• Electronics and Telecommunications Trends
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• v.39 no.3
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• pp.36-47
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• 2024

Low Earth Orbit (LEO) satellite communications has become a crucial technology for next-generation communication networks owing to its hyperconnectivity capabilities. We examine the progress and application areas of LEO satellite communication services. The LEO satellite communication industry has transitioned from being predominantly driven by governments and institutions to being led by the private sector, following the trajectory of the NewSpace movement. Leading corporations such as SpaceX Starlink and Eutelsat OneWeb are deploying LEO satellite networks to offer internet services, while Telesat is preparing to establish its satellite communication network. LEO satellite communications is expected to have a major impact on various sectors of society, particularly for upcoming sixth-generation services. Therefore, the South Korean government must promptly formulate policy support strategies aimed at invigorating the LEO satellite communication industry. This can be achieved through initiatives such as bolstering research and development and extending corporate assistance.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.465-468
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• 2000

The interference situation for the satellite networks using non-geostationary satellite orbit (NGSO) is more complicated than the situation between geostationary satellite orbit (GSO) networks because of the time varying orbital characteristics of NGSO systems. Most of frequency bands are allocated to fixed-satellite service and liked-service in co-primary basis. In this paper, the sharing criteria between NGSO/FSS systems and HDFS (High Density Fixed-Service) are examined.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.8
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• pp.2796-2813
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• 2014

This paper presents a new algorithm called the adaptive logarithmic increase and adaptive decrease algorithm (A-LIAD), which mainly addresses the Round-Trip Time (RTT) fairness problem in satellite networks with a very high propagation delay as an alternative to the current TCP congestion control algorithm. We defined a new increasing function in the fashion of a logarithm depending on the increasing factor ${\alpha}$, which is different from the other logarithmic increase algorithm adopting a fixed value of ${\alpha}$ = 2 leading to a binary increase. In A-LIAD, the ${\alpha}$ value is derived in the RTT function through the analysis. With the modification of the increasing function applied for the congestion avoidance phase, a hybrid scheme is also presented for the slow start phase. From this hybrid scheme, we can avoid an overshooting problem during a slow start phase even without a SACK option. To verify the feasibility of the algorithm for deployment in a high-speed and long-distance network, several aspects are evaluated through an NS-2 simulation. We performed simulations for intra- and interfairness as well as utilization in different conditions of varying RTT, bandwidth, and PER. From these simulations, we showed that although A-LIAD is not the best in all aspects, it provides a competitive performance in almost all aspects, especially in the start-up and packet loss impact, and thus can be an alternative TCP congestion control algorithm for high BDP networks including a satellite network.

• Journal of Communications and Networks
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• v.8 no.4
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• pp.451-460
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• 2006

Since low earth orbit (LEO) satellite constellations have important advantages over geosynchronous earth orbit (GEO) systems such as low propagation delay, low power requirements, and more efficient spectrum allocation due to frequency reuse between satellites and spotbeams, they are considered to be used to complement the existing terrestrial fixed and wireless networks in the evolving global mobile network. However, one of the major problems with LEO satellites is their higher speed relative to the terrestrial mobile terminals, which move at lower speeds but at more random directions. Therefore, handover management in LEO satellite networks becomes a very challenging task for supporting global mobile communication. Efficient and accurate methods are needed for LEO satellite handovers between the moving footprints. In this paper, we propose a new seamless handover management scheme for LEO satellites (SeaHO-LEO), which utilizes the handover management schemes aiming at decreasing latency, data loss, and handover blocking probability. We also present another interesting handover management model called satellite mobility pattern based handover management in LEO satellites (PatHO-LEO) which takes mobility pattern of both satellites and mobile terminals into account to minimize the handover messaging traffic. This is achieved by the newly introduced billboard manager which is used for location updates of mobile users and satellites. The billboard manager makes the proposed handover model much more flexible and easier than the current solutions, since it is a central server and supports the management of the whole system. To show the performance of the proposed algorithms, we run an extensive set of simulations both for the proposed algorithms and well known handover management methods as a baseline model. The simulation results show that the proposed algorithms are very promising for seamless handover in LEO satellites.

