Radio Determination Satellite Service Research Articles

Heterogeneously Integrated Filtering Power Amplifier for Radio Determination Satellite Service

Heterogeneously Integrated Filtering Power Amplifier for Radio Determination Satellite Service

Safety Assessment for Full Flight between Beidou Radio Determination Satellite Service Airborne Equipment and 5G System

The Beidou Radio Determination Satellite Service (RDSS) is an advantageous service of the Beidou system. However, due to the weak landing power of Beidou RDSS signals and an operating frequency close to the 5G frequency, the system is vulnerable to interference from ground signals. In this paper, from the perspective of civil aviation safety, different evaluation indicators are used for the takeoff and cruise phases, respectively, to study the impact caused by adjacent frequency interference on airborne Beidou RDSS equipment. In the takeoff phase, accurate aircraft position information is obtained by processing real trajectory files. Deterministic analysis methods are used to determine the safety distance for the coexistence of the two systems. During the cruise phase, ground-based 5G base stations have less influence on the airborne RDSS receiver due to the high flight altitude, so the main consideration is electromagnetic compatibility between the airborne Beidou RDSS system and the 5G ATG system. By establishing a Boeing 737–800 simulation model, the antenna isolation degree is used as the evaluation index, and a reasonable antenna layout is given according to the evaluation results. In this study, the theoretical simulation and real flight data are combined to summarise the exact range of adjacent frequency influence during the takeoff phase and a reasonable antenna layout during the cruise phase.

BDS-3 RDSS two-way time transfer with asymmetric delay compensation model

In the BeiDou navigation satellite system-3 (BDS-3) radio determination satellite service (RDSS), there exists a natural two-way link between the center station and the user site that can be used to achieve time transfer. Traditionally, RDSS two-way time transfer is realized by analogy with the two-way satellite time and frequency transfer (TWSTFT) technique. However, unlike TWSTFT, the signal propagation delays are not completely symmetrical in the RDSS two-way link because of the differences in signal emission time. In this study, a model of two-way time transfer with BDS-3 RDSS is presented. An asymmetric delay compensation method is introduced to solve the asymmetry of RDSS signals and improve the accuracy of two-way time transfer. In addition, BDS-3 RDSS common clock difference experiments are designed to test the performance of two-way time transfer with an asymmetric delay compensation model. Based on analyses of the experimental results, three conclusions can be drawn. First, the accuracy of RDSS two-way time transfer is improved when the asymmetric delay compensation model is applied. Second, BDS-3 RDSS two-way time transfers in different in-station beams and subbands do not show many discrepancies on the whole, and the standard deviation values of the BDS-3 RDSS time transfer results range from 1.7 ns to 2.6 ns for the test signals. Third, the two-way time transfer results are not generally affected by receiver coordinate errors.

Preliminary Analysis and Evaluation of BDS-3 RDSS Timing Performance

Radio determination satellite service (RDSS) is one of the characteristic services of Beidou navigation satellite system (BDS), and also distinguishes with other GNSS systems. BDS-3 RDSS adopts new signals, which is compatible with BDS-2 RDSS signals in order to guarantee the services of old users. Moreover, the new signals also separate civil signals and military signals which are modulated on different carriers to improve their isolation and RDSS service performance. Timing is an important part of RDSS service, which has been widely used in the field of the power, transportation, marine and others. Therefore, the timing accuracy, availability and continuity is an important guarantee for RDSS service. This paper summarizes the principle of one-way and two-way timing, and provides the evaluation method of RDSS timing accuracy, availability and continuity. Based on BDS-3 RDSS signal measurements of system, the performance of one-way timing and two-way timing is analyzed and evaluated for the first time. The results show that: (1) the accuracy of one-way timing and two-way timing is better than 30 ns and 8 ns respectively, which are better than the official claimed accuracy; (2) the RMS of one-way timing accuracy is 5.45 ns, which is 20% smaller than BDS-2, and the availability and continuity are 100%; (3) the RMS of two-way timing accuracy is 3.59 ns, which is 34% smaller than one-way timing, and both of the availability and continuity are 100%; (4) the orbit maneuver of GEO satellite make the one-way timing has 7.68 h recovery, but has no affection on the two-way timing.

