Direct-to-smartphone, as a potential technological means for achieving the integration of space and ground in the future, has received widespread attention from industry and academia.Compared with traditional satellite mobile communication, there are many challenges in the current direct-to-smartphone technology.The current development status and system architecture of two direct-to-smartphone technology routes based on synchronous orbit satellites and asynchronous orbit satellites were introduced, and the technical challenges from the air-interface side, satellite side, network side, and terminal side were summarized.Several solutions were proposed, included satellite-terrestrial synchronization, satellite-borne ultra-large array antenna, and satellite-terrestrial heterogeneous network roaming, providing technical support for the development of direct-to-smartphone technology.Finally, a brief outlook were provided.

The LEO satellite network become a powerful complement to the terrestrial network as it shows the advantage of low latency, low cost, low loss rate and global coverage.However, due to the uneven distribution of users and the variation of network traffic over time, some links may be congested and unbalanced.A load balancing routing algorithm based on genetic optimization and artificial bee colony in LEO satellite networks(GABC) was proposed, which combined genetic algorithm with artificial bee colony algorithm to avoid local optimization.Experimental results showed that compared with the shortest path routing and LBRA-CP algorithm, the proposed algorithm has higher data transmission rate and throughput with lower delay and overhead ratio.

The management of the satellite-terrestrial integrated network targeting giant constellations and large-scale networks, requires the comprehensive management of heterogeneous infrastructure, layered stereoscopic network, cross domain multi-dimensional resources, customized business services, the collaboration and efficiency of management directly affect the service capability of the network.Based on the concept of network as its essence and collaboration between satellites and networks, this paper explored the collaborative manage mechanism of constellation, network, and business, proposed the overall architecture of satellite-terrestrial integrated network management, designed the manage center function in detail, planed typical operational management processes, and analyzed its applicability in the management of giant constellations in orbit and large-scale cross domain network management.This paper provided technical support for the construction and operation management of the satellite-terrestrial integrated network.

In the space-air-ground integrated network, resources are unevenly distributed and dynamically change over time.Traditional optimization scheduling methods based on static resource representation only optimize scheduling within a single time slot, leading to low resource utilization.Moreover, frequent strategy adjustments are required when the network changes, resulting in significant migration costs.To address this issue, this paper proposed a method for spatiotemporal correlation representation of resources in the space-air-ground integrated network.This method computed node attention representations in both structural neighborhoods and chronological neighborhoods, enabled precise modeling of spatiotemporal resource correlations in the space-air-ground integrated network.Based on this, this paper proposed a resource precise embedding method based on spatiotemporal correlation representation, and introduced the trust region policy optimization method to adaptively learn and optimize algorithm parameters.

The large number of network elements in the mega-constellations pose a severe challenge to the existing network architecture and technical system.Based on the concept and characteristics of constellation architecture, combined with the development of domestic and foreign satellite constellations and technology prediction, a multi-layer and multi-domain hybrid intelligent cooperative network architecture was proposed, which consist of four layers (perception plane, data plane, control plane, intelligent management plane) and three layers (resource layer, transport layer, service layer) , the architecture of constellation network management and control, technology reference model and protocol architecture were designed.At the same time, accorded to the construction and development trend of constellation, this paper expounded and analyzed the evolution trend of the key technologies, such as constellation network addressing and routing, network robust agile guarantee, differentiated service bearing, end-to-end reliable transmission, etc.The research results could support the development and construction of LEO giant constellation network in our country.

At present, the frequency of non-geostationary orbit(NGSO) mobile satellite service is becoming more and more tense.Aimed at the complicated problem of frequency coordination of mobile direct connection to NGSO satellite service, firstly, an analysis was conducted on the current frequency usage status and trends of mobile direct connection to NGSO satellite service.Secondly, the frequency coordination scheme between mobile direct connection to NGSO satellite service and other same frequency space services in extended L-band was analyzed and studied.By analyzed the frequency coordination of mobile direct connection to NGSO satellite service in extended L-band, the space services that need to carry out frequency coordination work with mobile direct connection to NGSO satellite service were determined.The basic frequency coordination scheme of mobile direct connection to NGSO satellite service with each space service was studied and the coordination scheme suggestions were given, at the same time, the interference analysis and calculation involved in the specific coordination scheme were listed for example.The above research can be used as reference for the research of frequency coordination of mobile direct connection to NGSO satellite service system, as well as for the next step research of key technologies related to mobile direct connection to NGSO satellite service.

