Simulation of Propagation Loss Models and Antenna Designs for Naval Troposcatter and Tropospheric Duct Communications

Tropospheric Scattering(Troposcatter) and Tropospheric Ducting are two different mechanisms due to in-homogenoueties in the lower part of the Earths atmosphere.Their common influence in propagation of microwaves is studied here in order to achieve a feasible naval communication system.Although not new,Troposcatter together with Tropospheric Ducting communications are regaining popularity in current military and civil applications such as isolated islands and oil extraction facilities in the open sea.The innovation proposed here is the application of such systems in naval communications where at least one of the stations is mobile.Several propagation together with fading models are simulated using appropriate programs and scientific simulation packets in order to predict maximum range of such communication systems in each dominant mode of operation.Then appropriate antenna design proposals are given to overcome the high propagation loss and minimize possible interferences.

A 3-D Hybrid Dynamic Channel Model for Indoor THz Communications

To meet the demands for the explosive growth of mobile data rates and scarcity of spectrum resources in the near future,the terahertz(THz)band has widely been regarded as a key enabler for the upcoming beyond fifth-generation(B5G)wireless communications.An accurate THz channel model is crucial for the design and deployment of the THz wireless communication systems.In this paper,a three-dimensional(3-D)dynamic indoor THz channel model is proposed by means of combining deterministic and stochastic modeling approaches.Clusters are randomly distributed in the indoor environment and each ray is characterized with consideration of molecular absorption and diffuse scattering.Moreover,we present the dynamic generation procedure of the channel impulse responses(CIRs).Statistical properties are investigated to indicate the non-stationarity and feasibility of the proposed model.Finally,by comparing with delay spread and K-factor results from the measurements,the utility of the proposed channel model is verified.

A 3D Geometry-Based Scattering Model for Vehicleto-Vehicle Wideband MIMO Relay-Based Cooperative Channels

In this paper, a three-dimensional(3D) geometry- based stochastic scattering model(GBSSM) for wideband multi-input multi-output(MIMO) vehicle-to-vehicle(V2V) relay-based cooperative fading channel based on geometrical three-cylinder is proposed. Non-line-of-sight(NLOS) propagation condition is assumed in amplify-and-forward(AF) cooperative networks from the source mobile station(S) to the destination mobile station(D) via the mobile relay station(R). We extend the proposed narrowband model to wideband and also introduce the carrier frequency and bandwidth into the model. To avoid complicated procedure in deriving the analytical expressions of the channel parameters and functions, the channel is realized first. By using the realized channel matrix, the channel properties are further investigated.

Impacts of Transceiver Configuration on Ultraviolet Communication

In the channel estimation for ultraviolet communication, the single scattering power is usually used to approximate the received total power. This approximation error is affected by the transceiver configuration. Here, we employ the proportion of received single scattering power in received total power to indicate the approximation error of the single scattering model in different configurations. This is useful for reducing the approximation error by selecting a more appropriate transceiver configuration.

Study on the Characteristics of Scattering from Buildings

The scattering characteristics of electromagnetic waves from buildings are presented. The uniform geometric theory of diffraction (UTD) is employed to approximate the near field-far field distribution. The numerical results presented demonstrate that the UTD solution can be conveniently and efficiently applied to many practical problems. As such results are of importance to the mobile communication field.

A Simulation Study on Channel Estimation for Cooperative Communication System in Sand-dust Storm Environment

There are many factors that influence the propagation of electromagnetic wave in the sand-dust storm environment, the scattering effect of dust particle is one of the major factors, so this paper focuses on the dust particles scattering function. The scattering of dust particles inevitably brings the multipath transmission of the signal, multipath propagation will bring the multipath fading of the signal. In this paper, we first investigate the use of AF and DF modes in a sand-dust storm environment. Secondly, we present a low-order modulation method should be used in cooperative communication system. Lastly, we evaluate the system performance for both of the moving nodes and power allocation. Experimental results validate the conclusion of theoretical derivation: the multipath fading is one of the main factors that affect the quality of signal transmission. Cooperative communication technology has good anti-fading ability, which can guarantee the signal transmission timely and correctly.

