A Secure Key Management Scheme for Heterogeneous Secure Vehicular Communication Systems

Intelligent transportation system （ITS） is proposed as the most effective way to improve road safety and traffic efficiency. However, the future of ITS for large scale transportation infrastructures deployment highly depends on the security level of vehicular communication systems （VCS）. Security applications in VCS are fulfilled through secured group broadcast. Therefore, secure key management schemes are considered as a critical research topic for network security. In this paper, we propose a framework for providing secure key management within heterogeneous network. The seeurity managers （SMs） play a key role in the framework by retrieving the vehicle departnre infi^rmation, encapsulating block to transport keys and then executing rekeying to vehicles within the same security domain. The first part of this framework is a novel Group Key Management （GKM） scheme basing on leaving probability （LP） of vehicles to depart current VCS region. Vehicle＇s LP factor is introduced into GKM scheme to achieve a more effieient rekeying scheme and less rekeying costs. The second component of the framework using the blockchain concept to simplify the distributed key management in heterogeneous VCS domains. Extensive simulations and analysis are provided to show the effectiveness and effieiency of the proposed framework： Our GKM results demonstrate that probability-based BR reduees rekeying eost compared to the benchmark scheme, while the blockchain deereases the time eost of key transmission over heterogeneous net-works.

LoS MIMO Transmission for LEO Satellite Communication Systems

To provide global service with low latency, the broadband low earth orbits (LEO) satellite constellation based communication systems have become one of the focuses in academic and industry. To allow for wideband access for user links, the feeder link of LEO satellite is correspondingly required to support high throughput data communications. To this end, we propose to apply line-of-sight (LoS) multiple-input multiple-output (MIMO) transmission for the feeder link to achieve spatial multiplexing by optimizing the antenna arrangement. Unlike the LoS MIMO applications for static scenarios, the movement of LEO satellites make it impractical to adjust the optimal antenna separation for all possible satellite positions. To address this issue, we propose to design the antenna placement to maximize the ergodic channel capacity during the visible region of the ground station. We first derive the closed-form probability distribution of the satellite trajectory in visible region. Based on which the ergodic channel capacity can be then calculated numerically. The antenna placement can be further optimized to maximize the ergodic channel capacity. Numerical results verify the derived probability distribution of the satellite trajectory, and show that the proposed LoS MIMO scheme can significantly increase the ergodic channel capacity compared with the existing SISO one.

M3SC:A Generic Dataset for Mixed Multi-Modal(MMM)Sensing and Communication Integration

The sixth generation(6G)of mobile communication system is witnessing a new paradigm shift,i.e.,integrated sensing-communication system.A comprehensive dataset is a prerequisite for 6G integrated sensing-communication research.This paper develops a novel simulation dataset,named M3SC,for mixed multi-modal(MMM)sensing-communication integration,and the generation framework of the M3SC dataset is further given.To obtain multimodal sensory data in physical space and communication data in electromagnetic space,we utilize Air-Sim and WaveFarer to collect multi-modal sensory data and exploit Wireless InSite to collect communication data.Furthermore,the in-depth integration and precise alignment of AirSim,WaveFarer,andWireless InSite are achieved.The M3SC dataset covers various weather conditions,multiplex frequency bands,and different times of the day.Currently,the M3SC dataset contains 1500 snapshots,including 80 RGB images,160 depth maps,80 LiDAR point clouds,256 sets of mmWave waveforms with 8 radar point clouds,and 72 channel impulse response(CIR)matrices per snapshot,thus totaling 120,000 RGB images,240,000 depth maps,120,000 LiDAR point clouds,384,000 sets of mmWave waveforms with 12,000 radar point clouds,and 108,000 CIR matrices.The data processing result presents the multi-modal sensory information and communication channel statistical properties.Finally,the MMM sensing-communication application,which can be supported by the M3SC dataset,is discussed.

Resource Allocation in UAV-NOMA Communication Systems Based on Proportional Fairness

This paper investigates the power allocation problem in non-orthogonal multiple access(NOMA)integrated unmanned aerial vehicle(UAV)communication systems.In particular,we propose a novel resource allocation scheme to increase the transmission rate of the users that have relatively worse channel state information,while reducing the sum rate loss.To solve this problem efficiently,we decouple the optimization problem into three subproblems.First,we solve the problem of user pairing and subchannel allocation.Second,the optimum power proportional factor is derived to allocate transmit power among different users on the same subchannel.At last,different subchannels are allocated with appropriate power to improve the performance of the subchannels.Simulation results show that the proposed scheme can enjoy a better performance than the benchmark methods since it can achieve a proper trade-off between the system sum rate and the proportional fairness.

