Jamming Assisted Covert Wireless Communication in Multi-Channel Systems

This paper investigates the jammerassisted multi-channel covert wireless communication(CWC)by exploiting the randomness of sub-channel selection to confuse the warden.In particular,we propose two sub-channel selection transmission schemes,named random sub-channel selection(RSS)scheme and maximum sub-channel selection(MSS)scheme,to enhance communication covertness.For each proposed scheme,we first derive closed-form expressions of the transmission outage probability(TOP),the average effective rate,and the minimum average detection error probability(DEP).Then,the average effective covert rate(ECR)is maximized by jointly optimizing the transmit power at the transmitter and the number of sub-channels.Numerical results show that there is an optimal value of the number of sub-channels that maximizes the average ECR.We also find that to achieve the maximum average ECR,a larger number of subchannels are needed facing a stricter covertness constraint.

Photonics-assisted THz wireless communication enabled by wide-bandwidth packaged backilluminated modified uni-traveling-carrier photodiode

This paper presents a wide-bandwidth back-illuminated modified uni-traveling-carrier photodiode(MUTC-PD)packaged with standard WR-5 rectangular waveguide for high-speed wireless communications.With optimized epitaxy structure and coplanar waveguide electrodes,the fabricated 4-μm-diameter PD exhibits ultra-flat frequency response and high saturation power.Integrated passive circuits including low-loss bias-tee and E-plane probe are designed to package the PD into a compact module with waveguide output.The packaged PD module has demonstrated a flat frequency response with fluctuations within±2.75 d B over a broadband of 140–220 GHz and a high saturated output power of-7.8 d Bm(166μW)at 140 GHz.For wireless communication applications,the packaged PD is used to implement 1-m free space transmission at carrier frequencies of 150.5 and 210.5 GHz,with transmission rates of 75 and 90 Gbps,respectively.

Echo state network based symbol detection in chaotic baseband wireless communication

The Chaotic Baseband Wireless Communication System(CBWCS)is expected to eliminate the Inter-Symbol Interference(ISI)caused by multipath propagation by using the optimal decoding threshold that is the sum of the ISI caused by past decoded bits and the ISI caused by future transmitting bits.However,the current technique is only capable of removing partial effects of the ISI,because only past decoded bits are available for the suboptimal decoding threshold calculation.The unavailability of the future information needed for the optimal decoding threshold is an obstacle to further improve the Bit Error Rate(BER)performance.In contrast to the previous method using Echo State Network(ESN)to predict one future bit,the proposed method in this paper predicts the optimal decoding threshold directly using ESN.The proposed ESN-based threshold prediction method simplifies the symbol decoding operation by avoiding the iterative prediction of the output waveform points using ESN and accumulated error caused by the iterative operation.With this approach,the calculation complexity is reduced compared to the previous ESN-based approach.The proposed method achieves better BER performance compared to the previous method.The reason for this superior result is twofold.First,the proposed ESN is capable of using more future symbols information conveyed by the ESN input to obtain more accurate threshold rather than the previous method in which only one future symbol was available.Second,the proposed method here does not need to estimate the channel information using Least Squared(LS)method,which avoids the extra error caused by inaccurate channel information estimation.Simulation results and experiment based on a wireless open-access research platform under a practical wireless channel show the effectiveness and superiority of the proposed method.

Implementation of High-Q Embedded Band Pass Filter in Wireless Communication

At 12.8 MHz center frequency,the advanced miniaturized polymer-based planar high quality factor(Q)passive elements embedded bandpassfilter works in the L-band.Because most of the demands operate inside the spectrum,the wideband or high-speed operation necessary to enhance must be acquired in microwave frequency ranges.The channel has a quiet,high-performance micro-filter with wideband rejection.Capacitors and inductors are used in the high quality factor(Q)passive components,and related networks are incorporated in thefilter.Embedded layers are concatenated using Three-Dimensional Integrated Circuit(3D-IC)integration,parasitics are removed,and interconnection losses are negotiated using de-embedding methods.A wireless application-based Liquid Crystalline Polymer(LCP)viewpoint is employed as a substrate material in this work.The polymer processes,their properties,and the incorporated high-Q Band Pass Filter Framework.The suggestedfilter model is computed and manufactured utilizing the L-band frequency spectrum,decreasing total physical length by 31%while increasing bandwidth by 45%.

