Short Message Communication Research Articles

The In-Flight Realtime Trigger and Localization Software of GECAM

Realtime trigger and localization of bursts are the key functions of GECAM, an all-sky gamma-ray monitor launched on 2020 December 10. We developed a multifunctional trigger and localization software operating in the CPU of the GECAM Electronic Box. This onboard software has the following features: high trigger efficiency for real celestial bursts with a suppression of false triggers caused by charged particle bursts and background fluctuation, dedicated localization algorithm optimized for both short and long bursts, and low time latency of the trigger information which is downlinked through the Global Short Message Communication service of the global BeiDou navigation system. This paper provides a detailed description of the design and development of the trigger and localization software system for GECAM. It covers the general design, workflow, the main functions, and the algorithms used in the system. The paper also includes on-ground trigger tests using simulated gamma-ray bursts generated by a dedicated X-ray tube, as well as an overview of the performance for real celestial bursts during its in-orbit operation.

A new PPP one-way timing approach via BDS-3 PPP-B2b and short-message communication service

In the realm of time-frequency, precise point positioning (PPP) technology has been widely used, the current PPP time transfer or timing necessitates network communication for data transmission, which consequently leads to a reduction in the reliability of PPP timing. Based on the BDS-3 PPP service (PPP-B2b) and the global short message communication (GSMC) service, this study proposes a novel PPP one-way timing method that is not subject to distance limitations or the requirements of network communication. Users can directly obtain the difference with UTC(k). Then, the proposed PPP timing method was validated using four stations equipped with external high-performance atomic clocks, based on a dataset of eight days. According to the findings, the suggested PPP one-way timing technique might reach a timing accuracy of roughly 0.5 ns in environments without a network. In terms of frequency stability, the proposed PPP timing method exhibits a stability of approximately 1.4 × 10−13 at 960 s and a stability of about 3 × 10−14 at 15360 s. Further, even under GSMC communication delays of 1 min, 5 min, and 10 min, the proposed PPP one-way timing accuracy can still achieve better than 0.5 ns.

The GECAM Real-Time Burst Alert System

Abstract Gravitational Wave High-energy Electromagnetic Counterpart All-sky Monitor (GECAM), consisting of two micro-satellites, is designed to detect gamma-ray bursts associated with gravitational-wave events. Here, we introduce the real-time burst alert system of GECAM, with the adoption of the BeiDou-3 short message communication service. We present the post-trigger operations, the detailed ground-based analysis, and the performance of the system. In the first year of the in-flight operation, GECAM was triggered by 42 GRBs. GECAM real-time burst alert system has the ability to distribute the alert within ∼1 minute after being triggered, which enables timely follow-up observations.

Research on a Vehicle-Mounted Emergency Communication System Using BeiDou Regional Short Message Communication (RSMC) for Firefighting Operations in Forest Areas without a Public Network

The low coverage of public networks in pristine forest areas prevents on-site firefighters from communicating directly with remote command centers during forest fires, reducing firefighting efficiency. In this study, we designed a vehicle-mounted emergency communication system Using BeiDou RSMC (Regional Short Message Communication) for firefighting operations in forest areas without a public network to establish a satellite communication network and Zigbee self-organizing network technology to establish a local self-organizing network. Beidou RSMC is a satellite communication service developed and operated independently by China, and its signals now cover the entire globe. The combination of these two components ensures emergency communication in the event of a fire in a forest area without public network coverage. The performance of the system was tested by simulating a fire, and it was able to establish a reliable communication link between the firefighters on the scene and the remote command center in the absence of a public network. The proposed system solves the emergency communication problem that arises when a fire occurs in a forest area without a public network, enabling the remote command center to monitor fire information and dispatch various resources in real time, thereby improving firefighting efficiency and reducing casualties.

