To solve the issues with industrial traditional area measurement instruments equipped with infrared sensors, which are bulky and compute slowly, a planimetric measuring method based on machine vision is developed. The area of the plane is calculated through three processes: 3-D reconstruction by monocular camera calibration, top view by perspective transformation and image segmentation to obtain the proportion of the object to be measured. This paper enhances the calculation of the world coordinate points in the 3-D reconstruction process and lowers the measurement error from more than 1% to 0.28%. It solves the drawbacks of the conventional measuring device, which is huge and slow, and can correctly measure the planar area with less expensive hardware, which has certain application value. © 2023 SPIE.

With the rapid development of satellite IoT networks, massive IoT terminals may simultaneously access the satellites, resulting in an increasing demand for user capacity. Sparse code multiple access (SCMA) may increase user capacity and spectrum efficiency, through using sparse coding and multi-dimensional mapping method. However, codebook collisions may occur during the on-going wireless transmissions of IoT terminals, because of frequency drift and clock drift of the crystal used by IoT terminals. Relying on our analysis, codebook collisions may dramatically increase the bit error rate (BER). Thus, we conceive a joint contention resolution diversity slotted Aloha (CRDSA) and SCMA (J-CRDSA-SCMA) scheme, to mitigate the impacts on BER caused by codebook collisions. Moreover, the codebook-collision probability of the conceived J-CRDSA-SCMA scheme is also analyzed. Simulation results show that the conceived J-CRDSA-SCMA scheme can achieve a lower BER than the conventional pure SCMA scheme, demonstrating the superiority of the conceived J-CRDSA-SCMA scheme in terms of avoiding codebook collisions. © 2023 IEEE.

This paper investigates the spectrum sensing performance of a distributed satellite clusters (DSC), where the sensing signals received by each cooperative satellite can be fused at the signal-level to enhance the sensing ability of weak signals. In particular, by assuming that the satellite-relay link undergoes shadowed-Rician (SR) fading, we first derive a closed-form expression for correct detection probability (Pd) of the considered system with maximum ratio combining (MRC). However, when the channel state information can not meet the requirements, equal gain combining (EGC) provides an alternative to slightly reduce the complexity. Therefore, we provide another closed-form expression of Pd based on EGC, using the specially derived probability density function of the sum of SR random variables with independently identical distribution. Simulation results are provided to validate our theoretical analysis and to show that the proposed scheme can achieve the best spectrum-sensing performance, comparing with the traditional energy detection, eigenvalue ratio test and the generalized likelihood ratio test. © 2022 IEEE.

Satellite search and rescue positioning technology can provide effective means for mountain areas, deserts, oceans and other areas lacking communication infrastructure, which has attracted more attention recently. In this paper, we propose a joint time-frequency difference optimal location method for satellite search and rescue system to improve the performance of parameter estimation and location solution in the traditional passive dual satellite time-frequency difference location technology. Specifically, the fast Fourier transform is used to simplify the joint estimation of the time-frequency difference of the cross ambiguity function. Aiming at the burst low duty cycle transmission of search and rescue signals, a time-domain windowed comprehensive cross ambiguity function calculation model is proposed. Finally, a genetic algorithm is proposed to solve the positioning equation. Simulation results show that, compared with traditional methods, the proposed algorithm can improve the system fault tolerance and positioning accuracy, and reduce the computational complexity. © 2022 IEEE.

本文对通信卫星受到各种干扰的问题,介绍了几类单星干扰源定位技术。首先介绍了四种单星干扰源定位技术,分别是基于无人机辅助卫星定位、基于多普勒频移定位、基于功率波动定位和基于星载多波束天线定位,并总结了各自的优缺点,分析它们的定位精度,对他们的适用场景进行了说明。本文最后对上述定位技术进行了总结和建议。

随着信息化社会的到来,国际国内无线电通信技术飞速发展,用户对无线电通信的需求不断扩大。卫星通信以其频带宽、容量大、适用于多种业务等优势广泛应用于国际通信、移动通信以及广播电视等领域。然而由于干扰源的存在,会使卫星通信存在严重的安全问题。因此对干扰源目标位置快速有效的定位具有十分重要的意义。而无源定位技术因具备良好的隐蔽性、远作用距离等优势,目前在军用和民用系统中占据着越发关键的地位,是当今定位领域的研究热点。本文介绍了卫星干扰源定位系统,几种定位方法的原理和算法,卫星定位系统的新算法与新技术,最后对卫星干扰源定位的未来发展提出设想。

At present, the research on the single satellite frequency measurement and localization technology mainly focuses on the use of multiple satellite observation positions in a single flight orbit to forward the ground target source signals, but there are many limitations in locating the interference source with limited field of view. In this paper, based on the single-orbit single-satellite time-division frequency-measuring localization technology, a localization technology of single-satellite time-division Doppler frequency measurement in different orbits is proposed, which is based on the optimal observation satellite position. Firstly, the positioning model and the positioning equation of the single-satellite time-division Doppler frequency measurement and localization technology in different orbits are constructed. Secondly, a calculation formula for Geometric Dilution of Precision (GDOP) is derived and the optimal model of the observation satellite position is constructed. Finally, based on the positioning process, the minimum positioning error is targeted. Computer simulation results show that the availability and accuracy of the technique are improved significantly in the scene with limited field of view.
© 2021, ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering.

In this paper, we propose a cooperative beamforming ALOHA (CBA) scheme to improve the throughput of an asynchronous low earth orbit (LEO) satellite based Internet of Things (IoT) networks. Due to the multisatellite visible nature of a LEO satellite constellation, this scheme combines multi-satellite receive diversity of random access packets with cooperative beamforming technique to resolve contention of the packet collision at the satellite gateway. The proposed scheme is evaluated by theoretical analysis and Monte Carlo simulation. Simulation results show that CBA scheme has better throughput and packet loss ratio performance compared with the traditional P-ALOHA, S-ALOHA, and AC-ALOHA. © 2020 IEEE.

In this paper, we investigate the spectrum sensing of a weak signal based on multiple low earth orbit (LEO) satellites in the presence of a spectrum-sharing node, which can generate the interference imposed on the sensing LEO satellites. In order to improve the sensing ability of the weak signal, a cooperative spectrum sensing method relying on satellite formation is proposed. Specifically, firstly, some satellites will be chosen from multiple LEO satellites for formation purposes, where the specific number of satellites chosen can be adjusted by evaluating the probability of detection weak signal, as detailed later. Then, considering the object that both restraining the interference and magnifying the weak signal, the weighted value of each satellite for beamforming may be optimized with the aid of genetic algorithm, and the receive gains of the weak signal and the interference can be achieved. Finally, the probability of detecting the weak signal can be evaluated by calculating the signal to interference plus noise ratio (SINR), and the number of the chosen satellites can be decided accordingly. Simulation results show that the proposed method not only can suppress the interference imposed on the sensing satellites, but also can increase SINR of sensing satellites for the weak signal, resulting in improving the probability of detection.
© 2021, ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering.