Actual Channel Research Articles

Isolation of exosome from the culture medium of Nasopharyngeal cancer (NPC) C666-1 cells using inertial based Microfluidic channel.

Isolation of exosome from culture medium in an effective way is desired for a less time consuming, cost saving technology in running the diagnostic test on cancer. In this study, we aim to develop an inertial microfluidic channel to separate the nano-size exosome from C666-1 cell culture medium as a selective sample. Simulation was carried out to obtain the optimum flow rate for determining the dimension of the channels for the exosome separation from the medium. The optimal dimension was then brought forward for the actual microfluidic channel fabrication, which consisted of the stages of mask printing, SU8 mould fabrication and ended with PDMS microchannel curing process. The prototype was then used to verify the optimum flow rate with polystyrene particles for its capabilities in actual task on particle separation as a control outcome. Next, the microchip was employed to separate the selected samples, exosome from the culture medium and compared the outcome from the conventional exosome extraction kit to study the level of effectiveness of the prototype. The exosome outcome from both the prototype and extraction kits were characterized through zetasizer, western blot and Transmission electron microscopy (TEM). The microfluidic chip designed in this study obtained a successful separation of exosome from the culture medium. Besides, the extra benefit from this microfluidic channels in particle separation brought an evenly distributed exosome upon collection while the exosomes separated through extraction kit was found clustered together. Therefore, this work has shown the microfluidic channel is suitable for continuous separation of exosome from the culture medium for a clinical study in the future.

LOKO: Localization-aware Roll-out Planning for Future Mobile Networks

The roll-out phase of the next generation of mobile networks (5G) has started and operators are required to devise deployment solutions while pursuing localization accuracy maximization. Enabling location-based services is expected to be a unique selling point for service providers now able to deliver critical mobile services, e.g., autonomous driving, public safety, remote operations. In this paper, we propose a novel roll-out base station placement solution that, given a Throughput-Positioning Ratio (TPR) target, selects the location of new-generation base stations (among available candidate sites) such that the throughput and localization accuracy are jointly maximized. Moving away from the canonical position error bound (PEB) analysis, we develop a realistic framework in which each positioning measurement is affected by errors depending upon the actual wireless channel between the measuring base station and the target device. Our solution, referred to as LOKO, is a fast-converging algorithm that can be readily applied to current 5G (or future) roll-out processes. LOKO is validated by means of an exhaustive simulation campaign considering real existing deployments of a major European network operator as well as synthetic scenarios.

Markov Multi-Beamtracking on 60 GHz Mobile Channel Measurements

Beamforming training refers to the exhaustive scan over which the transmitter and receiver jointly steer their beams along a predefined set of double-directional angles to determine the beam pairs that coincide with the dominant propagation paths of the channel, for spatial multiplexing at millimeter-wave. When mobile, training necessitates a high refresh rate to maintain connectivity and so, to reduce overhead, beamtracking algorithms exploit the spatial-temporal consistency of the channel to localize the scan around the beam pairs determined at a previous time. The algorithms&#x2019; true performance, however, is still unknown since results reported to date are based on oversimplified channel models. In this paper, we propose a novel beamtracking algorithm formulated as a first-order Markov process that supports multiple beam pairs. The algorithm is evaluated through actual channel measurements &#x2013; <i>not a channel model</i> &#x2013; recorded with our high-precision 3D double-directional 60 GHz channel sounder. The measurement campaign, to our knowledge, is unprecedented: with 10, 895 large-scale measurements, spaced 8.8 cm apart on average to emulate continuous motion, over which the mobile receiver traversed a total of 900.2 m. We demonstrate that four beam pairs can be sustained always and that eight pairs can be sustained 57&#x0025; of the time.

Robust Reconstruction Method Based on QCQP Optimization for Multichannel SAR With Closely Singular Sampling

The conventional reconstruction algorithm allows for unambiguous recovery of the Doppler spectrum of multichannel synthetic aperture radar (SAR) system in azimuth with an accurately known channel response matrix. However, the available knowledge of the actual channel response matrix is imprecise due to channel errors. In this case, the SAR image will suffer from severe error-induced azimuth ambiguities if reconstructed by the conventional reconstruction algorithm, especially for the case of closely singular sampling. To this end, a novel method based on a quadratically constrained quadratic program (QCQP) optimization is proposed to increase the robustness to the channel errors. Accordingly, the error-induced azimuth ambiguities can be greatly suppressed by the proposed method. Furthermore, performance comparisons of the conventional reconstruction algorithm and the proposed method via numerical simulation are presented.

