Journal articles: 'Multipath environment'

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Hunegnaw, Addisu, and Felix Norman Teferle. "Evaluation of the Multipath Environment Using Electromagnetic-Absorbing Materials at Continuous GNSS Stations." Sensors 22, no. 9 (April 28, 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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TSUCHIMOTO, Kazuhiko, Nobuaki KUBO, Takuji EBINUMA, and Akio YASUDA. "Multipath Signal Error Correction in a Dominant Multipath Environment." Journal of Japan Institute of Navigation 118 (2008): 221–27. http://dx.doi.org/10.9749/jin.118.221.

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Sokhandan, Negin, Nesreen Ziedan, Ali Broumandan, and Gérard Lachapelle. "Context-Aware Adaptive Multipath Compensation Based on Channel Pattern Recognition for GNSS Receivers." Journal of Navigation 70, no. 5 (April 10, 2017): 944–62. http://dx.doi.org/10.1017/s0373463317000121.

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The possibility of identifying the type of multipath environment and receiver motion (e.g. pedestrian, vehicular) using pattern recognition approaches based on multipath parameters is investigated. This allows the receiver to adjust its tracking strategy and optimally tune its tracking parameters to mitigate code multipath effects. A Support Vector Machine (SVM) classification method with a modified Gaussian kernel is applied in this approach. A set of temporal and spectral features is extracted from the correlation samples of the received signals in different environments to train the classifier. The latter is then used in the structure of stochastic gradient-based adaptive multipath compensation and tracking techniques to tune the signal tracking parameters based on the environment and receiver motion. Simulation and real data measurements using Galileo E1B/C signals are performed to assess the validity of the proposed environment identification approaches and to evaluate the impact of the proposed context-based receiver parameter tuning techniques on tracking performance in multipath environments. Test results showed that the proposed classifiers have an accuracy between 86% and 92%, and the tracking performance improved by about 15%.

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Materum, Lawrence, and 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 (September 27, 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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Hu, Yili, Yongbo Zhao, and Sheng Chen. "Incoherent Integration Detection Method of Airborne Phased Array Radar in a Multipath Environment." International Journal of Antennas and Propagation 2021 (December 15, 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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Cuccaro, A., and R. Solimene. "Inverse Scattering in a Multipath Environment." Advanced Electromagnetics 5, no. 2 (September 1, 2016): 39. http://dx.doi.org/10.7716/aem.v5i2.395.

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In this contribution an inverse scattering problem is ad- dressed in a multipath environment. In particular, multipath is created by known ”extra” point-like scatterers (passive elements) expressely deployed between the scene under in- vestigation and the source/measurement domains. Through a back-projection imaging scheme, the role of the passive elements on the achievable performance is shown and com- pared to the free-space case.

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Alnaqbi, Abdulla, and Ahmed El-Rabbany. "Precise GPS Positioning with Low-Cost Single-Frequency System in Multipath Environment." Journal of Navigation 63, no. 2 (February 23, 2010): 301–12. http://dx.doi.org/10.1017/s0373463309990373.

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Low-cost, single-frequency GPS systems provide economical positioning solutions to many geomatics applications, including GIS and low-accuracy surveying applications. Unfortunately however, the positioning accuracy obtained with those systems is not sufficient for many surveying applications. This is mainly due to the presence of ionospheric delay and multipath. In this research ionospheric delay is accounted for using regional high-resolution ionospheric maps produced by the US National Oceanic and Atmospheric Administration (NOAA). The major remaining constraint and challenging problem is multipath. This is because multipath is environmentally-dependent, difficult to model mathematically and cannot be reduced through differential positioning. This research proposes a new approach to identify multipath-contaminated L1 measurements through wavelet analysis. First, the difference between the code and carrier-phase measurements is estimated, leaving essentially twice the ionospheric delay, multipath and system noise. The ionospheric delay is largely removed by using high-resolution ionospheric delay maps produced by NOAA. The remaining residuals contain mainly low-frequency multipath, if it exists, and high-frequency system noise, which are decomposed using Daubechies family wavelets (db8). A satellite signal is identified as contaminated by multipath based on the standard deviation of the low-frequency part of the residual component. The L1 measurements obtained from the satellites with the lowest multipath are used to compute the final positions using two software packages, namely Trimble Total Control (TTC) and Bernese scientific processing software. The Magellan AC12 low-cost single-frequency GPS receiver was extensively tested in static mode. It is shown that accuracies within 5 cm are routinely obtained for baselines up to 65 km under various multipath environments.

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Tiwari, Smita, Donglin Wang, Michel Fattouche, and Fadhel Ghannouchi. "A Hybrid RSS/TOA Method for 3D Positioning in an Indoor Environment." ISRN Signal Processing 2012 (March 1, 2012): 1–9. http://dx.doi.org/10.5402/2012/503707.

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This paper investigates 3D positioning in an indoor line of sight (LOS) and nonline of sight (NLOS) combined environment. It is a known fact that time-of-arrival-(TOA-) based positioning outperforms other techniques in LOS environments; however, multipath in an indoor environment, especially NLOS multipath, significantly decreases the accuracy of TOA positioning. On the other hand, received-signal-strength-(RSS-) based positioning is not affected so much by NLOS multipath as long as the propagation attenuation can be correctly estimated and the multipath effects have been compensated for. Based on this fact, a hybrid weighted least square (HWLS) RSS/TOA method is proposed for target positioning in an indoor LOS/NLOS environment. The identification of LOS/NLOS path is implemented by using Nakagami distribution. An experiment is conducted in the iRadio lab, in the ICT building at the University of Calgary, in order to (i) demonstrate the availability of Nakagami distribution for the identification of LOS and NLOS path, (ii) estimate the pass loss exponent for RSS technique, and (iii) verify our proposed scheme.

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Soubielle, J., I. Fijalkow, P. Duvaut, and A. Bibaut. "GPS positioning in a multipath environment." IEEE Transactions on Signal Processing 50, no. 1 (2002): 141–50. http://dx.doi.org/10.1109/78.972490.

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10

Madurasinghe, D. "Direction finding in a multipath environment." Electronics Letters 27, no. 1 (January 3, 1991): 61–62. http://dx.doi.org/10.1049/el:19910039.

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11

Wang, Yang, and Yang Zhou. "Multiple Parameters Estimation of BOC Signal in Multipath Environment." MATEC Web of Conferences 173 (2018): 03064. http://dx.doi.org/10.1051/matecconf/201817303064.

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For the multiple parameters estimation of BOC signal at the low SNR and multipath environment, the method which applies the characteristics of cyclic spectrum is developed. Firstly, the cyclic spectrum function of multipath BOC signal is derived. Then the cyclostationary property of BOC signal is analyzed. Finally, a novel parameter estimation algorithm of BOC signal, which makes use of the position of cyclic spectral peaks to estimate the carrier frequency, the subcarrier rate and PN code rate, is present. In the experiment the time-domain smoothing method is used to calculate the cyclic spectrum of BOC signal when the frequency is equal to zero in order to avoid the multidimensional search. At the same time using the method of the cumulative average can increase the SNR margin of the algorithm. Simulation results show that the multiple parameters of multipath BOC signal can be estimated effectively and the estimation performance is associated with the multipath environment.

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Avram, Alexandra, Volker Schwieger, and Noha El Gemayel. "Experimental results of multipath behavior for GPS L1-L2 and Galileo E1-E5b in static and kinematic scenarios." Journal of Applied Geodesy 13, no. 4 (October 25, 2019): 279–89. http://dx.doi.org/10.1515/jag-2019-0010.

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Abstract Current trends like Autonomous Driving (AD) increase the need for a precise, reliable, and continuous position at high velocities. In both natural and man-made environments, Global Navigation Satellite System (GNSS) signals suffer challenges such as multipath, attenuation, or loss-of-lock. As Highway Assist and Highway Pilot are AD next steps, multipath knowledge is necessary for this typical user-case and kinematic situations. This paper presents a multipath performance analysis for GPS and Galileo satellites in static, slow, and high kinematic scenarios. The data is provided from car test-drives in both controlled and unrestricted, near-natural environments. The Code-Minus-Carrier (CMC) and cycle-slip implementations are validated with measurement data from consecutive days. Multipath statistical models based on satellite elevation are evaluated for the three investigated scenarios. Static models derived from the car setup measurements for GPS L1, L2 and Galileo E1 and E5b show a good agreement with a state-of-the-art model as well as the enhanced Galileo signals performance. Slow kinematic multipath results in a controlled environment showed an improvement for both navigation systems compared to the static measurements at the same place. This result is confirmed by static and slow kinematic multipath simulations with the same GNSS receiver. Post-processing analysis on highway measurements revealed a bigger multipath bias, compared to the open-sky static and slow kinematic measurement campaigns. Although less critical as urban or rural, this indicates the presence of multipath in this kind of environment as well. The impact of different parameters, including receiver architecture and Signal-to-noise ratio (SNR) are analyzed and discussed. Differential position (DGNSS) based on code is computed for each epoch and compared against GNSS/INS integrated position for all three measurement campaigns. The most significant 3D absolute error occurs where the greatest multipath envelope is found.

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Alzamil, A. A. "Assessment of Uplink Massive MIMO in Scattering Environment." Engineering, Technology & Applied Science Research 10, no. 5 (October 26, 2020): 6290–93. http://dx.doi.org/10.48084/etasr.3743.

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This paper investigates the performance of massive MIMO systems under the effect of multipath propagation environment. Linear Minimum Mean Squared Error (MMSE) is considered to assess the performance of BPBK/OFDM based uplink massive MIMO transmission. Bit Error Rate (BER) and channel capacity in Non Line Of Site (NLOS) multipath fading environment are presented. The results show a correlation between the number of antennas and the performance of the system.

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Tsujii, Toshiaki, Kenta Yonebayashi, Takeshi Fujiwara, and Sohshi Ohsawa. "GNSS Array Antenna for Mitigating Multipath Errors in Urban Environment." E3S Web of Conferences 94 (2019): 03009. http://dx.doi.org/10.1051/e3sconf/20199403009.

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GNSS signal vulnerability has been a major concern especially for safety-of-life applications such as aircraft operations. Therefore, a GNSS array antenna technology was investigated focusing on beamforming to mitigate multipath errors in urban environment including airport surfaces. A commercial three-element GNSS antenna and RF-Front end were used to obtain digital IF data. The recorded In-phase/Quadrature IF data for three antennas were combined with proper weight to form beams towards satellites after so-called hardware biases were calibrated. Test results in multipath-rich environment demonstrated that 50-70% reduction of pseudorange errors due to multipath were possible if the beamforming algorithms were applied.

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Alabi, Oluwaseun Yinka, and Michael Kolawole. "Mitigating the Effects of Intereference in a Multipath Prone Environment for a DVB-T Transmission." International Journal of Informatics and Communication Technology (IJ-ICT) 4, no. 2 (August 1, 2015): 86. http://dx.doi.org/10.11591/ijict.v4i2.pp86-89.

