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1
Shen, Xi Zhong, i Pan Li. "Material Flaw Sizing by Ultrasonic Multipath Detection". Advanced Materials Research 712-715 (czerwiec 2013): 1067–70. http://dx.doi.org/10.4028/www.scientific.net/amr.712-715.1067.
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Sizing of material flaw is addressed in the multipath scene, and a method is developed to detect an isolated sized flaw and estimate its height based on imaging theory of different path profiles. A signal model based on the multipath higher order reflections of the flaw is built to detect the sized flaw. Multipaths are predicted and identified on the basis of the direct reflection path, which is relatively easy to be identified using the conventional flaw detection techniques. Direct reflection path and combined path are applied to detect the flaw from the top, and multipath w is to detect its bottom of the flaw. Ultrasonic imaging is formed and synthesized by all the identified multipaths, which shows the size of the material flaw. Simulations and experimentations demonstrate that the flaw sizing can be calculated utilizing the time-of-arrivals of the multipath signals.
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Chen, Zhigang, Lei Wang i Mengya Zhang. "Virtual Antenna Array and Fractional Fourier Transform-Based TOA Estimation for Wireless Positioning". Sensors 19, nr 3 (2.02.2019): 638. http://dx.doi.org/10.3390/s19030638.
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In this paper, a novel virtual antenna array and fractional Fourier transform (FRFT)-based 2-dimension super-resolution time-of-arrival (TOA) estimation algorithm for OFDM WLAN systems has been proposed. The proposed algorithm employs channel frequency responses (CFRs) at the equi-spaced positions on a line or quasi-line moving trajectory, i.e., the CFRs of a virtual antenna array, to extract multipaths’ TOA information. Meanwhile, a new chirp-like quadratic function is used to approximate the channel multipaths’ phase variation across the space dimension, which is more reasonable than the traditional linear function, especially for relatively big virtual antenna array sizes. By exploiting the property of chirp-like multipaths’ energy concentration in the FRFT domain, the FRFT can be first used to separate chirp-like multipath components, then the existing TOA estimation methods in frequency domain can be further employed on the separated multipath components to obtain the multipaths’ TOA estimates. Therefore, the proposed algorithm can make more use of the multipaths’ characteristics in the space dimension, thus it can efficiently enhance the multipath resolution and achieve better multipaths’ TOA estimation performance without requiring a real antenna array. Simulation results demonstrate the effectiveness of the proposed algorithm.
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Al Mtawa, Yaser. "Enhancing Network Availability: An Optimization Approach". Computation 11, nr 10 (9.10.2023): 202. http://dx.doi.org/10.3390/computation11100202.
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High availability is vital for network operators to ensure reliable services. Network faults can disrupt functionality and require quick recovery. Multipath networking enhances availability through load balancing and optimal link utilization. However, equal-cost multipath (ECMP) routing has limitations in effectively using multipaths, decreasing network availability. This paper proposes a three-phase disjoint-path framework that improves availability by directing traffic flows through separate paths. The framework provides effective load balancing and meets various service requirements. It includes the Optimization phase for identifying optimal multipath solutions, the Path Separation phase for dividing the multipath into working and backup sets, and the Quality Assessment phase for evaluating the robustness of both sets using topological metrics and micro-based characteristics. The simulations demonstrate the proposed framework’s validation and effectiveness in enhancing network availability.
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Blanza, Jojo. "Wireless Propagation Multipaths using Spectral Clustering and Three-Constraint Affinity Matrix Spectral Clustering". Baghdad Science Journal 18, nr 2(Suppl.) (20.06.2021): 1001. http://dx.doi.org/10.21123/bsj.2021.18.2(suppl.).1001.
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This study focused on spectral clustering (SC) and three-constraint affinity matrix spectral clustering (3CAM-SC) to determine the number of clusters and the membership of the clusters of the COST 2100 channel model (C2CM) multipath dataset simultaneously. Various multipath clustering approaches solve only the number of clusters without taking into consideration the membership of clusters. The problem of giving only the number of clusters is that there is no assurance that the membership of the multipath clusters is accurate even though the number of clusters is correct. SC and 3CAM-SC aimed to solve this problem by determining the membership of the clusters. The cluster and the cluster count were then computed through the cluster-wise Jaccard index of the membership of the multipaths to their clusters. The multipaths generated by C2CM were transformed using the directional cosine transform (DCT) and the whitening transform (WT). The transformed dataset was clustered using SC and 3CAM-SC. The clustering performance was validated using the Jaccard index by comparing the reference multipath dataset with the calculated multipath clusters. The results show that the effectiveness of SC is similar to the state-of-the-art clustering approaches. However, 3CAM-SC outperforms SC in all channel scenarios. SC can be used in indoor scenarios based on accuracy, while 3CAM-SC is applicable in indoor and semi-urban scenarios. Thus, the clustering approaches can be applied as alternative clustering techniques in the field of channel modeling.
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Sun, Junchang, Shuai Ma, Hui Zhou, Chun Du i Shiyin Li. "Measurement and Statistical Analysis of Distinguishable Multipaths in Underground Tunnels". International Journal of Antennas and Propagation 2020 (2.12.2020): 1–11. http://dx.doi.org/10.1155/2020/2501832.
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Compared with the line-of-sight (LOS) condition, the multipath effect is more serious in the non-line-of-sight (NLOS) condition. Therefore, the LOS and NLOS identification is necessary for the multipath analysis of signal propagation. The commonly used method is the support vector machine (SVM) method with high computational complexity. To tackle this problem, this paper adopts the SVM classifier based on fewer selected features of the normalized power delay profile (PDP). Therein, the PDP can be obtained using the sliding correlation method. The results show that the SVM-based classifier can achieve high accuracy on LOS and NLOS identification. We then analyze the impact of the signal-to-noise ratio (SNR) and transmitting-receiving (Tx-to-Rx) distance on distinguishable multipaths under LOS and NLOS conditions. According to statistical measurement results, a function of distinguishable multipath numbers is established. Finally, we investigate the multipath power and delay parameters of average delay spread and root mean square (RMS) delay spread based on multipath results. The outcomes of this paper provide a useful support for analyzing signal propagation characteristics.
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Materum, Lawrence, i Antipas T. Teologo Jr. "An Improved K-Power Means Technique Using Minkowski Distance Metric and Dimension Weights for Clustering Wireless Multipaths in Indoor Channel Scenarios". Journal of Information and Communication Technology 20, No.4 (27.09.2021): 541–63. http://dx.doi.org/10.32890/jict2021.20.4.4.
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Wireless multipath clustering is an important area in channel modeling, and an accurate channel model can lead to a reliable wireless environment. Finding the best technique in clustering wireless multipath is still challenging due to the radio channels’ time-variant characteristics. Several clustering techniques have been developed that offer an improved performance but only consider one or two parameters of the multipath components. This study improved the K-PowerMeans technique by incorporating weights or loads based on the principal component analysis and utilizing the Minkowski distance metric to replace the Euclidean distance. K-PowerMeans is one of the several methods in clustering wireless propagation multipaths and has been widely studied. This improved clustering technique was applied to the indoor datasets generated from the COST 2100 channel Model and considered the multipath components’ angular domains and their delay. The Jaccard index was used to determine the new method’s accuracy performance. The results showed a significant improvement in the clustering of the developed algorithm than the standard K-PowerMeans.
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Yuan, Zhenhua, Chen Chen i Ye Jin. "Erasure channel modelling–based secure bit allocation schemes for multipath routing in wireless sensor networks". International Journal of Distributed Sensor Networks 12, nr 12 (grudzień 2016): 155014771668360. http://dx.doi.org/10.1177/1550147716683605.
