Multipath Noise Research Articles

AirLock: Unlock in-air via hand rotation recognition

This paper proposes AirLock, an artificial intelligence solution meticulously crafted to elevate user authentication security in network-aware environments. With a focus on enhancing safety and convenience within indoor spaces, AirLock ingeniously employs conventional multi-antenna commercial wireless systems as a supplementary security bolster. The system makes substantial contributions in two pivotal domains. Firstly, it adeptly utilizes amplitude differences between antenna pairs to extricate individual biometrics and seamlessly eliminate multipath noise from signals. Secondly, it boasts a Seq2Seq attention network structure fortified with a precise coding strategy for authentication, ensuring swift mapping of behavior characteristics to an authenticated user. Across diverse real-world scenarios, AirLock impressively achieves an average AAR of 96.5%.

An adaptive algorithm for generating 3D point clouds of the human body based on 4D millimeter-wave radar.

The traditional algorithms for generating 3D human point clouds often face challenges in dealing with issues such as phantom targets and target classification caused by electromagnetic multipath effects, resulting in a lack of accuracy in the generated point clouds and requiring manual labeling of the position of the human body. To address these problems, this paper proposes an adaptive method for generating 3D human point clouds based on 4D millimeter-wave radar (Self-Adaptive mPoint, SA-mPoint). This method estimates the rough human point cloud by considering micro-motion and respiration characteristics while combining the echo dynamic with static information. Furthermore, it enhances the density of point cloud generation. It reduces interference from multipath noise through multi-frame dynamic fusion and an adaptive density-based clustering algorithm based on the center points of humans. The effectiveness of the SA-mPoint algorithm is verified through experiments conducted using the TI Millimeter Wave Cascade Imaging Radar Radio Frequency Evaluation Module 77G 4D cascade radar to collect challenging raw data consisting of single-target and multi-target human poses in an open classroom setting. Experimental results demonstrate that the proposed algorithm achieves an average accuracy rate of 97.94% for generating point clouds. Compared to the popular TI-mPoint algorithm, it generates a higher number of point clouds on average (increased by 87.94%), improves the average accuracy rate for generating point clouds (increased by 78.3%), and reduces the running time on average (reduced by 11.41%). This approach exhibits high practicality and promising application prospects.

Displacement Monitoring of a Bridge Based on BDS Measurement by CEEMDAN-Adaptive Threshold Wavelet Method.

From the viewpoint of BDS bridge displacement monitoring, which is easily affected by background noise and the calculation of a fixed threshold value in the wavelet filtering algorithm, which is often related to the data length. In this paper, a data processing method of Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN), combined with adaptive threshold wavelet de-noising is proposed. The adaptive threshold wavelet filtering method composed of the mean and variance of wavelet coefficients of each layer is used to de-noise the BDS displacement monitoring data. CEEMDAN was used to decompose the displacement response data of the bridge to obtain the intrinsic mode function (IMF). Correlation coefficients were used to distinguish the noisy component from the effective component, and the adaptive threshold wavelet de-noising occurred on the noisy component. Finally, all IMF were restructured. The simulation experiment and the BDS displacement monitoring data of Nanmao Bridge were verified. The results demonstrated that the proposed method could effectively suppress random noise and multipath noise, and effectively obtain the real response of bridge displacement.

Localization System for Vehicle Navigation Based on GNSS/IMU Using Time-Series Optimization with Road Gradient Constrain

In this paper, we propose a GNSS/IMU localization system for mobile robots when wheel speed sensors cannot be attached. Highly accurate location information is required for autonomous navigation of mobile robots. A typical method of acquiring location information is to use a Kalman filter for position estimation. The Kalman filter is a maximum-likelihood estimation method that assumes normally distributed noise. However, non-normally distributed GNSS multipath noise that frequently occurs in urban environments causes the Kalman filter to break down, and degrades the estimation performance. Other GNSS/IMU localization methods capable of lane-level estimation in urban environments use wheel speed sensors, which are unsuitable for the present situation. In this study, we aim to improve the performance of lane-level localization by adding a vehicle speed estimation function to adapt the method to those requiring wheel speed sensors. The proposed method optimizes time-series data to accurately compensate for accelerometer bias errors and reduce GNSS multipath noise. The evaluation confirmed the effectiveness of the proposed method, with improved velocity and position estimation performance compared with the Kalman filter method.