Investigation on photonic crystal nanobeam cavity based on mixed diamond–circular holes

A photonic crystal nanobeam cavity(M-PCNC)with a structure incorporating a mixture of diamond-shaped and circular air holes is pro-posed.The performance of the cavity is simulated and studied theoretically.Using thefinite-difference time-domain method,the parameters of the M-PCNC,including cavity thickness and width,lattice constant,and radii and numbers of holes,are optimized,with the quality factor Q and mode volume Vm as performance indicators.Mutual modulation of the lattice constant and hole radius enable the proposed M-PCNC to realize outstanding performance.The optimized cavity possesses a high quality factor Q 1.45105 and an ultra-small mode=×volume Vm 0.01(λ/n)[Zeng et al.,Opt Lett 2023:48;3981–3984]in the telecommunications wavelength range.Light can be progres-=sively squeezed in both the propagation direction and the perpendicular in-plane direction by a series of interlocked anti-slots and slots in the diamond-shaped hole structure.Thereby,the energy can be confined within a small mode volume to achieve an ultra-high Q/Vm ratio.

Joint User Scheduling and Antenna Selection in Distributed Massive MIMO Systems with Limited Backhaul Capacity

Massive MIMO systems offer a high spatial resolution that can drastically increase the spectral and/or energy efficiency by employing a large number of antennas at the base station(BS).In a distributed massive MIMO system,the capacity of fiber backhaul that links base station and remote radio heads is usually limited,which becomes a bottleneck for realizing the potential performance gain of both downlink and uplink.To solve this problem,we propose a joint antenna selection and user scheduling which is able to achieve a large portion of the potential gain provided by the massive MIMO array with only limited backhaul capacity.Three sub-optimal iterative algorithms with the objective of sumrate maximization are proposed for the joint optimization of antenna selection and user scheduling,either based on greedy fashion or Frobenius-norm criteria.Convergence and complexity analysis are presented for the algorithms.The provided Monte Carlo simulations show that,one of our algorithms achieves a good tradeoff between complexity and performance and thus is especially fit for massive MIMO systems.

Satellite Communications Integration with Terrestrial Networks

In this paper we evaluate the feasibility of seamless and efficient integration of terrestrial communication systems with satellite networks. This aspect is considered by standardisation bodies such as ETSI [1], 5 G-PPP [2] and 3 GPP [3]. A comprehensive system is designed and implemented in an emulation prototype, including standard 3 GPP LTE core network functionality [4] with its different layers: networking, data forwarding, control, management and monitoring and is validated through performance measurements. This work is a technical feasibility study of extending terrestrial communication systems with satellite networks as backhaul, increasing the energy efficiency, network robustness during natural disasters as well as being an alternative for peak-time data forwarding of the terrestrial communication services. Due to its global coverage property, terrestrial-satellite integration provides an obvious extension of communication services towards isolated and remote areas and an alternative for rural or highly distributed/highly mobile enterprise networks.

New Optimal Power Allocation for Bidirectional Communications in Cognitive Relay Network Using Analog Network Coding

Cognitive radio and cooperative communication can greatly improve the spectrum efficiency in wireless communications.We study a cognitive radio network where two secondary source terminals exchange their information with the assistance of a relay node under interference power constraints.In order to enhance the transmit rate and maintain fairness between two source terminals,a practical 2-phase analog network coding protocol is adopted and its optimal power allocation algorithm is proposed.Numerical results verify the superiority of the proposed algorithm over the conventional direct transmission protocol and 4-phase amplify-and-forward relay protocol.

MIMO-Terahertz in 6G Nano-Communications:Channel Modeling and Analysis

With the development of wireless mobile communication technology,the demand for wireless communication rate and frequency increases year by year.Existing wireless mobile communication frequency tends to be saturated,which demands for new solutions.Terahertz(THz)communication has great potential for the future mobile communications(Beyond 5G),and is also an important technique for the high data rate transmission in spatial information network.THz communication has great application prospects in military-civilian integration and coordinated development.In China,important breakthroughs have been achieved for the key techniques of THz high data rate communications,which is practically keeping up with the most advanced technological level in the world.Therefore,further intensifying efforts on the development of THz communication have the strategic importance for China in leading the development of future wireless communication techniques and the standardization process of Beyond 5G.This paper analyzes the performance of the MIMO channel in the Terahertz(THz)band and a discrete mathematical method is used to propose a novel channel model.Then,a channel capacity model is proposed by the combination of path loss and molecular absorption in the THz band based on the CSI at the receiver.Simulation results show that the integration of MIMO in the THz band gives better data rate and channel capacity as compared with a single channel.

