Satellite Base Stations Research Articles

Deep Reinforcement Learning-Based Power Allocation for Rate-Splitting Multiple Access in 6G LEO Satellite Communication System

Rate-splitting multiple access (RSMA) softly reconciles and decodes the extreme interference by non-orthogonal transmission, which can remarkably solve the spectrum scarcity for future six-generation (6G) low earth orbits (LEO) satellite communication system. In this letter, we investigate the power allocation problem in LEO satellite networks with RSMA mechanism based on the deep reinforcement learning (DRL) technique. Specifically, in order to achieve better RSMA performance, the LEO satellite base station (SBS) has to effectively allocate transmit power to common and private streams, which is very challenging due to the uncertain and limited information of the channel distribution. To solve this problem, a highly-effective proximal policy optimization (PPO) based scheme is further proposed, which enables the LEO SBS to learn an optimal power allocation strategy to maximize the sum rate of the system without knowing any prior information. Simulation results prove that the proposed scheme significantly outperforms the other three baseline schemes in terms of the sum rate metric with low computation complexity.

Smart Grazing in Tibetan Plateau: Development of a Ground-Air-Space Integrated Low-Cost Internet of Things System for Yak Monitoring

This paper analyzes the present situation and difficulties of yak breeding in the “Three Needy Autonomous Regions” of Sichuan Province, integrating the specific natural environments of Qinghai-Tibet Plateau. Research work focuses on the requirements of no network conditions, large-scale application, and ultralow use cost. We propose a smart grazing IoT system, in which collars and ear-tags are designed to collect the positions and physiological signs of yaks, BeiDou Satellite-Base Stations (BDS-BSs) are designed to build local area network and ultralong-distance communication, and what is more, UAV is designed to expand the communication range to hundreds of kilometers. According to the actual needs of grazing monitoring, we propose an effective data reduction method, so that BeiDou Satellite (BDS) short-message technology can be applied to the IoT communication with high efficiency and low cost. The author carried out a significant number of experiments and verification: (1) collar realized positioning and physiological signs collecting of yaks. (2) The local area network (LAN) scheme based on LoRa built a stable communication distance of more than 3 km. (3) Ultralong-distance communication scheme based on BDS short-message technology effectively solved the problem of no network and got excellent zero additional use cost. (4) A plateau mountainous grazing UAV is designed and developed to expand the communication range.

A Design of a Developable Automatic Avoidance System of UAV Based on ADS‐B

There are two primary defects in the existing UAV avoidance systems: the system is memoryless; airborne radars are used to detect long‐distance barriers, which are unreliable and expensive. The paper adopts the deep learning algorithm and ADS‐B communication system based on a satellite base station to solve the above problems. It divides the avoidance problem into two parts: short‐distance obstacle avoidance and long‐distance route planning. On the one hand, the system establishes the knowledge base storing the previous avoidance experience and the matching mechanism, realizing the correspondence between input and experience through a deep learning algorithm. They can dramatically improve the reaction speed and safety of UAVs. On the other hand, the system realizes the interconnection between UAV and the satellite base station through the ADS‐B communication system to replace the radars, putting the task of route planning on the satellite platform. Therefore, the satellite can achieve large‐scale and all‐weather detection to improve the overall safety of UAVs depending on its high and long‐range characteristics. The paper also illustrates the design elements of the RF baseband integrated ADS‐B transceiver and the simulation performance of the short‐distance avoidance system in the end, whose results show that the system can be applied to dense obstacle environments and significantly improve the security of UAVs in a complex domain.

Decreasing Big Data Application Latency in Satellite Link by Caching and Peer Selection

Although satellite communications have attracted wide attention in 6 G integrated space-air-ground networks, the link delay between the satellite and the satellite base station is a major issue with the advent of the era of big data. Considering this problem, this paper proposes cooperative strategies between peers in order to decrease the transmission latency for both downlink and uplink, respectively. In the downlink, we establish social relationship to find peer nodes who can cache contents and design a caching placement algorithm based on greedy methods to configure the cache. The approximation ratio of the solution obtained by the cache placement algorithm is no less than $1-1/e$ of the optimal solution. In the uplink, when channel conditions are severe, some users can be selected as relays to ensure the quality of communication. Such that another social relationship is established to prevent the disclosure of privacy in the process of data forwarding. We establish a dynamic optimization model, and propose a peer selection algorithm. Simulation results show that the performance of cache placement algorithm is more efficient other algorithms in the aspect of average latency and hit ratio in the downlink, and the peer selection algorithm outperforms other algorithms in terms of average channel rate and handover ratio in the uplink.