Key Generation Method Based on Multi-Satellite Cooperation and Random Perturbation.

In low-earth-orbit (LEO) satellite-to-ground communication, the size of satellite antennae is limited and the satellite motion trajectory is predictable, which makes the channel state information (CSI) of the satellite-to-ground channel easy to leak and impossible to use to generate a physical layer key. To solve these problems, we propose a key generation method based on multi-satellite cooperation and random perturbation. On the one hand, we use multi-satellite cooperation to form a constellation that services users, in order to increase the equivalent aperture of satellite antennae and reduce the correlation between the legal channel and the wiretap channel. On the other hand, according to the endogenous characteristics of satellite motion, a random perturbation factor is proposed, which reflects the randomness of the actual channel and ensures that the CSI of the legal channel is not leaked due to the predictability of satellite motion trajectory. Simulation results show that the proposed method can effectively reduce the leakage of the legal channel’s CSI, which makes the method of physical layer key generation safe and feasible in the LEO satellite-to-ground communication scene.

Analysis on the Path of Talent Cultivation in Higher Vocational Education under the Guidance of “Double High”

In today’s society, higher vocational colleges are an important place for cultivating high-quality talents. In the process of higher vocational education, talent training is an important task. Whether we can cultivate the outstanding talents needed by our society plays an important role in measuring the development and running level of higher vocational colleges. In the actual training of innovative and high-quality talents, it is not completed in a short time. For a long time, it is difficult to meet the actual development requirements of society when training outstanding talents. When cultivating outstanding talents, higher vocational colleges should innovate the actual training channels for outstanding talents, achieve a good combination of professional education and theoretical education, set goals for training outstanding talents, and fully demonstrate the quality and effects of higher vocational education. Cultivate outstanding talents for a modern society. Based on this, this article mainly explores and analyzes the talent training path of higher vocational education under the guidance of “double high”, so as to cultivate outstanding talents for our society and provide theoretical references for the smooth development of relevant research in the future.

Optical OFDM Error Floor Estimation by Means of OTDR Enhanced by Front-End Optical Preamplifier.

Optical time-domain reflectometer (OTDR) enables simple identification and localization of a plethora of refractive and reflective events on a fiber link, including splices, connectors and breaks, and measuring insertion/return loss. Specifically, large enough OTDR dynamic range (DR) and thus high signal-to-noise-ratio (SNR) enable clear far-end visibility of longer fibers. We point out here that, under such conditions, the optical bit-error-rate (BER) floor is dominantly determined by reflective events that introduce significant return loss. This complements the OTDR legacy tests by appropriate optical BER floor estimation in the field. As high SNR implies inter-symbol interference as dominating error generating mechanism, we could apply the classical time-dispersion channel model for the optical BER floor determined by the root-mean-square (rms) delay spread of the actual fiber channel power-delay profile. However, as the high-SNR condition is not always fulfilled mostly due to insufficient DR, we propose here inserting a low-noise optical preamplifier as the OTDR front-end to reduce noise floor and amplify the backscattered signal. In order to verify the model for the exemplar test situation, we measured BER on the same fiber link to find very good matching between the measured BER floor values and the ones predicted from the OTDR trace.

Non-radiative relaxation and nonlinear properties of YVO4:Yb3+, Er3+ upconversion nanoparticles

• Analysis of actual energy transfer channels in YVO 4 :Yb 3+ ,Er 3+ UCNP is presented. • Simple (reduced) model for energy transfer processes is proposed. • Pump power dependence of upconversion photoluminescence is yielded. • It is established that multiphonon transitions mainly effect on upconversion nonlinearity. • Theoretical results could be useful in UCNPs characterization by spectroscopic data analysis. We analyzed nonlinear emission properties of oxide nanocrystals YVO 4 doped with Yb 3+ and Er 3+ ions which are one of the most interesting types of upconverting nanoparticles (UCNPs). As is widely believed the deviation of the power-dependent upconversion phosphorescence intensity from a quadratic character is attributed to a saturation effect occurring at the relatively high pump power. In this paper, we focused on studying upconversion nonlinearity at the low pump power when excited states populations are considerably less then ground states populations. The analysis of actual energy transfer channels allowed us to propose a reduced model having simple solutions. The obtained analytic expressions for the dependences of upconversion photoluminescence intensity and its nonlinearity on the pump power revealed that multiphonon transitions are a main factor responsible for the variation of upconversion nonlinearity in a range between 1 and 2. This result could be used in spectroscopic experiments for simple and direct identification of the non-radiative relaxation efficiency in YVO 4 :Yb, Er UCNPs.