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In this article, we study secure multipath routing with energy efficiency for a wireless sensor network in the presence of eavesdroppers. We consider two objectives: (1) the multipath routing scheme for maximising the energy efficiency with security constraints and (2) the multipath routing scheme for maximising the secrecy capacity. The binary erasure channel model is adopted to describe the wireless channel states among neighbouring nodes. Based on the binary erasure channel model, the problem of multipath routing degrades to a problem of bit allocation for each path. We formulate the problems and find that the problems are both quasi-convex. For the first one, it is a linear fractional optimisation problem. The optimal solution is obtained by the Charnes–Cooper transformation. For the second one, we propose an iterative algorithm to obtain the [Formula: see text]-optimal solution. The performance analysis shows that the probability of the secure bit allocation increases along with the number of multipaths and decreases along with the number of hops per path and eavesdroppers. Simulation results are presented to illustrate the proposed algorithms.
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Su, Shuqin, i Richard D. Oleschuk. "A capillary and microchip-based nanoelectrospray emitter using a mesoporous membrane". Canadian Journal of Chemistry 86, nr 11 (1.11.2008): 1055–62. http://dx.doi.org/10.1139/v08-154.
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A method is described for the fabrication of multipath electrospray emitters using hydrophobic porous polymer membranes. Polysulphone (PSF) and polycarbonate (PC) membranes, which possess pores with well-defined sizes, are glued onto the exit aperture of fused-silica capillaries or microfluidic chips to create multipaths to assist electrospray at moderate nano flow rates (e.g., 50–500 nL/min). A capillary-based multipath emitter fabricated with either PSF or PC membranes was prepared with a fused-silica capillary with 75 µm inner diameter and 360 µm outer diameter. Relative effects on electrospray performance at different flow rates, electrospray voltages, and solvent compositions are probed. The sensitivity and stability of electrospray signals were enhanced through spraying from multiple pores on the membrane. An embossed polycarbonate microchip was also interfaced to the mass spectrometer using the meso porous membrane approach.Key words: nanoelectrospray, membrane, emitter, multipaths, microchip.
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Lee, Yongjun, i Byungwoon Park. "Nonlinear Regression-Based GNSS Multipath Modelling in Deep Urban Area". Mathematics 10, nr 3 (27.01.2022): 412. http://dx.doi.org/10.3390/math10030412.
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As the necessity of location information closely related to everyday life has increased, the use of global navigation satellite systems (GNSS) has gradually increased in populated urban areas. Contrary to the high necessity and expectation of GNSS in urban areas, GNSS performance is easily degraded by multipath errors due to high-rise buildings and is very difficult to guarantee. Errors in the signals reflected by the buildings, i.e., multipath and non-line-of-sight (NLOS) errors, are the major cause of the poor accuracy in urban areas. Unlike other GNSS major error sources, the reflected signal error, which is a user-dependent error, is difficult to differentiate or model. This paper suggests training a multipath prediction model based on support vector regression to obtain a function of the elevation and azimuth angle of each satellite. To extract an unbiased multipath from the GNSS measurements, the clock error of high-elevation QZSS was estimated, and the clock offset with other constellations was also calculated. A nonlinear multipath map was generated, as a result of training with the extracted multipaths, by a Support Vector Machine, which appropriately reflected the geometry of the building near the user. The model was effective at improving the urban area positioning accuracy by 58.4% horizontally and 77.7% vertically, allowing us to achieve a 20 m accuracy level in a deep urban area, Teheran-ro, Seoul, Korea.
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Hunegnaw, Addisu, i Felix Norman Teferle. "Evaluation of the Multipath Environment Using Electromagnetic-Absorbing Materials at Continuous GNSS Stations". Sensors 22, nr 9 (28.04.2022): 3384. http://dx.doi.org/10.3390/s22093384.
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To date, no universal modelling technique is available to mitigate the effect of site-specific multipaths in high-precision global navigation satellite system (GNSS) data processing. Multipaths affect both carrier-phase and code/pseudorange measurements, and the errors can propagate and cause position biases. This paper presents the use of an Eccosorb AN-W-79 microwave-absorbing material mounted around a GNSS antenna that reflects less than −17 dB of normal incident energy above a frequency of 600 MHz. To verify the feasibility and effectiveness of the Eccosorb, we installed two close stations by continuously operating multi-GNSS (BeiDou, GLONASS, Galileo and GPS) in a challenging location. One station is equipped with the Eccosorb AN-W-79, covering a square area of 3.35 m2 around the antenna, and the second station operates without it. The standard deviation reductions from single point positioning estimates are significant for all the individual GNSS solutions for the station equipped with microwave-absorbing material. The reductions are as follows: for GPS, between 15% and 23%; for Galileo, between 22% and 45%; for GLONASS, 22%; and for BeiDou, 4%. Furthermore, we assess the influence of multipaths by analysing the linear combinations of code and carrier phase measurements for various GNSS frequencies. The Galileo code multipath shows a reduction of more than 60% for the station with microwave-absorbing material. For GLONASS, particularly for the GLOM3X and GLOM1P code multipath combinations, the reduction reaches 50%, depending on the observation code types. For BeiDou, the reduction is more than 30%, and for GPS, it reaches between 20% and 40%. The Eccosorb AN-W-79 microwave-absorbing material shows convincing results in reducing the code multipath noise level. Again, using microwave-absorbing material leads to an improvement between 15% and 60% in carrier phase cycle slips. The carrier-phase multipath contents on the post-fit residuals from the processed GNSS solutions show a relative RMS reduction of 13% for Galileo and 9% for GLONASS and GPS when using the microwave-absorbing material. This study also presents power spectral contents from residual signal-to-noise ratio time series using Morlet wavelet transformation. The power spectra from the antenna with the Eccosorb AN-W-79 have the smallest magnitude, demonstrating the capacity of microwave-absorbing materials to lessen the multipath influence while not eliminating it.
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She, Feng, Hsiao Hwa Chen i Hongyang Li. "Joint Angular and Time Diversity of Multi-Antenna CDMA Systems in Wireless Fading Channels". International Journal of Wireless Networks and Broadband Technologies 1, nr 1 (styczeń 2011): 1–14. http://dx.doi.org/10.4018/ijwnbt.2011010101.
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In this paper, a multi-antenna based receiver structure for direct sequence code division multiple access (DS/CDMA) system is proposed. The proposed scheme exploits the excellent time resolution of a CDMA RAKE receiver and uses an antenna array beamforming structure to resolve multipath returns in both angular and time domains. A much higher diversity gain than that based only on the time domain diversity can be achieved. This work suggests a new space-time diversity paradigm, namely angular-time diversity, which differs from traditional Alamouti-type space-time coded schemes. The impairments caused by multipath and multiuser interference are analyzed. The performance of the proposed receiver in multipath fading channel is explicitly evaluated. An expression for uncoded system bit error probability is derived. Simulation results show the performance improvement in terms of BER due to the use of multi-antenna in the receiver, and the results illustrate that the multi-antenna based receiver works effectively in resolving multipaths in both angular and time domains to achieve performance improvement due to angular and time diversity gain provided by the multi-antenna system.
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A. Rida, Jafaar Fahad. "Improvement for performance radio frequency in wireless communication based on impulse signal". Indonesian Journal of Electrical Engineering and Computer Science 18, nr 2 (1.05.2020): 903. http://dx.doi.org/10.11591/ijeecs.v18.i2.pp903-916.