Featured services and performance of BDS-3

BeiDou Global Navigation Satellite System (BDS-3) not only performs the normal positioning, navigation and timing (PNT) functions, but also provides featured services, which are divided into geostationary orbit (GEO) and medium earth orbit (MEO) satellite-based featured services in this paper. The former refers to regional services consisting of the regional short message communication service (RSMCS), the radio determination satellite service (RDSS), the BDS satellite-based augmented service (BDSBAS) and the satellite-based precise point positioning service via B2b signal (B2b-PPP). The latter refers to global services consisting of the global short message communication service (GSMCS) and the MEO satellite-based search and rescue (MEOSAR) service. The focus of this paper is to describe these featured services and evaluate their performances. The results show that the inter-satellite link (ISL) contributes a lot to the accuracy improvement of orbit determination and time synchronization for the whole constellation. Compared with some other final products, the root mean squares (RMS) of the BDS-3 precise orbits and broadcast clock are 25.1 cm and 2.01 ns, respectively. The positioning accuracy of single frequency is better than 6 m, and that of the generalized RDSS is usually better than 12 m. For featured services, the success rates of RSMCS and GSMCS are better than 99.9% and 95.6%, respectively; the positioning accuracies of single and dual frequency BDSBAS are better than 3 and 2 m, respectively; the positioning accuracy of B2b-PPP is better than 0.6 m, and the convergence time is usually smaller than 30 min; the single station test shows that the success rate of MEOSAR is better than 99%. Due to the ISL realization in the BDS-3 constellation, the performance and capacities of the global featured services are improved significantly.

A new time delay calibration method to improve the service performance of RDSS in the BDS

The radio determination satellite service (RDSS) is an advantageous and unique aspect of the BeiDou Navigation Satellite System (BDS) because other satellite navigation systems do not incorporate the RDSS. Due to the ageing of RDSS equipment, there is a long-term drift in various types of RDSS equipment time delays. There are some differences in the RDSS positioning accuracy with the change in the out-station beams, which seriously affects the positioning accuracy and service capability of the RDSS system. At present, the time delay calibration method involves sending the device to the equipment verification field to remeasure the time delay, which is cumbersome and time-consuming. The service performance and availability of the RDSS system have become greatly degraded. Therefore, a simple and efficient RDSS time delay calibration method has become an important topic for the global BeiDou system. In this study, the time delays of all channels, in-station beams, and out-station beams were obtained by the O-C method (O is the measured value and C is the theoretical value). The experiments were performed using BeiDou RDSS data in continuous 8-day tests involving five RDSS users. The results showed that the time delay accuracies of the RDSS channels, in-station beams, and out-station beams were 2.37 ns, 1.63 ns, and 2.39 ns, respectively. The positioning tests were performed based on the original and adjusted delays. The mean horizontal positioning accuracy of the five RDSS users improved from 19.71 to 4.14 m, with an average increase of 77%. The positioning accuracy achieved in this paper is much better than that of 20 m in the Beijing calibration area at present.