QPSK Demodulator Based on Wideband Acquisition System

The paper describes the design of the QPSK demodulator based satellite base station. The most important requirement of the design process is to have wide band acquisition range of 100 kHz under narrow Phase Lock Loop (PLL) bandwidth and low input Signal to Noise Ratio (SNR). The efficiency of the technique is verified with extensive simulations in MATLAB.

The Calculation Of The Normal Height Of The State Geodetic Network Point Based On The Local Quasigeoid Model

The data obtained during GPS observations is the basis for the creation of local quasigeoid models and obtaining differences in the heights of normal and ellipsoid surfaces of WGS-84. The network of satellite base stations located in the Rostov region is used as points of the state geodetic network (SGN). The gravimetric model is used as a model of the quasigeoid height (QH). The model of the quasigeoid is calculated and developed on the basis of gravimetric data. Five base stations located within the city of Rostov-on-Don are selected to obtain the normal heights of SGN points. The above points are recalculated from the local system to the WGS-84 system. The equation of the plane, approximating the local quasigeoid is constructed. The gravimetric heights of the quasigeoid are obtained by substituting the coordinate values of each point. The calculation of the normal heights of points is made after an estimation of the model accuracy.

Broadband LEO Satellite Communications: Architectures and Key Technologies

This article aims to provide a comprehensive overview for key issues in broadband LEO satellite communication systems. First of all, the network architecture is introduced, which is the basis of the whole system. The space-based LEO system with ISL, which requires a small number of ground gateways, is the focus. In this system, the satellite constellation design is important with impact on key system performances such as coverage. Two popular LEO constellations, the walker Delta and Star constellations, are introduced. Given satellite constellations, proper beam coverage schemes should be employed at satellites to provide seamless coverage all over the world. A hybrid wide and spot beam coverage scheme is presented, where the LEO provides a wide beam for large area coverage and several steering spot beams for highspeed data access. Moreover, special coverage schemes should be designed in broadband LEO systems for the interference coordination between LEO and GEO. To protect GEO communications, LEO satellites should be turned off if they cause interference to GEO. In this case, to provide services for users covered by the turned-off LEO satellites, a progressive pitch method and a coverage expanding method can be employed. Finally, the coverage performance of LEO is also closely related to resource management schemes. The global resource management for broadband LEO systems is complicated, involving a large amount of data, and a two-level management structure should be employed. Using this structure, an NMC with powerful storage and processing capabilities is employed to carry out the first-level management, making strategies based on all information collected from the whole system. Then satellite base stations with limited capabilities are employed to respond to the strategies generated by NMC in real time.

Mining maritime traffic conflict trajectories from a massive AIS data

The growing volume of maritime traffic is proving a hindrance to navigational safety. Researchers have sought to improve the safety of maritime transportation by conducting statistical analysis on historical collision data in order to identify the causes of maritime collisions. However, this approach is hindered by the limited number of incidents that can be collected in a given area over a given period of time. Automatic Identification System (AIS) has made available enormous quantities of maritime traffic data. Trajectory data are collected through the electronic exchange of navigational data among ships and terrestrial and satellite base stations. Due to a massive AIS data of recording ship movement, such data provide great opportunity to discover maritime traffic knowledge of movement behavior analysis, route estimation, and the detection of anomalous behaviors. Our objective in this paper was to identify potential between-ship traffic conflicts through the discovery of AIS data. Traffic conflict refers to trajectories that could lead to a collision if the ships do not take any evasive action. In other words, conflicting trajectories can be treated as a near-collision cases for analysis. The prevention of collisions requires an efficient method by which to extract conflicting trajectories from a massive collection of AIS data. To this end, we developed a framework CCT Discovery that allows the automated identification of clusters of conflicting trajectories (CCTs) from AIS data without supervision. Experiments based on real-world data demonstrate the efficacy of the proposed framework in terms of accuracy and efficiency. For improvement in the navigational traffic safety, the discovered data of conflict trajectory can contribute to numerous applications, such as collision situation awareness and prediction, anti-collision behaviors modeling and recommendation, and conflict area analysis for maritime traffic flow management.