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<p><span>This research presents the improved performance of mobile wireless communication channel is based on non-line of sight because the mobile propagation channel is very hard to work with direct path between the transmitter and mobile receiver because of city-based area has objects such as rise building, trees, surround structures, and other objects. The mobile wireless spread radio channels have radio propagation mechanisms as a reflection, diffraction, and scattering effect on radio signal as lessening, </span>and distortion or spread time. The most important thing to make real is that the wireless channel is a multipath radio channel. Multipath copies of the same signal with distinct amplitudes, stages and delay times for all multipaths between the transmitter and the receiver. The multipath fading is defined by its impulse response, which includes the facts about the relative time of the recipient's arrival of various indices of multipath additives. The impulse response expresses great characteristics in the time domain such the large bandwidth frequencies and the amplitude output only the value impulse response δ(t) equal to one when the value of time t=0, otherwise, the value impulse response δ(t) equal to zero in all values of the time. Over a time period reaction, the cellular radio channel could be designed as a linear filter with various impulses.</p>
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Wischik, Damon. "Multipath". Communications of the ACM 54, nr 1 (styczeń 2011): 108. http://dx.doi.org/10.1145/1866739.1866761.
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Garg, Roopali, i Guneet Kaur. "Multipath Routing protocol: NCPR and QAMR". INTERNATIONAL JOURNAL OF COMPUTERS & TECHNOLOGY 11, nr 10 (10.12.2013): 3065–70. http://dx.doi.org/10.24297/ijct.v11i10.2975.
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Mobile ad hoc network is an assembly of mobile nodes with no centralized server. Due to mobility of nodes and decentralized network it is difficult to maintain the quality of service (QoS) in routing the packets from source to destination. QoS can be defined in terms of various metrics like delay, bandwidth, packet loss, routing overhead, jitter. Routing can be unicast, multicast or multipath. This paper presents the description about the QoS multipath routing algorithm.
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Yang, Yiping, Chuan Chen, Yong Jia, Guolong Cui i Shisheng Guo. "Non-Line-of-Sight Target Detection Based on Dual-View Observation with Single-Channel UWB Radar". Remote Sensing 14, nr 18 (11.09.2022): 4532. http://dx.doi.org/10.3390/rs14184532.
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Non-line-of-sight (NLOS) target detection utilizing multipath plays an important role in anti-terrorism, urban warfare, indoor rescue and intelligent driving. In this paper, an imaging method based on single-channel ultra-wideband (UWB) radar and dual-view observation is proposed for detecting NLOS targets. First, the cause of producing ghosts from a single view in a previous study is analyzed in detail. On this basis, with focusing on dual-view observation, the ghost problem is handled at two levels. From the level of the radar echo, path partition is conducted with the utilization of dual-view observation, solving the problem of uneven energy among multipaths. After that, two images are generated by multipath imaging, respectively, which reduces the accumulation of ghosts. From the level of the image, owing to the distinct distribution of ghosts between the imaging result, the ghosts at different locations are eliminated by image fusion. Experimental results demonstrate that compared with single view and direct multipath imaging, the approach based on dual-view observation successfully eliminates most ghosts while retaining the targets in both single-target and double-targets scenarios, which verifies the effectiveness of the method.
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Zhang, Yimin D., Xizhong Shen, Ramazan Demirli i Moeness G. Amin. "Ultrasonic Flaw Imaging via Multipath Exploitation". Advances in Acoustics and Vibration 2012 (1.08.2012): 1–12. http://dx.doi.org/10.1155/2012/874081.
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We consider ultrasonic imaging for the visualization of flaws in a material. Ultrasonic imaging is a powerful nondestructive testing (NDT) tool which assesses material conditions via the detection, localization, and classification of flaws inside a structure. We utilize reflections of ultrasonic signals which occur when encountering different media and interior boundaries. These reflections can be cast as direct paths to the target corresponding to the virtual sensors appearing on the top and bottom side of the target. Some of these virtual sensors constitute a virtual aperture, whereas in others, the aperture changes with the transmitter position. Exploitations of multipath extended virtual array apertures provide enhanced imaging capability beyond the limitation of traditional multisensor approaches. The waveforms observed at the physical as well as the virtual sensors yield additional measurements corresponding to different aspect angles, thus allowing proper multiview imaging of flaws. We derive the wideband point spread functions for dominant multipaths and show that fusion of physical and virtual sensor data improves the flaw perimeter detection and localization performance. The effectiveness of the proposed multipath exploitation approach is demonstrated using real data.
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Muqaibel, Ali H., Moeness G. Amin i Fauzia Ahmad. "Target Localization with a Single Antenna via Directional Multipath Exploitation". International Journal of Antennas and Propagation 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/510720.
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Target localization in urban sensing can benefit from angle dependency of the pulse shape at a radar receiver antenna. We propose a localization approach that utilizes the embedded directivity in ultra-wideband (UWB) antennas to estimate target positions. A single radar unit sensing operation of indoor targets surrounded by interior walls is considered, where interior wall multipaths are exploited to provide target cross-range. This exploitation assumes resolvability of the multipath components, which is made possible by the virtue of using UWB radar signals. The proposed approach is most attractive when only few multipaths are detectable due to propagation obstructions or owing to low signal-to-noise ratios. Both simulated and experimental data are used to demonstrate the effectiveness of the proposed approach.
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Lee, Seunghwa, i Joon Yoo. "Reinforcement Learning Based Multipath QUIC Scheduler for Multimedia Streaming". Sensors 22, nr 17 (23.08.2022): 6333. http://dx.doi.org/10.3390/s22176333.
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With the recent advances in computing devices such as smartphones and laptops, most devices are equipped with multiple network interfaces such as cellular, Wi-Fi, and Ethernet. Multipath TCP (MPTCP) has been the de facto standard for utilizing multipaths, and Multipath QUIC (MPQUIC), which is an extension of the Quick UDP Internet Connections (QUIC) protocol, has become a promising replacement due to its various advantages. The multipath scheduler, which determines the path to which each packet should be transmitted, is a key function that affects the multipath transport performance. For example, the default minRTT scheduler typically achieves good throughput, while the redundant scheduler gains low latency. While the legacy schedulers may generally give a desirable performance in some environments, however, each application renders different requirements. For example, Web applications target low latency, while video streaming applications require low jitter and high video quality. In this paper, we propose a novel MPQUIC scheduler based on deep reinforcement learning using the Deep Q-Network (DQN) that enhances the quality of multimedia streaming. Our proposal first takes into account both delay and throughput as a reward for reinforcement learning to achieve a low video chunk download time. Second, we propose a chunk manager that informs the scheduler of the video chunk information, and we also tune the learning parameters to explore new random actions adequately. Finally, we implement our new scheduler on the Linux kernel and give results using the Mininet experiments. The evaluation results show that our proposal outperforms legacy schedulers by at least 20%.
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Blanza, Jojo, Emmanuel Trinidad i Lawrence Materum. "Scedasticity descriptor of terrestrial wireless communications channels for multipath clustering datasets". International Journal of Electrical and Computer Engineering (IJECE) 13, nr 6 (1.12.2023): 6547. http://dx.doi.org/10.11591/ijece.v13i6.pp6547-6557.