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This paper develops a novel simulation method that seeks to mitigate the effects of interference in a multipath prone environment for a DVB-T transmission by using the AWGN and the Multipath Rayleigh Fading Channel. The channel parameters were optimized until desired result was obtained. The reception performance of the DVB-T system shows that interference though not totally eliminated, can be minimized while transmitting in a multipath prone environment.

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Katbay, Zahra, Dimitrios Sounas, and Mohammed Ismail. "Scatterers in the Rx Near Field for RF Energy Harvesting Efficiency Enhancement." Energies 15, no. 6 (March 14, 2022): 2109. http://dx.doi.org/10.3390/en15062109.

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In this paper, we investigate the enhancement of RF–RF energy harvesting efficiency (erf–rf) in multipath environments in the context of wireless power transfer (WPT). For this, we used a retrodirective transmitting (Tx) antenna array resonating at 2.4 GHz and a receiving (Rx) antenna surrounded by scatterers placed in the Rx near field. The Rx resides in the Tx far field. We showed that in a medium made of a random distribution of scatterers, a time-reversed wave field interacts with the random medium to regenerate not only the propagating waves but also the evanescent waves required to refocus the energy at the receiver location. The system was enclosed inside a 3 m3 cubical reverberating room to create a strong multipath environment. The study was done for homogeneous (free space) and heterogeneous (multipath environment) media. Different WPT scenarios were considered for different applications: 4 × 1, 4 × 2 and 4 × 4 multi input-multi output (MIMO) systems. The simulation results show that using near-field scattering generates signal focusing at the source location, which increases the RF–RF energy harvesting efficiency, especially in a multipath environment. The average received power in the frequency band 2.4–2.5 GHz was greatly enhanced in the presence of the scatterers. The investigated WPT approach showed encouraging results for charging/powering-up sensors, IoT and smart devices in indoor environments.

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Gao, Jun Yao, Jing Shu Yang, and Jia Zhao. "GPS Cross Correlation Mitigation Technique in Multipath Environment." Key Engineering Materials 439-440 (June 2010): 715–20. http://dx.doi.org/10.4028/www.scientific.net/kem.439-440.715.

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The paper investigates the cross correlation mitigation (CCM) technique in the multipath propagating environment. It analyses the impact of cross correlation firstly, then expounds the universal technique in CCM, at last presents an improved DPIC (Delayed Parallel Interference Cancellation) method based on MEDLL. The algorithm estimates the parameters of multipath by using MEDLL, reconstructs the strong signals IF utilizing these parameters, and mitigates the cross correlation with the aid of DPIC method. At last, simulation results prove the validity of this method.

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Jadviščok, Petr, Gabriela Ovesna, and Miroslav Konečny. "MULTIPATH AND ITS MANIFESTATIONS IN THE REAL ENVIRONMENT OF GEODETIC PRACTICE." Geodesy and cartography 42, no. 2 (June 22, 2016): 47–52. http://dx.doi.org/10.3846/20296991.2016.1198573.

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The paper is concerned with the negative manifestation of the multipath factor in application of the GNSS technology. It points to manifestations of the multipath effect in a specific situation of surveying practice. The evaluation is based on a model situation under intentionally deteriorated observational conditions by the presence of a building.

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Yuan, Muzi, Du Li, Baiyu Li, Huaming Chen, and 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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Wang, Zhiren, Wen Chen, Danan Dong, Chenglong Zhang, Yu Peng, and Zhengqi Zheng. "An Advanced Multipath Mitigation Method Based on Trend Surface Analysis." Remote Sensing 12, no. 21 (November 2, 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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Špánik, Peter, and Ján Hefty. "Multipath detection with the combination of SNR measurements – Example from urban environment." Geodesy and Cartography 66, no. 2 (December 20, 2017): 305–16. http://dx.doi.org/10.1515/geocart-2017-0020.

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Abstract Multipath is one of the most severe station-dependent error sources in both static and kinematic positioning. Relatively new and simple detection technique using the Signal-to-Noise (SNR) measurements on three frequencies will be presented based on idea of Strode and Groves. Exploitation of SNR measurements is benefi cial especially for their unambiguous character. Method is based on the fact that SNR values are closely linked with estimation of pseudo-ranges and phase measurements during signal correlation processing. Due to this connection, combination of SNR values can be used to detect anomalous behavior in received signal, however some kind of calibration in low multipath environment has to be done previously. In case of multipath, phase measurements on different frequencies will not be affected in the same manner. Specular multipath, e.g. from building wall introduces additional path delay which is interpreted differently on each of the used carrier, due to different wavelengths. Experimental results of multipath detection in urban environment will be presented. Originally proposed method is designed to work with three different frequencies in each epoch, thus only utilization of GPS Block II-F and Galileo satellites is possible. Simplification of detection statistics to use only two frequencies is made and results using GPS and GLONASS systems are presented along with results obtained using original formula.

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Bortz, G., J. J. van Schalkwyk, and W. Louw. "Range determination in a multipath prone environment." Electronics Letters 26, no. 16 (1990): 1253. http://dx.doi.org/10.1049/el:19900807.

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Chen, S. W., C. K. Seow, and S. Y. Tan. "Single reference mobile localisation in multipath environment." Electronics Letters 49, no. 21 (October 2013): 1360–62. http://dx.doi.org/10.1049/el.2013.1731.