Design and operation of App-based intelligent landslide monitoring system: the case of Three Gorges Reservoir Region

Nowadays, mobile applications (Apps) have become a main form of mobile Internet services, and related applications in the geological disaster monitoring domain must follow this development trend. In this study, an innovative remote and intelligent landslide monitoring system was designed and developed, which can capture the in-depth sliding force state of the slope in real time. When it reaches the early warning threshold, the system immediately transmits the warning information to user terminals and warns users to initiate corresponding risk-avoidance plans. Next, using the developed system, an App of early warning information publishing program was developed to transmit the acquired sliding-force data by field monitoring devices to servers via Beidou Satellite or GPRS base station. The App can inquire background servers via WiFi or 4G for acquiring the monitoring data and curves of the side slope. Finally, the developed system was applied for the monitoring of the sliding mass in Zhoujiawan, Badong County, the Three Gorges Reservoir Region. The monitoring personnel could locate and inspect the failure characteristics of the deformation region in a timely manner using the developed App. The App data exhibited significant correlation and consistency with the monitored results, thus enhancing the inspection efficiency and allowing an effective emergency response.

A low‐profile broadband circular polarization filtering antenna

AbstractA low‐profile circular polarization filtering antenna with broadband is introduced in this research. The effect of filtering can be achieved by using multi‐layer coupled radiation structure. The bandwidth of the antenna can be expanded by changing the feed line to the gradual deformation structure. Manufacturing and testing of the antenna, the impedance bandwidth (VSWR < 1.5) can reach 28.96% (3.16‐4.23GHz) and the 3 dB axial ratio bandwidth is 16.7% (3.18‐3.76GHz), meanwhile, the maximum simulated gain is 7.5 dBi, outside the working band, the gain of the antenna can be reduced 20 dBi compared by the maximum. The height of the antenna is 5.535 mm, 0.064λ at the center frequency of 3.5 GHz. After investigation and analysis, the antenna can be a good candidate for the 5G anti‐interference wireless and satellite base station communication system.

Exploiting AIS Data for Intelligent Maritime Navigation: A Comprehensive Survey From Data to Methodology

The automatic identification system (AIS) tracks vessel movement by means of electronic exchange of navigation data between vessels, with onboard transceiver, terrestrial, and/or satellite base stations. The gathered data contain a wealth of information useful for maritime safety, security, and efficiency. Because of the close relationship between data and methodology in marine data mining and the importance of both of them in marine intelligence research, this paper surveys AIS data sources and relevant aspects of navigation in which such data are or could be exploited for safety of seafaring, namely traffic anomaly detection, route estimation, collision prediction, and path planning.

The national broadband network: challenges and opportunities for telecommunications infrastructure planning

The National Broadband Network (NBN) is one of the largest infrastructure projects in Australia's history. NBN Co is currently rolling out the NBN network across Australia which includes a network of interconnected infrastructure such as optical fibre cables, street cabinets, exchange buildings, depots, wireless towers and satellite base stations. Some of this infrastructure is installed in accordance with the utilising NBN Co's powers under schedule 3 of the Telecommunication Act 1997 (Cth) (the Telco Act) in areas of environmental significance as defined in the Telco Act. In these areas NBN Co seeks exemptions or approvals under a range of federal, state and territory legislation. To assist in this process on a national scale NBN Co has developed a mapping tool that combines telecommunications infrastructure design, the location of construction activities and mapped areas of Heritage, Environmental and Cultural (HEC) considerations. This tool forms part of a systematic analysis of potential impacts enabling early identification of potential approval requirements. NBN Co also works with key approval authorities to identify opportunities to streamline approval requirements and identify possible exemptions. Further, the significant improvements and advances in telecommunications infrastructure and access arising from the NBN may be harnessed by the wider planning community in current and future development, plans and strategies as the NBN is expected to change how people live, learn and work.

Diversity performance of the intelligent quadrifilar helix 6 antenna in mobile satellite systems

An investigation, via measurement, is presented of the potential for using a quadrifilar helix antenna (QHA) as a diversity antenna within a mobile satellite communications environment where there is a non-line-of-sight (LOS) link between the satellite base station and the mobile. Received signals from the four elements of the QHA were collected at different sites, such that the effects of the presence of both buildings and trees were observed. Diversity gains of up to 14 dB relative to a standard QHA have been observed in areas where the signal is greatly shadowed. However, there is a penalty of up to 6 dB due to the noise from the extra receivers when using maximum ratio diversity combining within areas where the signals are not decorrelated, such as in LOS situations or in areas where there is little shadowing or multipath effect. A potential solution to the performance degradation in LOS situations is by applying complex weights to the signals and summing them prior to the receiver, rather than applying them after the receiver chain at baseband. However, there are complexity and cost penalties associated with this solution.