With the deepening of the support of remote sensing satellites for all kinds of applications, the external environment faced by satellite mission planning system is complex and changeable, such as satellite orbit adjustment, sudden failure in orbit, random arrival of tasks, changes in imaging conditions, etc., and the randomness of emergency events is greatly improved.The traditional periodic centralized mission planning framework is gradually unable to meet the requirements of high timeliness and high response.By analyzed the types and changing rules of the external environment of the system, the task planning framework of segmented sub-strategy adjustment was designed, as well as the corresponding scheduling strategy and object state management mechanism, and the efficient response ability to emergency emergencies was realized.The technical framework was adopted in a remote satellite mission management and control system project and the corresponding software was developed.The actual operation results of the system showed that the technical framework of mission planning with segmented strategy proposed in this paper basically met the requirements of high adaptability and high response caused by dynamic changes of external environment, and greatly improved the automation degree and timeliness index of the system.

A mission planning algorithm based on genetic algorithm was designed for LEO satellite IoT constellation with no inter-satellite links, aimed to achieve real-time data communication through multiple ground stations while maximized the resource allocation of satellites and ground stations.Firstly, the objective function to maximized the service duration of satellites in orbit and the constraints on clashed tasks were designed, constructed the mission planning model for LEO satellite IoT constellation.Then, based on genetic algorithm, clashed tasks and early stopping mechanism were introduced, and the mission planning algorithm for the LEO satellite IoT constellation was designed.On this basis, experiments were conducted use a constellation of 18 LEO communication satellites without inter-satellite links and 4 ground stations.In addition, in order to verified the performance of the algorithm, first come first service (FCFS) algorithm was also used for mission planning of the experimental data.The experiments compared with FCFS showed that the designed mission planning algorithm for LEO satellite IoT constellation could significantly improve the scheduling capacity of ground stations for receiving data of communication satellites, addressed the contradiction of insufficient ground stations with a large number of satellites.

Remote sensing systems are important means of space-based Earth observation, due to issues such as delayed measurement and control commands, data transmission, data processing, and product distribution in the ＆quot;collection-processing-distribution＆quot; process, it is difficult to effectively achieve real-time intelligent remote sensing application services that cover all day, all weather, and the world.The combination of low earth orbit communication and remote sensing satellite constellations is an effective way to solve service delay and separate control problems in existing systems.It summarized the current situation of communication and remote sensing integration over the world, and then imagined the architecture, development stages, and service modes of the integration of communication and remote sensing.Finally, key technologies under the communication and remote sensing integration architecture were proposed, and the application process of communication and remote sensing integration used typical application scenarios were explored.

The paper initially provided a brief comparison of the direct-to-satellite solution of three LEO satellite communication companies: Starlink, AST SpaceMobile and Lynk Global.While Starlink has successfully conducted with SMS, Voice and Data service test, AST SpaceMobile and Lynk Global have not made significant progress.Although all are in early stages, their technological paths demonstrate the future trends of direct-to-satellite communication.Focused on Starlink's success, the paper analyzed its business model and explored the primary technological pathways for future integration of space, air and ground telecommunication systems, which was a hot topic in the industry.Based on publicly available information about Starlink, the paper utilized the business model canvas theory to delved into its direct-to-satellite service, detailing aspects like core value, key resources, customer segments, cost structure, customer relations, key partnership, and revenue streams.It then discussed Starlink's network architecture strategies, compared and analyzed the self-built core network and shared core network approaches, ultimately inferring the most viable network technology solution for Starlink.

This article proposed a fusion and innovative solution - a dual-mode communication terminal, which integrated the advantages of low-orbit satellite communications and terrestrial wireless self-organizing networks to provide flexible communication solutions.The terminal could obtain cluster routing in real time and autonomously switch between satellite channels and ground ad hoc network channels, reduced the pressure on satellite Internet space and ground transmission channels and realized diversified communication needs.Within the self-organizing network, the terminal used the terrestrial wireless self-organizing network to transmit information, established user clusters and maintain routes.When exceeded the boundary of the self-organizing network, the terminal automatically switched to satellite communication mode and maintained the network.This technology is expected to meet the communication needs of various scenarios, including emergency response and rapid on-site deployment.