Channel characteristics and formation mechanism of Ganjiang River

Relative straight channel of the middle and upper reaches of Ganjiang has been formed due to thecontraction of mountains and hills being composed of bedrocks on both banks of the river. But however, At the lower reaches, branching channel predominates due to limited contracting force of the river banks as the evolution and development of branching channels are closely related with locations and controle effect of nodal points. There are sufficient water containing less sediments in Ganjiang River where the sharp rise and fall of the flow discharge makes the grain size of the particles rather coars. Gravels mingled with sand dominate the channel bed and components of central bars are also much coarser than those in sandy bed of the middle and lower reaches of the Yangtze River.

Channel Characteristics Based on Ray Tracing Methods in Indoor Corridor at 300 GHz

With the rapid development of communication technology,people's demand for ultra-high-speed wireless links becomes higher,among which terahertz spectra are considered as one of the most promising spectra.In this paper,we analyze the channel characteristics at 300 GHz in indoor corridor based on ray tracing methods,including the large-scale and small-scale fading parameters.Simulation results show that it is suitable for short distance transmission due to its large path loss(PL).Firstly,compared with line-of-sight(LoS),the correlation of frequency components in non-line-of-sight(NLoS)is much better,but LoS has more abundant circle angular spread(CAS).Then,a stochastic model is well derived to describe the distance-dependent behaviour of root-mean-square delay spread(RMS-DS)as well as root-mean-square CAS(RMS-CAS).Besides,we find that the channel capacity can effectively increase by increasing the transmitted power in both LoS and NLoS.Finally,it can be seen that the RMS-DS can be significantly reduced in LoS and the channel capacity can increase by changing the position of the transceivers.The simulation results will provide references for future indoor communication.

The Channel Characteristics Analysis of Two River Types in Lee's Ferry Area

Discovery showed that some of the rivers in Lee＇s Ferry area run on bedrocks while some are on the alluvium,based on geomorphology,the different kinds of channel characteristics can influence whether these rivers run on bed rock or alluvium. By analyzing the velocity,discharge,width and depth,hydraulic radius and comparing the different channel characteristics of rivers in other areas with Lee＇s Ferry,it is observed that the channel discharge,velocity and the hydraulic radius play an important role in controlling the transport-limited river and these factors can be inferred to be correct even for all the river channels in Arizona.

Secure transmission technology based on direct modulation with random channel characteristics

Aiming at the problem of insufficient security in the existing wireless data trans-mission,a security transmission technology based on direct modulation with random channel characteristics is proposed.The method first estimates channel characteristics using the preamble in the communication frame,and then embeds channel characteristics into the I/Q modulator.After that,the modulated constellation diagram undergoes random hopping of the constellation position compared with the original constellation diagram,thus achieving the effect of secure transmission.Due to the reciprocity of the uplink and downlink channels,channel characteristics estimated by the downlink receiver are almost the same as those esti-mated by the uplink receiver,and the correct plaintext data can be recovered by performing corresponding demodulation with them.Compared with the existing scheme of quantizing channel characteristics and then encrypting data,the method reduces the performance loss caused by quantization.In addition,its bit error rate is lower than that of the quantization method.In general,it has higher security and convenience.

Statistical Channel Modeling for Indoor VLC Communications Based on Channel Measurements

Visible light communication(VLC)has attracted much attention in the research of sixthgeneration(6G)systems.Furthermore,channel modeling is the foundation for designing efficient and robust VLC systems.In this paper,we present extensive VLC channel measurement campaigns in indoor environments,i.e.,an office and a corridor.Based on the measured data,the large-scale fading characteristics and multipath-related characteristics,including omnidirectional optical path loss(OPL),K-factor,power angular spectrum(PAS),angle spread(AS),and clustering characteristics,are analyzed and modeled through a statistical method.Based on the extracted statistics of the above-mentioned channel characteristics,we propose a statistical spatial channel model(SSCM)capable of modeling multipath in the spatial domain.Furthermore,the simulated statistics of the proposed model are compared with the measured statistics.For instance,in the office,the simulated path loss exponent(PLE)and the measured PLE are 1.96and 1.97,respectively.And,the simulated medians of AS and measured medians of AS are 25.94°and 24.84°,respectively.Generally,the fact that the simulated results fit well with measured results has demonstrated the accuracy of our SSCM.