Proposal of spread spectrum MSK for BDS RDSS signal modulation

BPSK is the basis of current GNSS (Global Navigation Satellite System) signals. BDS (Beidou navigation satellite system) RDSS (Radio Determination Satellite Service) system also adopts BPSK to realize communication and ranging simultaneously. To realize higher system capacity, RDSS signals overlap in time and frequency domain. The signal performance is heavily determined by the MAI (Multiple Access Interference) between overlapping signals. In this paper, SSMSK (spread spectrum MSK) is proposed. The signal performance is investigated under four conditions considering the main lobe bandwidth and the receiver bandwidth. The maximum number of overlapping signals for SSMSK is 11.7% higher than BPSK when the receiver bandwidth is for the side subcarrier. And the value is 10.6% when the receiver bandwidth is. SSMSK can be received utilizing BPSK local signal. When the receiving bandwidth is 2 R c , the correlation peak of SSMSK_BPSK is identical to BPSK. The tracking accuracy of SSMSK is higher than BPSK when the correlation interval is between 0.2-1 chips. The accuracy of SSMSK_BPSK is higher than BPSK when the correlation interval is 0.5 chips. The disadvantage of SSMSK is larger quantization word length. SSMSK is a better modulation for RDSS based on the comprehensive performance.

Research on BeiDou anti-spoofing technology based on comprehensive radio determination satellite service

The BeiDou system (BDS) plays a significant role in people’s lives, but its security is easily affected by spoofing attacks. The radio determination satellite service (RDSS) is a special service of BDS that provides two-way communication, positioning, and timing services independently of the traditional radio navigation satellite service (RNSS). It can additionally be combined with RNSS to provide a comprehensive RDSS (CRDSS) service. In RDSS, after receiving a signal from the master station, the user needs to send a response signal back to the master station through a satellite. Therefore, the RDSS signal is difficult to spoof. In this study, based on the security feature of RDSS signals, an anti-spoofing method based on CRDSS is proposed to detect and mitigate spoofing attacks, verifying the advantages of the BeiDou system over other satellite navigation systems.

A CMOS RF BeiDou-1 Transceiver for Regional Positioning and Short Message Service Applications

This paper presents a fully integrated CMOS radio-frequency (RF) transceiver for BeiDou-1, a radio determination satellite service system which can provide regional positioning and short message service. The proposed transceiver incorporates a low-IF receiver and a BPSK transmitter to realize a dual-way communication between users and the central control station via satellites. The receiver (RX) RF front-end down-converts the 2491.75 MHz RF signals to a 12.24 MHz IF band with a bandwidth of 8.16 MHz. The complex band-pass filter utilizes passive compensation technique to compensate the phase lag and achieve in-band flatness. The 4.08 Mchip/s baseband signal alternatively selects one of the differential 1615.68 MHz local signals to achieve BPSK modulation for the transmitter (TX). Besides, on-chip low dropout regulators adopt improved power supply rejection ratio techniques by integrating active filtering to obtain stable 1.5 V supply voltages. The transceiver is fabricated in a 130 nm CMOS technology and occupies an area of 5.88 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with electrostatic discharge circuitry and pads included. The RX channel achieves a 106 dB maximum voltage gain with a 65 dB dynamic range, a 4.95 dB noise figure and a 46 dB image rejection ratio. The output power for the TX ranges from -10 dBm to 5 dBm, with a phase error less than 1.5 degree.

Precise time and frequency transfer combined BeiDou\u2019s RDSS and RNSS signals

Unlike other satellite navigation systems such as GPS (Global Positioning System), the BeiDou satellite navigation system broadcasts RDSS (Radio Determination Satellite Service) and RNSS (Radio Navigation Satellite Service) signals simultaneously on its GEO (geostationary earth orbit) satellites and provides related navigation services. This paper studies the method of using the RDSS and RNSS signals of BeiDou to achieve accurate frequency and time transmission. We analyze the generation mechanism of RDSS signal and RNSS signal of BeiDou GEO satellite, establish a mathematical model of RDSS and RNSS signal frequency transfer, and derive an equation based on BeiDou’s RDSS and RNSS signals for accurate frequency and time transmission. We also verified the relevant performance of the method through computer simulation. The results show that the combination of RDSS and RNSS signals from the BeiDou satellite system provides a new solution for its application in precise time and frequency transmission. This method is different from other satellite navigation systems such as GPS and is unique to the BeiDou system, with high accuracy and low dependence on satellite orbit accuracy.