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Wang, Manyi, Zhonglei Wang, Xiongzhu Bu, and Enjie Ding. "An adaptive weighting algorithm for accurate radio tomographic image in the environment with multipath and WiFi interference." International Journal of Distributed Sensor Networks 13, no. 1 (January 2017): 155014771668382. http://dx.doi.org/10.1177/1550147716683826.

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Radio frequency device-free localization based on wireless sensor network has proved its feasibility in buildings. With this technique, a target can be located relying on the changes of received signal strengths caused by the moving object. However, the accuracy of many such systems deteriorates seriously in the environment with WiFi and the multipath interference. State-of-the-art methods do not efficiently solve the WiFi and multipath interference problems at the same time. In this article, we propose and evaluate an adaptive weighting radio tomography image algorithm to improve the accuracy of radio frequency device-free localization in the environment with multipath and different intensity of WiFi interference. Field experiments prove that our approach outperforms the state-of-the-art radio frequency device-free localization systems in the environment with multipath and WiFi interference.

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Bradbury, J., M. Ziebart, P. A. Cross, P. Boulton, and A. Read. "Code Multipath Modelling in the Urban Environment Using Large Virtual Reality City Models: Determining the Local Environment." Journal of Navigation 60, no. 1 (December 15, 2006): 95–105. http://dx.doi.org/10.1017/s0373463307004079.

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Positioning in the urban environment using GNSS is hampered by poor satellite availability due to signal obstruction created by both man-made and natural features of the urban environment. In addition, range measurement to satellites for positioning and for navigation is severely degraded by the multipath effect. The arrival and continuous enhancement of computerised geometric city models makes it possible to tackle these problems through modelling. In this paper description is given of a method for determining the local multipath environment, defined by the surfaces within a city model that will cause disruptive signal reflections to be presented to a receiver. An example simulation is performed, and graphical and numerical results are produced.

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Wang, Jin Peng, Qi Ming Zhu, Fan Cao, Ping Li, and Nian Yu Zou. "A Study on Turbo Codes and Rake Received Mixed Algorithm in Multipath Fading Environment." Applied Mechanics and Materials 321-324 (June 2013): 2877–82. http://dx.doi.org/10.4028/www.scientific.net/amm.321-324.2877.

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In this paper, a Turbo codes and Rake received mixed algorithm in multipath fading environment is proposed to solve the problems in signal reception in a fading environment of the mobile communication system. Compared to the traditional multi-path reception methods, the advantage of the algorithm can significantly improve system performance; reduce the system error rate by approximately 2.5dB. Moreover, the performance of the system will be improved a lot if the antenna power is equal. Firstly a mixed algorithm in AWGN channel and multipath fading channel is introduced and derived theoretically and then a computer simulation is carried out and the impact of various parameters on network performance is anglicized. The results show that the algorithm can effectively reduce the effects of multipath fading environment on the transmission power attenuation, lower bit error rate, and improve the effectiveness to resistance to multipath fading significantly.

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Li, Lixun, Baiyu Li, Huaming Chen, and Feixue Wang. "Phase Errors Simulation Analysis for GNSS Antenna in Multipath Environment." International Journal of Antennas and Propagation 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/962627.

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High-precision GNSS application requires the exact phase center calibration of antenna. Various methods are published to determine the locations of the phase center. In the outfield, when the phase errors that arose by multipath exceed the phase center variations (PCV) tolerance, the calibration values may be not useful. The objective of this paper is thus to evaluate the phase errors that arose by multipath signals. An improved model of antenna receiving signal is presented. The model consists of three main components: (1) an antenna model created by combination of right hand circular polarization (RHCP) and left hand circular polarization (LHCP), (2) a multipath signals model including amplitude, phase, and polarization, and (3) a ground reflection model applying to circular polarization signals. Based on the model, two kinds of novel up-to-down(U/D)ratios are presented. The performance of the model is assessed against the impact of up-to-down ratio of antenna on phase errors.

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Ning, Yipeng, Junye Cui, Wenshuo Zhao, Dashuai Chai, Yingjun Sun, Jianping Xing, and Shengli Wang. "A Novel Cycle Slips Detection and Repair Method with AR Model of BDS-3 Dual-Frequency Signal in Severe Multipath Environments." Applied Sciences 13, no. 1 (December 20, 2022): 27. http://dx.doi.org/10.3390/app13010027.

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High-level applications of geo-processing services generally lack accurate temporal and spatial information. BDS-3 provides high precision temporal and spatial reference for geoprocessing services, but their signal is prone to cycle slips in a severe multipath environment. Aiming at the problem of the reliable detection and repair of cycle slips in BDS-3 (B1c+B2a) dual-frequency positioning in a severe multipath environment, an AR (autoregressive) model-assisted MW+GF BDS dual-frequency combined detection method (AMG method) is proposed in this research. A sliding-window autoregressive prediction strategy is introduced to correct the pseudorange observations interfered by a multipath, then an AR+MW+GF cycle slips detection model is constructed, and a cycle slips statistical completeness test index is established to verify the effectiveness of the algorithm. Six groups of cycle slips are artificially added into the different constellations and dual-frequency point phase observations of BDS-3 (B1c and B2a) in a multipath environment to demonstrate the cycle slips’ detection performance. The experimental results show that the traditional MW+GF method fails, but the proposed AMG method still maintains accurate cycle slip detection and repair capabilities. The detection success rate and repair success rate obtained by using the new method are significantly improved by 63.4%, and the cycle slips’ false detection rate and missed detection rate are reduced by 64.5% and 42.0%, respectively, even in harsh environments.