Artificial Intelligence Based Multi-Scenario mmWave Channel Modeling for Intelligent High-Speed Train Communications

A large amount of mobile data from growing high-speed train(HST)users makes intelligent HST communications enter the era of big data.The corresponding artificial intelligence(AI)based HST channel modeling becomes a trend.This paper provides AI based channel characteristic prediction and scenario classification model for millimeter wave(mmWave)HST communications.Firstly,the ray tracing method verified by measurement data is applied to reconstruct four representative HST scenarios.By setting the positions of transmitter(Tx),receiver(Rx),and other parameters,the multi-scenarios wireless channel big data is acquired.Then,based on the obtained channel database,radial basis function neural network(RBF-NN)and back propagation neural network(BP-NN)are trained for channel characteristic prediction and scenario classification.Finally,the channel characteristic prediction and scenario classification capabilities of the network are evaluated by calculating the root mean square error(RMSE).The results show that RBF-NN can generally achieve better performance than BP-NN,and is more applicable to prediction of HST scenarios.

Secure transmission technology based on direct modulation with random channel characteristics

Aiming at the problem of insucient security in the existing wireless data trans-mission,a security transmission technology based on direct modulation with random channel characteristics is proposed.The method rst estimates channel characteristics using the preamble in the communication frame,and then embeds channel characteristics into the I/Q modulator.After that,the modulated constellation diagram undergoes random hopping of the constellation position compared with the original constellation diagram,thus achieving the e ect of secure transmission.Due to the reciprocity of the uplink and downlink channels,channel characteristics estimated by the downlink receiver are almost the same as those esti-mated by the uplink receiver,and the correct plaintext data can be recovered by performing corresponding demodulation with them.Compared with the existing scheme of quantizing channel characteristics and then encrypting data,the method reduces the performance loss caused by quantization.In addition,its bit error rate is lower than that of the quantization method.In general,it has higher security and convenience.

AG Channel Measurements and Characteristics Analysis in Hilly Scenarios for 6G UAV Communications

As an important part of sixth generation(6G)integrated space-air-ground-sea networks,unmanned aerial vehicle(UAV)communications have aroused great attention and one of its typical application scenarios is the hilly environments.The related UAV air-ground(AG)channel characteristics analysis is crucial for system design and network evaluation of future UAV communications in hilly scenarios.In this paper,a recently conducted channel measurements campaign in a hilly scenario is presented,which is conducted at the center frequencies of 2.585 GHz and 3.5 GHz for different flight trajectories.Based on the measurement data,some key channel characteristics are analyzed,including path loss(PL),shadow fading(SF),Rician K-factor,root mean square(RMS)delay spread(DS),and temporal auto-correlation function(ACF).Finally,the comparison of typical channel characteristics under circular and straight trajectories is given.The related results can provide a theoretical reference for constructing future UAV communication system in hilly scenarios.

ANALYSIS ON CHARACTERISTICS OF AERONAUTICAL WIRELESS CHANNELS

In aeronautical mobile communication systems,wireless channels characteristics are dif-ferent in scenarios of Parking,En-Route,Taxi,and Arrival/Take-off.By considering fading types,power spectrum density and delay characterization of aeronautical wireless channels,typical parame-ters of aeronautical wireless channels model are investigated to analyze characteristics of aeronautical wireless channels.

MIMO Channel Measurement and Characterization at 6.0-6.4 GHz Under Typical Classroom Environment

An extensive 4 × 4 MIMO channel measurement is carried out at 6. 0- 6. 4 GHz under a typical classroom environment with channel sounder based on vector network analyzer. Both LOS and NLOS scenarios are considered. The results on path loss,delay spread and spatial correlation are presented. The measurement shows that,for corridor coverage,2×2 MIMO is more economical than 4×4 MIMO due to high correlation. In order to identify the unique characteristics at the high frequency band,the measured channel parameters at 6. 0-6. 4 GHz are compared with those at 2. 45 GHz. The comparison shows that the shortened wavelength of this higher frequency band results in a great difference of channel characteristics. Therefore,our measurement results provide new guidance for the design and development of the system working on 6. 0-6. 4 GHz band.

EXPERIMENTAL STUDY ON TURBULENT FEATURES IN THE NEGATIVE TRANSPORT REGION OF ASYMMETRIC PLANE CHANNEL FLOW

Turbulent features of streamwise and vertical components of velocity in the negative transport region of asymmetric plane channel flow have been studied experimentally in details. Experiments show that turbulent fluctuations in negative transport region are suppressed, and their probability distributions are far from Gaussian. Besides, the skewness factors attain their negative maxima at the position of the maximum mean velocity, whereas the flatness factors attain their positive maxima at the same position.