Acceleration Method for Software Signal Simulators of BDS Navigation Signals and RDSS Signals Based on GPGPU

General purpose graphics processing unit (GPGPU) has a great advantage in parallel computation, which is appropriate in the development of signal simulators for global navigation satellite system (GNSS) signals. Real-time software signal simulators for BeiDou navigation satellite system (BDS) signals, including navigation signals and radio determination satellite service (RDSS) signals, are developed in this paper. The characteristics of the continuous signal simulation and the burst signal simulation are considered in the development of GPU algorithms. The GPU algorithm optimization considers memory usage, signal combination method, and GPU block design under the goal of the least time consumption. To get the best GPU block design, a generalized block design model is built in this paper. The optimized GPU block parameters are got for the BDS B1 signal simulation and the RDSS signal simulation, separately. For the BDS B1 simulation, when the parameters are not optimized, the time consumption is more than three times of the optimized result. For the RDSS signal simulation, this value is 4.5 times. The correctness of the signals is verified in many aspects, including the power spectral density (PSD) and the pseudo range precision.

Improved design of control segment in BDS‐3

The Chinese BeiDou Navigation Satellite System (BDS) is accelerating its development and has been applied in various fields. Compared with other satellite navigation systems in the world, BDS has many unique features such as multiservices integrated with Radio Determination Satellite Service (RDSS), Radio Navigation Satellite Service (RNSS), and Satellite-Based Augmentation Service (SBAS), a mixed-orbit satellite constellation, and flexible navigation messages, etc. This paper presents the distinctive innovative designs as well as processing strategies in BDS. First, this paper introduces the characteristics of BeiDou navigation messages broadcast by the hybrid constellation of satellites in Geostationary Earth Orbit (GEO), Inclined Geo-Synchronization Orbit (IGSO), and Medium Earth Orbit (MEO). Next, the innovative design and operation of the control segment are discussed. Finally, highlights of the unique usage algorithm of the BDS navigation message information are presented, such as the BDS satellite clock correction and TGD parameters, satellite ephemeris and almanac, and ionospheric delay parameters.

Timing performance evaluation of Radio Determination Satellite Service (RDSS) for Beidou system

Radio Determination Satellite Service (RDSS) is the advantage and particular characteristics of Beidou, which is different from other satellite navigation systems. According to the rare existing researches of its timing service, this article evaluates timing performance of one-way and two-way using the time series analysis method. Moreover, this paper systematically studies the one-way timing and two-way timing principle and introduces Beidou measured data and analysis method. By analyzing the clock error total curve, the mean value segment, noise situation and timing accuracy, we have the conclusions: (1) one-way timing accuracy is less than 30 ns, and its Root Mean Square (RMS) is less than 6.81 ns; (2) two-way timing accuracy is less than 20 ns, and its Root Mean Square (RMS) is less than 3.60 ns; (3) there exist period switching phenomenon of timing data of one-way and two-way in each beam, and stratification of one-way timing data. These conclusions can be used for the difference compensation of Radio Determination Satellite Service (RDSS), which can provide reference for the clock error consistency of Beidou system, and then improve the system service precision.

A substitute for BOC modulation based on SS-CPM

CPM (continuous phase modulation) has been widely used in the field of satellite communication, which has high spectrum efficiency and constant envelope. This paper explores the applicability of CPM to satellite navigation. A SS-CPM (Spread-Spectrum CPM) modulation is investigated. The SS-CPM with tuned parameters can resemble the spectrum of Binary Offset Carrier (BOC) modulation and yields comparable performance in terms of tracking accuracy, multipath mitigation, anti-jamming, and compatibility. The BOC-like SS-CPM signal maintains the constant envelope at transmission and less out-band emission in radio determination satellite service (RDSS) band, which provides a reference modulation for COMPASS satellite navigation signal.

