scholarly journals An Optimization Synchronization Algorithm for TDDM Signal

2016 ◽  
Vol 2016 ◽  
pp. 1-7
Author(s):  
Fang Liu ◽  
Yongxin Feng
Keyword(s):  
Spread Spectrum ◽  
Sequence Structure ◽  
Estimation Formula ◽  
Synchronization Algorithm ◽  
Local Sequence ◽  
Threshold Mechanism ◽  
Global Navigation Satellite ◽  
Time Division ◽  
Synchronization Accuracy ◽  
Better Than

The time division data modulation (TDDM) mechanism is recommended to improve the communications quality and enhance the antijamming capability of the spread spectrum communication system, which will be used in the next generation global navigation satellite (GNSS) systems. According to the principle and the characteristics of TDDM signal, an optimization synchronization algorithm is proposed. In the new algorithm, the synchronization accuracy and environmental adaptability have been improved with the special local sequence structure, the multicorrelation processing, and the proportion threshold mechanism. Thus, the inversion estimation formula was established. The simulation results demonstrate that the new algorithm can eliminate the illegibility threat in the synchronization process and can adapt to a lower SNR. In addition, this algorithm is better than the traditional algorithms in terms of synchronization accuracy and adaptability.

scholarly journals A Fast Acquisition Algorithm Overcoming Fuzz Problems for TDDM Spread Spectrum Signal

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Fang Liu ◽  
Yongxin Feng
Keyword(s):  
Spread Spectrum ◽  
Phase Error ◽  
Satellite System ◽  
Position Estimation ◽  
Frequency Error ◽  
Next Generation ◽  
Error Message ◽  
Fast Acquisition ◽  
Global Navigation Satellite ◽  
Time Division

TDDM (time division data modulation) technique will be used in the next generation GNSS (global navigation satellite system) to improve processing performance and to reduce inter-GNSS interference; however, the emergence of TDDM signal causes the estimation frequency and message reversal fuzz problems in the acquisition process of a GNSS receiver. At present, the traditional acquisition methods have some limitations and shortcomings. Therefore, aiming at the unique characteristics of TDDM signal, a fast acquisition algorithm is proposed to overcome these fuzz problems in this paper. In the proposed algorithm, three stages are obtained by some key technologies, which are theI-Qfrequency compensation, superposition processing, subsection processing, and reversion position estimation. Besides, the algorithm is simulated from carrier frequency error, code phase error, message inversion error, and processing speed. Theoretical and simulation results show that the new algorithm can quickly overcome the fuzz problems, and the new algorithm is better than the existing algorithm in the speed and accuracy, which demonstrates that this new algorithm is an effective search scheme for the next generation GNSS signals.

scholarly journals NLOS Multipath Classification of GNSS Signal Correlation Output Using Machine Learning

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2503
Author(s):  
Taro Suzuki ◽  
Yoshiharu Amano
Keyword(s):  
Machine Learning ◽  
Satellite System ◽  
Training Data ◽  
Support Vector ◽  
Positioning Errors ◽  
Automated Method ◽  
Global Navigation Satellite ◽  
Better Than ◽  
Signal Correlation

This paper proposes a method for detecting non-line-of-sight (NLOS) multipath, which causes large positioning errors in a global navigation satellite system (GNSS). We use GNSS signal correlation output, which is the most primitive GNSS signal processing output, to detect NLOS multipath based on machine learning. The shape of the multi-correlator outputs is distorted due to the NLOS multipath. The features of the shape of the multi-correlator are used to discriminate the NLOS multipath. We implement two supervised learning methods, a support vector machine (SVM) and a neural network (NN), and compare their performance. In addition, we also propose an automated method of collecting training data for LOS and NLOS signals of machine learning. The evaluation of the proposed NLOS detection method in an urban environment confirmed that NN was better than SVM, and 97.7% of NLOS signals were correctly discriminated.

scholarly journals Code Synchronization Algorithm Based on Segment Correlation in Spread Spectrum Communication

Algorithms ◽  
2015 ◽  
Vol 8 (4) ◽  
pp. 870-894 ◽  
Author(s):  
Aohan Li ◽  
Ziheng Yang ◽  
Renji Qi ◽  
Feng Zhou ◽  
Guangjie Han
Keyword(s):  
Spread Spectrum ◽  
Spread Spectrum Communication ◽  
Code Synchronization ◽  
Synchronization Algorithm

scholarly journals Monitoring Aircraft Position Using EGNOS Data for the SBAS APV Approach to the Landing Procedure

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 1945 ◽  
Author(s):  
Kamil Krasuski ◽  
Damian Wierzbicki
Keyword(s):  
Research Method ◽  
Satellite System ◽  
Civil Aviation ◽  
International Civil Aviation Organization ◽  
Positioning Accuracy ◽  
Research Findings ◽  
Global Navigation Satellite ◽  
Service Data ◽  
Computational Strategy ◽  
Better Than