5G High Mobility Wireless Communications: Challenges and Solutions

The fifth generation(5G) network is expected to support significantly large amount of mobile data traffic and huge number of wireless connections,to achieve better spectrum- and energy-efficiency,as well as quality of service(QoS) in terms of delay,reliability and security.Furthermore,the 5G network shall also incorporate high mobility requirements as an integral part,providing satisfactory service to users travelling at a speed up to 500 km/h.This paper provides a survey of potential high mobility wireless communication(HMWC) techniques for 5G network.After discussing the typical requirements and challenges of HMWC,key techniques to cope with the challenges are reviewed,including transmission techniques under the fast timevarying channels,network architecture with mobility support,and mobility management.Finally,future research directions on 5G high mobility communications are given.

Developing MXenes from Wireless Communication to Electromagnetic Attenuation

There is an urgent global need for wireless communication utilizing materials that can provide simultaneous flexibility and high conductivity.Avoiding the harmful effects of electromagnetic(EM)radiation from wireless communication is a persistent research hot spot.Two-dimensional(2D)materials are the preferred choice as wireless communication and EM attenuation materials as they are lightweight with high aspect ratios and possess distinguished electronic properties.MXenes,as a novel family of 2D materials,have shown excellent properties in various fields,owing to their excellent electrical conductivity,mechanical stability,high flexibility,and ease of processability.To date,research on the utility of MXenes for wireless communication has been actively pursued.Moreover,MXenes have become the leading materials for EM attenuation.Herein,we systematically review the recent advances in MXene-based materials with different structural designs for wireless communication,electromagnetic interference(EMI)shielding,and EM wave absorption.The relationship governing the structural design and the effectiveness for wireless communication,EMI shielding,and EM wave absorption is clearly revealed.Furthermore,our review mainly focuses on future challenges and guidelines for designing MXene-based materials for industrial application and foundational research.

Adaptive modulation in MIMO optical wireless communication systems

In the intensity modulation and direct detection （IM/DD） multiple-input multiple-output （MIMO） optical wireless communication systems, a direct-current-biased adaptive modulation scheme is proposed to guarantee the nonnegative property of transmitted signals, and the MIMO channel is converted to a parallel channel by using a singular value decomposition. Besides, a QR decomposition and successive interference cancellation based adaptive modulation scheme is proposed, and the MIMO channel can be simplified to a parallel channel under the bit error ratio （BER） target constraint. The power is optimally allocated to each sub-channel to maximize the data rate. Simulation results show that the proposed adaptive modulation schemes can effectively improve the transmission rate of the systems under the BER target and constant optical power constraints. The proposed adaptive modulation schemes make use of the multiplexing gain of the MIMO techniques, and can further improve the spectrum efficiency of optical wireless systems.

Channel Estimation and Throughput Evaluation for 5G Wireless Communication Systems in Various Scenarios on High Speed Railways

The fifth generation （5G） wireless communication is currently a hot research topic and wireless communication systems on high speed railways （HSR） are important applications of 5G technologies. Existing stud- ies about 5G wireless systems on high speed railways （HSR） often utilize ideal channel parameters and are usually based on simple scenarios. In this paper, we evaluate the down- link throughput of 5G HSR communication systems on three typical scenarios including urban, cutting and viaduct with three different channel estimators. The channel parameters of each scenario are generated with tapped delay line （TDL） models through ray-tracing sim- ulations, which can be considered as a good match to practical situations. The channel estimators including least square （LS）, linear minimum mean square error （LMMSE）, and our proposed historical information based ba- sis expansion model （HiBEM）. We analyze the performance of the HiBEM estimator in terms of mean square error （MSE） and evaluate the system throughputs with different channel estimates over each scenario. Simulation results are then provided to corroborate our proposed studies. It is shown that our HiBEM estimator outperforms other estimators and that the sys-tem throughput can reach the highest point in the viaduct scenario.