Improvement of orbit determination for geostationary satellites with VLBI tracking

China’s COMPASS satellite navigation system consists of five or more geostationary (GEO) satellites. The roles of GEO satellites are to improve the regional user’s positioning accuracy and provide the continuous Radio Determination Satellite Service. The motion of GEO satellites relative to a ground tracking station is almost fixed, and regular orbit maneuvers are necessary to maintain the satellites’ allocated positions above the equator. These features present difficulties in precise orbit determination (POD). C-band ranging via onboard transponders and the L-band pseudo-ranging technique have been used in the COMPASS system. This paper introduces VLBI tracking, which has been successfully employed in the Chinese lunar exploration programs Chang’E-1 and Chang’E-2, to the POD of GEO satellites. In contrast to ranging, which measures distances between a GEO satellite and an observer, VLBI is an angular measurement technique that constrains the satellite’s position errors perpendicular to the satellite-to-observer direction. As a demonstration, the Chinese VLBI Network organized a tracking and orbit-determination experiment for a GEO navigation satellite lasting 24 h. This paper uses the VLBI delay and delay-rate data, in combination with C-band ranging data, to determine the GEO satellite’s orbit. The accuracies of the VLBI delay and delay rate data are about 3.6 ns and 0.4 ps/s, respectively. Data analysis shows that the VLBI data are able to calibrate systematic errors of the C-band ranging data, and the combination of the two observations improves orbit prediction accuracy with short-arc data, which is important for orbital recovery after maneuvers of GEO satellites. With the implementation of VLBI2010, it is possible for VLBI to be applied in the COMPASS satellite navigation system.

BeiDou Navigation Satellite System and its time scales

The development and current status of BeiDou Navigation Satellite System are briefly introduced. The definition and realization of the system time scales are described in detail. The BeiDou system time (BDT) is an internal and continuous time scale without leap seconds. It is maintained by the time and frequency system of the master station. The frequency accuracy of BDT is superior to 2 × 10−14 and its stability is better than 6 × 10−15/30 days. The satellite synchronization is realized by a two-way time transfer between the uplink stations and the satellite. The measurement uncertainty of satellite clock offsets is less than 2 ns. The BeiDou System has three modes of time services: radio determination satellite service (RDSS) one-way, RDSS two-way and radio navigation satellite service (RNSS) one-way. The uncertainty of the one-way time service is designed to be less than 50 ns, and that of the two-way time service is less than 10 ns. Finally, some coordinate tactics of UTC from the viewpoint of global navigation satellite systems (GNSS) are discussed. It would be helpful to stop the leap second, from our viewpoint, but to keep the UTC name, the continuity and the coordinate function unchanged.

Intelligent SINS/RDSS integrated algorithms for land vehicle navigation

This is a discussion of the design of strap-down inertial navigation systems (SINS) and radio determination satellite service (RDSS) integrated navigation algorithms. The research aims at testing the effectiveness of artificial intelligence (AI)-aided Kalman filtering (KF) approaches for land vehicle applications. A back-propagation neural network (BPNN)-aided K*F algorithm and a fuzzy inference-based KF algorithm are presented in order to overcome the time delay of RDSS positioning provided by a double-star positioning system in China. Traditional KF causes biased solutions, and indeed, leads to filter instability easily since the time delay of RDSS positioning, in an active mode, is hard to be modeled and sometimes suffers from RDSS outages. Therefore, a fuzzy inference is used to correct the variance matrix of KE measurement noises adaptively; and a trained BPNN corrects the outputs of the Kalman filter. The algorithms proposed herein have been verified on real SINSIRDSS data. collected in land vehicle tests and are compared with other approaches. The results demonstrate that fuzzy inference-based KF algorithms improve the positioning accuracy to over 40 % better than KF algorithms, and BPNN-aided KF algorithms have the same precision as GPS which is the reference station In dynamic experiments without RDSS outages. The test results with RDSS outages indicate that the fuzzy inference-based KF is feasible but with positioning errors of hundreds of meters, so the BPNN-aided KF is designed to efficiently compensate for RDSS outages and improve system performance.