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Fifth-generation (5G) wireless systems increased the bandwidth, improved the speed, and shortened the latency of communications systems. Various channel models are developed to study 5G. These channel models reproduce the stochastic properties of multiple-input multiple-output (MIMO) antennas by generating wireless multipath components (MPCs). The MPCs that have similar properties in delay, angles of departure, and angles of arrival form clusters. The multipaths and multipath clusters serve as datasets to understand the properties of 5G. These datasets generated by the Cooperation in Science and Technology 2100 (COST 2100), International Mobile Telecommunications-2020 (IMT-2020), quasi deterministic radio channel generator (QuaDRiGa), and wireless world initiative new radio II (WINNER II) channel models are tested for their homoscedasticity based on Johansen's procedure. Results show that the COST 2100, QuaDRiGa, and WINNER II datasets are heteroscedastic, while the IMT-2020 dataset is homoscedastic.
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Tao, Yuan, Chao Liu, Tianyang Chen, Xingwang Zhao, Chunyang Liu, Haojie Hu, Tengfei Zhou i Haiqiang Xin. "Real-Time Multipath Mitigation in Multi-GNSS Short Baseline Positioning via CNN-LSTM Method". Mathematical Problems in Engineering 2021 (4.01.2021): 1–12. http://dx.doi.org/10.1155/2021/6573230.
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Multipath is the main systematic error of the Global Navigation Satellite System (GNSS) short baseline positioning. Multipath cannot be eliminated by the double-differenced technique and is difficult to parameterize, which severely restrict the high-precision GNSS positioning application. Based on the spatiotemporal repeatability of multipath, the sidereal filtering in coordinate-domain (SF-CD), the sidereal filtering in observation-domain (SF-OD), and the multipath hemispherical map (MHM) can be used to mitigate the multipath in real-time. However, the multipath model with large matrix for multi-GNSS multipath mitigation is difficult to achieve lightweight calculation and the SF-CD cannot be applied to mitigate the multi-GNSS multipath. In this paper, we propose a new multipath mitigation strategy in the coordinate-domain that shakes off the formation mechanism of multipath, a CNN (convolutional neural network)-LSTM (long short-term memory) method is used to mine the deep multipath features in GNSS coordinate series. Furthermore, multipath will be mitigated in real-time by constantly predicting the value of the next epoch. The experimental results show that the CNN-LSTM effectively mitigates the multi-GNSS multipath. The method can reduce the average RMS (root-mean square) of multi-GNSS positioning errors in the east, north, and vertical directions by 62.3%, 70.8%, and 66.0%. Moreover, comparing with the SF-CD, SF-OD, and MHM, CNN-LSTM can more effectively mitigate the effects of the GPS multipath, and the ability of multipath mitigation is almost not affected over time.
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Yuan, Muzi, Du Li, Baiyu Li, Huaming Chen i Gang Ou. "Assessment Method of Multipath Mitigation Performance for GNSS Antenna with Receiver Algorithms". International Journal of Antennas and Propagation 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/1957572.
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Multipath is one of the most important sources of positioning error in GNSS. Well-designed antennas can mitigate multipath signals and enhance the performance of GNSS receivers. This paper concentrates on methods to assess multipath mitigation performance for GNSS antennas. We propose a model to describe multipath environment in GNSS ground stations. The model analyzes effects caused by inclined reflective surfaces and multipath mitigating algorithms in receivers. A method to assess multipath mitigation performance is put forward by analyzing pseudorange code phase errors caused by multipath signals after signal processing. Based on the model and method, principles in site selection for GNSS antenna are introduced to minimize effects caused by multipath.
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Zhang, Bo, Qing Wang, Wenqing Xia, Yu Sun i Jinling Wang. "Pseudolite Multipath Estimation Adaptive Mitigation of Vector Tracking Based on Ref-MEDLL". Remote Sensing 15, nr 16 (15.08.2023): 4041. http://dx.doi.org/10.3390/rs15164041.
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Among many indoor positioning technologies, pseudolite positioning technology has become an important supplement to GNSS. In indoor open environments, pseudolite positioning technology can usually perform high-precision positioning. However, in a complex environment, the pseudolite receiver is seriously interfered by multipath and other interference signals, which will lead to a serious decline in the observation accuracy, signal lock loss or even no positioning results. Therefore, this work proposes a pseudolite indoor anti-multipath receiver based on reference multipath estimating delay lock loop (Ref-MEDLL). It adds the Ref-MEDLL multipath estimator module and the multipath mitigation module to the traditional receiver signal processing architecture. In the multipath mitigation module, the multipath estimation adaptive mitigation of vector tracking (MEAM-VT) method and the multipath estimation direct mitigation (MEDM) method for multipath mitigation is proposed. Experimental results show that the Ref-MEDLL multipath estimation method has good adaptability to multipath signals that have different time delays and different amplitudes; both the MEDM receiver and the MEAM-VT receiver have good multipath mitigation performance. The MEAM-VT method performs better than the MEDM method in multipath mitigation and tracking, but the stability of the pseudorange observations of the MEAM-VT method is not as good as that of the MEDM method. The positioning accuracy of the MEDM receiver and the MEAM-VT receiver has been improved to different degrees in static positioning experiments and dynamic positioning experiments.
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Hui, Yong Tao, Bing Bing Li, Zhao Tong, Xing Wang Zhong i Hao Liu. "A Short-Delay Multipath Mitigation Algorithm Based on Variable Step-Size LMS Adaptive Filtering". Applied Mechanics and Materials 571-572 (czerwiec 2014): 368–75. http://dx.doi.org/10.4028/www.scientific.net/amm.571-572.368.
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The multipath in the inter-spacecraft microwave ranging system is the short-delay multipath generally. The performance of existing multipath mitigation algorithms degrade in the short-delay scenario, and therefore an adaptive filtering algorithm based on variable step-size LMS is exploited for estimating the parameters of multipath signals. Firstly, the equation of variable step-size LMS is deduced. Then, the signals parameters are estimated recursively though the adaptive filtering algorithm. Multipath elimination is performed by substracting the estimated multipath effects from the measured correlation function. Simulation results validate that the proposed method is superior to the existing algorithms in the aspect of convergence rate and ranging accuracy for the short delay multipath. Therefore, it is a viable solution for achieving high accuracies measurements in microwave ranging system with short-delay multipath.
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Wang, Zhiren, Wen Chen, Danan Dong, Chenglong Zhang, Yu Peng i Zhengqi Zheng. "An Advanced Multipath Mitigation Method Based on Trend Surface Analysis". Remote Sensing 12, nr 21 (2.11.2020): 3601. http://dx.doi.org/10.3390/rs12213601.
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Among various ways to eliminate the multipath effect in high-precision global navigation satellite system positioning, the multipath hemispherical map (MHM) is a typical multipath correction method based on spatial domain repeatability, which is suitable for not only static environments, but also some dynamic carriers, such as ships and aircraft. So, it has notable advantages and is widely used. The MHM method divides the sky into grids according to the azimuth and elevation angles of satellite, and calculates the average of the residuals within the grid points as its multipath calibration value. It is easy to implement, but it will inevitably lead to excessive or insufficient multipath correction in the grid. The trend surface analysis-based multipath hemispherical map (T-MHM) method makes up for this deficiency by performing trend surface analysis on the multipath spatial changes within the grid points. However, the effectiveness of T-MHM is limited and less capable of resisting noise interference due to the multicollinearity between the independent variables caused by the special spatial distribution of multipath sampling and the overfitting problem caused by ignoring the multipath anisotropy. Thus, we proposed an improved multipath elimination method named AT-MHM (advanced trend surface analysis-based multipath hemispherical model), which cautiously judges the occurrence of the above problems and gives corresponding solutions. This was extended to double-difference mode, which expands the scope of application. The performance of AT-MHM in GPS pseudorange multipath mitigation was verified on geodetic receiver and low-cost receiver in a strong multipath environment with high occlusion.