Design and Implementation of An Active Multibeam Antenna System with 64 RF Channels and 256 Antenna Elements for Massive MIMO Application in 5G Wireless Communications

This paper focuses on the design and implementation of an active multibeam antenna system for massive MIMO applications in 5G wireless communications.The highly integrated active multibeam antenna system is designed and implemented at 5.8 GHz with 64 RF Channels and 256 antenna elements.The 64-channel highly integrated active multibeam antenna system provides a verification platform for digital beamforming algorithm and massive MIMO channel estimation for next generation wireless communications.

Wireless communication and wireless power transfer system for implantable medical device

Traditional magnetically coupled resonant wireless power transfer technology uses fixed distances between coils for research,to prevent fluctuations in the receiving voltage,and lead to reduce transmission efficiency.This paper proposes a closed-loop control wireless communication wireless power transfer system with a wearable four-coil structure to stabilize the receiving voltage fluctuation caused by changes in the displacement between the coils.Test results show that the system can provide stable receiving voltage,no matter how the distance between the transmitting coil and the receiving coil is changed.When the transmission distance is 20 mm,the power transfer efficiency of the system can reach 18.5%under the open-loop state,and the stimulus parameters such as the stimulation period and pulse width can be adjusted in real time through the personal computer terminal.

Integrated Wireless Communication System Using MANET for Remote Pastoral Areas of Tibet

To reduce the network deployment cost and provide voice, message and low rate data services in remote pastoral areas of Tibet effectively, an integrated wireless communication system utilizing MANET(Mobile Ad hoc Network) is proposed. The sparse mobile devices, assisted with the solar-powered multi-functional standing stations mainly on networking maintenance and routing arrangement, self-organize into a MANET. The topology of the standing stations is designed for networking robust and to simplify the routing method and energy strategy. Then in the OMNe T++(Objective Modular Network Test bed in C++) simulation, the energy consumption is analysis while adjusting routing with the different energy status of the standing stations. The result shows that the standing stations should adjust routing as well as control the mobile devices' activity level according to the energy states of the standing stations and their adjacent mobile devices.

Strain-Insensitive Hierarchically Structured Stretchable Microstrip Antennas for Robust Wireless Communication

As the key component of wireless data transmission and powering,stretchable antennas play an indispensable role in flexible/stretchable electronics.However,they often suffer from frequency detuning upon mechanical deformations;thus,their applications are limited to wireless sensing with wireless transmission capabilities remaining elusive.Here,a hierarchically structured stretchable microstrip antenna with meshed patterns arranged in an arched shape showcases tunable resonance frequency upon deformations with improved overall stretchability.The almost unchanged resonance frequency during deformations enables robust on-body wireless communication and RF energy harvesting,whereas the rapid changing resonance frequency with deformations allows for wireless sensing.The proposed stretchable microstrip antenna was demonstrated to communicate wirelessly with a transmitter(input power of−3 dBm)efficiently(i.e.,the receiving power higher than−100 dBm over a distance of 100 m)on human bodies even upon 25%stretching.The flexibility in structural engineering combined with the coupled mechanical-electromagnetic simulations,provides a versatile engineering toolkit to design stretchable microstrip antennas and other potential wireless devices for stretchable electronics.

