Low Earth Orbit Satellite Systems Research Articles

Improving Satellite Multicast Security Scalability by Reducing Rekeying Requirements

As multicasting technologies grow in popularity, so does the need for scalable security architectures to support the user base. Significant research efforts are ongoing in the areas of group-key distribution and management. However, little research has addressed the security of very large, distributed groups communicating via low-earth orbit satellite networks. In this article, we review the requirements common to most secure, multicast networking environments; discuss existing scalable multicast security architectures; and present a novel modular scalable architecture for secure multicast, adapted to a low-earth orbit satellite system. Simulated results reveal a twelve-fold reduction in average user rekeying and an order of magnitude reduction in required key distribution versus the baseline architecture.

QoS handover management for multimedia LEO satellite networks

Low earth orbit (LEO) satellite systems gained considerable interest towards the end of the previous decade by virtue of some of the appealing features that are endowed with, such as low propagation delay and the ability to communicate with handheld terminals. However, after the limited commercial success of the first networks of this kind, future satellite networks are now conceived as complementary rather than competitive to terrestrial networks. In this paper, we focus on one of the most influential factors in system performance, that is, the handover of a call. First, we provide a succinct review of the handover strategies that have been proposed in the literature. Then we propose two different satellite handover techniques for broadband LEO satellite systems that capitalize upon the satellite diversity that a system may provide. The proposed schemes cater for multimedia traffic and are based on the queuing of handover requests. Moreover, a deallocation scheme is also proposed according to which capacity reservation requests are countermanded when the capacity that they strive to reserve is unlikely to be used. Simulation studies further document and confirm the positive characteristics of the proposed handover schemes.

Research on handover algorithm to reduce the blocking probability in LEO satellite network

Abstract Based on the characteristics of guaranteed handover (GH) algorithm, the finite capacity in one system makes the blocking probability (PB) of GH algorithm increase rapidly in the case of high traffic load. So, when large amounts of multimedia services are transmitted via a single low earth orbit (LEO) satellite system, the PB of it is much higher. In order to solve the problem, a novel handover scheme defined by multi-tier optimal layer selection is proposed. The scheme sufficiently takes into account the characteristics of double-tier satellite network, which is constituted by LEO satellites combined with medium earth orbit (MEO) satellites, and the multimedia transmitted by such network, so it can augment this systematic capacity and effectively reduces the traffic load in the LEO which performs GH algorithm. The detailed processes are also presented. The simulation and numerical results show that the approach integrated with GH algorithm achieves a significant improvement in the PB and practicability, as compared to the single LEO layer network.

Handover schemes in satellite networks: state-of-the-art and future research directions

Low Earth Orbit (LEO) satellites will work as an important component in future data communication networks. LEO satellites provide low end-toend delays and efficient frequency spectrum utilization, making them suitable for personal communication. However, due to high satellite speed, ongoing communication using LEO constellations experiences frequent handover. In this article we provide an up-to-date, comprehensive literature survey on proposed handover schemes for LEO satellite systems. We also present a detailed classification of handover schemes based on a common framework. We first classify the schemes into link-layer and network-layer handover schemes. Link-layer handover schemes are further classified into three categories: spotbeam handover schemes, satellite handover schemes, and ISL handover schemes. Spotbeam handover schemes are categorized based on channel capacity, handover guarantee, and handover prioritization techniques. Network-layer handover schemes are also classified depending on connection transfer strategies. Finally, we compare the handover schemes using different quality of service (QoS) criteria.

Analytic study of doppler-based handover management in LEO satellite systems

The problem of dynamic handover management in low Earth orbit (LEO) satellite systems is addressed. Particularly, an analytical study of a newly proposed method for handover management, called dynamic Doppler-based handover prioritization scheme (DDBHP), is presented. DDBHP utilizes Doppler shift monitoring of each communicating user terminal onboard the satellite and geometric characteristics to accurately predict the handover load. As a result, handover requests are more effectively managed, resulting in an improved performance in terms of blocking and forced termination probabilities. Moreover, by supporting guaranteed handovers, DDBHP can be used to provide QoS to users of future broadband satellite networks. An extensive mathematical model that justifies Doppler shift monitoring is presented along with a detailed queueing model used not only to evaluate DDBHP performance but also to provide a methodology for associating DDBHP operational parameters with desired performance. Comparison of analytical and simulation results validate the proposed model.