An Efficient Lossless Compression Algorithm for Maritime Safety Information Using Byte Encoding Network

The short message function of the BeiDou satellite system, due to its strong concurrent processing capabilities, can quickly and accurately send information to the target location in emergency situations. However, because of data redundancy and limitations on message length, a single piece of information often requires multiple transmissions through BeiDou short messages to be completed, resulting in limited transmission capacity. To improve the transmission capacity of information, it is necessary to compress the information during transmission using BeiDou’s short message communication function for maritime safety information. This paper proposes a Byte Encoding-enhanced Prediction by Partial Matching, variant D (BPPMd) algorithm that is particularly suitable for transmitting maritime safety information. Combined with a maritime safety information encoding algorithm (ME), it further improves compression efficiency, optimizes byte space, reduces information redundancy, and ensures the accuracy of the information. In this study, we constructed a maritime safety information dataset that includes three categories of information: meteorological warnings, navigation warnings, and disaster warnings. Experimental results show that the proposed algorithm is particularly suitable for compressing the maritime safety information dataset and outperforms other benchmark algorithms. Therefore, this study indicates that the proposed lossless compression method can be a feasible and effective solution for BeiDou short message communication.

An Attention-Averaging-Based Compression Algorithm for Real-Time Transmission of Ship Data via Beidou Navigation System

The real-time transmission of ship status data from vessels to shore is crucial for live status monitoring and guidance. Traditional reliance on expensive maritime satellite systems for this purpose is being reconsidered with the emergence of the global short message communication service offered by the BeiDou-3 navigation satellite system. While this system presents a more cost-effective solution, its bandwidth is notably insufficient for handling real-time ship status data. This inadequacy necessitates the compression of such data. Therefore, this paper introduces an algorithm tailored for real-time compression of sequential ship status data. The algorithm is engineered to ensure both accuracy and the preservation of valid data range integrity. Our methodology integrates quantization, predictive coding employing an attention-averaging-based predictor, and arithmetic coding. This combined approach facilitates the transmission of succinct messages through the BeiDou Navigation System, enabling the live monitoring of ocean-going vessels. Experimental trials conducted with authentic data obtained from ship monitoring systems validate the efficiency of our approach. The achieved compression rates closely approximate theoretical minimum values. Consequently, this method exhibits substantial promise for the real-time transmission of parameters across various systems.

Ocean decimeter-level real-time BDS precise point positioning based on short message communication

Ocean decimeter-level real-time BDS precise point positioning based on short message communication

Reliable transmission technology of spaceborne remote sensing data based on BeiDou short message communication

Reliable transmission technology of spaceborne remote sensing data based on BeiDou short message communication

An Efficient Dual-Stage Compression Model for Maritime Safety Information Based on BeiDou Short-Message Communication

In the context of utilizing BeiDou short-message communication (SMC) for transmitting maritime safety information, challenges arise regarding information redundancy and limited message length. To address these issues, compressing the data content of SMC becomes essential. This paper proposes a dual-stage compression model based on Beidou SMC for compressing maritime safety information, aiming to achieve efficient compression and reduce information redundancy. In the first stage, a binary encoding method (MBE) specifically designed for maritime safety information is proposed to optimize the byte space of the short messages, ensuring the accuracy, integrity, and reliability of the information. In the second stage, we propose a data compression algorithm called XH based on a hash dictionary, which efficiently compresses maritime safety information and reduces information redundancy. Different maritime data have corresponding structures and compositions, which can have a significant impact on the evaluation of compression algorithms. We create a database considering six categories of objects: waves, sea ice, tsunamis, storms, weather, and navigation warnings. Experimental results demonstrate that the proposed model achieves significant compression efficiency and performance on the maritime safety data set, outperforming other benchmark algorithms.

Maintaining real-time precise point positioning during outages of the corrections broadcast by BDS-3 global short-message communication

Real-time precise point positioning (RTPPP) is a popular technique for precision applications, which is based on real-time service (RTS) products. However, one serious problem for RTPPP users is the potential communication break for a period from a few minutes to an hour. A significant decline in positioning accuracy may occur since the receiving of the RTS corrections is discontinuous. In this study, the real-time orbit and clock corrections are converted into the equivalent range corrections and broadcast by BeiDou global navigation satellite system (BDS-3) global short-message communication (GSMC). We focus on maintaining global navigation satellite systems (GNSS) RTPPP during outages of the range corrections. Three prediction methods are presented, including “linear function”, “mean value” and “last value” methods. The predicted corrections will be carried out with only at most 5 latest epochs of the registered corrections. The “last value” method shows the optimal prediction performance and the prediction errors of Galileo are minimal compared to GPS and BDS. Both simulated and vehicle kinematic experiments are conducted to evaluate the performance of RTPPP with the predicted corrections. The results show that the three proposed predicted corrections can maintain centimeter-to decimeter-level accuracy in both static and kinematic mode during outages of the BDS-3 GSMC that may be from a few minutes to an hour. Using the last registered equivalent range correction value is the most recommended choice to maintain multi-GNSS RTPPP.