• Journal of Satellite, Information and Communications
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• v.9 no.2
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• pp.18-22
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• 2014

Satellite communications consist of communications between base stations of the ground and satellites. For efficient satellite communications, ground networks should be organically utilized. Grid networks are frequently used in and outside the country for wireless communications. The performance of wireless communications is determined by mobility, topography, and jamming signals. Therefore, continuous studies of grid networks are necessary for the utilization of next period satellite networks. Since military communications are used based on wireless systems, they can be considered as a sample of utilization of grid networks. Therefore, this paper presented the results of simulations conducted for the improvement of the performance of the grid networks used in military communications that employing the OSPF, a popular routing protocol for military applications. First we investigate the effects of changing the bit error rate (BER) and number of routers. Then we discuss the effects of maximum segment size (MSS) on network behavior and stability. In this way, we can determine the appropriate MSS for a grid network under various values of BER and number of routers. Such results can be also applied to commercial grid network evaluations.

• Journal of Communications and Networks
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• v.7 no.2
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• pp.135-143
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• 2005

This paper presents an investigation of satellite radio access technology for beyond IMT-2000 systems. Although we could not see any active role of a satellite system in the 3G networks, satellite system will provide strong advantages in future systems for certain applications. Because a satellite link has longer round trip delay than a terrestrial link, we need technologies that would make the satellite component especially efficient. After presenting the satellite radio interface of the 3G system, we suggest several points which need to be considered in the beyond 3G systems. We also suggest a few candidate technologies with various simulation results.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.458-460
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• 2003

This paper proposes new algorithms for cloudy area detection by GHA (Generalized Hebbian Algorithm) and SOFM (Self-Organized Feature Map). SOFM and GHA are unsupervised neural networks and are used for pattern classification and shape detection of satellite image. Proposed algorithm is based on block based image processing that size is 16${\times}$16. Results of proposed algorithm shows good performance of cloudy area detection except blur cloudy area.

• Journal of Communications and Networks
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• v.12 no.6
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• pp.592-599
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• 2010

In recent years, significant improvements have been made to the techniques used for analyzing satellite communication and attacking satellite systems. In 2003, a research team at Los Alamos National Laboratory, USA, demonstrated the ease with which civilian global positioning system (GPS) spoofing attacks can be implemented. They fed fake signals to the GPS receiver so that it operates as though it were located at a position different from its actual location. Moreover, Galileo in-orbit validation element A and Compass-M1 civilian codes in all available frequency bands were decoded in 2007 and 2009. These events indicate that cryptography should be used in addition to the coding technique for secure and authenticated satellite communication. In this study, we address this issue by using an authenticated key-exchange protocol to build a secure and authenticated communication channel for satellite communication. Our protocol uses identity-based cryptography. We also prove the security of our protocol in the extended Canetti-Krawczyk model, which is the strongest security model for authenticated key-exchange protocols, under the random oracle assumption and computational Diffie-Hellman assumption. In addition, our protocol helps achieve high efficiency in both communication and computation and thus improve security in satellite communication.

• Journal of IKEEE
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• v.7 no.1 s.12
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• pp.80-87
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• 2003

This paper proposes a routing scheme for multi-hop LEO satellite networks with inter-satellite links aiming for reducing the number of link handovers while keeping the efficient use of network resource. The proposed routing scheme controls the link handovers by taking account of the deterministic LEO satellite system dynamics, geographical location of a ground terminal and statistic information of call duration. The performance of the proposed routing scheme has been evaluated and compared with previous routing schemes in terms of average number of link handovers during a call, the call blocking and dropping probability, and the network utilization.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.5
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• pp.1013-1027
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• 2011

In this paper we propose ATCS, a practical TCP protocol coding scheme based on network coding for satellite IP networks. The proposal is specially designed to enhance TCP performance over satellite networks. In our scheme, the source introduces a degree of redundancy and transmits a random linear combination of TCP packets. Since the redundant packets are utilized to mask packet loss over satellite links, the degree of redundancy is determined by the link error rates. Through a simple and effective method, ATCS estimates link error rates in real time and then dynamically adjusts the redundant factor. Consequently, ATCS is adaptable to a wide range of link error rates by coding TCP segments with a flexible redundancy factor. Furthermore, the scheme is compatible with traditional TCP variants. Simulation results indicate that the proposal improves TCP performance considerably.