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Liu, Jun Jian, Jiu Lei Jiang i Jiao Zhang. "Multipath Routing". Applied Mechanics and Materials 519-520 (luty 2014): 288–93. http://dx.doi.org/10.4028/www.scientific.net/amm.519-520.288.
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Multipath routing can be effectively used for maximum utilization of network resources. It gives the node a choice of next hops for the same destination. We present two tree based algorithms, which we call MSPT and MBFT that can help a node to find multiple next hops for a destination. Both of them are distributed algorithm, allowing the traffic to switch off the shortest path and fully exploiting the path diversity of the network. MSPT has lower cost, while MBFT has less hops between the source and destination, end system can select next hop according to the application requirements. The simulation show that our algorithms can find more selectable next hops and have good reliability and fast recovery performance. In the process of simulation, we discovery that MSPT and MBFT have more disjoint paths, therefore we provide an Algorithm 2 to combine the MSPT and MBFT, the performance of Algorithm 2 is obviously superior than independently employs
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Combes, Richard, Habib Sidi i Salah Elayoubi. "Multipath Streaming". ACM SIGMETRICS Performance Evaluation Review 44, nr 1 (30.06.2016): 391–92. http://dx.doi.org/10.1145/2964791.2901485.
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Paasch, Christoph, i Olivier Bonaventure. "Multipath TCP". Queue 12, nr 2 (luty 2014): 40–51. http://dx.doi.org/10.1145/2578508.2591369.
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Paasch, Christoph, i Olivier Bonaventure. "Multipath TCP". Communications of the ACM 57, nr 4 (kwiecień 2014): 51–57. http://dx.doi.org/10.1145/2578901.
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Luo, Haolan, Wenqiang Zhang, Zhaoting Ren, Chuantian Tang, Yu Ou, Guolong Cui i Shisheng Guo. "Analysis of Electromagnetic Wave and Multipath Suppression from Overhead Perspective". Remote Sensing 15, nr 20 (10.10.2023): 4903. http://dx.doi.org/10.3390/rs15204903.
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The multipath problem in indoor target detection has always been a long-standing research hotspot. Although there are many solutions to the multipath problem in a horizontal line of sight, the multipath problem of single-station radar from an overhead perspective still needs to be solved. At present, there is a lack of detailed analysis on the multipath propagation law of electromagnetic waves from an overhead perspective. This paper first analyzes the multipath propagation law of overhead perspective and reveals a combination multipath propagation phenomenon that is easily overlooked, which is formed by walls, ground, and targets. In addition, during the analysis process, the influence of coherent sources generated by multipath on angle estimation was fully considered, and verified through simulation and measured data. Then, based on the result of propagation analysis, this paper proposes a multipath ghost target suppression method. This method first establishes a multipath ghost target location dictionary based on building information, and then matches the tracking results with the dictionary to suppress successfully matched multipath ghost targets. Finally, several experiments are carried out to verify the effectiveness of this method.
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Visentin, Tristan, Jürgen Hasch i Thomas Zwick. "Analysis of multipath and DOA detection using a fully polarimetric automotive radar". International Journal of Microwave and Wireless Technologies 10, nr 5-6 (3.04.2018): 570–77. http://dx.doi.org/10.1017/s1759078718000284.
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AbstractMultipath propagation occurs in many situations of radar measurements in complex environments. The unwanted effects range from interference over the radar channels, which causes amplitude fading and a corrupted direction of arrival (DOA) estimation, to the detection of ghost targets in an angle of arrival of the multipath direction. Due to the different number of reflections, polarimetric radars are capable to separate certain multipaths from direct paths if the target is known in advance. Furthermore, it is possible to separate objects with different polarimetric features in DOA that are located in the same radial distance to the radar. In this paper, a new approach to DOA detection based on the coherent Pauli decomposition is presented. With this approach, important multipath and DOA effects are analyzed and measurement results at 77 GHz on canonical objects in an anechoic chamber are presented. The results prove the feasibility of the approach and demonstrate the occurring effects.
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Ng, Benjamin K., i Chan-Tong Lam. "Single-Carrier Rotation-Interleaved Space-Time Code for Frequency-Selective Fading Channels". Applied Sciences 12, nr 24 (13.12.2022): 12803. http://dx.doi.org/10.3390/app122412803.
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A novel single-carrier-based space-time code construction scheme to exploit the advantages of a frequency-selective fading channel is investigated in this paper. The proposed construction scheme is based on multiplexing independent streams of phase-rotated space-time codes in a time-interleaved fashion. The advantage of such design is that it guarantees full space-time-multipath diversity by using traditional space-time codes or MIMO signaling schemes originally designed for flat fading channels as the constituent codes. Another advantage is that this approach incurs no loss in bandwidth efficiency and it alleviates the problem of high PAPR in OFDM-based space-time codes. By employing random or algebraic rotations, the design is potentially suitable for any number of transmit antennas or multipaths. The simulation results indicate that full space-time-multipath diversity is attained using this new approach, and comparisons with some existing space-time codes designed for frequency-selective channels are made to show its performance advantage.
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Guan, Yunchong, Weimin Lei, Wei Zhang, Yuzhuo Zhan, Hao Li i Songyang Zhang. "A Multi-Dimension Spatial Method for Topology Awareness and Multipath Generating". Symmetry 11, nr 7 (3.07.2019): 870. http://dx.doi.org/10.3390/sym11070870.
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Multipath diversity significantly impacts multipath transmission quality. Enough multipath diversity would minimize the negative influence brought by an individual path, thus improving tolerance capability of network congestion and failure. However, multipath diversity is hard to guarantee on overlay networks because of inaccurate awareness of underlay network and multipath generating methods considering little about underlay diversity. In this paper, we design a multi-dimension spatial method for topology awareness and multipath generating. Analyzing that the complicated underlay networks with multiple autonomous systems reduce the accuracy of network positioning for topology awareness, we decompose the underlay networks into multiple dimensions, namely intra and inter autonomous system dimensions. We generate independent views for each autonomous system and merge views by embedding exchange points. Then, we design some spatial mechanisms to evaluate link diversity and to constrain multipath generating. Based on the multi-dimensional view, multipath generating is conducted in inter and intra autonomous system phases. Experiments demonstrate that the proposed method improves topology awareness accuracy and guarantees multipath diversity better and the transmission quality is improved.
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Tamazin, Mohamed, Aboelmagd Noureldin, Michael J. Korenberg i Ahmed M. Kamel. "A New High-Resolution GPS Multipath Mitigation Technique Using Fast Orthogonal Search". Journal of Navigation 69, nr 4 (3.02.2016): 794–814. http://dx.doi.org/10.1017/s0373463315001022.
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The Delay Locked Loop (DLL) tracking algorithm is one of the most widely used in GPS receivers. It uses different correlators such as the Early-Late Slope (ELS) correlator and High-Resolution Correlator (HRC) to mitigate code phase multipath. These techniques are effective for weak multipath environments but they may not be suitable for challenging multipath environments. The Multipath Estimating Delay Lock Loop (MEDLL) shows better performance than the classical methods. However, MEDLL still has limited capabilities in severe multipath environments. This paper introduces a robust multipath mitigation technique based on fast orthogonal search to obtain better delay estimation for GPS receivers. This research utilised a SPIRENT Global Navigation Satellite Systems (GNSS) simulator to compare the performance of the proposed method with other multipath mitigation techniques. Experimental results demonstrated that the performance of the proposed algorithm was better than the classical and advanced techniques under the multipath scenarios tested.