Evaluation of Preamble Based Channel Estimation for MIMO-FBMC Systems

Filter-bank multicarrier （FBMC） with offset quadrature amplitude modulation （OQAM） is a candidate waveform for future wireless communications due to its advantages over orthogonal frequency division multiplexing （OFDM） systems. However, because of or-thogonality in real field and the presence of imaginary intrinsic interference, channel estimation in FBMC is not as straightforward as OFDM systems especially in multiple antenna scenarios. In this paper, we propose a channel estimation method which employs intrinsic interference cancellation at the transmitter side. The simulation results show that this method has less pilot overhead, less peak to average power ratio （PAPR）, better bit error rate （BER）, and better mean square error （MSE） performance compared to the well-known intrinsic approximation methods （IAM）.

Quantum Secure Direct Intercommunication with Superdense Coding and Entanglement Swapping

A quantum secure direct intercommunication scheme is proposed to exchange directly the communicators'secret messages by making use of swapping entanglement of Bell states.It has great capacity to distribute the secretmessages since these messages have been imposed on high-dimensional Bell states via the local unitary operations withsuperdense coding.The security is ensured by the secure transmission of the travel sequences and the application ofentanglement swapping.

Quality incentive based congestion control for multimedia communication over IP networks

In this paper we introduce a framework for using quality as an incentive to promote proper application level congestion control. Through integrating a joint-source channel coder and feedback-based congestion control scheme, we are able to construct accurate and efficient quality incentives. The framework is applicable in all network architectures where end-to-end congestion control may be used, and is as such not specific to either best-effort or traffic class-based architectures. The concept is presented along with preliminary simulations that highlight the resulting rate control accuracy. We also discuss how to implement some well-known congestion control schemes within our framework.

New Parallel N-Input Voting for Large Scale Fault-Tolerant Control Systems

Average （mean） voter is one of the commonest voting methods suitable for decision making in highly-available and long-missions applications where the availability and the speed of the system are critical.In this paper,a new generation of average voter based on parallel algorithms and parallel random access machine（PRAM） structure are proposed.The analysis shows that this algorithm is optimal due to its improved time complexity,speed-up,and efficiency and is especially appropriate for applications where the size of input space is large.

SMART COMMUNICATIONS AND NETWORKING FOR FUTURE DEEP-SPACE EXPLORATION

Since the first space probe flew to the Moon in 1959,over 200 deep-space exploration missions have already been carried out on the eight planets,various asteroids and comets in the solar system.Amount of deepspace scientific experiments promoted people to understand about the origin and evolution of the universe.

5G Ultra-Dense Network Fingerprint Positioning Method Based on Matrix Completion

The problem of high-precision indoor positioning in the 5G era has attracted more and more attention.A fingerprint location method based on matrix completion(MC-FPL)is proposed for 5G ultradense networks to overcome the high costs of traditional fingerprint database construction and matching algorithms.First,a partial fingerprint database constructed and the accelerated proximal gradient algorithm is used to fill the partial fingerprint database to construct a full fingerprint database.Second,a fingerprint database division method based on the strongest received signal strength indicator is proposed,which divides the original fingerprint database into several sub-fingerprint databases.Finally,a classification weighted K-nearest neighbor fingerprint matching algorithm is proposed.The estimated coordinates of the point to be located can be obtained by fingerprint matching in a sub-fingerprint database.The simulation results show that the MC-FPL algorithm can reduce the complexity of database construction and fingerprint matching and has higher positioning accuracy compared with the traditional fingerprint algorithm.

Triangular code:Near-optimal linear time fountain code

In this paper,we propose Triangular Code(TC),a new class of fountain code with near-zero redundancy and linear encoding and decoding computational complexities of OeLklog kT,where k is the packet batch size and L is the packet data length.Different from previous works where the optimal performance of codes has been shown under asymptotic assumption,TC enjoys near-zero redundancy even under non-asymptotic settings for smallmoderate number of packets.These features make TC suitable for practical implementation in batteryconstrained devices in IoT,D2D and M2M network paradigms to achieve scalable reliability,and minimize latency due to its low decoding delay.TC is a non-linear code,which is encoded using the simple shift and XOR addition operations,and decoded using the simple back-substitution algorithm.Although it is nonlinear code at the packet level,it remains linear code when atomized at the bit level.We use this property to show that the backsubstitution decoder of TC is equivalent to the Belief Propagation(BP)decoder of LT code.Therefore,TC can benefit from rich prolific literature published on LT code,to design efficient code for various applications.Despite the equivalency between the decoders of TC and LT code,we show that compared to state-of-the-art optimized LT code,TC reduces the redundancy of LT code by 68%-99% for k reaching 1024.