Study on PPP Time Comparison Based on BeiDou-3 New Signal

The Chinese BeiDou Navigation Satellite System (BDS-3) has completed the network construction and begun to provide high-precision Positioning, Navigation, and Timing (PNT) services for users all over the world. In this paper, we study the Precision Point Positioning (PPP) time comparison based on the BDS-3 new signal. The data presented in this paper includes the observation data from the National Time Service Center of Chinese Academy of the Sciences (NTSC) and the Electronics Academy of Sciences in Czech Republic (TP), and the precise product data released by the International GNSS Service (IGS), which includes the high-precision clock and orbit products. The results show that the multipath noise of the BDS-3 new signal (B1C and B2a) is less than that of the Asia-Pacific region BDS-2 (B1I and B2I), and the standard deviation (STD) of the multipath noise of B2a is the least. When the BDS-3 PPP is applied to the common clock short-baseline time comparison, the standard deviations of the BDS-3 and BDS-2 signals are 0.0296 ns and 0.0341 ns, respectively, the standard deviation of BDS-3 is smaller than that of BDS-2, and therefore the short-baseline time comparison performance of BDS-3 PPP is better than that of BDS-2, the standard deviation of BDS-3 PPP has increased by 13.19% compared with BDS-2. For long-baseline time comparisons between UTC (NTSC) and UTC (TP), the results based on the BDS-3 single system, or BDS-3 with other navigation system fusion PPP time comparison, follow the same trend as the results released by the International Bureau of Weights and Measures (BIPM). The residual standard deviations relative to the BIPM are 0.7039 ns and 0.2994 ns respectively. The stability of the BDS-3 new signal PPP and multi-GNSS fusion PPP time comparison has the same magnitude as the BIPM. As a result, with the completion of BDS-3, the high-precision time comparison based on BDS-3 expected to offer better services for users. The experimental results demonstrate that BDS-3 could be used to calculate the Coordinated Universal Time (UTC) in the future.

An Adaptive Lossly Quantization Technique for Key Extraction Applied in Vehicular Communication

Security in vehicular ad hoc network (VANET) is one of the major challenging topics and the secure key interchange between two legitimate vehicles is an important issue. The multi-environment of VANET has been exploited to extract the secret key and employed security services in VANET. However, it offered more excellence randomness owed to fading, noise multi-path, and velocity difference. Some of the factors like Bit-rate, complication and memory requests are reduced by using a process known as quantization. This paper proposes a new quantization method to extract the secret key for vehicular communications that uses a lossy quantizer in combination with information reconciliation and privacy amplification. Our work focuses on the quantization phase for the secret generation procedure. The comprehensive simulations display the propose method increases the zone and number of the quantization levels to utilize the maximum number of measurements to reduce reasonably the wasted measurements.

Numerical Integration-Based Performance Analysis of Amplitude-Comparison Monopulse Algorithm in Correlated Noise

In this paper, the performance analysis of the amplitude-comparison monopulse (ACM) algorithm under a correlated noise effect is dealt with. The noise received by a monopulse antenna is caused by various sources, such as jamming, multipath, clutter, and thermal noise. The noise variables caused by these noise sources may be correlated with each other when received by the antenna elements. We explicitly analyzed the angle estimation performance of the monopulse algorithm when a correlated noise is received by deriving the probability density function (PDF) of the channel noise variables. In this process, correlation coefficients between noise variables received by antenna elements are defined, and variance and correlation coefficients of channel noise variables are derived. The performance of the angle estimation is analyzed by calculating the root mean square error (RMSE) for various variances and correlation coefficients of the received noise variables. The expectation operation required for calculating the RMSE is performed via numerical integration. Consequently, the analytically derived RMSE results show excellent agreements with the Monte Carlo simulation-based RMSE result, and it is confirmed that the RMSE decreases as the correlation coefficient between the received noise variables increases. When the SNR is high and on-axis, the RMSE decreases by 20% whenever the correlation coefficient between the reception noise variables increases by 0.2.

Evaluation of the Multipath Environment Using Electromagnetic-Absorbing Materials at Continuous GNSS Stations.

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 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 m 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 ; for Galileo, between 22% and ; for GLONASS, ; and for BeiDou, . 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 for the station with microwave-absorbing material. For GLONASS, particularly for the GLOM3X and GLOM1P code multipath combinations, the reduction reaches , depending on the observation code types. For BeiDou, the reduction is more than , and for GPS, it reaches between and . 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 and 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 for Galileo and 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.