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Dan, Zesheng, Baowang Lian, and Chengkai Tang. "Robust Multipath-Assisted SLAM with Unknown Process Noise and Clutter Intensity." Remote Sensing 13, no. 9 (April 21, 2021): 1625. http://dx.doi.org/10.3390/rs13091625.

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In multipath-assisted simultaneous localization and mapping (SLAM), the geometric association of specular multipath components based on radio signals with environmental features is used to simultaneously localize user equipment and map the environment. We must contend with two notable model parameter uncertainties in multipath-assisted SLAM: process noise and clutter intensity. Knowledge of these two parameters is critically important to multipath-assisted SLAM, the uncertainty of which will seriously affect the SLAM accuracy. Conventional multipath-assisted SLAM algorithms generally regard these model parameters as fixed and known, which cannot meet the challenges presented in complicated environments. We address this challenge by improving the belief propagation (BP)-based SLAM algorithm and proposing a robust multipath-assisted SLAM algorithm that can accommodate model mismatch in process noise and clutter intensity. Specifically, we describe the evolution of the process noise variance and clutter intensity via Markov chain models and integrate them into the factor graph representing the Bayesian model of the multipath-assisted SLAM. Then, the BP message passing algorithm is leveraged to calculate the marginal posterior distributions of the user equipment, environmental features and unknown model parameters to achieve the goals of simultaneous localization and mapping, as well as adaptively learning the process noise variance and clutter intensity. Finally, the simulation results demonstrate that the proposed approach is robust against the uncertainty of the process noise and clutter intensity and shows excellent performances in challenging indoor environments.

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Kim, Jungbeom, Minhuck Park, Yonghwan Bae, O.-Jong Kim, Donguk Kim, Bugyeom Kim, and Changdon Kee. "A Low-Cost, High-Precision Vehicle Navigation System for Deep Urban Multipath Environment Using TDCP Measurements." Sensors 20, no. 11 (June 7, 2020): 3254. http://dx.doi.org/10.3390/s20113254.

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In this study, we developed a low-cost, high-precision vehicle navigation system for deep urban multipath environments using time-differenced carrier phase (TDCP) measurements. Although many studies are being conducted to navigate autonomous vehicles using the global positioning system (GPS), it is difficult to obtain accurate navigation solutions due to multipath errors in urban environments. Low-cost GPS receivers that determine the solution based on pseudorange measurements are vulnerable to multipath errors. We used carrier phase measurements that are more robust for multipath errors. Without correction information from reference stations, the limited information of a low-cost, single-frequency receiver makes it difficult to quickly and accurately determine integer ambiguity of carrier phase measurements. We used TDCP measurements to eliminate the need to determine integer ambiguity that is time-invariant and we combined TDCP-based GPS with an inertial navigation system to overcome deep urban multipath environments. Furthermore, we considered a cycle slip algorithm for its accuracy and a multi-constellation navigation system for its availability. The results of dynamic field tests in a deep urban area indicated that it could achieve horizontal accuracy of at the submeter level.

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Li, Rong. "Digital Modulation Recognition in Different Environments." Advanced Materials Research 1049-1050 (October 2014): 2084–87. http://dx.doi.org/10.4028/www.scientific.net/amr.1049-1050.2084.

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For the using of multi-modulation, the precondition of receiving and demodulating signal is to determine the type of the modulation, so automatic recognition of modulation signal has significant influence on the analysis of the signals. In this paper, digital modulation recognition is studied respectively in different environment of White Gaussian Noise (WGN), stationary interference and multipath interference. The simulation results show that the recognition success rate is the highest in stationary interference environment and the lowest in multipath interference environment with the same signal to noise ratio (SNR).

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Li, Xiangzhi, Weijia Cui, Haiyun Xu, Bin Ba, and Yankui Zhang. "A Novel Method for DOA and Time Delay Joint Estimation in Multipath OFDM Environment." International Journal of Antennas and Propagation 2020 (January 30, 2020): 1–11. http://dx.doi.org/10.1155/2020/3952175.

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Joint time delay and direction of arrival estimation based on uniform linear arrays in Orthogonal Frequency Division Multiplexing (OFDM) systems has to face the problems posed by coherent multipath environments and high computational complexity. In this paper, a novel fast method is proposed to achieve a joint direction-of-arrival (DOA) and time-dealy (TD) estimation of multipath OFDM signals by fully using space-frequency characteristics. Firstly, we construct an extended virtual array by combining the array structure and frequency-domain information. Then, we calculate the extended channel frequency response matrix and adopt smoothing processing to eliminate the multipath effect. Next, we get the result of DOA estimation by using a closed-form solution, which costs little complexity and can achieve fast estimation. Finally, we conduct a one-dimensional spectral search using the obtained DOA values to estimate time delays. Simulation results show that our proposed methods have excellent performance even under low SNR conditions in different multipath environments. Furthermore, methods proposed in this paper have much less computational complexity and better estimation performance compared with the multidimensional spectral peak search methods.

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Cheng, Lan, Kai Wang, Mifeng Ren, and Gaowei Yan. "Adaptive Filter Approach for GPS Multipath Estimation Under Correntropy Criterion in Dynamic Multipath Environment." IEEE Transactions on Signal Processing 67, no. 22 (November 15, 2019): 5798–810. http://dx.doi.org/10.1109/tsp.2019.2946028.

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Suyoto, Suyoto, Iskandar Iskandar, Sugihartono Sugihartono, and Adit Kurniawan. "Improved Timing Estimation Using Iterative Normalization Technique for OFDM Systems." International Journal of Electrical and Computer Engineering (IJECE) 7, no. 2 (April 1, 2017): 905. http://dx.doi.org/10.11591/ijece.v7i2.pp905-911.