Insights on the interaction of serpentine channels and gas diffusion layer in an operating polymer electrolyte fuel cell: Numerical modeling across scales

Three-dimensional direct numerical simulations were performed for investigating the flow in a serpentine channel and the under-laying porous gas diffusion layer (GDL) of a micro polymer electrolyte fuel cell (PEFC). The flow field comprised three straight sections and two U-turns. The geometry was acquired with high-resolution (2.9 μm) in situ X-ray tomographic measurements on an operating cell. Simulations considered the GDL under dry and partially saturated conditions, whereby saturation was established via electrochemically produced water. A lattice Boltzmann (LB) methodology was adopted for simulating the single-phase (gas) transport in the actual 3D channel and porous GDL geometry. The global pressure drop in the dry GDL was dominated by the turns in the gas channel, while the pressure drops were quite small along the straight channel sections. In the wet GDL case, however, the pressure drop was mainly dictated by the neck-shaped passages created by the large water clusters inside the channel. Owing to the water blockage, the local accumulated cross-flows along the serpentine channel length, when normalized by the inlet channel flow, were substantially higher in the wet GDL, reaching local values up to 45% compared to 18% for the dry GDL. The implications are that in an electrochemically operating cell, the GDL under the rib would receive more gas (and thus O2). The creation of cross-flows through the porous GDL would enhance cell performance under the ribs since diffusion will not be the main driving mechanism for oxygen transport and water evaporation. The analysis indicated that the flow field, although designed as serpentine, behaved like half-interdigitated (with a rib of 1.5 mm, half-serpentine flow field, depending on the state of channel flooding).

Output-Feedback Control Under Hidden Markov Analog Fading and Redundant Channels

This brief investigates the output-feedback control problem with redundant channels, in which the output measurements may suffer from the Markov analog fading when transmitting through the independent primary channel and redundant channels. The actual channel mode obeys a two-state time-homogeneous Markov chain, and the expectation of fading amplitude in the good mode is much higher than the one in the bad mode. The mode detectors are employed to estimate the status of both the primary and redundant channels, by which the better measurement signals may be selected for the controller. Thus, a token-dependent output-feedback controller is constructed, and then, the stability condition is obtained via the actual mode-dependent Lyapunov function method. Finally, the proposed output-feedback control scheme is applied to an operational amplifier (OPA) circuit under the hidden Markov analog fading channels.

A low-complexity channel training method for efficient SVD beamforming over MIMO channels

Singular value decomposition (SVD) beamforming is an attractive tool for reducing the energy consumption of data transmissions in wireless sensor networks whose nodes are equipped with multiple antennas. However, this method is often not practical due to two important shortcomings: it requires channel state information at the transmitter and the computation of the SVD of the channel matrix is generally too complex. To deal with these issues, we propose a method for establishing an SVD beamforming link without requiring feedback of actual channel or SVD coefficients to the transmitter. Concretely, our method takes advantage of channel reciprocity and a power iteration algorithm (PIA) for determining the precoding and decoding singular vectors from received preamble sequences. A low-complexity version that performs no iterations is proposed and shown to have a signal-to-noise-ratio (SNR) loss within 1 dB of the bit error rate of SVD beamforming with least squares channel estimates. The low-complexity method significantly outperforms maximum ratio combining diversity and Alamouti coding. We also show that the computational cost of the proposed PIA-based method is less than the one of using the Golub–Reinsch algorithm for obtaining the SVD. The number of computations of the low-complexity version is an order of magnitude smaller than with Golub–Reinsch. This difference grows further with antenna array size.

CSI intelligent feedback for massive MIMO systems in V2I scenarios

With the rapid development of the Internet of vehicles (IoV), vehicle to everything (V2X) has strict requirements for ultra-reliable and low latency communications (URLLC), and massive multi-input multi-output (MIMO) channel state information (CSI) feedback can effectively support URLLC communication in 5G vehicle to infrastructure (V2I) scenarios. Existing research applies deep learning (DL) to CSI feedback, but most of its algorithms are based on low-speed outdoor or indoor environments and assume that the feedback link is perfect. However, the actual channel still has the influence of additive noise and nonlinear effects, especially in the high-speed V2I scene, the channel characteristics are more complex and time-varying. In response to the above problems, this paper proposes a CSI intelligent feedback network model for V2I scenarios, named residual mixnet (RM-Net). The network learns the channel characteristics in the V2I scenario at the vehicle user (User Equipment, UE), compresses the CSI and sends it to the channel; the roadside base station (Base Station, BS) receives the data and learns the compressed data characteristics, and then restore the original CSI. The system simulation results show that the RM-Net training speed is fast, requires fewer training samples, and its performance is significantly better than the existing DL-based CSI feedback algorithm. It can learn channel characteristics in high-speed mobile V2I scenarios and overcome the influence of additive noise. At the same time, the network still has good performance under high compression ratio and low signal-to-noise ratio (SNR).