Electromagnetic Environment Impact of Mobile Communication Iron Tower on Adjacent Building and Its Countermeasures

For several lightning-strike disasters related to base station iron tower of mobile communication carrier operator, disaster-inducing factors were analyzed. The reason was as below： after lightning receptor of base station iron tower of mobile communication carder operator was struck by lightning, electromagnetic radiation was generated in the process lightning current leaking into the ground. In addition, it was lightning scattered- strike phenomenon induced by overhead lightning rod, that is, ground lightning falling density around overhead lightning rod was larger than mean at the site. Finally, some improvement measures were put forward.

Redundancy Ring Design for Transponder Subsystem in the VX-SAT Communication Satellite

Modem communications is an indispensable tool for modem social economy and modem social life. The payload of a communication satellite provides radio relay for links between earth stations. With most commercial communication satellites the payload consists of two distinct parts with well defined interfaces： the repeater and the antennas. The repeater designates the electronic equipment which performs a range of functions on the signals from the receiving antenna before delivering them to the transmitting antenna. The VX-SAT project is a system engineering exercise, realized in the China Academy of Space Technology （CAST） with the objective of training the persons in charge of designing futures communication satellites in the Bolivarian Agency of Space Activities （ABAE） in Venezuela. This paper includes an overview of the VX-SAT system, the preliminary design of the communications payload and finally the method used to design the redundancy ring of the transponder subsystem.

Absorption and scattering effects of Maalox,chlorophyll, and sea salt on a micro-LED-based underwater wireless optical communication [Invited]

In this work,a blue gallium nitride(GaN)micro-light-emitting-diode(micro-LED)-based underwater wireless optical communication(UWOC)system was built,and UWOCs with varied Maalox,chlorophyll,and sea salt concentrations were studied.Data transmission performance of the UWOC and the influence of light attenuation were investigated systematically.Maximum data transmission rates at the distance of 2.3 m were 933,800,910,and 790 Mbps for experimental conditions with no impurity,200.48 mg/m3 Maalox,12.07 mg/m3 chlorophyll,and 5 kg/m3 sea salt,respectively,much higher than previously reported systems with commercial LEDs.It was found that increasing chlorophyll,Maalox,and sea salt concentrations in water resulted in an increase of light attenuation,which led to the performance degradation of the UWOC.Further analysis suggests two light attenuation mechanisms,e.g.,absorption by chlorophyll and scattering by Maalox,are responsible for the decrease of maximum data rates and the increase of bit error rates.Based on the absorption and scattering models,excellent fitting to the experimental attenuation coefficient can be achieved,and light attenuation by absorption and scattering at different wavelengths was also investigated.We believe this work is instructive apply UWOC for practical applications.

Single scattering turbulence model based on the division of effective scattering volume for ultraviolet communication

In this Let ter,a single scattering turbulence model in a narrow beam case for ultraviolet(UV)communication is proposed based on the division of the effective scattering volume.This model takes the variation of atmospheric scattering,absorption,and turbulence in different paths into account.Meanwhile,the applicable transceiver configurations of this model are provided by analyzing path loss error caused by the single scattering assumption in the UV channel.Furthermore,we investigate the effect of turbulence on the probability density function of the arriving power in both coplanar and non-coplanar scenarios.The averaging effect of multipath propagation on the arriving power's fluctuations is presented.Then,the bit-error-rate performance is also studied.This work provides an efficient way for UV turbulence channel estimation.

Compound parabolic concentrator applied as receiving antenna in scattering optical communication

The two-dimensional（2D） compound parabolic concentrator＇s（CPC） characteristics are analyzed.It is shown that CPC＇s height is taller and its light collecting ability is stronger with the CPC＇s field of view decreasing when the bottom radius is unchanged.According to the ZEMAX analysis,CPC is good at collecting optical signal,and the antenna combining CPC with hemispherical lens can gather more optical signal than a single CPC or CPCs combined in series.The light propagation of scattering optical communication based on multiple scattering is simulated by Monte Carlo method,and the results show that using CPC as receiving antenna can strengthen communication system＇s signal collecting ability and increase its communication distance.

