International Journal of Satellite Communications and Networking最新文献

The beam-hopping technology can solve the problems of uneven user distribution and uneven service demand and improve the efficiency of resource utilization. It is one of the important technologies of future satellite–ground integrated communication. However, the mobility of LEO satellites and the on-demand scheduling of beams make each satellite beam correspond to multiple ground wave positions, which brings great difficulties to data processing. In this paper, after analyzing the difficulties of the data forwarding buffer of the beam-hopping system, a double-linked list structure of user state chain and data buffer chain is proposed, which solves the problem of data forwarding between the satellite and users in the dynamic state and provides an efficient solution for the data exchange of the beam-hopping LEO satellite.

The rapid development of satellite internet networks has given rise to a new vision for the sixth generation of networking technology. However, the Doppler effect is relatively serious in satellite internet networks because a satellite moves quickly relative to a ground terminal. Therefore, there is an urgent need to study intelligent and dynamic synchronization methods to solve the problem of the rapidly changing Doppler frequency offset. Traditional methods do not consider the impact of spatial changes and typically focus on enhancing the estimation range or accuracy. We analyze various scenarios under phased array beam hopping and establish constraints between the terminal location, satellite ephemeris, subsatellite point track, elevation angle, and carrier frequency offset. We introduce dynamic game theory into frequency synchronization to optimize multiple Doppler estimation performance under rapidly changing channel conditions. We take the combination of carrier frequency offset estimation algorithm strategies at the current moment as the game entity. Simulation results demonstrate that the proposed method can achieve an estimation accuracy of 100 Hz and an estimation range of ±800 kHz. During the onboard test, the probability of achieving complete synchronization (when the synchronization success rate is 1) is 0.65, which is much higher than the 0.15 of the single method.

The enormous growth of mobile broadband traffic is a catalyst for expanding terrestrial communication systems and their integration with satellite communication systems. This results in sharing frequencies allocated to satellite communication systems with terrestrial systems. As this can lead to interference between the incumbent and the upcoming service, coexistence studies are conducted. In the case of sharing satellite uplink frequencies with terrestrial communication systems, interference from base stations (BSs) is dominant. While there are methods to estimate the number of BSs that may be deployed, it is unclear where the BSs will be located. The BS locations play a pivotal role in interference calculation, as the values of link budget parameters are highly dependent on the longitude and latitude of interfering transmitters. This article presents an intelligent method which balances network capacity and coverage for simulating base stations (BSs) in coexistence studies. A realistic BS distribution is generated using weighted K-means clustering (WKMC) algorithm and incorporating population density along with Haversine distance. The paper provides a case study of co-frequency, co-coverage interference in the satellite uplink in the C-band to demonstrate the impact of BS distribution on the results of coexistence studies. This paper will find applications in upcoming frequency sharing and coexistence studies and the design of integrated satellite-terrestrial communication networks.

This paper presents the latest achievements concerning 3GPP Release-17 adjacent band coexistence simulation work on 5G new radio non-terrestrial networks (NTNs) for satellite communications. For the first time, 3GPP considered the introduction of mobile satellite service (MSS) frequency bands for 3GPP user equipment (UE) direct connectivity with satellites and had to consider the coexistence in adjacent bands with terrestrial networks (TNs). This paper will further explain the most challenging and the main surprising outcomes of this work, which opened new market opportunities for both terrestrial and non-terrestrial stakeholders. The main conclusions can be summarized as follows: (1) NTN UE can reuse the current requirements of the TN UE, (2) the satellite connectivity does not require a dedicated satellite waveform, and (3) TN can co-exist with NTN on adjacent channels with relaxed ACIR requirements for the tested simulation scenario.

Connectivity in satellite networks is governed by the spacecraft nodes' orbital dynamics together with the planet's continuous rotation where ground nodes are located. The resulting time-dynamic but predictable topology demands the design of specific distributed routing schemes. However, terrestrial Internet routing schemes' maturity, proven scalability, and efficiency shall be leveraged whenever possible to facilitate space-terrestrial integration while reducing risk and costs. In line with this reflection, we introduce SATNET-OSPF: a backward-compatible satellite extension for the widely used Open Shortest Path First routing protocol. The key features of SATNET-OSPF are (a) accurate routing interface mapping to inter-satellite links and ground-to-satellite links, (b) accelerated link-up/link-down event detection adapted to space-specific wireless technologies, (c) proactive routing and forwarding mechanism to take advantage of predicted link-down events, and (d) low memory footprint topology model to efficiently propagate the forthcoming space connectivity events via constrained telecommand links. Leveraging existing IPv6 and OSPFv3 open-source stacks, we implemented SATNET-OSPF in an actual space router comprising a space-grade SPARC V8 CPU and a radiation-hardened FPGA. Furthermore, we present the details of an emulation test bench supporting various configurations with COTS terrestrial OSPF routers that enabled a realistic performance evaluation of the SATNET-OSPF. Results show that SATNET-OSPF reduced OSPFv3 routing protocol overhead by up to 31%; shortened the link event detection delay by four orders of magnitude; decreased the routing outage by a factor of 22; and ensured flooding control message generation and forwarding times, as well as routing computing time, satisfy the original requirements (192, 37, and 17 ms, respectively).

With the development of the massive satellite constellation and the on-orbit laser-based communication equipment, wavelength routing optical satellite networks (WROSN) becomes a potential solution for on-orbit, high-capacity, and high-speed communication. Since the inter-satellite links (ISLs) are time-varying, one of the fundamental considerations in the construction of the WROSN is assigning limited laser communication terminals for each satellite to establish ISLs with the visible satellites. Therefore, we propose a links assignment scheme (LAS) based on the potential edges importance matrix (PEIM) algorithm to construct a temporarily stable topology for a dual-layer WROSN (DWROSN). The simulation results showed that the LAS based on the PEIM algorithm diminishes the long-hops route path, reduces the average node-to-node distance, and saves the wavelength demand of the DWROSN. The node pair connectivity and wavelength demand in the DWROSN is a trade-off problem. The research in this paper also brings a novel method for optimizing the route paths and reducing the wavelength demand of wavelength routing optical satellite networks, that is through designing the topology with a links assignment algorithm.

The tasks of a space-based information network are complex and diverse, but the resources of a space-based environment are minimal. The existing methods are challenging to match task demand to resource supply accurately. Aiming at the problem of accurate prediction from task to resource, we propose a resource prediction adjustment strategy. First, we propose a multidimensional resource prediction algorithm based on improved particle swarm optimization and back propagation (IPSO-BP) neural network. The improved PSO is used to optimize the weight and threshold of BP neural network to make up for the defects that BP neural network is easy to fall into local minimum and the predicted output value is not unique. Second, to meet the quality of service (QoS) of tasks, we propose a density-based performance evaluation algorithm (DPEA) to adjust resources. This method uses the idea of local sensitive hash to select the evaluation subset for the configuration task, then dynamically selects the $�k$ nearest neighbors of the configuration task, and uses the idea of weighted average to evaluate the QoS performance index of the configuration task. Simulation results show that the proposed resource prediction and adjustment strategy effectively reduces the scheduling time overhead and improves resource utilization.