GeoWEPP과 SWAT 모델을 이용한 산지 유역 강우-유출량 특성 분석

Due to recent climate change, continuous soil loss is occurring in the mountainous watershed. The development of geographic information systems allows the spatial simulation of soil loss through hydrological models, but more researches applied to the mountain watershed areas in Korea are needed. In this study, prior to simulating the soil loss characteristics of the mountainous watershed, the field monitoring and the SWAT and GeoWEPP models were used to simulate and analyze the rainfall and runoff characteristics in the mountainous watershed area of Jirisan National Park. As a result of monitoring, runoff showed a characteristic of a rapid response as rainfall increased and decreased. In the simulation runoff results of calibrated SWAT models, R², RMSE and NSE was 0.95, 0.03, and 0.95, respectively. The runoff simulation results of the GeoWEPP model were evaluated as 0.89, 0.30, and 0.83 for R², RMSE, and NSE, respectively. These results, therefore, imply that the runoff simulated through SWAT and GeoWEPP models can be used to simulate soil loss. However, the results of the two models differ from the parameters and base flow of actual main channel, and further consideration is required to increase the model’s accuracy.

Riverbed fluctuation and erosion property of cohesive sediment based on long-term topographic surveys in a macrotidal estuary

The feature of large scouring process of cohesive sediment and the long term seasonal riverbed fluctuation at the estuarine turbidity maximum (ETM) zone of the macrotidal Chikugo River estuary, Japan were studied using the intensive periodical transverse surveys of riverbed topography and sediment sampling along with continuous monitoring of water level, salinity and turbidity during 2005–2017. The results revealed that substantial erosion occurs (increase in channel capacity) when the river discharge exceeds 2,000 m3 s−1 while deposition occurs (decrease in channel capacity) when the flow falls under 100 m3 s−1. During the normal flows, the bed shear stress (values ranging from 0.2–4.0 N m−2) showed a harmonious behavior driven by the fortnightly tidal variations. Conversely, rapid variations in bed shear stress values (2.0–22.7 N m−2) were observed during the flood events. Further, a critical shear stress value of 1.8 N m−2 was estimated as the erosion threshold of mud deposit in the estuary. Finally, an erodibility coefficient of 0.0015 s2 m−2 was determined based on the reasonable relationship (R2=0.767) between erosion depth and accumulated friction velocity from the actual field data. This value is several times lower than those reported in previous studies due to the differences in deposition and consolidation properties of sediments between actual and experimental channels. This indicates that the erosion of cohesive sediments in estuaries is not only influenced by the magnitude of shear velocity, but also by its consolidation characteristics.

Channel Autoencoder for Wireless Communication: State of the Art, Challenges, and Trends

To tackle the sub-optimization problem of the conventional block structure communication systems, recently, a novel concept named end-to-end communication system that can optimize the whole system jointly has been proposed. A channel autoencoder (AE) is one of the methods, which regards the wireless communication system as an AE along with a channel model. In this article, we present a comprehensive overview of the recent advancements of channel AEs, whose practicability mainly depends on the robustness of the impairments in actual channels. Among existing works, assuming the imperfect channel models before training or constructing a communication system without channel models are both viable methods to deal with channel impairments. Therefore, we divide the channel AEs into two categories, model-assumed and model-free channel AEs, for each of which a universal structure is investigated, namely radio transformer network and gradient generation network, respectively. Then their performance is compared extensively, and the open research issues are discussed in the end to provide some directions for future study.

Autoencoder-bank based design for adaptive channel-blind robust transmission

The idea of employing deep autoencoders (AEs) has been recently proposed to capture the end-to-end performance in the physical layer of communication systems. However, most of the current methods for applying AEs are developed based on the assumption that there exists an explicit channel model for training that matches the actual channel model in the online transmission. The variation of the actual channel indeed imposes a major limitation on employing AE-based systems. In this paper, without relying on an explicit channel model, we propose an adaptive scheme to increase the reliability of an AE-based communication system over different channel conditions. Specifically, we partition channel coefficient values into sub-intervals, train an AE for each partition in the offline phase, and constitute a bank of AEs. Then, based on the actual channel condition in the online phase and the average block error rate (BLER), the optimal pair of encoder and decoder is selected for data transmission. To gain knowledge about the actual channel conditions, we assume a realistic scenario in which the instantaneous channel is not known, and propose to blindly estimate it at the Rx, i.e., without any pilot symbols. Our simulation results confirm the superiority of the proposed adaptive scheme over existing methods in terms of the average power consumption. For instance, when the target average BLER is equal to 10^{-4}, our proposed algorithm with 5 pairs of AE can achieve a performance gain over 1.2 dB compared with a non-adaptive scheme.