A gear fault diagnosis method based on improved accommodative random weighting algorithm and BB-1D-TP

As an essential component of a gearbox, gears can damage a structure or even an entire gear transmission system in case of failures. As a result, advanced fault diagnosis methods are crucial to system's operation. Currently, single-signal-driven gear fault diagnosis techniques have been applied in many fields, but multipath noise and single-sensor sampling errors inevitably affected the accuracy of diagnosis. This paper proposes a gear fault diagnosis method based on a novel accommodative random weighting theory and a balanced binary one dimension ternary pattern (BB-1D-TP) model. It can accurately diagnose the types of gear failures under the circumstances of multiple channels and strong background noise. The novel accommodative random weighting algorithm reduces the total mean-square error (MSE) by adaptively adjusting the proportional connection between a measured value at a present state and a historical state. Then the balanced binary algorithm extracts texture features of fault signals for signal enhancement. In the end, the classification is done by using Support Vector Machine (SVM) method. The result of experiments demonstrated that the method in this article effectively improves accuracy and efficiency of gear fault identification.

Precise Relative Orbit Determination for Chinese TH-2 Satellite Formation Using Onboard GPS and BDS2 Observations

TH-2 is China’s first short-range satellite formation system used to realize interferometric synthetic aperture radar (InSAR) technology. In order to achieve the mission goal of InSAR processing, the relative orbit must be determined with high accuracy. In this study, the precise relative orbit determination (PROD) for TH-2 based on global positioning system (GPS), second-generation BeiDou navagation satellite system (BDS2), and GPS + BDS2 observations was performed. First, the performance of onboard GPS and BDS2 measurements were assessed by analyzing the available data, code multipath errors and noise levels of carrier phase observations. The differences between the National University of Defense Technology (NDT) and the Xi’an Research Institute of Surveying and Mapping (CHS) baseline solutions exhibited an RMS of 1.48 mm outside maneuver periods. The GPS-based orbit was used as a reference orbit to evaluate the BDS2-based orbit and the GPS + BDS2-based orbit. It is the first time BDS2 has been applied to the PROD of low Earth orbit (LEO) satellite formation. The results showed that the root mean square (RMS) of difference between the PROD results using GPS and BDS2 measurements in 3D components was 2.89 mm in the Asia-Pacific region. We assigned different weights to geostationary Earth orbit (GEO) satellites to illustrate the impact of GEO satellites on PROD, and the accuracy of PROD was improved to 7.08 mm with the GEO weighting strategy. Finally, relative orbits were derived from the combined GPS and BDS2 data. When BDS2 was added on the basis of GPS, the average number of visible navigation satellites from TH-2A and TH-2B improved from 7.5 to 9.5. The RMS of the difference between the GPS + BDS2-based orbit and the GPS-based orbit was about 1.2 mm in 3D. The overlap comparison results showed that the combined orbit consistencies were below 1 mm in the radial (R), along-track (T), and cross-track (N) directions. Furthermore, when BDS2 co-worked with GPS, the average of the ambiguity dilution of precision (ADOP) reduced from 0.160 cycle to 0.153 cycle, which was about a 4.4% reduction. The experimental results indicate that millimeter-level PROD results for TH-2 satellite formation can be obtained by using onboard GPS and BDS2 observations, and multi-GNSS can further improve the accuracy and reliability of PROD.