Variable-Target Admission Control for Nonstationary Handover Traffic in LEO Satellite Networks

Handover management is of great importance in a low Earth orbit (LEO) satellite system. However, the blocking performance of handover traffic in an LEO satellite system is not easily formulated with an acceptable level of accuracy because of the nonstationary nature of handover traffic, which causes difficulty in quantitatively making optimal decisions for channel assignment to meet a given quality-of-service requirement. Even though many challenging schemes have been proposed to dynamically determine the number of guard channels, most either use heuristic methods or are based on simplifying assumptions, causing invalid decision results. As an alternative, we suggest a quantified method to minimize the fraction of the number of blocked calls out of the number of total calls under nonstationary handover traffic. We develop new mathematical formulations of those fraction and optimization models with efficient exact solution algorithms. Performance analysis shows that the proposed method improves the blocking probabilities of handovers and new calls; this improvement results from a highly adaptive and reactive characteristic to the fluctuating handover traffic condition.

Design issues and QoS handover management for broadband LEO satellite systems

Today, the wider spectrum of applications that wireless networks are called to support, presses the designers of low earth orbit (LEO) satellite systems for a more efficient exploitation of the limited radio spectrum. The limited commercial success of the first LEO satellite networks, which were geared towards narrowband services, has been the main motive for the reconsideration of the set of services that these networks should provide. In this context, a broadband LEO satellite system is examined in the paper. In this kind of networks, the handing-over of a call between contiguous cells or satellites is one of the dominant factors that degrade the quality of the provided services. In the paper, a satellite handover technique is proposed and evaluated for systems that present partial satellite diversity in order to provide an efficient handover strategy and QoS in multimedia applications, examining the impact of the footprint's overlapping area on the system performance as well.

The performance of turbo coding over power-controlled fading channel in Ka-band LEO satellite systems

The integration of power control and turbo coding is adopted to achieve reliable communications over Ka-band code-division multiple-access (CDMA)-based low Earth orbit (LEO) satellite systems. The effect of imperfect power control on the bit error ratio (BER) performance is analyzed, and the upper bounds on BER are also derived for the case of slow and fast imperfect power control. The analytical and simulation results show that power-control error (PCE) degrades the BER performance of turbo-decoded systems significantly in the waterfall region. In the region of the error floor, the degradation effect slows down and the BER obtained under imperfect power control eventually converges with the BER under perfect power control. Moreover, in the waterfall region, the correlation characteristics of the PCE fluctuation do not degrade the BER performance as anticipated.

Demographically weighted traffic flow models for adaptive routing in packet-switched non-geostationary satellite meshed networks

In this paper, a performance analysis of adaptive routing is presented for packet-switched inter-satellite link (ISL) networks, based on shortest path routing and two alternate link routing forwarding policies. The selected routing algorithm and link-cost function are evaluated for a low earth orbit satellite system, using a demographically weighted traffic flow model. Two distinct traffic flow patterns are modelled: hot spot and regional. Performance analysis, in terms of quality of service and quantity of service, is derived using specifically developed simulation software to model the ISL network, taking into account topology adaptive routing only, or topology and traffic adaptive routing.

Performance of Low Earth Orbit Satellite Systems with Coding

The effect of block, convolutional and Turbo coding on the probability of error and the capacity are investigated for CDMA Low Earth Orbit (LEO) Satellite systems. The model employed assumes a contaminated Gaussian traffic model to be more compatible with different population areas. The conventional Gaussian distribution can be considered as a special case.

Adoption of Low Earth Orbit Satellite Systems: A Diffusion Model under Competition

Low Earth Orbit Satellite (LEOS) systems have started providing communication with one phone number throughout the world. In this paper, the diffusion process of the two LEOS systems is analyzed under competition. We simulate the diffusion process under different scenarios. In these scenarios, we analyze issues related to the timing of product introduction, technology advantage and potential customer base. A model of the potential customer base with network externality is presented. We found that the timing of product introduction can have significant impact on the follower in the market. We found that a follower firm with more advanced technology would have higher probability to succeed in competing against the first mover. In addition, the increase in the potential customer base favors the firm with advanced technology. The network externality effect in the growth of the customer base favors both firms but could be an barrier for the follower to create a critical mass and beat the incumbent firm.

Russian low earth and elliptical orbit satellite communication systems: The competing projects

A number of Russian projects for low earth and elliptical orbit communication satellite systems are struggling for the status of a federal system, which means governmental support. The systems taking part in this competition are reviewed in the light of the published parts of the Russian Federal Space Program. It is shown that some systems included in the plan are old-fashioned and new rivals not included in the Program have a greater chance to become feasible. The current situation concerning Russian non-geostationary communications satellite systems will be examined and their histories, technical specifications, state of readiness and commercial viability discussed. The impact of western systems and companies as collaborators or competitors is assessed.