In situ probing of cell-cell communications with surface- enhanced Raman scattering （SERS） nanoprobes and microfluidic networks for screening of immunotherapeutic drugs

Discovering novel drugs for cancer immunotherapy requires a robust in vitro drug screening platform that allows for straightforward probing of cell-ceil communications. Here, we combined surface-enhanced Raman scattering （SERS） nanoprobes with microfluidic networks to monitor in situ the cancer-immune system intercellular communications. The microfluidic platform links up immune cells with cancer cells, where the cancer-cell secretions act as signaling mediators. First, gold@silver core--shell nanorods were employed to fabricate SERS immunoprobes for analysis of the signaling molecules. Multiple cancer secretions in a tumor microenvironment were quantitatively analyzed by a SERS-assisted three-dimensional （3D） barcode immunoassay with high sensitivity （1 ng/mL）. Second, in an on-chip cell proliferation assay, multiple immunosuppressive proteins secreted by cancer cells were found to inhibit activation of immune cells, indicating that the platform simulates the physiological process of cancer-immune system communications. Furthermore, potential drug candidates were tested on this platform. A quantitative SERS immunoassay was performed to evaluate drug efficacy at regulating the secretion behavior of cancer cells and the activity of immune cells. This assay showed the suitability of this platform for in vitro drug screening. It is expected that the fully integrated and highly automated SERS-microfluidic platform will become a powerful analytical tool for probing intercellular communications and should accelerate the discovery and clinical validation of novel druKs.

Numerical study of radio wave propagation in clear air acoustic scatterer

This paper numerically investigates the radio wave scattering by the artificial acoustic disturbance in the atmospheric boundary layer. The numerical model is based on the finitedifference time-domain（FDTD） method for radio wave propagation and fluid simulation for atmospheric disturbance by acoustics waves. The characteristics of radio wave scattering propagation in the artificial acoustic perturbations are investigated by this numerical model. The numerical simulation results demonstrate that the radio wave propagation scattered by acoustic scatterer has the characteristic of forward tropospheric scatter. When the radio waves are scattered, they distribute in all directions; a majority of radio waves continues to propagate along the original direction, and only a small part of the energy is scattered. For the same acoustic scatterer, if we merely change the radio wave emission elevation, the horizontal spans of forward scattering radio wave packets centers gradually decrease with the increasing of emission elevations; and the energy of wave packets increases firstly and then decreases with launching elevation, reaching the maximum at a certain angle. If we merely change the wave emitting position, the horizontal spans decrease with the increasing of emission positions, and the energy of wave packets also increases firstly and then decreases with launch position, reaching the maximum at a certain position. This approach can be very promising for atmospheric scatter communications.

Study on forward stimulated Brillouin scattering in a backward pumped fiber Raman amplifier

Strong multi-order forward stimulated Brillouin scattering (SBS) has been observed in the backward pumped S-band distributed fiber Raman amplifier (PRA) with tunable narrow signal source (less than 100 MHz) when the pump power of FRA reached the SBS threshold. This does not obey the theory that only weak backward SBS lines exist according to the conservation of energy and momentum and the wave vector selected rule. This is because the sound waveguide characteristic weakens the wave vector rule, and the forward transmitted sound waveguide Brillouin scattering lines are generated and amplified in FRA. When the pump power is further increased, 11 orders of SBS lines and comb-like profile are observed. For the excited line, the frequency is 197.2296 THz and the power is 0 dBm. The even order SBS lines are stronger than odd order SBS lines, the power of the 2nd and 4th order SBS lines is 1.75 dBm, which is 16 dB higher than that of the 1st and 3rd order SBS lines. The odd order SBS lines are named Brillouin Rayleigh scattering lines.

The effect of turbulence on NLOS underwater wireless optical communication channels [Invited]

Conventional line-of-sight underwater wireless optical communication(UWOC)links suffer from huge signal fading in the presence of oceanic turbulence due to misalignment,which is caused by variations in the refractive index in the water.Non-line-of-sight(NLOS)communication,a novel underwater communication configuration,which has eased the requirements on the alignment,is supposed to enhance the robustness of the UWOC links in the presence of such turbulence.This Letter experimentally and statistically studies the impact of turbulence that arises from temperature gradient variations and the presence of different air bubble populations on NLOS optical channels.The results suggest that temperature gradient-induced turbulence causes negligible signal fading to the NLOS link.Furthermore,the presence of air bubbles with different populations and sizes can enhance the received signal power by seizing the scattering phenomena from an ultraviolet 377 nm laser diode.