Research on Time Comparison Based on Galileo PPP

Time comparison based on global navigation satellite system (GNSS) is one of the main techniques in Coordinated Universal Time (UTC) calculation. At present, there is a goal to promote the Galileo system to join the UTC calculation to provide high-precision services for users all over the world. In this paper, the Precision Point Positioning (PPP) time comparison based on Galileo is studied. The data used in this paper include the original data of pseudo-range and carrier phase from National Time Service Center of Chinese Academy of Sciences (NTSC) and Royal Observatory of Belgium (ROB), and the data of precision orbit and clock offset released by International GNSS Service (IGS) which includes the German Research Center for Geoscience (GFZ), Centre for Orbit Determination in Europe (CODE) and Shanghai Astronomical Observatory (SHAO). The results show that the pseudo-range multipath noise of E1 and E5a are all less than ±1 m. When the Galileo PPP is applied to the short baseline common clock time comparison, the time difference by using the precision products of three analysis centers are less than ±0.5 ns, and the standard deviation of the time difference are less than 0.2 ns. For long baseline of Asia Europe time comparison, based on the precision products of three IGS analysis centers, the time comparison between UTC(NTSC) and UTC(TP) by using Galileo PPP have the same trend as the GPS PPP, which is released by International Bureau of Weights and Measures (BIPM), the stability of Galileo PPP is the same with GPS PPP, and it can reach to E-15/ day. As a result, with the performance improvement of Galileo system, the high-precision time comparison based on Galileo will provide better services for users, and the experiment results indicate that the Galileo can also be used as one of the formal methods by BIPM for precision time comparison in the future.

A dynamic network coding MAC protocol for power line communication

Recently, power line communication (PLC) is receiving attention from academic and industry researchers worldwide. In particular, PLC systems have been largely investigated as a medium for transmitting control signals, diagnostic information, or data measured by sensors in Smart Grid. However, PLC systems face several challenges, such as multipath effects and impulsive noise, which may degrade data communication performance. To surpass such issues we propose CodePLC, a dynamic network coding MAC protocol for PLC. CodePLC relies on a single, yet dynamically chosen, relay node. This node stores and forwards linear combinations of PLC frames, which are then combined on their final destinations. We have evaluated the performance of CodePLC through simulations in a PLC system based on a time division multiple access orthogonal frequency-division multiplexing scheme. Simulation results indicate that, in broadcast transmissions, CodePLC enhances system performance. When compared to a PLC system that does not consider the use of CodePLC, based on a stop&wait MAC layer protocol, our new protocol presents an average of 115% of goodput increase. Moreover, CodePLC reduces the average network buffers occupancy by 112%. Finally, our protocol is capable of reducing the mean end-to-end latency by 400%.

Искажения диаграмм направленности фазированных антенных решеток под влиянием периодических и флуктуационных помех.

Issues related to determination of distortions of directional patterns of phased antenna arrays under the influence of periodic and fluctuating multiplicative (modulating) noise are in the focus of the paper. Expressions are obtained for instantaneous directional patterns in terms of voltage and power, as well as the average value of the directional pattern in terms of voltage under the influence of periodic multiplicative noise. So far, since the phase ratios in these instantaneous diagrams change over time, the pattern of the grating fluctuates. The condition is defined under which the structure of the grating pattern «crumbles». At the same time, lower frequencies of acting multiplicative noise lead to distortion of the diagram: its main maximum expands, the level of side lobes increases and lateral reception directions are «smoothed». It is noted that in synthesized arrays, «scattering» of the directional pattern can occur at relatively small values​ of the frequency of multiplicative noise. In lattices with delay lines, periodic multiplicative noise does not cause significant distortion of the directional patterns. Expressions are obtained for determining average directional patterns by voltage and power under the influence of fluctuating multipath noise, including those obtained using correlation function of noise modulation. It has been shown that under the influence of stationary multiplicative noise, the beam pattern on the power of the grating with phase shifters is a convolution of the undistorted diagram on an undistorted scale and the energy spectrum of the noise modulation function. The upper limit of increasing the width of the main lobe of the beam pattern caused by multiplicative noise is determined. It is also shown that as the noise correlation time decreases and the phase distortion depth increases, the diagram expands and its side lobes smooth. It is noted that for distortions of the directional pattern of synthesized arrays, all the basic provisions for phased antenna arrays with phase shifters are true. For lattices with delay lines in the presence of multiplicative noise, the maximum of the average power of the beam pattern does not shift regardless of the shape of the energy spectrum of the noise modulation function. Multiplicative noise can cause only some expansion of the main lobe of the diagram and smoothing of the zero reception directions. Distortions of the grating pattern when exposed to slow fluctuation multiplicative noise are shown. These distortions are determined by changes in the phase and amplitude of the signal over time corresponding to the time shift between the signals in the individual elements of the array, and with slow multiplicative noise, the distortions are small. It is also shown that slow multiplicative noise leads to some reduction in the maximum beam pattern and to smoothing the pattern in the area of the side lobes. In the presence of such noise, the zero reception directions disappear.

Improvement of Reliability Determination Performance of Real Time Kinematic Solutions Using Height Trajectory.