Multi-channel generation of vortex beams with controllable polarization states and orbital angular momentum

Optical vortices with tunable polarization states and topological charges are widely investigated in various physical systems and practical devices for high-capacity optical communication.However,this kind of structured light beams is usually generated using several polarization and spatial phase devices,which decreases the configurability of optical systems.Here,we have designed a kind of polarized optical multi-vortices generator based on the Stokes-Mueller formalism and cross-phase modulation.In our scheme,multi-channel generation of polarized vortex beams can be realized through a single optical element and a single-input Gaussian beam.The polarization states and orbital angular momentum of the generated light beams are all-optically controllable.Furthermore,the proposed polarized optical multi-vortices generator has also been demonstrated experimentally through one-step holographic recording in an azobenzene liquid-crystalline film and the experimental results agree with theoretical analysis.

Adaptive Time Slot Resource Allocation in SWIPT IoT Networks

The rapid advancement of Internet of Things(IoT)technology has brought convenience to people’s lives;however further development of IoT faces serious challenges,such as limited energy and shortage of network spectrum resources.To address the above challenges,this study proposes a simultaneous wireless information and power transfer IoT adaptive time slot resource allocation(SIATS)algorithm.First,an adaptive time slot consisting of periods for sensing,information transmission,and energy harvesting is designed to ensure that the minimum energy harvesting requirement ismet while the maximumuplink and downlink throughputs are obtained.Second,the optimal transmit power and channel assignment of the system are obtained using the Lagrangian dual and gradient descent methods,and the optimal time slot assignment is determined for each IoT device such that the sum of the throughput of all devices is maximized.Simulation results show that the SIATS algorithm performs satisfactorily and provides an increase in the throughput by up to 14.4%compared with that of the fixed time slot allocation(FTS)algorithm.In the case of a large noise variance,the SIATS algorithm has good noise immunity,and the total throughput of the IoT devices obtained using the SIATS algorithm can be improved by up to 34.7%compared with that obtained using the FTS algorithm.

Generation of hyperentangled photon pairs based on lithium niobate waveguide

Generation of hyperentangled photon pairs is investigated based on the lithium niobate straight waveguide.We propose to use the nonlinear optical process of spontaneous parametric down-conversion(SPDC)and a well-designed lithium niobate waveguide structure to generate a hyperentangled(in the polarization dimension and the energy-time dimension)two-photon state.By performing numerical simulations of the waveguide structure and calculating the possible polarization states,joint spectral amplitudes(JSA),and joint temporal amplitudes(JTA)of the generated photon pair,we show that the generated photon pair is indeed hyperentangled in both the polarization dimension and the energy-time dimension.

Performance analysis of quantum key distribution using polarized coherent-states in free-space channel

In free space channel,continuous-variable quantum key distribution(CV-QKD)using polarized coherent-states can not only make the signal state more stable and less susceptible to interference based on the polarization non-sensitive of the free-space channel,but also reduce the noise introduced by phase interference.However,arbitrary continuous modulation can not be carried out in the past polarization coding,resulting in that the signal state can not obtain arbitrary continuous value in Poincare space,and the security analysis of CV-QKD using polarized coherent-states in free space is not complete.Here we propose a new modulation method to extend the modulation range of signal states with an optical-fiber-based polarization controller.In particular,in terms of the main influence factors in the free-space channel,we utilize the beam extinction and elliptical model when considering the transmittance and adopt the formulation of secret key rate.In addition,the performance of the proposed scheme under foggy weather is also taken into consideration to reveal the influence of severe weather.Numerical simulation shows that the proposed scheme is seriously affected by attenuation under foggy weather.The protocol fails when visibility is less than 1 km.At the same time,the wavelength can affect the performance of the proposed scheme.Specifically,under foggy weather,the longer the wavelength,the smaller the attenuation coefficient,and the better the transmission performance.Our proposed scheme can expand the modulation range of signal state,and supplement the security research of the scheme in the free-space channel,thus can provide theoretical support for subsequent experiments.