Power-Domain Collision-Tolerant Random Access Method with Auxiliary Beam for Satellite Internet of Things:A New Solution

There are numerous terminals in the satellite Internet of Things(IoT).To save cost and reduce power consumption,the system needs terminals to catch the characteristics of low power consumption and light control.The regular random access(RA)protocols may generate large amounts of collisions,which degrade the system throughout severally.The near-far effect and power control technologies are not applicable in capture effect to obtain power difference,resulting in the collisions that cannot be separated.In fact,the optimal design at the receiving end can also realize the condition of packet power domain separation,but there are few relevant researches.In this paper,an auxiliary beamforming scheme is proposed for power domain signal separation.It adds an auxiliary reception beam based on the conventional beam,utilizing the correlation of packets in time-frequency domain between the main and auxiliary beam to complete signal separation.The roll-off belt of auxiliary beam is used to create the carrier-to-noise ratio(CNR)difference.This paper uses the genetic algorithm to optimize the auxiliary beam direction.Simulation results show that the proposed scheme outperforms slotted ALOHA(SA)in terms of system throughput per-formance and without bringing terminals additional control burden.

A Novel Orthogonal LoRa Multiple Access Algorithm for Satellite Internet of Things

In recent years,LoRa has been extensively researched in the satellite Internet of Things(IoT).However,the multiple access technology of LoRa is still one of the bottlenecks of satellite IoT.To improve the multiple access performance of LoRa satellite IoT,based on the orthogonality of LoRa symbols in the fractional domain,this paper proposes a low complexity Orthogonal LoRa Multiple Access(OLMA)algorithm for multiple LoRa users occupying the same frequency bandwidth.The algorithm introduces the address code to divide the fractional bandwidth into multiple parts,and the OLMA users with different address codes occupy different parts to transmit the information code,thus avoiding mutual interference caused by collisions in the same frequency bandwidth.The multiple access capability of OLMA can be flexibly configured only by simply adjusting the length of the address code according to the actual application requirements of data transmission.Theoretical analysis and simulation results show that the OLMA algorithm can greatly improve the multiple access capability and the total transmission bit rate of LoRa IoT without changing the existing LoRa modulation parameters and process.

Non-Orthogonal Multi-Carrier Transmission for Internet via Satellite

As the important complementary to terrestrial mobile communications, Internet via satellite can extend the coverage of communication and improve the continuity of data services. To build a space-terrestrial integrated communication system is the inevitable trend in the future. Taking into account combination of 5th generation(5G) terrestrial mobile communication system and satellite communication system, it is necessary to evaluate the promising 5G air interface waveform which can be adopted by satellite. In this paper, several non-orthogonal multi-carrier transmission schemes are evaluated and generalized frequency division multiplexing(GFDM) is advised as potential scheme of space-terrestrial integrated communication system. After the overview of GFDM, the implementation of GFDM transceiver is discussed respectively in time-domain and in frequency-domain. By deriving and comparing implementation complexity, GFDM modulation in time-domain is more suitable for satellite communication system. Then the properties of demodulation algorithms are specified. Based on designed pilot subcarriers, a new improved receiving algorithm is proposed in the end of the paper. The improved algorithm solves the problem of inter subcarriers interference(ICI) in matched filtering(MF) receiver and improves the re-ceiving symbol error rate(SER) obviously. The simulation and analysis prove that the proposed algorithm is effective.

From Earth to Space:A First Deployment of 5G Core Network on Satellite

Recent developments in the aerospace industry have led to a dramatic reduction in the manufacturing and launch costs of low Earth orbit satellites.The new trend enables the paradigm shift of satelliteterrestrial integrated networks with global coverage.In particular,the integration of 5G communication systems and satellites has the potential to restructure nextgeneration mobile networks.By leveraging the network function virtualization and network slicing,the satellite 5G core networks will facilitate the coordination and management of network functions in satellite-terrestrial integrated networks.We are the first to deploy a 5G core network on a real-world satellite to investigate its feasibility.We conducted experiments to validate the satellite 5G core network functions.The validated procedures include registration and session setup procedures.The results show that the satellite 5G core network can function normally and generate correct signaling.

Steady-State Performance Evaluation of Linux TCPs versus TCP Wave over Leaky Satellite Links

Internet access is becoming even more heterogeneous, including different wireless backhauling links, with Ka-band satellites as a possible alternative. Since communication path is unknown a priori, adoption of PEP solutions to optimize TCP performance over satellite is discouraged to allow dynamic network reconfigurations. To opposite, an endto-end TCP performance evaluation on such a challenging scenario, with possible large latency and transmission losses, is herein considered of paramount importance. Several TCP variants exist to tackle different aspects of communication networks. In Linux, the different TCP congestion control schemes differ from the theoretical formulations and RFC specifications, introducing a varying set of optimizations and options. This aspect makes difficult to identify a standard/reference TCP version for the proposed scenario, while testing with the real protocol stacks is deemed necessary to obtain consistent results. In addition, an innovative end-to-end TCP, namely TCP Wave, is introduced to replace the traditional window-based transmission with a burst-based strategy, representing a valid alternative to Linux TCP. To offer a fair, realistic and comprehensive evaluation, we configured a simulation setup where different Linux TCPs can be run within ns-3 network simulator and compared with TCP Wave.

Adaptability Analysis of IP Routing Protocol in Broadband LEO Constellation Systems

With the inclusion of satellite Internet as the information infrastructure in China's "new infrastructure" category,relevant domestic industries and scientific research institutes have successively carried out the design of broadband low earth orbit(LEO) constellation systems and key technical research.As the core technology for the satellite-to-ground network communications of a broadband LEO constellation system,routing technology is extremely important for the efficient and reliable transmission of various service data.Focusing on the two important broadband LEO constellation systems in China,in-depth analysis and simulation of the high dynamics of the satellite-to-ground satellites are conducted in this paper to obtain more accurate network topology changes and characteristics;then the adaptability of the ground standard IP routing protocol to the broadband LEO constellation system is analyzed,and an LEO constellation simulation scenario is built with the Opnet software.The simulation results of the convergence performance of the standard IP routing protocol are produced.The results show that the IP protocol does not perform well for LEO satellite constellation networks.Based on the studies,some solutions are proposed to take full advantages of the characteristics of LEO satellite systems.These can also provide a reference for the choice of intersatellite routing architecture and protocol technology for broadband LEO constellation in the future development.

Design and performance evaluation of a novel ranging signal based on an LEO satellite communication constellation

Driven by improvements in satellite internet and Low Earth Orbit(LEO)navigation augmenta-tion,the integration of communication and navigation has become increasingly common,and further improving navigation capabilities based on communication constellations has become a significant challenge.In the context of the existing Orthogonal Frequency Division Multiplexing(OFDM)communication systems,this paper proposes a new ranging signal design method based on an LEO satellite communication constellation.The LEO Satellite Communication Constellation Block-type Pilot(LSCC-BPR)signal is superimposed on the com-munication signal in a block-type form and occupies some of the subcarriers of the OFDM signal for transmission,thus ensuring the continuity of the ranging pilot signal in the time and frequency domains.Joint estimation in the time and frequency domains is performed to obtain the relevant distance value,and the ranging accuracy and communication resource utilization rate are determined.To characterize the ranging performance,the Root Mean Square Error(RMSE)is selected as an evaluation criterion.Simulations show that when the number of pilots is 2048 and the Signal-to-Noise Ratio(SNR)is 0 dB,the ranging accuracy can reach 0.8 m,and the pilot occupies only 50%of the communication subcarriers,thus improving the utilization of communication resources and meeting the public demand for communication and location services.