Autonomous driving support systems and self-driving cars require the determination of reliable vehicle positions with high accuracy. The real time kinematic (RTK) algorithm with global navigation satellite system (GNSS) is generally employed to obtain highly accurate position information. Because RTK can estimate the fix solution, which is a centimeter-level positioning solution, it is also used as an indicator of the position reliability. However, in urban areas, the degradation of the GNSS signal environment poses a challenge. Multipath noise caused by surrounding tall buildings degrades the positioning accuracy. This leads to large errors in the fix solution, which is used as a measure of reliability. We propose a novel position reliability estimation method by considering two factors; one is that GNSS errors are more likely to occur in the height than in the plane direction; the other is that the height variation of the actual vehicle travel path is small compared to the amount of movement in the horizontal directions. Based on these considerations, we proposed a method to detect a reliable fix solution by estimating the height variation during driving. To verify the effectiveness of the proposed method, an evaluation test was conducted in an urban area of Tokyo. According to the evaluation test, a reliability judgment rate of 99% was achieved in an urban environment, and a plane accuracy of less than 0.3 m in RMS was achieved. The results indicate that the accuracy of the proposed method is higher than that of the conventional fix solution, demonstratingits effectiveness.

Sign Language Recognition Using Two-Stream Convolutional Neural Networks with Wi-Fi Signals

Sign language is an important way for deaf people to understand and communicate with others. Many researchers use Wi-Fi signals to recognize hand and finger gestures in a non-invasive manner. However, Wi-Fi signals usually contain signal interference, background noise, and mixed multipath noise. In this study, Wi-Fi Channel State Information (CSI) is preprocessed by singular value decomposition (SVD) to obtain the essential signals. Sign language includes the positional relationship of gestures in space and the changes of actions over time. We propose a novel dual-output two-stream convolutional neural network. It not only combines the spatial-stream network and the motion-stream network, but also effectively alleviates the backpropagation problem of the two-stream convolutional neural network (CNN) and improves its recognition accuracy. After the two stream networks are fused, an attention mechanism is applied to select the important features learned by the two-stream networks. Our method has been validated by the public dataset SignFi and adopted five-fold cross-validation. Experimental results show that SVD preprocessing can improve the performance of our dual-output two-stream network. For home, lab, and lab + home environment, the average recognition accuracy rates are 99.13%, 96.79%, and 97.08%, respectively. Compared with other methods, our method has good performance and better generalization capability.

Efficient Recognition of Informative Measurement in the RF-Based Device-Free Localization.

Device-Free Localization (DFL) based on the Radio Frequency (RF) is an emerging wireless sensing technology to perceive the position information of the target. To realize the real-time DFL with lower power, Back-projection Radio Tomographic Imaging (BRTI) has been used as a lightweight method to achieve the goal. However, the multipath noise in the RF sensing network may interfere with the measurement and the BRTI reconstruction performance. To resist the multipath interference in the observed data, it is necessary to recognize the informative RF link measurements that are truly affected by the target appearance. However, the existing methods based on the RF link state analysis are limited by the complex distribution of the RF link state and the high time complexity. In this paper, to enhance the performance of RF link state analysis, the RF link state analysis is transformed into a decomposition problem of the RF link state matrix, and an efficient RF link recognition method based on the low-rank and sparse decomposition is proposed to sense the spatiotemporal variation of the RF link state and accurately figure out the target-affected RF links. From the experimental results, the RF links recognized by the proposed method effectively reflect the target-induced RSS measurement variation with less time. Besides, the proposed method by recognizing the informative measurement is helpful to improve the accuracy of BRTI and enhance the efficiency in actual DFL applications.

A New Path Planning Algorithm Using a GNSS Localization Error Map for UAVs in an Urban Area