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Quan, Yiming, Lawrence Lau, Gethin Wyn Roberts, Xiaolin Meng i Chao Zhang. "Convolutional Neural Network Based Multipath Detection Method for Static and Kinematic GPS High Precision Positioning". Remote Sensing 10, nr 12 (17.12.2018): 2052. http://dx.doi.org/10.3390/rs10122052.
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Global Positioning System (GPS) has been used in many aerial and terrestrial high precision positioning applications. Multipath affects positioning and navigation performance. This paper proposes a convolutional neural network based carrier-phase multipath detection method. The method is based on the fact that the features of multipath characteristics in multipath contaminated data can be learned and identified by a convolutional neural network. The proposed method is validated with simulated and real GPS data and compared with existing multipath mitigation methods in position domain. The results show the proposed method can detect about 80% multipath errors (i.e., recall) in both simulated and real data. The impact of the proposed method on positioning accuracy improvement is demonstrated with two datasets, 18–30% improvement is obtained by down-weighting the detected multipath measurements. The focus of this paper is on the development and test of the proposed convolutional neural network based multipath detection algorithm.
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Jiang, Lin, Haojiang Deng i Shoujiang Dang. "A Multipath Transmission System for Information-Centric Networking Based on Standalone Name Resolution". Applied Sciences 13, nr 7 (25.03.2023): 4195. http://dx.doi.org/10.3390/app13074195.
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Information-Centric Networking (ICN) essentially supports multipath transmission. However, current multipath schemes in ICN either necessitate major network infrastructure updates or necessitate specific network settings for terminal devices. To solve these problems, we propose MPTS-ICN, a multipath transmission system for ICN that realizes end-to-end multipath transmission. Taking the ICN architecture based on the standalone name resolution approach as a basis, MPTS-ICN is easier to implement and deploy than other ICN multipath schemes. Moreover, we have extended the original network layer protocol to support multipath data transmission in ICN. To set up concurrent transmission multipath efficiently, we propose a heuristic algorithm for the selection of multipath service nodes. Extensive experimental comparisons with existing data transmission methods show that in bandwidth-constrained scenarios, MPTS-ICN outperforms the best-route method by 83.6% and the ECMP method by 79.7% in average flow completion time.
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Sun, Jie, Zuping Tang, Chuang Zhou i Jiaolong Wei. "Characterization of BDS Multipath Effect Based on AT-Conv-LSTM Network". Remote Sensing 16, nr 1 (24.12.2023): 73. http://dx.doi.org/10.3390/rs16010073.
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Multipath effects are the most challenging error sources for the Global Navigation Satellite System receiver, affecting observation quality and positioning accuracy. Due to the non-linear and time-varying nature, multipath error is difficult to process. Previous studies used a homogeneous indicator to characterize multipath effects and only revealed the temporal or spatial correlations of the multipath, resulting in limited correction performance. In this study, we consider the code multipath to be influenced not only by the elevation and azimuth angle of certain stations to satellites but also to be related to satellite characteristics such as nadir angle. Hence, azimuth angle, elevation angle, nadir angle and carrier-to-noise power density ratio are taken as multiple indicators to characterize the multipath significantly. Then, we propose an Attention-based Convolutional Long Short-Term Memory (AT-Conv-LSTM) that fully exploits the spatiotemporal correlations of multipath derived from multiple indicators. The main processing procedures using AT-Conv-LSTM are given. Finally, the AT-Conv-LSTM is applied to a station for 16 consecutive days to verify the multipath mitigation effectiveness. Compared with sidereal filtering, multipath hemispherical map (MHM) and trend-surface analysis-based MHM, the experimental results show that using AT-Conv-LSTM can decrease the root mean square error and mean absolute error values of the multipath error more than 60% and 13%, respectively. The proposed method can correct the code multipath to centimeter level, which is one order of magnitude lower than the uncorrected code multipath. Therefore, the proposed AT-Conv-LSTM network could be used as a powerful alternative tool to realize multipath reduction and will be of wide practical value in the fields of standard and high-precision positioning services.
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Meng, Ling Jing, Dong Li i Hai Bo Liu. "Impact of Multipath Effect on Low-Altitude Elevation Measurement of Radar". Applied Mechanics and Materials 602-605 (sierpień 2014): 1879–82. http://dx.doi.org/10.4028/www.scientific.net/amm.602-605.1879.
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The main impact of multipath effect on low-altitude radar measurement is elevated in this paper. The influence of multipath effect on monopulse radar measurement of elevation is analyzed. Examples suggest that the multipath error caused by the signals from pattern main lobe of radar antenna should be mainly considered in the actual project. According to the three elevation range of reflected signal entering the radar beam area, the multipath error model of elevation is established. The problem of anti-multipath interference for low-altitude target tracking with radar is solved by analyzing the error source which causes multipath effect.
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Huang, Long, Zukun Lu, Zhibin Xiao, Chao Ren, Jie Song i Baiyu Li. "Suppression of Jammer Multipath in GNSS Antenna Array Receiver". Remote Sensing 14, nr 2 (13.01.2022): 350. http://dx.doi.org/10.3390/rs14020350.
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Interference multipath is an important factor to affect the anti-jamming performance for the global navigation satellite system (GNSS) antenna array receiver. However, interference multipath must be considered in practical application. In this paper, the antenna array model for interference multipath is analyzed, and an equivalent model for interference multipath is proposed. According to the equivalent interference multipath model, the influence of interference multipath on anti-jamming performance is analyzed from the space only processing (SOP) and space-time adaptive processing (STAP). Interference multipath can cause loss of the degree of freedom (DoF) of SOP. Through analysis of the equivalent model and STAP mechanism, it further reveals how the STAP can solve the interference multipath. The simulation experiments prove that the equivalent model is effective, and the analysis conclusion is correct. This paper also points out that the interference bandwidth is wider and more taps in STAP are required, under the same experiment conditions.
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Xiao, Ling, Changzhe Si, Xin Ye, Bangshuang Zhang, Gang Qin i Yue Bai. "A multipath migration method for common clock source SDCP observation using polynomial fitting technique". Journal of Physics: Conference Series 2253, nr 1 (1.04.2022): 012009. http://dx.doi.org/10.1088/1742-6596/2253/1/012009.
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Abstract The multipath error is the major error source for high precision positions. One sidereal filtering multipath migration method is proposed for single difference carrier phase(SDCP) measurement based on polynomial fitting technique. The multipath error prediction is estimated by constructing a piecewise polynomial function based on polynomial fitting of one sidereal period multipath errors. Then the multipath error of the measurement is eliminated by subtracting the corresponding prediction. The effectiveness of the proposed method was verified by field experiments. The experimental results show that the 3-dimension (3D) accuracy of proposed method is improved by 68.9%, compared with the results that without multipath error eliminating.
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So, Hyoungmin, Ghangho Kim, Taikjin Lee, Sanghoon Jeon i Changdon Kee. "Modified High-Resolution Correlator Technique for Short-Delayed Multipath Mitigation". Journal of Navigation 62, nr 3 (15.06.2009): 523–42. http://dx.doi.org/10.1017/s037346330900530x.
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Multipath is one of the main error sources in global navigation satellite system (GNSS) positioning. The high-resolution correlator (HRC) is a multipath mitigation technique well known for its outstanding performance for mid-delayed multipath, but still has a remaining error for the short-delayed multipath. This paper proposes a modified HRC scheme that can remove or reduce the error for short-delayed multipath signals. It estimates the HRC tracking error and augments the conventional HRC with the estimates. The method was implemented with a software receiver and the test results show short-delayed multipath-induced errors were reduced to about one third of those from the conventional HRC.