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Conventional timing estimation schemes based on autocorrelation experience performance degradation in the multipath channel environment with high delay spread. To overcome this problem, we proposed an improvement of the timing estimation for the OFDM system based on statistical change of symmetrical correlator. The new method uses iterative normalization technique to the correlator output before the detection based on statistical change of symmetric correlator is applied. Thus, it increases the detection probability and achieves better performance than previously published methods in the multipath environment. Computer simulation shows that our method is very robust in the fading multipath channel

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Zou, Xuan, Zhiyuan Li, Yangyang Li, Yawei Wang, Weiming Tang, Chenlong Deng, Jianhui Cui, and Ruinan Fu. "A Novel Method to Mitigate the Multipath Error for BDS-2 Dam Deformation Monitoring." Remote Sensing 13, no. 9 (May 4, 2021): 1787. http://dx.doi.org/10.3390/rs13091787.

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The multipath effect on carrier-phase observations is related to the observational environment of the station, and cannot be eliminated or attenuated by the differential method. In the actual dam environment of deformation monitoring, multipath is very complicated. It is the main error source of BDS-2 for high precision data processing. In this paper, a new method called the multi-point hemispherical grid model (MHGM) is studied and evaluated. This method uses the hemispheric grid model to attenuate the influence of multipath errors. The effectiveness and improvement of the new method with respect to the popular sidereal filter (SF) method were assessed and verified by the actual dam monitoring data with only the BDS-2. The MHGM and SF approach calculates the multipath corrections from multi-days historical data, and then corrects the multipath error from the observations on the day of interest. Compared with the SF method, the MHGM can also effectively provide a graphical display of multipath error interference around the stations, which matches the surrounding observation environment. The results show that the double-differenced (DD) residuals of the MHGM for GEO/IGSO and MEO satellites are slightly better than those of SF, but the RMS of MHGM for GEO/IGSO+MEO DD residuals is improved by about 17.0%. The performance of the MHGM method for different satellite constellations is consistent and not affected by the different orbital repeat times, which could solve the “zero mean” assumption problem of the SF method. Meanwhile, the RMS of static with a 2 h interval and kinematic positioning errors of the MHGM method in the horizontal and vertical direction can be up to 1.7, 3.6 and 2.4, 8.1 mm, respectively. The MHGM model could avoid the multipath reference problem caused by different orbital repetition periods, making it more suitable for the combined multipath modeling of BDS-2 and BDS-3.

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Narayanan, Ram M., Brian R. Phelan, and Erik H. Lenzing. "Source Geolocation in Urban Environments Using Multipath Fingerprinting." International Journal of Antennas and Propagation 2015 (2015): 1–11. http://dx.doi.org/10.1155/2015/453157.

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A method for determining the location of Global Systems for Mobile Communications (GSM) mobile transmitters is proposed. Our approach estimates the location of a source without the use of multilateration or Line-of-Sight (LOS) techniques. A Multipath Characteristic Database (MCD) containing the multipath feature vectors, for each possible transmitter location within an area of interest, is populated via ray-tracing software simulations. The multipath characteristics of interest are angle-of-arrival (AOA) (azimuth) and time-of-arrival (TOA). By minimizing the “distance” between estimated and simulated multipath feature vectors, an estimate for the actual source location can be obtained. The development of the estimation method is presented, followed by a detailed analysis of its estimation accuracy. Since the proposed method utilizes a simulated multipath signature database based upon the knowledge of the environment and the terrain, the need fora priorisoundings from the area of interest is eliminated, thus making this location estimation system suitable for application in denied territories. Location accuracies compare favorably with the requirements for the location of wireless 9-1-1 callers as recommended by the Federal Communications Commission (FCC).

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Aram, Mohammad, Ahmed El-Rabbany, Sri Krishnan, and Alagan Anpalagan. "Single Frequency Multipath Mitigation Based On Wavelet Analysis." Journal of Navigation 60, no. 2 (April 20, 2007): 281–90. http://dx.doi.org/10.1017/s0373463307004146.

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Multipath is still one of the major error sources that degrades the accuracy of GPS positioning. The amount of multipath is highly dependent on the antenna's environment, which makes it difficult to isolate. Usually there is at least one in-view satellite which is more susceptible to multipath, particularly the one with the lowest elevation angle. To increase the positioning the best satellites must be selected (i.e. by least square or multipath mitigation) for computing a position. In this paper we propose an algorithm which picks up the best satellites (when there are more than four satellites in view) based on wavelet analysis for calculating a position. In this experiment, code and carrier measurements were collected in 15-minute segments by exploiting a single frequency (L1), stationary, navigation-grade receiver in a high-multipath environment. The magnitudes of these pseudoranges were often inflated by multipath error. We then post-processed the received data by applying wavelet filtering to the residuals (code minus carrier) to approximate the multipath values, and compute the receiver's position based on the selected satellites. Satellites were selected based on the residual values. To compare the results with the raw measurements, statistical elements were computed. The results showed significant improvement in variance of the estimated positions and, most importantly, a normalization of the data scatter-distribution was observed.

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Zhao, Junhui, Lei Li, Hao Zhang, and Yi Gong. "Signal path reckoning localization method in multipath environment." China Communications 14, no. 3 (March 2017): 182–89. http://dx.doi.org/10.1109/cc.2017.7897333.

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Andreev, Yu V., A. S. Dmitriev, and A. V. Kletsov. "Amplification of chaotic pulses in a multipath environment." Journal of Communications Technology and Electronics 52, no. 7 (July 2007): 779–87. http://dx.doi.org/10.1134/s1064226907070108.