Real-time multi-GNSS precise point positioning with ambiguity resolution based on the BDS-3 global short-message communication function

Real-time multi-GNSS precise point positioning with ambiguity resolution based on the BDS-3 global short-message communication function

Design of Lithium Battery Monitoring System Based on GPRS Short Message Communication

The lithium battery in the new energy system works in the wilderness environment, and its data remote monitoring is often realized based on wireless communication, and this transmission method needs to set up exclusive base stations, which is costly. General Packet Radio Service (GPRS) short message communication realizes data transmission through satellite without setting up base stations. Based on the above situation, a lithium battery monitoring system based on GPRS short message communication is designed, and the system consists of monitoring terminal, GPRS receiver, and remote monitoring cloud platform. For the software and hardware requirements of data acquisition, data monitoring and GPRS short message communication, the corresponding design ideas and implementation scheme are given. Meanwhile, considering the impact of wilderness environment on satellite communication, a transmission error control method based on data backup is proposed to improve its transmission reliability. Finally, through practical testing, it is verified that the system can effectively transmit monitoring data and locate lithium batteries, and maintenance personnel can monitor data in real time through the cloud platform to reduce the construction and maintenance costs of remote monitoring.

Integrated Navigation and Communication Service for LEO Satellites Based on BDS-3 Global Short Message Communication

Massive global Low Earth Orbit (LEO) constellations have been developed rapidly with the characteristics of larger number and shorter orbital periods of LEO satellites in recent years. The increasing requirements of real-time orbit determination and emergency data transfer in full arc can hardly meet the traditional strategies based on regional ground stations. An integrated communication and navigation service architecture based on the third phase of the BeiDou system (BDS-3) Global Short Message Communication (GSMC) is proposed, which enables global coverage and random access. The GSMC downlink single-frequency signal is used for real-time orbit determination, and is further combined with B1C navigation signal for real-time dual-frequency high-precision orbit determination. Considering fast moving of LEO satellites and short burst of uplink messages, the uplink BDS-3 satellite selection strategy based on carrier-to-noise ratio, and uplink high-precision compensation of frequency shift are adopted to increase the communication success rate. The service architecture proposed can improve the precision of the autonomous orbit determination and enhance the capability of real-time command transmission of LEO satellites even without the traditional ground stations involved. Integrated communication and navigation service has been validated by simulation and on-board BDS-3 GSMC test data. The precision of single-frequency real-time orbit determination can reach 2.86m, and the precision of dual-frequency can reach 0.26m. The average time delay of communication is about 11.45s, and the success rate is about 99.8%. The method may provide alternative means of real-time high-precision orbit determination and emergency data transfer of LEO satellites.

Requirement-Oriented TT&C Method for Satellite Based on BDS-3 Short-Message Communication System

With the increasing number of satellites being launched in China, the demand for Telemetry, Tracking, and Command (TT&C) resources is also increasing. Because of the global coverage and resource requirements of TT&C management, this paper proposes a TT&C scheme based on the Global Short-Message Communication System (GSMCS) of the BeiDou-3 Navigation Satellite System (BDS-3). The system composition, workflow, and functions of satellite TT&C are analyzed using the GSMCS of BDS-3. Through the coverage analysis of the Medium Earth Orbit (MEO) constellation of BDS-3, scheme’s applicability is pointed out, and the correctness of the analysis results is verified via simulation. The value range of the link distance is derived by calculating the range of the distance variation between any 2 satellites in the BDS-3 MEO constellation and combining the intersatellite routing scheme. The calculation results show that the response time range of the autonomous request management application of in-orbit satellites based on the GSMCS of BDS-3 is 1.407 to 2.448 s. This can meet the requirements of TT&C service.

