological nanomachines which form a biological system. Distinct from the current telecommunication paradigm, molecular communication uses molecules as the carriers of information; sender biological nanomachines encode information on molecules and release the molecules in the environment, the molecules then propagate in the environment to receiver biological nanomachines, and the receiver biological nanomachines biochemically react with the molecules to decode information. Current molecular communication research is limited to small-scale networks of several biological nanomachines. Key challenges to bridge the gap between current research and practical applications include developing robust and scalable techniques to create a functional network from a large number of biological nanomachines. Developing networking mechanisms and communication protocols is anticipated to introduce new avenues into integrating engineered and natural biological nanomachines into a single networked system. In this paper, we present the state-of-the-art in the area of molecular communication by discussing its architecture, features, applications, design, engineering, and physical modeling. We then discuss challenges and opportunities in developing networking mechanisms and communication protocols to create a network from a large number of bio-nanomachines for future applications.     

Gold Nanoparticle‐Based Sensors Activated by External Radio Frequency Fields

A novel molecular beacon (a nanomachine) is constructed that can be actuated by a radio frequency (RF) field. The nanomachine consists of the following elements arranged in molecular beacon configuration: a gold nanoparticle that acts both as quencher for fluorescence and a localized heat source; one reporter fluorochrome, and; a piece of DNA as a hinge and recognition sequence. When the nanomachines are irradiated with a 3 GHz RF field the fluorescence signal increases due to melting of the stem of the molecular beacon. A control experiment, performed using molecular beacons synthesized by substituting the gold nanoparticle by an organic quencher, shows no increase in fluorescence signal when exposed to the RF field. It may therefore be concluded that the increased fluorescence for the gold nanoparticle‐conjugated nanomachines is not due to bulk heating of the solution, but is caused by the presence of the gold nanoparticles and their interaction with the RF field; however, existing models for heating of gold nanoparticles in a RF field are unable to explain the experimental results. Due to the biocompatibility of the construct and RF treatment, the nanomachines may possibly be used inside living cells. In a separate experiment a substantial increase in the dielectric losses can be detected in a RF waveguide setup coupled to a microfluidic channel when gold nanoparticles are added to a low RF loss liquid. This work sheds some light on RF heating of gold nanoparticles, which is a subject of significant controversy in the literature.     

Enhancing data rate of molecular communication system using Brownian motion

Inter‐symbol and co‐channel interferences restrict the capacity of molecular communication (MC) systems. In this study, the effect of these interferences on the data rate of MC systems is investigated to design an efficient MC system. To this end, the authors propose an analytical model for a diffusion‐based MC system comprised of two nanomachines when they exploit On/Off keying modulation. They model the Brownian motion of molecules in a one‐dimensional environment as a wiener process and the life expectancy of diffused molecules as an exponential process. First, they consider the inter‐symbol interference to derive the data rate of the MC system as a function of the receiver decision threshold and the symbol time duration. Hence, they propose an algorithm to obtain the optimal values of MC system parameters. Then, the effect of co‐channel interference is considered by assuming parallel MC systems. They propose a minimum distance between adjacent MC systems that their co‐channel interferences effect to be negligible. Moreover, they verify the accuracy of the analytical results by Monte–Carlo simulations. Results show a remarkable improvement in the data rate of MC systems. The derived results may find application in nanonetworks where nanomachines connect together to perform complex tasks.Inspec keywords: channel capacity, Monte Carlo methods, intersymbol interference, stochastic processes, Brownian motion, cochannel interferenceOther keywords: enhancing data rate, molecular communication system, Brownian motion, co‐channel interference, efficient MC system, diffusion‐based MC system, inter‐symbol interference, MC system parameters, parallel MC systems, adjacent MC systems, co‐channel interferences effect     

Improving adaptive receivers performance in molecular communication via diffusion