Immediate Implant in Maxillary Central Incisors and Prosthetic Screw Channel: A CBCT Feasibility Study.

This study aimed to assess how frequently the maxilla anatomy allows for lingualized immediate implants in the central incisor region with a screw channel that has an ideal distance of 1.5 mm from the incisal margin. The effect of abutments with angle correction on case selection will also be verified. A retrospective cross-sectional study of 181 CBCT scans was carried out. Using an implant-planning software, implant placement was simulated in the lingual aspect of the socket. The location of the prospective screw channel was registered as incisal, lingual, or facial. The angle between the actual screw channel and the position of the ideal one was calculated. The effect of angle correction on allowing an ideal screw channel configuration was computed. Out of 161 eligible cases, 144 presented favorable anatomy for an immediate implant. The screw channel had an incisal position in 40 cases (28%), a lingual position in 60 cases (42%), and a facial position in 44 cases (30%). The screw channel could be placed at the planned distance from the incisal edge in 35 cases (24%). The position was unfavorable in the remaining 109 cases. In 103 of these cases, an abutment with an angled screw channel could make the conditions feasible. Within the simulated conditions, a majority of maxillary central incisors present favorable ridge anatomy for lingualized immediate implant placement. Achieving a proper location of the screw channel requires abutments with angle correction in a majority of cases.

Progressive Rate-Filling: A Framework for Agile Construction of Multilevel Polar-Coded Modulation

We propose the progressive rate-filling method as a framework to study agile construction of multilevel polar-coded modulation. We show that the bit indices within each component polar code can follow a fixed, precomputed ranking sequence (e.g., the Polar sequence in the 5G standard) while their allocated rates (i.e., the number of information bits of each component polar code) can be fast computed by exploiting the target sum-rate approximation and proper rate-filling methods. In particular, we propose two rate-filling methods based on the capacity and the rate considering the finite blocklength effect. The proposed construction methods can be performed independently of the actual channel condition with ${O(m)}$ ( ${m}$ denotes the modulation order) complexity and robust to diverse modulation and coding schemes (MCSs) in the 5G standard, which is a desired feature for practical systems.

Theory of three-magnon interaction in a vortex-state magnetic nanodot

We use vector Hamiltonian formalism (VHF) to study theoretically three-magnon parametric interaction (or three-wave splitting) in a magnetic disk existing in a magnetic vortex ground state. The three-wave splitting in a disk is found to obey two selection rules: (i) conservation of the total azimuthal number of the resultant spin-wave modes, and (ii) inequality for the radial numbers of interacting modes, if the mode directly excited by the driving field is radially symmetric (i.e. if the azimuthal number of the directly excited mode is $m = 0$). The selection rule (ii), however, is relaxed in the "small" magnetic disks, due to the influence of the vortex core. We also found, that the efficiency of the three-wave interaction of the directly excited mode strongly depends on the azimuthal and radial mode numbers of the resultant modes, that becomes determinative in the case when several splitting channels (several pairs of resultant modes) simultaneously approximately satisfy the resonance condition for the splitting. The good agreement of the VHF analytic calculations with the experiment and micromagnetic simulations proves the capability of the VHF formalism to predict the actual splitting channels and the magnitudes of the driving field thresholds for the three-wave splitting.

Research on Node localization Algorithm in WSN Based on TDOA

Many applications of wireless sensor networks (WSN) require nodes to know their location information. Monitoring data without node location information is meaningless in many situations. Since the node positioning efficiency of WSN directly affects the performance of the network, designing an efficient positioning algorithm is the focus of WSN research. Based on the principle of TDOA positioning in WSN, it studies two main positioning algorithms: Chan and Taylor algorithm. Meanwhile the least square (LS) method is used to provide the initial position for Taylor algorithm and the first calculation result for Chan algorithm. Simulation results under different conditions show that the Chan algorithm has a good positioning accuracy and less computation than that of Taylor algorithm in the line of sight (LOS) environment. However, under the actual channel, due to the influence of No Line of Sight (NLOS), the positioning accuracy of Taylor algorithm is better than that of Chan algorithm, but its computation is large.