The aim of this paper is to present the problem of the implementation of the EGNOS (European Geostationary Navigation Overlay Service) data for the processing of aircraft position determination. The main aim of the research is to develop a new computational strategy which might improve the performance of the EGNOS system in aviation, based on navigation solutions of an aircraft position, using several GNSS (Global Navigation Satellite System) onboard receivers. The results of an experimental test conducted by the Cessna 172 at EPDE (European Poland Deblin) (ICAO (International Civil Aviation Organization) code, N51°33.07’/E21°53.52’) aerodrome in Dęblin are presented and discussed in this paper. Two GNSS navigation receivers with the EGNOS positioning function for monitoring changes in the parameters of the aircraft position in real time during the landing phase were installed onboard a Cessna 172. Based on obtained research findings, it was discovered that the positioning accuracy was not higher than 2.1 m, and the integrity of positioning did not exceed 19 m. Moreover, the availability parameter was found to equal 1 (or 100%); also, no intervals in the continuity of the operation of the EGNOS system were recorded. In the paper, the results of the air test from Dęblin were compared with the parameters of positioning quality from the air test conducted in Chełm (ICAO code: EPCD, N51°04’57.8” E23°26’15”). In the air test in Chełm, the obtained parameters of EGNOS quality positioning were: better than 4.9 m for accuracy, less than 35.5 m for integrity, 100% for availability, and no breaks in continuity. Based on the results of the air tests in Dęblin and Chełm, it was concluded that the parameters of the EGNOS positioning quality in aviation for the SBAS (Satellite Based Augmentation System) APV (Approach to Vertical guidance) procedure were satisfied in accordance with the ICAO (International Civil Aviation Organization) requirements. The presented research method can be utilized in the SBAS APV landing procedure in Polish aviation. In this paper, the results of PDOP (Position Dilution of Precision) are presented and compared to the two air tests in Dęblin and Chełm. The maximum results of PDOP amounted to 1.4 in the air test in Dęblin, whereas they equaled 4.0 in the air test in Chełm. The paper also shows how the EGNOS system improved the aircraft position in relation to the only GPS solution. In this context, the EGNOS system improved the aircraft position from about 78% to 95% for each ellipsoidal coordinate axis.

LOCAL SEQUENCE-STRUCTURE MOTIFS IN RNA

2004 ◽  
Vol 02 (04) ◽  
pp. 681-698 ◽  
Author(s):  
ROLF BACKOFEN ◽  
SEBASTIAN WILL
Keyword(s):  
Information Structure ◽  
Structure Alignment ◽  
General Definition ◽  
Local Alignment ◽  
Sequence Information ◽  
Sequence Structure ◽  
Worst Case ◽  
Rna Molecules ◽  
Alignment Algorithms ◽  
Local Sequence

Ribonuclic acid (RNA) enjoys increasing interest in molecular biology; despite this interest fundamental algorithms are lacking, e.g. for identifying local motifs. As proteins, RNA molecules have a distinctive structure. Therefore, in addition to sequence information, structure plays an important part in assessing the similarity of RNAs. Furthermore, common sequence-structure features in two or several RNA molecules are often only spatially local, where possibly large parts of the molecules are dissimilar. Consequently, we address the problem of comparing RNA molecules by computing an optimal local alignment with respect to sequence and structure information. While local alignment is superior to global alignment for identifying local similarities, no general local sequence-structure alignment algorithms are currently known. We suggest a new general definition of locality for sequence-structure alignments that is biologically motivated and efficiently tractable. To show the former, we discuss locality of RNA and prove that the defined locality means connectivity by atomic and non-atomic bonds. To show the latter, we present an efficient algorithm for the newly defined pairwise local sequence-structure alignment (lssa) problem for RNA. For molecules of lengthes n and m, the algorithm has worst-case time complexity of O(n2·m2· max (n,m)) and a space complexity of only O(n·m). An implementation of our algorithm is available at . Its runtime is competitive with global sequence-structure alignment.

Inscribing in to an Control Attempt against Jammer Attack Using FB Decoding Mechanism

2014 ◽  
Vol 573 ◽  
pp. 412-417
Author(s):  
G. Sona ◽  
P. Annapandi ◽  
Boopathy Yamni
Keyword(s):  
Spread Spectrum ◽  
Cost Effective ◽  
Original Data ◽  
Overhead Cost ◽  
Storage Overhead ◽  
Node Spreading ◽  
Time Required ◽  
Key Scheduling ◽  
Secured Communication ◽  
Better Than

Previously Spread Spectrum (SS) communication involve by setting up preconfigured keys among the communicating nodes that are constrained to possess synchronous behaviour. This extends to several issues creating circular dependency problem, offering less energy efficiency and thereby leading to insecure short-lived communication. In this paper, an opponent resilient secret sharing concept is introduced without any establishment of pre-shared keys by FB (Forward Backward) decoding. It illustrates using time reversed message extraction and key scheduling at receiver side that enables secured transmission over wireless communication even when the receiver node remains inactive and attaining jammer not to obtain the original data sent by the sender node. Spreading the data involves use of DSSS as it would be more compatible in adjusting to multiple bandwidths. Main goal is to transmit the message in such a way that the time required to deliver the secret must be less than the time for the opponent to find key during transmission. Further, it come up with minimal storage overhead, cost effective and sustains long-lived secured communication among the interacting nodes. Evaluation of various parameters is performed using NS-2 toolkit to prove that this newer approach is better than earlier work.

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