Forthcoming applications for molecular communications (MC) such as drug‐delivery and health monitoring will require robust receiver capabilities to mitigate channel memory and inter symbol interference caused by previous transmitted symbols. Here, the authors introduce an adaptive weighted algorithm to reduce the influence of these factors. This novel signal detection is deployed on to a concentration‐based MC system with absorbing receiver which is based on the so‐called first passage time concept. The proposed detector has low complexity and does not require explicit channel knowledge. To evaluate authors’ proposed algorithm, a theoretical approach is developed to derive the bit error rate (BER). Numerical results also carried out to verify the accuracy of these formulations and establish that the new detector will achieve better performance in comparison with other common low‐complex detectors under certain scenarios. Additionally, the authors propose a simple pre‐coding technique to combat the sequence of consecutive ones in low ISI scenarios. Also a comparison between detectors is given, which is based on the variation of distance, symbol period, signal‐to‐noise ratio (SNR), and number of molecules.Inspec keywords: radio receivers, error statistics, signal detection, intersymbol interferenceOther keywords: low‐complex detectors, low ISI scenarios, symbol period, signal‐to‐noise ratio, adaptive receivers performance, molecular communication, drug‐delivery, health monitoring, robust receiver capabilities, channel memory, inter symbol interference, previous transmitted symbols, adaptive weighted algorithm, novel signal detection, concentration‐based MC system, absorbing receiver, passage time concept, low complexity, explicit channel knowledge, authors, theoretical approach, bit error rate, numerical results     

大气光通信中Turbo码的最大后验概率译码

为了精确实现对空间物体的测量,提出了利用线激光、单CCD相机、小孔成像与激光面约束模型的激光线测量法。引进三维信息已知的标准阶梯块作为激光面约束的标定块;由计算机控制摄像头对实物连续拍摄和实时处理,提取激光线上的像素坐标;利用建立的模型将二维坐标转换成三维坐标,再以点云的形式重构出物体,实现三维自动测量。实践中检测系统测量精度可达到0.05mm。     

Efficient DFT-based channel estimation for OFDM systems on multipath channels

An improved discrete Fourier transform (DFT)-based channel estimation for orthogonal frequency division multiplexing systems is proposed. Conventional DFT-based channel estimations improve the performance by suppressing time domain noise. However, they potentially require information on channel impulse responses and may also result in mean-square error (MSE) floor due to incorrect channel information such as channel delay spread. In contrast, our purposed channel estimation can improve the performance by deciding significant channel taps adaptively without requiring any channel statistical information. Significant channel taps are detected on the basis of a predetermined threshold. The optimal threshold to reduce the MSE of the estimation is also derived, and it is confirmed by computer simulation. Simulation results demonstrate that the proposed algorithm can improve the MSE performance ~6.5 dB compared with the conventional DFT-based estimation, and the MSE floor is not observed in any channels.     

Exploration of nanostructured channel systems with single-molecule probes

Molecular movement in confined spaces is of broad scientific and technological importance in areas ranging from molecular sieving and membrane separation to active transport through ion channels. Whereas measurements of ensemble diffusion provide information about the overall behaviour of the guest in a porous host, tracking individual molecules provides insight into both the heterogeneity and the mechanistic details of molecular diffusion as well as into the structure of the host. Here, we show how single dye molecules can be used as nanoscale probes to map out the structure of mesoporous silica channel systems prepared as thin films via cooperative self-assembly of surfactant molecules with polymerizable silicate species. The dye molecules act as beacons while they diffuse through the different structural phases of the host: the structure of the trajectories, the diffusivities and the orientation of single molecules are distinctive for molecules travelling in the lamellar and the hexagonal mesophases. These experiments reveal unprecedented details of the host structure, its domains and the accessibility as well as the connectivity of the channel system.     

水声通信中变步长神经网络盲均衡算法研究

在水声通信领域多途引起的码间干拢可以用均衡消减。盲均衡不需要训练序列,这将有效的节省通信带宽,提高通信效率及通信性能。实际中的通信信道不可能是完全线性的,神经网络作为一种非线性动态系统,具有大规模并行处理及高度的鲁棒性特征,将其应用于水声信道盲均衡切实可行。文中对变步长BP算法的前馈神经网络进行了理论和算法分析,并通过计算机对其实现水声信道盲均衡进行了仿真。仿真结果表明采用变步长BP算法比采用传统BP算法的神经网络盲均衡器收敛速度快,均衡性能明显提高。     

Timing Recovery for IEEE 1588 Applications in Telecommunications

IEEE 1588 is being proposed as a solution to transport synchronization information within telecommunication networks, both for infrastructure use and for use in applications where time and frequency are required. The requirements of synchronization in these cases, however, are quite different from the traditional use of IEEE 1588 for synchronization in control and instrumentation applications. For successful deployment in communication applications, it is necessary to consider the unique aspects of telecom sync and the interrelation of these factors with timing recovery using IEEE 1588. This paper discusses the error considerations that must be applied toward timing recovery in packet-timing implementations, particularly those targeted toward telecom sync. A review of basic rate-recovery concepts is used to identify the various sources of error and their effects. Simulation and experimental results are used to illustrate the impact of different factors on the recovered timing.      