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Li, Qianxia, Linyuan Xia, Ting On Chan, Jingchao Xia, Jijun Geng, Hongyu Zhu i Yuezhen Cai. "Intrinsic Identification and Mitigation of Multipath for Enhanced GNSS Positioning". Sensors 21, nr 1 (30.12.2020): 188. http://dx.doi.org/10.3390/s21010188.
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In global navigation satellite system (GNSS)-based positioning and applications, multipath is by far the most obstinate impact. To overcome paradoxical issues faced by current processing approaches for multipath, this paper employs an intrinsic method to identify and mitigate multipath based on empirical mode decomposition (EMD) and Hilbert–Huang transform (HHT). Frequency spectrum and power spectrum are comprehensively employed to identify and extract multipath from complex data series composed by combined GNSS observations. To systematically inspect the multipath from both code range and carrier phase, typical kinds of combinations of the GNSS observations including the code minus phase (CMP), differential correction (DC), and double differential (DD) carrier phase are selected for the suggested intrinsic approach to recognize and mitigate multipath under typical positioning modes. Compared with other current processing algorithms, the proposed methodology can deal with multipath under normal positioning modes without recourse to the conditions that satellite orbits are accurately repeated and surrounding environments of observing sites remain intact. The method can adaptively extract and eliminate multipath from solely the GNSS observations using intrinsic decomposition mechanism. From theoretical discussions and validating tests, it is found that both code and carrier phase multipath can be identified and distinguished from ionospheric delay and other impacts using the EMD based techniques. The resultant positioning accuracy is therefore improved to an obvious extent after the removal of the multipath. Overall, the proposed method can form an extensive and sound technical frame to enhance localization accuracy under typical GNSS positioning modes and harsh multipath environments.
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Hu, Yili, Yongbo Zhao i Sheng Chen. "Incoherent Integration Detection Method of Airborne Phased Array Radar in a Multipath Environment". International Journal of Antennas and Propagation 2021 (15.12.2021): 1–10. http://dx.doi.org/10.1155/2021/8699512.
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Airborne phased array radar (PAR) suffers from multipath problems when flying over a calm sea surface. The existence of a multipath phenomenon will cause the electromagnetic echo of the same target to be reflected back to the airborne PAR from two paths, namely, direct path (DP) and multipath. Compared with the ground-based radar, the target echo received by airborne PAR in the multipath environment has two important characteristics: one is that the DP signal and the multipath signal exist in different range bins, and the other is that the radar cross section (RCS) in the DP direction may be smaller than that in the multipath direction. Considering these two characteristics, this paper first proposes a target pairing algorithm for matching the DP range and multipath range of the same target in signal detection, and then, combined with the cell-averaging constant false alarm rate (CA-CFAR) detection model, an incoherent integration detection method for airborne PAR in the multipath environment is proposed. In the target pairing process, the geometric structure relationship of the airborne PAR model can be fully utilized. After a successful target pairing process, the energy of the multipath signal will be incoherently accumulated into the corresponding DP range bin, so as to improve the probability of DP range bin data passing the detection threshold. In essence, the proposed method makes full use of multipath energy to improve the detection capability of airborne PAR in the multipath environment. Finally, the detection probability of the proposed method is given, and the detection performance is analyzed.
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Hu, Bin, Xueyong Shen, Min Jiang i Kaiheng Zhao. "Off-Grid DOA Estimation Based on Compressed Sensing on Multipath Environment". International Journal of Antennas and Propagation 2023 (10.04.2023): 1–6. http://dx.doi.org/10.1155/2023/9315869.
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Due to the existence of multipath propagation, the array will receive the multipath propagation signals at the same time while receiving the target signal and the performance of directional of arrival (DOA) estimation will be influenced. In this paper, an off-grid DOA estimation technique based on compressed sensing (CS) on multipath environment is proposed. To deal with the off-grid problem and the multipath propagation problem, we present a compressed sensing based method. This method regards the multipath propagation coefficients vector as a superparameter and the grid as an adjustable parameter. Then, the problem of multipath propagation coefficients estimation is converted to the estimation of an error matrix and the grid is refined iteratively. The simulation results show that the method can achieve off-grid DOA estimation in the presence of the multipath propagation signals.
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Lin, Yun, Ziwei Tian, Yanping Wang, Yang Li, Wenjie Shen i Zechao Bai. "Enhancing SAR Multipath Ghost Image Suppression for Complex Structures through Multi-Aspect Observation". Remote Sensing 16, nr 4 (8.02.2024): 637. http://dx.doi.org/10.3390/rs16040637.
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When Synthetic Aperture Radar (SAR) observes complex structural targets such as oil tanks, it is easily interfered with by multipath signals, resulting in a large number of multipath ghost images in the SAR image, which seriously affect the image clarity. To address this problem, this paper proposes a multi-aspect multipath suppression method. This method observes complex structural targets from different azimuth angles to obtain a multi-aspect image sequence and then uses the difference in sequence features between the target image and the multipath ghost image with respect to aspect angle to separate them. This paper takes a floating-roof oil tank as an example to analyze the propagation path and the ghost image characteristics of multipath signals under different observation aspects. We conclude that the scattering center of the multipath ghost image changes with the radar observation aspect, whereas the scattering center of the target image does not. This paper uses the Robust Principal Component Analysis (RPCA) method to decompose the image sequence matrix into two parts: a sparse matrix and a low-rank matrix. The low-rank matrix represents the aspect-stable principal component in the image sequence; that is, the real scattering center. The sparse matrix represents the part of the image sequence that deviates from the principal component; that is, the signal that varies with aspect, mainly including multipath signals, sidelobes, anisotropic signals, etc. By reconstructing the low-rank matrix and the sparse matrix, respectively, we can obtain the image after multipath signal suppression and also the multipath ghost image. Both the target and the multipath signal provide useful information. The image after multipath signal suppression is useful for obtaining the structural information of the target, and the multipath ghost image is useful for analyzing the multipath phenomenon of the complex structure target. This paper conducts experimental verification using real airborne SAR data of an external floating roof oil tank and compares three methods: RPCA, PCA, and sub-aperture fusion method. The experiment shows that the RPCA method can better separate the target image and the multipath ghost image.
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Lu, Bo, Jian Ping Jin, Wen Yi Duan, Liang Jin Chen i Hong Ye Guan. "Research of GPS Signal Multipath Effects Based on GAMIT TRACK". Advanced Materials Research 588-589 (listopad 2012): 912–19. http://dx.doi.org/10.4028/www.scientific.net/amr.588-589.912.
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GPS multipath disturbance is a bottleneck problem that limits accuracy of GPS positioning. The function of single epoch kinematic positioning of GAMIT TRACK is used to study GPS signal multipath effects. A filtering method for separating signal and noise based on the wavelet analysis is established. The decomposition level for wavelet filter is confirmed according to the high correlation of the multipath effects between adjacent sidereal days by using the maximum correlation coefficient method. The accurate multipath corrections in GPS coordinate series are acquired with the proposed method making use of TRACK and the repeating property of multipath effects is used to weaken multipath effects in subsequent days, and therefore improve the precision of the GPS positioning.
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Gajanada, I. Gede Arya Gangga, Nyoman Pramaita i I. Gusti Agung Komang Diafari Djuni Hartawan. "Design of Orthogonal Variable Spreading Factor (OVSF) Performance Simulation Program in Multipath Fading Channels". Journal of Electrical, Electronics and Informatics 4, nr 2 (31.08.2020): 64. http://dx.doi.org/10.24843/jeei.2020.v04.i02.p05.