An analytical model to predict the probability density function of elevation angles for LEO satellite systems

Based on Earth-satellite geometry, an analytical model is proposed to predict the probability density function (pdf) of elevation angles from an Earth station to a circular low-Earth-orbit (LEO) satellite constellation. Unlike currently available empirical models using a great deal of path data for model-fitting to obtain results applicable only to the specified systems (for example, the Iridium or Globalstar systems), the proposed model is fast, exact and provides greater flexibility for the user-specified satellite systems. The results may help to develop the LEO satellite communication channel models under the propagation environments characterized by various empirical elevation-angle-dependent channel models.

Performance of Low Earth Orbit Satellite Systems with a Gaussian Mixtures Traffic Distribution

ABSTRACTA new traffic model for Low Earth Orbit (LEO) Satellite system is proposed. Two different cases are considered. The first case represents the situation in which the traffic load follows a bimodal contaminated Gaussian distribution. The second case considers the trimodal distribution. The parameters of this new distribution model are introduced and their effects on the Signal to Interference Ratio (SIR) and the capacity are investigated.

Air target detection via bistatic radar based on LEOS communication signals

The paper discusses the bistatic radar parameters for the case when the transmitter is a satellite emitting communication signals. The model utilises signals from an Iridium-like low earth orbiting satellite system. The maximum detection range, when thermal noise-limited, is discussed at the theoretical level and these results are compared with experimentation. Satellite-radar signal levels and the power of ground reflections are evaluated.

Generalized performance evaluation of low Earth orbit satellite systems

A novel three-dimensional distribution traffic is proposed for low Earth orbit (LEO) satellite systems. The effect of the traffic geographical nonuniformity on the performance of these satellite systems is discussed.

Connection admission control for capacity-varying networks with stochastic capacity change times

Many connection-oriented networks, such as low Earth orbit satellite (LEOS) systems and networks providing multipriority service using advance reservations, have capacities which vary over time. Connection admission control (CAC) policies which only use current capacity information may lead to intolerable dropping of admitted connections whenever network capacity decreases. We present the admission limit curve (ALC) for capacity-varying networks with random capacity change times. We prove the ALC is a constraint limiting the conditions under which any connection-stateless CAC policy may admit connections and still meet dropping guarantees on an individual connection basis. The ALC also leads to a lower bound on the blocking performance achievable by any connection-stateless CAC policy which provides dropping guarantees to individual connections. In addition, we describe a CAC policy for stochastic capacity change times which uses knowledge about future capacity changes to provide dropping guarantees on an individual connection basis and which achieves blocking performance close to the lower bound.

PERFORMANCE OF LOW EARTH ORBIT SATELLITE SYSTEMS WITH A GAUSSIAN MIXTURES TRAFFIC DISTRIBUTION

ABSTRACTA new traffic model for Low Earth Orbit (LEO) Satellite system is proposed. Two different cases are considered. The first case represents the situation in which the traffic load follows a bimodal contaminated Gaussian distribution. The second case considers the trimodal distribution. The parameters of this new distribution model are introduced and their effects on the Signal to Interference Ratio (SIR) and the capacity are investigated.

PERFORMANCE OF LOW EARTH ORBIT SATELLITE SYSTEMS WITH A GAUSSIAN MIXTURES TRAFFIC DISTRIBUTION

ABSTRACTA new traffic model for Low Earth Orbit (LEO) Satellite system is proposed. Two different cases are considered. The first case represents the situation in which the traffic load follows a bimodal contaminated Gaussian distribution. The second case considers the trimodal distribution. The parameters of this new distribution model are introduced and their effects on the Signal to Interference Ratio (SIR) and the capacity are investigated.

An efficient scheme to reduce handoff dropping in LEO satellite systems

The problem of handoffs in cellular networks is compounded in a low earth orbit (LEO) satellite-based cellular network due to the relative motion of the satellites with respect to a stationary observer on earth. Typically, the velocity of motion of mobiles can be ignored when compared to the very high velocity of the footprints of satellites. We exploit this property of LEO satellite systems and propose a handoff scheme based on a channel sharing approach that results in a substantial decrease in handoff dropping. For the same handoff dropping performance, our scheme has significantly lower new call blocking probability than the conventional reservation scheme. We also present an analytical approximation that is in very good accord with simulation results.