Comparative Study on Galvanic-Coupled Intrabody Channel Characteristic Measurement Methods

The galvanic-coupled intrabody communication(GCIBC)uses the human body as the channel for data transmission.The signal flow through different paths within different measure-ment schemes,resulting in distinct deviations in the experimental results.This method completely uses human body channel to transmit low-power signals,and has good anti-interference perform-ance.However,for a long time,the channel research of GCIBC has not determined a set of recog-nized and accurate measurement methods and standards.However,few researcher analyze the dif-ferences and principles between different measurement methods.This paper aims at three com-monly used measurement methods.Abstract the equivalent schematic diagrams of three measure-ment schemes:direct measurement,using high-precision differential probe and using balun.The sig-nal return paths generated by three measurement methods are analyzed,the impedance matching and energy transmission efficiency are compared.According to the analysis,the empirical expres-sions in different cases are listed.The mechanism between the channel measurement results gener-ated by the set experimental configuration and the comparison experiment is clarified.The compar-ison experiment with complete floating measurement is carried out as a reference to verify the pro-posed opinion.The measurement error caused by different experimental configurations is verified.This study can provide a reference opinions for the experimental error analysis of GCIBC research in the future,and provide suggestions for the selection of experimental configuration.

Effects of Boundary Current on Electromagnetic Dispersion Characteristics for a Relativistic Electron Beam

With betatron oscillation characteristics of the electron beam and ion channel effect taken into account,dispersion characteristics of electrostatic modes and TM modes for a relativistic electron beam guided by ion channel are studied.Dispersion relations are derived and solved numerically to investigate the dependence of the dispersion characteristics for electrostatic modes and TM modes on the betatron oscillation frequency and the ratio of the relativistic electron beam radius to the waveguide radius.The effects of the boundary current on the dispersion characteristic of the TM modes and the interaction between the betatron modes and TM modes are analyzed.When considering the boundary current,for a strong ion channel,a new low-frequency branch of the TM modes arises and the interaction frequency between the betatron modes and the TM01modes is increased with the same parameters.

Characteristics and modeling of UAV-vehicle MIMO wideband channels

A geometry-based stochastic model(GBSM) for unmanned aerial vehicle to vehicle(UAV-V) multiple-input multiple-output(MIMO) wideband channel is proposed to investigate the characteristics of UAV-V channel. Based on the proposed model, a three-dimensional(3D) wideband channel matrix regarding channel numbers, time and delay is constructed. And some important channel characteristics parameters, such as power delay profile(PDP), root mean square(RMS) delay spread, RMS Doppler spread, channel gain and Doppler power spectral density(PSD) are investigated with different vehicle velocities. It is much simpler and clearer compared with the complex analytical derivations. The results are compared with validated analysis to confirm the theoretical analysis.

Numerical analysis of seepage flow characteristic of collapse column under the influence of mining

Based on the importance of fractured rock mass seepage research, in order to analyze seepage flow characteristics of collapse column under the influence of mining, a method by embedding fractured rock mass flow solid coupling relationship into FLAC3D internal flow models is presented according to fluid-solid coupling theory and strength criterion. A calculation model of numerical analysis was established, and the influences of mining pressure and plastic damage to pore water pressure and seepage vector change rule were studied. The results show that collapse column is the main channel of confined water seepage upward. The impact is not big when the workface is away from the collapse column. But when the workface is nearing a collapse column, there will be a seepage channel on a side near the workface, in which seepage vector and head are comparatively large. With workface pushing through collapse column, the seepage channel transfers to the other side of the column. In addition, when the plastic damage area within the collapse column breaks through, a "pipeline flow" will be formed within the column, and seepage field will change remarkably and the possibility of water bursting will be greater.

Stability analysis of wireless network with improved fluid model

Wireless communication is easily disturbed by unfortunate factors which drive the wireless environment unstable and complicated. Therefore, it is essential to consider these factors in stability analysis of the wireless network. However, wireless channel characteristics and packets collisions are neglected in the classical fluid model. A wireless TCP fluid model （WTFM） for stability analysis of wireless network is proposed based on cross layers, which not only makes the congestion control based on random early detection （RED） available for wireless network, but also provides a more accurate model to analyze the stability of wireless system theoretically. In the proposed model, active queue management, abnormality of wireless channels and packets collisions are taken into consideration. The comparisons between evaluating results from the WTFM and the practical performance from NS2 simulations validate the accuracy of the proposed WTFM in the perspectives of delay, dropping probability, throughput, sliding window size and queue length. A set of comparisons among the proposed WTFM, the classical fluid model and the convex optimization model are conducted. The results demonstrate that the proposed WTFM model performs better than other schemes in comprehensive aspects on capturing the characteristic of the wireless network and computing complexity.