Eavesdropping Area for Evaluating the Security of Wireless Communications

Compared with wired communication,the wireless communication link is more vulnerable to be attacked or eavesdropped because of its broadcast nature.To prevent eavesdropping,many researches on transmission techniques or cryptographic methods are carried out.This paper proposes a new index parameter named as eavesdropping area,to evaluate the anti-eavesdropping performance of wireless system.Given the locations of legitimate transmitter and receiver,eavesdropping area index describes the total area of eavesdropping regions where messages can be wiretapped in the whole evaluating region.This paper gives detailed explanations about its concept and deduces mathematical formulas about performance curves based on region classification.Corresponding key system parameters are analyzed,including the characteristics of eavesdropping region,transmitted beam pattern,beam direction,receiver sensitivity,eavesdropping sensitivity,path loss exponent and so on.The proposed index can give an insight on the confirmation of high-risk eavesdropping region and formulating optimal transmitting scheme for the confidential communications to decrease the eavesdropping probability.

Green indoor optical wireless communication systems:Pathway towards pervasive deployment

The Optical Wireless Communication(OWC)offers the high capacity of optical fiber communication with the flexibility of wireless communication.Since it works in the optical region of the ElectroMagnetic(EM)spectrum,it guarantees safety and security which are critical in radio and microwave frequency communication.The principal objective of this paper is to analyze the indoor OWC systems on these guaranteed features,and safety and security are jointly denoted by the term green.The high obstacle impermeability of optical signals and their directivity strengthen the security of indoor OWC data transmission.The confidentiality and authenticity of optical wireless data can also be preserved with the Quantum Key Distribution(QKD).This paper provides a technological overview and a review of literature about the OWC system that helps to identify the challenges in the path of a ubiquitous deployment of green wireless communication systems.Significant advancements in the sources and detectors are discussed together with the coding,modulation and multiplexing techniques for making highly robust OWC links.The ubiquitous deployment of green OWC necessitates the development of optical transmitters and receivers,performance enhancement techniques,incorporation of uplink and energy harvesting abilities,and safety and security enhancement techniques.Hence,a special emphasis is placed on these aspects and their challenges towards the green implementation.Furthermore,the paper explores some significant indoor applications based on the OWC that have great impacts on the Next Generation Networks(NGN)and the Internet of Things(IoT).

Toward intelligent wireless communications:Deep learning-based physical layer technologies

Advanced technologies are required in future mobile wireless networks to support services with highly diverse requirements in terms of high data rate and reliability,low latency,and massive access.Deep Learning(DL),one of the most exciting developments in machine learning and big data,has recently shown great potential in the study of wireless communications.In this article,we provide a literature review on the applications of DL in the physical layer.First,we analyze the limitations of existing signal processing techniques in terms of model accuracy,global optimality,and computational scalability.Next,we provide a brief review of classical DL frameworks.Subsequently,we discuss recent DL-based physical layer technologies,including both DL-based signal processing modules and end-to-end systems.Deep neural networks are used to replace a single or several conventional functional modules,whereas the objective of the latter is to replace the entire transceiver structure.Lastly,we discuss the open issues and research directions of the DL-based physical layer in terms of model complexity,data quality,data representation,and algorithm reliability.

Precoder Design and Impulsive Noise Mitigation Scheme for Industrial Wireless Communications

In industrial wireless scenarios,the impulsive noise(IN)incurred by machine running or operation causes a serious influence on the powerlimited industrial wireless communications.It is challenging to ensure efficient and reliable transmission with quality of service(QoS)guarantee for machinetype communication devices(MTCDs).Considering the IN in the industrial process,this paper establishes the multiuser multiple-input single-output(MU-MISO)orthogonal frequency division multiplexing(OFDM)system model,which combines transmitter and receiver design.Two precoding schemes are designed to improve communication effectiveness at the transmitter.More specifically,the precoder design scheme which combines semi-definite relaxation(SDR)with difference-of-two-convex-function(D.C.)iterative algorithm,is developed by utilizing the Dinkelbach method to improve the system effectiveness.To decrease the computational complexity,we devise the quadratic-based fractional programming(QFP)algorithm,which decouples the variables by using a quadratic transform method.On this basis,the IN mitigation scheme is studied to reduce the system error rate(SER)at the receiver.With the goal of improving the reliability of industrial wireless communications,we propose a hybrid nonlinear IN mitigation(HNINM)scheme and then derive its closed-form expression of SER.The simulation results show that the proposed QFP algorithm achieves superior performance while the HNINM scheme decreases the SER of industrial wireless communications.