Impact of spontaneous Raman scattering on quantum channel wavelength-multiplexed with classical channel in time domain

In the quantum key distribution system, quantum channel is always affected by spontaneous Raman scattering noise when it transmits with classical channels that act as synchronization and data channels on a shared fiber. To study the effect of the noise exactly, the temporal distribution characteristics of the Raman scattering noise are analyzed theoretically and measured by a single-photon detector. On the basis of this, a scheme to decrease the noise is proposed.

Multipath dispersion of pulse signals in a non-line-of-sight optical scattering channel

Multipath-induced pulse broadening in a non-line-of-sight （NLOS） optical scattering channel is investigated. Expressions for impulse response and digital signal-to-noise ratio （DSNR） penalty induced by intersymbol interference （ISI） of a NLOS ultraviolet （UV） scattering communication are introduced based on a single-scattering model, and simulated results for some typical atmospheric condition and configuration of geometry are given in the paper. It is shown that the multipath dispersion is one of the most important factors limiting the system performances, and return-to-zero （RZ） format is more suitable for the optical scattering communications than non-return-to-zero （NRZ） format. The method proposed here can be used to predict available bandwidth and data rate of the communication system operating in a NLOS optical scattering channel. OCIS codes： 060.4510, 290.1310, 060.5530.

Path loss of non-line-of-sight ultraviolet light communication channel in polydisperse aerosol systems

Performance of non-line-of-sight(NLOS) ultraviolet(UV) communication is closely related with the system geometry, the communication range, and the atmospheric parameters. In this paper, we implement a full numerical analysis of the relations of path loss of NLOS UV communication with these factors using the Mie scattering theory and the Monte-Carlo method. In the numerical simulations, the actual polydisperse aerosol systems are used as the transmission medium. Since for the actual aerosol systems the atmosphere conditions may be similar within a short period, the path loss may be exclusively determined by the atmosphere visibility. Hence, we build a relation between the path loss of the communication channel and the atmosphere visibility. Simulation results reveal that for a relatively small communication range, the path loss increases with the visibility. On the other hand, low elevation of the transceiver may reduce the path loss. Our simulation results are useful for the evaluation of performance of the real NLOS UV communication systems.

Propagation Properties of Radio Wave in Multipath Scattering Mobile Channel

Based on a physical model for the radio wave propagation in multipath scattering environments, this paper analyses and simulates the propagation properties as well as time-selective behavior of radio waves in different urban microcellular mobile radio channels. The approach of propagation properties causes a generation of complex impulse responses to be like that given by the statistics of the underlying channel behavior. Fading characteristics of the multipath structures can be efficiently simulated by reproducing the physical wave interference process, thereby incorporating the different channel characteristics that are observed in different urban environments.

Characterization of Blue-Green Light Non-Line-of-Sight Transmission in Seawater

The blue-green light in the 450 nm to 550 nm band is usually used in underwater wireless optical communication (UWOC). The blue-green light transmission in seawater is scattered by the seawater effect and can achieve communication in non-line-of-sight (NLOS) transmission mode. Compared to line-of-sight (LOS) transmission, NLOS transmission does not require alignment and can be adapted to various underwater environments. The scattering coefficients of seawater at different depths are different, which makes the scattering of light in different depths of seawater different. In this paper, the received optical power and bit error rate (BER) of the photodetector (PD) were calculated when the scattering coefficients of blue-green light in seawater vary from large to small with increasing depth for NLOS transmission. The results show that blue-green light in different depths of seawater in the same way NLOS communication at the same distance, the received optical power and BER at the receiver are different, and the received optical power of green light is greater than that of blue light. Increasing the forward scattering coverage of the laser will suppress the received optical power of the PD, so when performing NLOS communication, appropriate trade-offs should be made between the forward scattering coverage of the laser and the received optical power.