CGAN BeiDou Satellite Short-Message-Encryption Scheme Using Ship PVT

The transmission standard and format of short-message communication in the BeiDou satellite-navigation-system are open, the civilian channel adopts a direct-transmission plaintext mechanism, and the content of short messages is at risk of data leaks. Aiming at addressing the problem of safely transmitting BeiDou short messages, this study proposes a CGAN BeiDou satellite short-message-encryption scheme, using ship PVT (position, speed, and time). Various BeiDou commands with ship position, speed, or time are employed as the input. The two communicating parties use the CGAN (conditional generative adversarial network) confrontation mechanism to encrypt and decrypt the ship-PVT information and generate a symmetrically encrypted key, while the receiver parses only the sender data within the specified PVT-range. Additionally, because the BeiDou system has a positioning error and transmission delay, and considering the ship mobility, the concept of a dynamic tolerance region is introduced at the receiver, to improve the scheme’s decryption success-rate. Finally, the proposed scheme is verified, using simulation and experiments. The proposed algorithm achieves good security, with acceptable efficiency. Furthermore, the experimental platform built by this study is used to prove the feasibility of the scheme applied to BeiDou short-message encryption and decryption.

Reliable design of communication link for power emergency vehicle mobile station based on Beidou satellite

In order to establish a reliable power emergency communication network and speed up the efficiency of power rescue, a vehicle-mounted reliable communication link based on Beidou short message protocol is designed. Aiming at the unreliability of Beidou short message communication and the limitation of communication capacity, the enhanced data handshake mechanism is adopted to enhance the reliability of data transmission, and the multi-card cooperative transmission mechanism is adopted to improve the efficiency of data transmission. The example results show that the transmission success rate of the proposed reliable communication link is significantly higher than that of the traditional method, which can improve the reliability of mobile station data transmission and provide communication guarantee for power recovery.

Polar Code Based on Nested Rate Adaptation Sequence for BDS-3 Regional Short Message Communication

Polar Code Based on Nested Rate Adaptation Sequence for BDS-3 Regional Short Message Communication

New Orbit Determination Method for GEO Satellites Based on BeiDou Short-Message Communication Ranging

The radio determination service system (RDSS), a navigation and positioning system independently developed by China, features services such as short-message communication, position reporting, and international search and rescue. The L-band pseudo-range and phase data are the primary data sources in precise orbit determination (POD) for geostationary Earth orbit (GEO) satellite in the BeiDou system, especially in the orbit manoeuvre period. These data are the only data sources in the POD for GEOs. However, when the pseudo-range and phase data is abnormal due to unforeseen reasons, such as satellite hardware failure or monitoring receiver abnormalities, the data abnormality leads to orbit determination abnormalities or even failures for GEOs, then the service performance and availability of the RDSS system are greatly degraded. Therefore, a new POD method for GEOs based on BeiDou short-message communication ranging data has gained research attention to improve the service reliability of the BeiDou navigation satellite system (BDS)-3, realising the deep integration of communication and navigation services of the BDS. This problem has not been addressed so far. Therefore, in this study, a new POD method for GEO satellites is investigated using high-precision satellite laser ranging (SLR) data and RDSS data. The SLR data are used as the benchmark to calibrate the time delay value of RDSS equipment, and RDSS data are only used in the orbit determination process by fixing the corrected RDSS time delay value, and the satellite orbit parameters and dynamic parameters are solved. Experimental analysis is conducted using the measured SLR and RDSS data of the BDS, and the orbit accuracy in this paper is evaluated by the precise ephemeris of the Multi-GNSS pilot project (MGEX) and SLR data. The results show that the orbit accuracy in the orbital arc and the 2-h orbital prediction arc for GEOs are 6.01 m and 6.99 m, respectively, compared with the ephemeris of MGEX, and the short-arc orbit accuracy after 4 h of manoeuvring is 11.11 m. The orbit accuracy in the radial component by SLR data is 0.54 m. The required orbit accuracy for GEO satellites in the RDSS service of the BDS-3 is 15 m. The orbit accuracy achieved in this paper is superior to that of this technical index. This method expands the application field of the RDSS data and greatly enriches the POD method for GEOs. It can be adopted as a backup technology for the POD method for GEOs based on RNSS data, significantly improving the service reliability of the BeiDou RDSS service.

Real-time precise point positioning based on BDS-3 global short message communication

Real-time precise point positioning based on BDS-3 global short message communication

Multi-GNSS real-time precise point positioning using BDS-3 global short-message communication to broadcast corrections

Multi-GNSS real-time precise point positioning using BDS-3 global short-message communication to broadcast corrections