Message encoding and decoding using an asynchronous chaotic laser diode transmitter-receiver array

We have numerically investigated a chaotic laser diode transmitter-receiver array scheme (CLDTRAS), which is a secure digital communication scheme using a difference between two types of transmitter-receiver array consisting of two self-pulsating laser diodes (LDs), i.e., a receiver LD and a transmitter LD. By analyzing the bit error rate, particularly its dependence on the parameter mismatches of the hardware and channel noise and on the correlation coefficient between a transmitter LD and receiver LD, we examined the problems of sensitivity to parameter mismatches and channel noise and a dependence on chaos synchronization between a transmitter LD and a receiver LD. The former makes communication difficult, and the latter makes it possible for an eavesdropper to estimate the receiver LD using chaos synchronization and to forge the hardware. Then we studied the effects of the bit error rate for various values of the threshold, which determines a binary message, and for various numbers of transmitters-receivers making up a LD transmitter-receiver array. It has been shown that a highly noise-tolerant and hardware-dependent communication scheme can be achieved with the LD transmitter-receiver array, whose transmitter and receiver LDs are asynchronous with respect to each other, by choosing the proper threshold and increasing the number of LD transmitters-receivers. Since it is possible to communicate without chaos synchronization, it becomes difficult to forge hardware and to eavesdrop with the forged hardware even if the key is stolen.     

基于OFDM的大气激光通信湍流抑制关键技术研究

文章在分析无线激光通信(FSO)存在两种主要的大气信道问题的基础上,针对激光大气信道问题尤其是在复杂湍流环境下的频率选择性衰落问题和多径效应问题,提出了基于正交频分复用(OFDM)的湍流效应抑制方法,构建了FSO-OFDM系统,研究了该系统的基带模型以及信号的多载波调制与解调方法。分析了无线激光通信中存在复杂湍流环境下的大气信道问题,讨论了大气湍流影响下的平面波激光通信系统模型,建立了大气湍流影响下对数正态湍流通道的高斯光束空间光通信系统模型,推导了光波强度的概率密度函数,研究了利用信噪比概率密度函数分析各种大气湍流效应对系统性能影响的方法;设计了无线光通信系统的OFDM多载波调制方案,构建了FSO-OFDM系统基带模式模型,并基于该模型研究了其信号的调制与解调原理。最后,采用MATLAB编程实现FSO-OFDM系统,对多径干扰下的FSO通信系统进行仿真实验,进行了不同保护间隔下的误码率特性实验,验证了FSO-OFDM系统具有很强的抗多径干扰和频谱选择性衰落能力以及良好的BER性能,可有效解决码间干扰大、链路不可靠的问题,具有非常广泛的应用前景和使用价值。     

低声能辐射下的两种水声跳频通信方法对比研究

水声信道是一个极其复杂的时变-空变-频变信道,因而进行水声通信,必须克服时变多途干扰等困难。将抗干扰能力强的跳频通信技术应用于水声通信领域,对于隐蔽性、保密性要求高的系统来说,该体制有着卓越的特性。在仿真环境下,对比研究了m序列和基于二维logistic映射的混沌序列的相关性、平衡性、功率谱特性、多址性等性能。构建了一种在低声能条件下的水声跳频通信系统,给出了系统编解码技术的实现方法。发射的帧信号由激活信号、同步信号、时延信号和三组(15,11)汉明码循环3次组成,采用了时间与频率的双分集技术进行纠错解码,从而增强了系统的保密性。通过外场试验,验证了利用m序列和混沌序列进行水声跳频通信的可行性,并对试验结果进行了对比研究。由于混沌序列的数量巨大且性能优异,非常适用于水声组网通信和保密性要求高的水声通信系统。因此,混沌序列在今后的水声跳频通信领域应有更广阔的应用前景。     

Recent Progress on Man‐Made Inorganic Nanomachines

The successful development of nanoscale machinery, which can operate with high controllability, high precision, long lifetimes, and tunable driving powers, is pivotal for the realization of future intelligent nanorobots, nanofactories, and advanced biomedical devices. However, the development of nanomachines remains one of the most difficult research areas, largely due to the grand challenges in fabrication of devices with complex components and actuation with desired efficiency, precision, lifetime, and/or environmental friendliness. In this work, the cutting‐edge efforts toward fabricating and actuating various types of nanomachines and their applications are reviewed, with a special focus on nanomotors made from inorganic nanoscale building blocks, which are introduced according to the employed actuation mechanism. The unique characteristics and obstacles for each type of nanomachine are discussed, and perspectives and challenges of this exciting field are presented.     