Study on a Method of Calculating the Ionosphere TEC Using RDSS System Observation Data

提出了一种基于无线测定卫星业务(RDSS)系统观测数据提取电离层TEC参数的方法,利用此方法计算分析了2006年5月地面中心地区电离层垂向TEC的日变化趋势.研究结果表明,利用RDSS系统观测数据提取的电离层垂向TEC,在北京时间每日凌晨0400时左右达到最小值,在午后1400时左右达到最大值,符合电离层TEC参数受太阳活动影响较大的物理规律.结果说明研究方法是可行且有效的,文章还对可能存在的误差进行了探讨.

The proposal about constructing the National Disaster Monitoring, Forecast and Control System

It is known that different kinds of natural disaster cause big loss in people's lives and damage in properties every year in many countries, and the monitoring, forecast and control to prevent as mitigate the harm is very important indeed. Some kinds of disasters might be foreseen and the developing trend may be understood from the observation facilities under management of professional department. Here we suggest that the existing domestic and foreign monitoring systems, especially the space systems already in use, should be utilized for disaster mitigation purpose before some new system being developed specially for it. The information collection part of the Disaster Monitoring, Forecast and Control System (DMFCS) may be composed of three layers of sensing implements, the earth observing satellites, the remote sensing airplanes and the local ground sensing instruments whose data could be sent to the centers concerned through the data collcetion system (DCS) of various kinds of satellits. In coordination with the monitoring systems, the position fixing satellite system, the Global Positioning System (GPS/GLONASS) or the Radiodetermination Satellite Service (RDSS) which in China was named the Bisatellite Position Determination System (BPDS) under developing is also indispensable. In DMFCS the nucleus is the Control Center (DMFCC). It is connected with the centers of the existing professional organizations and the Regional Disaster Control Centers (RDCC). In this paper we pay more attention to the construction of DMFCC. The center should be led by the department particularly concerned with disaster prevention, preparedness and relief (as it has been announced by the United Nations). The Centers will fully utilize the real time information from the monitoring means and the information stored in the data base to display the state of the disasters, to help the decision of the department leader to issue instructions to the Regional Centers to take measures for controlling, rescue and salvation. It is also pointed out that the fundamental research works are necessary for the study of the cause, prediction and the social effect of natural disasters and the accumulation of data is important for further use too.

Coordination Between the Radioastronomy Service and the Radiodetermination Satellite Service in the 1612 MHZ Band

The Radiodetermination Satellite Service (RDSS) provides radiolocation and limited communication for users of aeronautical, marine and terrestrial vehicles. A system of the RDSS is being developed in the United States by the Geostar Corporation (Rothblatt, 1988). In this system signals from a control center are transmitted to transceivers on users’ vehicles through one of a series of two or three satellites spaced along the geostationary orbit, and responses are received through each of these satellites. If three satellites are used, locations of vehicles can be determined from the measured times of transmission from the control center to the user and back via different satellite paths. If two satellites are used the timing data must be supplemented by information such as altitude data from a terrain map, or an altimeter reading from the user’s vehicle, which can be encoded in the response transmitted back. Computation of the vehicle location is performed at the control center. The equipment at the vehicle can be relatively simple since its basic function is that of a transponder, and intervention by the vehicle operator is not necessarily required. However, provision can also be made for the inclusion of short coded messages from the vehicle, so the unit on the vehicle is usually referred to as a transceiver. The system is designed to meet the needs of various users; for example, trucking companies which must periodically monitor the locations of vehicles in a widely distributed fleet. Position information can be relayed to the company headquarters as well as to the vehicle operator. The role played by the central control computer in determining the locations requires that all vehicles using the service identify themselves by a transmitted code. Thus developers and operators of RDSS systems can lease their services to vehicle users.