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The characteristics of wireless channel are determined by multipath propagation. The transmitted signal will be scattered so that it produces fading. Fading influenced by multipath component will cause delay spread which damages the signal. Thus, spread spectrum technology is used by using a bandwidth that is greater than the original signal. The objective of this study was to determine the effect of the number of multipath components on orthogonal variable spreading factor (OVSF) codes on multipath fading channels viewed from values and Bit Error Rate (BER) graphs versus Energy Bits per Noise (Eb/No). This study would compare the performance of OVSF code communication system on multipath channels by varying multipath components of 4, 8, 12, 16 and the length of OVSF codes used of 16, 8 and 4. The simulation results showed an increase in BER values when the number of multipath components was added. The more the number of multipath components used, the more the number of reflected signals that will interfere with the desired signal in the receiver. The length of the OVSF code influences the performance of the OVSF code on the multipath fading channel, because each code has a different processing gain value that is affected by the length of the code used
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Zhang, Qiuzhao, Longqiang Zhang, Ao Sun, Xiaolin Meng, Dongsheng Zhao i Craig Hancock. "GNSS Carrier-Phase Multipath Modeling and Correction: A Review and Prospect of Data Processing Methods". Remote Sensing 16, nr 1 (2.01.2024): 189. http://dx.doi.org/10.3390/rs16010189.
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A multipath error is one of the main sources of GNSS positioning errors. It cannot be eliminated by forming double-difference and other methods, and it has become an issue in GNSS positioning error processing, because it is mainly related to the surrounding environment of the station. To address multipath errors, three main mitigation strategies are employed: site selection, hardware enhancements, and data processing. Among these, data processing methods have been a focal point of research due to their cost-effectiveness, impressive performance, and widespread applicability. This paper focuses on the review of data processing mitigation methods for GNSS carrier-phase multipath errors. The paper begins by elucidating the origins and mitigation strategies of multipath errors. Subsequently, it reviews the current research status pertaining to data processing methods using stochastic and functional models to counter multipath errors. The paper also provides an overview of filtering techniques for extracting multipath error models from coordinate sequences or observations. Additionally, it introduces the evolution and algorithmic workflow of sidereal filtering (SF) and multipath hemispherical mapping (MHM), from both coordinate and observation domain perspectives. Furthermore, the paper emphasizes the practical significance and research relevance of multipath error processing. It concludes by delineating future research directions in the realm of multipath error mitigation.
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Tian, Zhenyu, Xiaowei Cui i Mingquan Lu. "Multipath Mitigation for BOC Signals Based on Prompt-Assisted-Offset Correlator". Remote Sensing 15, nr 4 (8.02.2023): 937. http://dx.doi.org/10.3390/rs15040937.
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Tracking ambiguity and multipath are two serious threats in processing binary offset carrier (BOC) signals that are widely used in global navigation satellite systems (GNSS). Three-loop tracking methods, such as dual binary phase-shift keying tracking (DBT), use a delay lock loop (DLL), a phase lock loop (PLL), and a subcarrier PLL (SPLL) to track the code, carrier, and subcarrier, respectively, thus solving the tracking ambiguity problem. However, the multipath remains an important factor in the ranging performance deterioration of these tracking methods. Using the offset correlator (OC) technique in the SPLL can effectively mitigate subcarrier multipath errors, but it substantially raises thermal noise errors. To solve this contradiction, this paper proposes a prompt-assisted-offset correlator (PAOC) technique that combines the prompt and offset correlators in a complementary way to mitigate multipath for BOC signals. Compared with the original OC technique, the PAOC technique has less thermal noise performance loss. Moreover, this paper discovers and quantifies the interaction between carrier and subcarrier multipath errors by analyzing the coupling effect between SPLL and PLL. Most multipath mitigation methods for BOC signals ignore the carrier multipath in the PLL, so their subcarrier multipath performance is not optimal. Thus, this paper further proposes applying the PAOC technique in both PLL and SPLL to mitigate carrier and subcarrier multipath errors simultaneously. Theoretical analysis and experimental results demonstrate that the proposed method can significantly improve the multipath performance with small noise performance loss.
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Alcock, Matthew, i Paul Blunt. "A Novel Single Differencing Measurement for Multipath Detection". Remote Sensing 15, nr 22 (10.11.2023): 5312. http://dx.doi.org/10.3390/rs15225312.
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Increased global dependence on Global Navigation Satellite Systems (GNSSs) has resulted in a high demand for greater precision and reliable measurements from GNSS receivers. The multipath problem is the single largest source of errors in modernised GNSSs. Double differencing techniques, such as Code Minus Carrier (CMC) have been shown to accurately detect and measure multipath, allowing for corrections to be made via Ground Base Augmentation Systems (GBAS), for example. However, these techniques require at least two receivers and the protection provided is not extended to stand-alone receivers. This paper introduces a new single differencing technique for the accurate detection of multipath in standalone GNSS receivers receiving modernised Binary Offset Carrier (BOC)-modulated signals. Similarities to CMC are drawn before the novel measurement, Code minus Subcarrier, (CMS) is characterised statistically and a threshold for multipath detection is determined. The effectiveness and sensitivity of this novel measurement as a multipath detection technique are analysed through simulation and multipath error envelope analysis. It will be shown that multipath echos capable of inducing a psuedorange error larger than the threshold are detectable at any amplitude. The method is finally verified using simulated fixed offset multipath, confirming that when code and subcarrier early–late spacings are optimal, all ranges of multipath delays, even as small as 21 meters, are detectable. This novel method of multipath detection requires no additional complex correlators than already exist in the chosen tracking algorithm, thus, providing excellent detection with minimum complexity added to the receiver structure.
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Chung, Gwo Chin, Pravin Kumar A/L Sivakumar, Jun Jiat Tiang, Wai Leong Pang i Chu Liang Lee. "Performance Study of Multipath Effect in 5G Millimeter-Wave Channel". International Journal on Advanced Science, Engineering and Information Technology 13, nr 6 (31.12.2023): 2128–35. http://dx.doi.org/10.18517/ijaseit.v13i6.19033.
Pełny tekst źródłaStreszczenie:
5G has been essentially a buzzword for several years, but according to the experts, from 2022 onward, there will be an inflection point between network maturity and the availability of 5G. To make 5G a reality, we must minimize all propagation losses. One of the possible factors that reduces the performance of 5G transmission is the multipath effect. In this paper, we investigate the severity of the multipath effect in the 5G millimeter-wave (mmWave) channel and mitigate the multipath effect using adaptive equalization based on the least mean square (LMS) algorithm to improve the performance of 5G wireless signal transmission. A mmWave channel simulator, NYUSIM, provides complete data for all resolvable multipaths in a specific channel configuration. An analysis of bit-error-rate (BER) based on the minimum BER (MBER) and minimum mean square error (MMSE) optimization criterion is performed to measure the improved performance of a 5G data channel simulated under line-of-sight (LOS) and non-LOS (NLOS) paths. A good overall performance of BER based on the MBER and MMSE criteria is attained using the LMS equalization method in a micro-urban area at a maximum data rate of 50 Mbps. For both LOS and NLOS conditions, the increase in data rate to 55.56 Mbps and 62.5 Mbps causes a significant decrease in BER performance. In conclusion, the primary factor affecting the BER performance is the data rate, not the frequency or transmitter-to-receiver distance.