Communication Mechanism and Algorithm of Composite Location Analysis of Emergency Communication based on Rail

The emergency communication system based on rail is an unconventional emergency communication mode, it is a complement equipment for that conventional communication system can’t work while tunnel mine accident occurs. Medium of transmission channel is the widely existing rail in the tunnel. In this paper we analyzed the characteristics of the rail transmission channel, verified the feasibility that information is transmitted by vibration signal in rail, we proposed the realization plan of the system. Communication protocol and processing mechanism suitable for rail transmission are designed according to the characteristics of channel bandwidth and low data transmission. Information communication with low bit rate and low bit error is realized in the communication simulation model. In the simplified model, we realized to transmit recognition speech information, and the error rate of the key text information is low to accept. The most concerned problem of personnel location in the mine disaster rescue is proposed, the composite algorithm is based on the model of signal amplitude attenuation, key node information and data frame transmission delay. Location information of hitting point can be achieved within the simplified model of the experiment. Furthermore, we discuss the characteristics of vibration signals passing through different channels.     

Atomic-scale STM experiments on semiconductor surfaces: towards molecular nanomachines

The electronic or quantum control of individual molecules with the scanning tunnelling microscope offers exciting perspectives on operating molecular nanomachines. This implies the use of semiconductor surfaces rather than metallic surfaces which would rapidly quench the electronic excitations. We review recent results illustrating the state of the art and the main problems which need to be solved: the choice, design and properties of functionalized organic molecules on semiconductor surfaces; the control of the inelastic electronic channels through a single molecule; and the search for well-controlled atomic-scale wide-band-gap semiconductor surfaces.     

Herding nanotransporters: localized activation via release and sequestration of control molecules

A challenge for nanotechnology is the dynamic and specific control of nanomachines by the user. Molecular shuttles, consisting of cargo-binding microtubules propelled by surface-immobilized kinesin motor proteins, are an example of a nanoscale system that ideally can be selectively activated at programmable locations and times. Here we discuss a biomimetic solution where activating molecules are delivered locally via photolysis of a caged compound and subsequently sequestered in an enzymatic network. The controlled sequestration of the activator not only creates a rapid deactivation when the stimulus is removed but also sharpens the concentration profile of the rapidly diffusing activator. This improvement comes at the expense of a reduced efficiency in the utilization of the activator molecules, suggesting that these nanosystems are most efficiently addressed as a swarm rather than as individuals. Our work represents a step toward transferring the cellular control strategies of molecular activation to bionanotechnology.     

虚拟时间反转镜PDS水声通信双向均衡方案

虚拟时间反转镜（Virtual Time Reversal Mirror,VTRM）引导了空间聚焦和信道均衡,将其应用在Pattern时延差编码（Pattern Time Delay Shift Coding,PDS）水声通信体制,构成VTRM-PDS系统,可增强抗多途干扰的能力。但当通信节点间存在缓慢运动,即信道缓慢时变时,在一帧信号中,信道均衡的效果会随时间逐渐降低,产生失配现象。提出了双向均衡方案,在没有信道先验知识的前提下,通过前向和后向信道均衡,充分利用探测信号和信道信息,提高了信道均衡效果。湖试结果证明了该方案的优越性。     

水声通信中无边带信息峰均比抑制算法

主要研究了多输入多输出正交频分复用水声通信中的峰均功率比抑制技术。针对传统选择性映射算法(Selective Mapping,SLM)需要将所选加扰相位序列的序号作为边带信息传递给接收端的缺点,提出了一种改进SLM算法,从判决反馈的角度设计图样检测器对所选加扰相位序列的序号进行判断,节约了边带信息传输,克服了传统SLM算法系统的误比特率性能依赖于边带信息准确性的问题,提高了系统的频带利用率。通过仿真验证,改进SLM方法能在不损失峰均功率比抑制性能的前提下,在接收端能够准确地解算出所选择的加扰相位序列序号,实现无边带信息传输的可靠水声通信。