The mission of future parcel delivery will be performed by unmanned aerial vehicles (UAVs). However, the localization of global navigation satellite systems (GNSS) in urban areas experiences the notorious multipath effect and non-line-of-sight (NLOS) reception which could potentially generate approximately 50 meters of positioning error. This misleading localization result can be hazardous for UAV applications in GNSS-challenged areas. Due to multipath complexity, there is no general solution to eliminate this effect. A solution to guide UAV operation is to plan an optimal route that smartly avoids the area with a strong multipath effect. To achieve this goal, the impact of the multipath effect in terms of positioning error at different locations must be predicted. This paper proposes to simulate the reflection route by a ray-tracing technique, aided by predicted satellite positions and the widely available 3D building model. Thus, the multipath effect in the pseudorange domain can be simulated using the reflection route and multipath noise envelope according, according to specific correlator designs. By constructing the multipath-biased pseudorange domain, the predicted positioning error can be obtained using a least square positioning method. Finally, the predicted GNSS error distribution of a target area can be further constructed. A new A* path planning algorithm is developed to combine with the GNSS error distribution. This paper designs a new cost function to consider both the distance to the destination and the positioning error at each grid. By comparing the conventional and the proposed path planning algorithms, the planned paths of the proposed methods experienced fewer positioning errors, which can lead to safer routes for UAVs in urban areas.

A Tightly Coupled RTK/INS Algorithm with Ambiguity Resolution in the Position Domain for Ground Vehicles in Harsh Urban Environments.

Vehicles driving in urban canyons are always confronted with a degraded Global Navigation Satellite System (GNSS) signal environment. The surrounding obstacles may cause signal reflections or blockages, which lead to large multipath noises and intermittent GNSS reception. Under these circumstances, it is not feasible to use conventional real-time kinematic (RTK) algorithms to maintain high-precision performance for positioning. In order to meet the special requirements of safety-critical applications under non-ideal observation conditions, a novel tightly coupled RTK/Inertial Navigation System (INS) algorithm is proposed in this paper, which can provide accurate and reliable positioning results continuously. Our integrated RTK/INS algorithm has three features. Firstly, INS measurements are used to help search for integer ambiguities in the position domain. INS solutions can provide a more accurate initial location and a more efficient search region. Secondly, the criterion for determining whether a candidate position is the correct solution is only related to the fractional value of the carrier-phase measurement. Thus, the new algorithm is immune to cycle slips as well as large pseudorange noises. Thirdly, our algorithm can provide more accurate ranging information than the pseudorange, even though it may not necessarily be fixed successfully, because it selects the weighted ambiguity solution as the result rather than the candidate point with maximum probability. The proposed algorithm is demonstrated on both simulated and real datasets. Compared with single epoch RTK and conventional tightly coupled RTK/INS integrations that search integer ambiguities in the ambiguity domain, our method attains better accuracy and stability in a simulated environment. Moreover, the real experimental results are presented to validate the performance of the new integrated navigation algorithm.

An Unambiguous Tracking Technique for Sine-BOC(kn,n) Modulated GNSS Signals

Binary offset carrier modulation is applied in several signals of the global navigation satellite system (GNSS). It enhanced the robustness of GNSS against the impact of multipath and make the compatibility of GNSS better. However, it has the main drawback of potentially giving biased measurements in acquisition and tracking. The technique we proposed is based on linear fitting with multi-correlator to accomplish unambiguous tracking. The coefficient of each correlator was deduced in this paper. The theoretical analysis and simulation results indicate that the proposed method can performs well on multipath and thermal noise.

Low‐density parity check coded orthogonal frequency division multiplexing for PLC in non‐Gaussian noise using LLRs derived from effective noise probability density functions

In this study, the performance of irregular low-density parity check (LDPC) coded orthogonal frequency division multiplexing (COFDM) utilising 4096 quadrature amplitude modulation (4096-QAM) is investigated over multipath power-line communication (PLC) channel. The effective complex-valued ratio distributions of the noise samples at the zero-forcing equaliser output considering both frequency-selective multipath PLCs, background and impulsive noise are derived, in addition to the condition for optimum detection of 4096-QAM and the bit error rate (BER). Moreover, the performance of the LDPC decoder is improved by computing the log-likelihood ratios (LLRs) required for soft decoding based on the derived probability density functions. Numerical results obtained using the newly derived LLRs demonstrate a significant performance improvement compared to the conventional receiver that uses blanking impulsive noise mitigation method and LLR computed based on the Gaussian distribution. Furthermore, EXtrinsic Information Transfer chart analysis demonstrates that the proposed approach requires fewer iterations for convergence compared to the conventional receiver. Finally, utilising channel bandwidth of 22.4 MHz, the proposed system offers an improvement of 111 Mbps over the conventional system to reach a maximum data throughput of 256 Mbps for a signal-to-noise ratio of 39 dB and BER of 10 -5 .