Guest editorial: special issue on high mobility wireless communications

The high-speed railway and high-way networks are now expanding at a phenomenal speed in Chinaand in many other parts of the world. The related broadband wireless communication over high-speed trains and highway vehicles is a very challenging task due to hostile transmission channel conditions. The demand for such services is growing rapidly, following the proliferation of laptop/tablet computers and smart phones. This motivates the research on wireless communications in the high mobility environments.

A novel mutual authentication and key agreement protocol based on NTRU cryptography for wireless communications

In this paper, the authors present a novel mutual authentication and key agreement protocol based on the Number Theory Research Unit (NTRU) public key cryptography. The symmetric encryption, hash and “challenge-response” techniques were adopted to build their protocol. To implement the mutual authentication and session key agreement, the proposed protocol contains two stages: namely initial procedure and real execution stage. Since the lightweight NTRU public key cryptography is employed, their protocol can not only overcome the security flaws of secret-key based authentication protocols such as those used in Global System for Mobile Communications (GSM) and Universal Mobile Telecommunications System (UMTS), but also provide greater security and lower computational complexity in comparison with currently well-known public key based wireless authentication schemes such as Beller-Yacobi and M.Aydos protocols.

Power Allocation Strategy for Secret Key Generation Method in Wireless Communications

Secret key generation(SKG)is an emerging technology to secure wireless communication from attackers.Therefore,the SKG at the physical layer is an alternate solution over traditional cryptographic methods due to wireless channels’uncertainty.However,the physical layer secret key generation(PHY-SKG)depends on two fundamental parameters,i.e.,coherence time and power allocation.The coherence time for PHY-SKG is not applicable to secure wireless channels.This is because coherence time is for a certain period of time.Thus,legitimate users generate the secret keys(SKs)with a shorter key length in size.Hence,an attacker can quickly get information about the SKs.Consequently,the attacker can easily get valuable information from authentic users.Therefore,we considered the scheme of power allocation to enhance the secret key generation rate(SKGR)between legitimate users.Hence,we propose an alternative method,i.e.,a power allocation,to improve the SKGR.Our results show 72%higher SKGR in bits/sec by increasing power transmission.In addition,the power transmission is based on two important parameters,i.e.,epsilon and power loss factor,as given in power transmission equations.We found out that a higher value of epsilon impacts power transmission and subsequently impacts the SKGR.The SKGR is approximately 40.7%greater at 250 from 50 mW at epsilon=1.The value of SKGR is reduced to 18.5%at 250 mW when epsilonis 0.5.Furthermore,the transmission power is also measured against the different power loss factor values,i.e.,3.5,3,and 2.5,respectively,at epsilon=0.5.Hence,it is concluded that the value of epsilon and power loss factor impacts power transmission and,consequently,impacts the SKGR.

Towards Converged Millimeter-Wave/Terahertz Wireless Communication and Radar Sensing

Converged communication and radar sensing systems have attained increasing attention in recent years.The development of converged radar-data systems is reviewed,with a special focus on millimeter/terahertz systems as a promising trend.Firstly,we present historical development and convergence technology concept for communication-radar systems,and highlight some emerging technologies in this area.We then provide an updated and comprehensive survey of several converged systems operating in different microwave and millimeter frequency bands,by providing some selective typical communication and radar sensing systems.In this part,we also summarize and compare the system performance in terms of maximum range/range resolution for radar mode and Bit Error Rate(BER)/wireless distance for communication mode.In the last section,the convergence of millimeter/terahertz communication-radar system is concluded by analyzing the prospect of millimeter-wave/terahertz technologies in providing ultrafast data rates and high resolution for our smart future.