KEYWORDS: Clouds, Modulation, Data processing, Computing systems, Data storage, Defense technologies, Electromagnetism, Signal processing, Signal to noise ratio, Signal detection
With the increase of the number of frequency terminals, the electromagnetic spectrum resource becomes particularly important. The traditional electromagnetic spectrum monitoring system is faced with the problems of insufficient transmission bandwidth, shortage of monitoring node resources and large human interference factors. In this paper, edge computing technology is applied to electromagnetic spectrum monitoring, and edge computing processing framework KubeEdge is used to establish a spectrum monitoring system. The system is divided into cloud and edge monitoring node, and multiple distributed spectrum monitoring nodes can be deployed. Taking the signal modulation recognition application as an example, the results show that the system can effectively deploy spectrum monitoring applications to intelligently identify signal modulation modes, and the recognition accuracy of some modulation modes is close to more than 90%.
This paper proposes the use of RLS real-time high-precision positioning algorithm in high-precision real-time positioning of space-based internet of things loads, which overcomes the traditional least-squares high order of inverse matrix, large amount of calculation and easy to appear ill-conditioned matrix that can’t seek the inverse, can continuously obtaining estimates in real time, suitable for satellite on-orbit applications. The article analyzes the positioning accuracy grade distribution of RLS real-time high-precision positioning algorithm in detail. The analysis results show that the positioning accuracy is mainly affected by the error of frequency measurement, position error and velocity error, and the error of frequency measurement has a great influence. When the satellite position error is 5m,the velocity error is 0.01m/s, and the Doppler error is 0.1Hz, the probability of positioning error less than 1000m is 95.5%, which satisfies the normal distribution standard deviation 2σ distribution (95.5%).
Wireless ad hoc sensor networks have been used more and more in recent years, and they are mainly used in the continuous monitoring of complex environment. The low power and dual frequency characteristics of the SimpleLink CC1350 LaunchPad micro control platform are very suitable for the research of wireless ad hoc sensor networks. Because the synchronization of each node clock is the premise of the normal work of wireless sensor network, this paper mainly studies the time synchronization problem of CC1350 development board. In this paper, the advantages and disadvantages of the existing time synchronization methods are analyzed, then the LTSP algorithm is selected at the end, and the experimental verification is carried out on MATLAB software platform and CC1350 system. The experiment result shows that the time synchronization precision and extensibility of the algorithm can meet the requirement of networking.
In the presence of narrowband interference (NBI), the ranging receivers should not only remain steady but also satisfy the requirement of ranging precision. By taking into account both the system stability and the precision requirement, this paper defined the anti-jamming margin of a ranging system (RS-AJM) to provide a comprehensive evaluation of anti-jamming capability. A margin reference factor was introduced to describe the relationship between the two requirements, which was used to divide the margin calculation into three cases. When the system is in the high stability region, the system stability is more important than the ranging precision. When the system is in the high precision region, the anti-jamming margin mainly depends on the precision requirement. When the system is in the middle region, the two requirements determine the anti-jamming capability together. The middle region can be further divided into another two zones according to the center frequency of NBI. The margin reference factor and the performance scenario division present a clear and comprehensive description of the anti-jamming capability, which is also verified using numerical results.
In the design of a multi-frequency multi-constellation GNSS software defined radio receivers is becoming more and more popular due to its simple architecture, flexible configuration and good coherence in multi-frequency signal processing. It plays an important role in navigation signal processing and signal quality monitoring. In particular, GNSS software defined radio receivers driving the sampling clock of analogue-to-digital converter (ADC) by FPGA implies that a more flexible radio transceiver design is possible. According to the concept of software defined radio (SDR), the ideal is to digitize as close to the antenna as possible. Whereas the carrier frequency of GNSS signal is of the frequency of GHz, converting at this frequency is expensive and consumes more power. Band sampling method is a cheaper, more effective alternative. When using band sampling method, it is possible to sample a RF signal at twice the bandwidth of the signal. Unfortunately, as the other side of the coin, the introduction of SDR concept and band sampling method induce negative influence on the performance of the GNSS receivers. ADC’s suffer larger sampling clock jitter generated by FPGA; and low sampling frequency introduces more noise to the receiver. Then the influence of sampling noise cannot be neglected. The paper analyzes the sampling noise, presents its influence on the carrier noise ratio, and derives the ranging error by calculating the synchronization error of the delay locked loop. Simulations aiming at each impact factors of sampling-noise-induced ranging error are performed. Simulation and experiment results show that if the target ranging accuracy is at the level of centimeter, the quantization length should be no less than 8 and the sampling clock jitter should not exceed 30ps.
In this paper, we address the problem of semantically generating hierarchical and meaningful content for soccer video by mapping low-level features to high-level semantics. Our goal is to construct a hierarchical and compact content abstraction of soccer video that can serve as an effective index table, allowing users to browse through lots of soccer videos in a flexible and efficient way. And we generated three-layer semantic hierarchies of soccer video according to characteristics of soccer video through bridging the gap between features and semantics. Some experimental results are presented and discussed in the paper.
A new method of displacement measurement using single grating is put forward in the paper. Wide range and high-resolution displacement measurement is realized by means of a general coarse metric-grating and a spectroscope. The method solves the traditional problem that high frequency grating can't be manufactured too long. The optical configuration and the principle of measurement are presented in the paper. Its feasibility is proved by experiment. In the experiment, a metric-grating with frequency of 50 rulings/mm is used and optical subdivision more than 32 is received.
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