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Zhang, Yufeng, Zhongfu Ye, and Chao Liu. "An efficient DOA estimation method in multipath environment." Signal Processing 90, no. 2 (February 2010): 707–13. http://dx.doi.org/10.1016/j.sigpro.2009.08.004.

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Wazenski, M., and D. Alexandrou. "Active, wideband detection in an uncertain multipath environment." Journal of the Acoustical Society of America 95, no. 5 (May 1994): 2982. http://dx.doi.org/10.1121/1.408964.

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Zhang, Yimin, Kehu Yang, and Yoshio Karasawa. "Subband CMA adaptive arrays in multipath fading environment." Electronics and Communications in Japan (Part I: Communications) 83, no. 11 (November 2000): 43–54. http://dx.doi.org/10.1002/(sici)1520-6424(200011)83:11<43::aid-ecja5>3.0.co;2-y.

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Minato, Kenji, Yasuyuki Okumura, and Ryozo Kishimoto. "Multipath allocation algorithm for the distributed computer environment." Electronics and Communications in Japan (Part I: Communications) 77, no. 4 (April 1994): 21–33. http://dx.doi.org/10.1002/ecja.4410770403.

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Zhang, Li, and Volker Schwieger. "Reducing multipath effect of low-cost GNSS receivers for monitoring by considering temporal correlations." Journal of Applied Geodesy 14, no. 2 (April 26, 2020): 167–75. http://dx.doi.org/10.1515/jag-2019-0059.

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AbstractThe investigations on low-cost single frequency GNSS receivers at the Institute of Engineering Geodesy (IIGS) show that u-blox GNSS receivers combined with low-cost antennas and self-constructed L1-optimized choke rings can reach an accuracy which almost meets the requirements of geodetic applications (see Zhang and Schwieger [25]). However, the quality (accuracy and reliability) of low-cost GNSS receiver data should still be improved, particularly in environments with obstructions. The multipath effects are a major error source for the short baselines. The ground plate or the choke ring ground plane can reduce the multipath signals from the horizontal reflector (e. g. ground). However, the shieldings cannot reduce the multipath signals from the vertical reflectors (e. g. walls).Because multipath effects are spatially and temporally correlated, an algorithm is developed for reducing the multipath effect by considering the spatial correlations of the adjoined stations (see Zhang and Schwieger [24]). In this paper, an algorithm based on the temporal correlations will be introduced. The developed algorithm is based on the periodic behavior of the estimated coordinates and not on carrier phase raw data, which is easy to use. Because, for the users, coordinates are more accessible than the raw data. The multipath effect can cause periodic oscillations but the periods change over time. Besides this, the multipath effect’s influence on the coordinates is a mixture of different multipath signals from different satellites and different reflectors. These two properties will be used to reduce the multipath effect. The algorithm runs in two steps and iteratively. Test measurements were carried out in a multipath intensive environment; the accuracies of the measurements are improved by about 50 % and the results can be delivered in near-real-time (in ca. 30 minutes), therefore the algorithm is suitable for structural health monitoring applications.

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Ba, Bin, Weijia Cui, Daming Wang, and Jianhui Wang. "Maximum Likelihood Time Delay Estimation Based on Monte Carlo Importance Sampling in Multipath Environment." International Journal of Antennas and Propagation 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/4215293.

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In multipath environment, the computation complexity of single snapshot maximum likelihood for time delay estimation is huge. In particular, the computational complexity of grid search method increases exponentially with the increase of dimension. For this reason, this paper presents a maximum likelihood estimation algorithm based on Monte Carlo importance sampling technique. Firstly, the algorithm takes advantage of the channel frequency response in order to build the likelihood function of time delay in multipath environment. The pseudoprobability density function is constructed by using exponential likelihood function. Then, it is crucial to choose the importance function. According to the characteristic of the Vandermonde matrix in likelihood function, the product of the conjugate transpose Vandermonde matrix and itself is approximated by the product of a constant and an identity matrix. The pseudoprobability density function can be decomposed into product of many probability density functions of single path time delay. The importance function is constructed. Finally, according to probability density function of multipath time delay decomposed by importance function, the time delay of the multipath is sampled by Monte Carlo method. The time delay is estimated via calculating weighted mean of sample. Simulation results show that the performance of proposed algorithm approaches the Cramér-Rao bound with reduced complexity.

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Wang, Kan, Ahmed El-Mowafy, Weijin Qin, and Xuhai Yang. "Integrity Monitoring of PPP-RTK Positioning; Part I: GNSS-Based IM Procedure." Remote Sensing 14, no. 1 (December 23, 2021): 44. http://dx.doi.org/10.3390/rs14010044.