A Comparative Study of the Electrodes Gels’Electrical Properties in the Measurement Issues of Intrabody Communication

Intrabody communication(IBC)technology is becoming progressively more standard-ized due to its low power consumption and high security features incorporated into the third phys-ical layer of the IEEE 802.15.6 standard.Even then,there are still many challenges in normalizing the measurement issues of IBC.A major concern that should not be overlooked is the electrodes in the IBC,especially the popular use of gel electrodes.In the channel measurements,gel electrodes are commonly employed to improve the signal-to-noise ratio and prevent electrodes from falling off.In this paper,a comparative study of the electrical properties of gel was investigated during the measurement of human channel characteristics and to clarify the differences of them.Firstly,the basis of electrostatic field pole plate measurements and electromagnetic theory were introduced to interpretate how the relative permittivity and conductivity of different gels will influence the meas-urement results.Then the in vivo experiments with different gel or dry electrodes were performed to compare the differences induced by the gel.The results indicate that the influence of the gel on the human channel measurement is mainly concentrated below 400 kHz(the attenuation is re-duced by 16.7 dB on average),and the stability of the permittivity and conductivity of the gel has a direct impact on the stability of its measurement of the human channel.This result may provide a meaningful reference for the standardization of electrode usage in IBC.

Separation of hexane isomers by introducing“triangular-like and quadrilateral-like channels”in a bcu-type metal-organic framework

The separation of hexane isomers is of vital importance to produce high quality gasoline in the petrochemical industry.However,the similar vapor pressure and boiling point of hexane isomers bring great difficulties and challenges in the separation process.Sieving effect,which allowing smaller molecules pass through and preventing others,should be a powerful strategy to solve this problem by making good use of porous materials.Therefore,physical separation by metal-organic framework(MOF)materials appears and becomes a burgeoning separation technique in industry.Due to the weak interaction between hexane isomers with absorbents,it puts forward higher requirements for the accurate design of MOF materials with optimal pore system.To address this issue,a novel MOF[Zn_(9)(tba)_(9)(dabco)_(3)]·12DMA-6MeOH(abbreviation:Zn_(9)(tba)_(9)(dabco)_(3);H_(2)tba=4-(1H-tetrazol-5-yl)-benzoic acid;dabco=1,4-diazabicyclo[2.2.2]octane;DMA=N,N-dimethylacetamide)with bcu network has been designed and synthesized by reticular chemistry strategy.Benefiting from the pre-designed topology and suitable linear ligand H_(2)tba and dabco,the structure of Zn_(9)(tba)_(9)(dabco)_(3)exhibits two types of channels with triangular-like and quadrilateral-like geometry.Zn_(9)(tba)_(9)(dabco)_(3)with appropriate channel size and shape displays potential selective adsorption capacity of vapor-phase hexane isomers through sieving effect.Moreover,outstanding gas adsorptive separation properties of Zn_(9)(tba)_(9)(dabco)_(3)could also be speculated by theoretical ideal adsorbed solution theory(IAST),suggesting Zn_(9)(tba)_(9)(dabco)_(3)can be regarded as a potential adsorbent material for purification natural gas_Breakthrough experiments show that Zn_(9)(tba)_(9)(dabco)_(3)is capable of discriminating all four hexane isomers at 298 K,and the corresponding research octane number(RON)of the eluted mixture closes to 95,which is higher than the standard for industrially refined hexane blends(about 83).We speculate that sieving effect and diffusion are a synergetic contributory factor in their elution dynamics,which may be ascribed to temperature-dependent interaction between pore aperture and each isomer.This work presents a typical example for design of efficient MOF absorbents by reticular chemistry strategy.

A novel PLC channel modeling method and channel characteristic analysis of a smart distribution grid

Power line carrier(PLC)technology plays an increasingly important role in the realization of cost-effective communication in a smart distribution grid.No current channel modeling method is universally applicable to more complex topologies that may emerge in smart grids,such as ring and mesh topologies.This paper presents a novel PLC channel modeling method based on the information node concept,and the universality and feasibility of the proposed method are demonstrated with applications in modeling networks with ring and mesh topologies.The factors that affect the channel characteristics of the networks and the laws that govern their behaviors for different types of topologies are analyzed.The validity and effectiveness of the proposed method are proven using simulation and laboratory tests.This paper provides the necessary theoretical basis and technical means to design the PLC modulation method for smart distribution grids.

A less complicated adaptive equalization for UWB channels

In this paper,a new adaptive equalization scheme aiming at the intersymbol and interuser interfer-ences in the multiuser ultra-wide band(UWB)channels is presented specially for direct-sequence UWB/time-hopping UWB(DS-UWB/TH-UWB)receivers.Its computational complexity and convergence rate are compared with the conventional algorithms.The simulation results show that the computational complexity of this scheme is less than employing the RLS method alone and the convergence rate of this scheme is farther off employing LMS method alone.