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Nowadays, integrity monitoring (IM) is required for diverse safety-related applications using intelligent transport systems (ITS). To ensure high availability for road transport users for in-lane positioning, a sub-meter horizontal protection level (HPL) is expected, which normally requires a much higher horizontal positioning precision of, e.g., a few centimeters. Precise point positioning-real-time kinematic (PPP-RTK) is a positioning method that could achieve high accuracy without long convergence time and strong dependency on nearby infrastructure. As the first part of a series of papers, this contribution proposes an IM strategy for multi-constellation PPP-RTK positioning based on global navigation satellite system (GNSS) signals. It analytically studies the form of the variance-covariance (V-C) matrix of ionosphere interpolation errors for both accuracy and integrity purposes, which considers the processing noise, the ionosphere activities and the network scale. In addition, this contribution analyzes the impacts of diverse factors on the size and convergence of the HPLs, including the user multipath environment, the ionosphere activity, the network scale and the horizontal probability of misleading information (PMI). It is found that the user multipath environment generally has the largest influence on the size of the converged HPLs, while the ionosphere interpolation and the multipath environments have joint impacts on the convergence of the HPL. Making use of 1 Hz data of Global Positioning System (GPS)/Galileo/Beidou Navigation Satellite System (BDS) signals on L1 and L5 frequencies, for small- to mid-scaled networks, under nominal multipath environments and for a horizontal PMI down to 2×10−6, the ambiguity-float HPLs can converge to 1.5 m within or around 50 epochs under quiet to medium ionosphere activities. Under nominal multipath conditions for small- to mid-scaled networks, with the partial ambiguity resolution enabled, the HPLs can converge to 0.3 m within 10 epochs even under active ionosphere activities.

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Chen, Liang-wei. "Network Service Method under Cloud Environment of Wireless Sensor Networks in Disaster Situation." International Journal of Online Engineering (iJOE) 12, no. 11 (November 24, 2016): 16. http://dx.doi.org/10.3991/ijoe.v12i11.6231.

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The sensor networks are characterized by tiny, inexpensive, and advanced communication technology. However, wireless ad-hoc sensor networks (WASNs) have some issues such as the limited amount of energy, multipath fading, and some other issues when they applied in disaster situations. For reducing power consumption, we show mathematical analysis of energy saving, and enhanced error symbol probability. The simulation results prove our analysis. As for the multipath fading, we also show the mathematical analysis of fading channel characteristics and channel model, as well as how to mitigate the multipath fading by modulation and diversity techniques. From the simulation results, we prove the proposed system with amplify-and-forward (AF) relaying can achieve a 2.5 dB performance gain the BER 10-4 whereas the achievable improvement is almost a 4 dB at the BER 10-5 when using maximal ratio combining.

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Liu, Jiejie, Yanfeng Bai, Xianwei Huang, Wei Tan, Suqin Nan, Xuanpengfan Zou, and Xiquan Fu. "Research on Multipath Correlated Imaging with the Grayscale Target in Endoscopic Applications." Applied Sciences 11, no. 9 (April 30, 2021): 4115. http://dx.doi.org/10.3390/app11094115.

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The application of correlated imaging in endoscope, one of the research hotspots, may lead to multipath effect in the closed endoscopic environment. The model of multipath correlated imaging with a grayscale object is given, where the mismatch ratio and the reflection ratio are two key factors affecting imaging quality. The theoretical and experimental results show that multipath effect has an influence on the grayscale distribution and imaging quality of the reconstructed image, and the effect of the mismatch ratio is stronger than that of the reflection ratio. The conditions that the disturbance from multipath effect can be ignored in endoscopic applications are given.

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Ji, Ai Guo, Tao Wang, and Zhi Gang Zhu. "DOA Estimation Based on the Multipath of the MIMO Radar Target." Applied Mechanics and Materials 229-231 (November 2012): 2029–32. http://dx.doi.org/10.4028/www.scientific.net/amm.229-231.2029.

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The DOA Estimation of the MIMO radar is widely used to determine the position of the objects. Having been considered the multipath communication environment, this paper estimates the DOA information of low elevation targets using beam space MUSIC algorithm based on the model of uniform linear array of MIMO radar. Simulations have shown that the algorithm is effective in the multipath spread environment, and the resolution of the DOA estimation of angular is about 0.5°

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Wang, Yawei, Xuan Zou, Chenlong Deng, Weiming Tang, Yangyang Li, Yongfeng Zhang, and Jin Feng. "A Novel Method for Mitigating the GPS Multipath Effect Based on a Multi-Point Hemispherical Grid Model." Remote Sensing 12, no. 18 (September 18, 2020): 3045. http://dx.doi.org/10.3390/rs12183045.

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The multipath effect is a crucial error source caused by the environment around the station and cannot be eliminated or mitigated by differential algorithms. Theoretically, the maximum value for the carrier phase is a quarter the wavelength, i.e., about 4.8 cm for the GPS L1 signal. Considering the increasing demands of high-precision applications, the multipath error has become a major factor affecting the accuracy and reliability of GPS millimeter-level data processing. This paper proposes a multi-point hemispherical grid model (MHGM) to mitigate the multipath effect. In this method, the hemisphere centered on each station is divided into a grid, and the multipath error at the station is estimated based on the parameterization of the grid points. The double-differenced (DD) observed-minus-calculated (OMC) values on some previous days are treated as the observation values to model the present multipath error. Contrary to the present methods which rely much on the platform of data collection and processing, MHGM can be potentially applied to GPS data processing with the existing hardware and software. Experiments in high-multipath and low-multipath environments are designed by mounting a baffle or not. The experimental results show that MHGM is effective in mitigating the multipath effect. When using data from the previous day, an average improvement of about 63.3% in the RMS of DD OMC can be made compared with that without correction, and this is basically consistent with the sidereal filtering (SF) method which is 63.0%. Furthermore, the effectiveness of the above two methods is better than that of the empirical site model (ESM). The kinematic positioning results are also basically consistent with the statistical results of the RMS values of DD OMC. Historical data from more than one day can more explicitly and effectively model the MHGM. Furthermore, compared with the SF method, the MHGM can be used not only to mitigate the multipath error, but also to orientate the sources of the multipath error around the station, and give guidance in the physical elimination of these sources.

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Journal articles on the topic 'Multipath environment'

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