The chapter highlights techniques to simulate the behavior of real-time and non real-time satellite systems and clarifies possible application fields and motivations. Communication systems and, in particular, satellite components have increased their complexity. Simulation is a reality to explore new solutions without increasing hazards and costs: long phases of space missions are completely dedicated to forecast the behavior of the systems to be implemented and simulations are widely used. The chapter focuses on methods to evaluate the efficiency of a simulator, underlines some traffic models suited to simulate communication systems and explains particular topics where the authors have direct experience. A couple of tools are presented applied to the satellite environment: a C-language based non-real­ time software simulator and a real-time simulator (emulator), where real machines can be attached to the tool, so as to avoid traffic modeling. Performance results are reported to better explain the concepts of the chapter.

http://link.springer.com/content/pdf/10.1007/978-1-4419-9218-5_7.pdf

Techniques and applications

Broadband Satellite Communications for Internet Access is a systems engineering methodology for satellite communication networks. It discusses the implementation of Internet applications that involve network design issues usually addressed in standard organizations. Various protocols for IP- and ATM-based networks are examined and a comparative performance evaluation of different alternatives is described. This methodology can be applied to similar evaluations over any other transport medium.

Broadband satellite communications for Internet access

The exploitation of adaptive coding and modulation techniques for broadband multi-beam satellite communication networks operating at Ka-band and above has been shown to theoretically provide large system capacity gains. In this paper, the problem of how to accurately estimate the time-variant channel and how to adapt the physical layer taking into account the effects of estimator errors and (large) satellite propagation delays is analyzed, and practical solutions for both the forward and the reverse link are proposed. A novel pragmatic solution to the reverse link physical layer channel estimation in the presence of time-variant bursty interference has been devised. Physical layer adaptation algorithms jointly with design rules for hysteresis thresholds have been analytically derived. The imperfect physical layer channel estimation impact on the overall system capacity has been finally derived by means of an original semi-analytical approach. Through comprehensive system simulations for a realistic system study case, it is showed that the devised adaptation algorithms are able to successfully track critical Ka-band fading time series with a limited impact on the system capacity while satisfying the link outage probability requirement. Copyright © 2008 John Wiley & Sons, Ltd.

Channel estimation and physical layer adaptation techniques for satellite networks exploiting adaptive coding and modulation

The future media rich applications such as media streaming, content delivery distribution and broadband access require a network infrastructure that offers greater bandwidth and service level guarantees. As the demand for new applications increases, ‘best effort’ service is inadequate and results in lack of user satisfaction. End-to-end quality of service (QoS) requires the functional co-operation of all network layers. To meet future application requirements, satellite is an excellent candidate due to features such as global coverage, bandwidth flexibility, broadcast, multicast and reliability. At each layer, the user performance requirements should be achieved by implementation of efficient bandwidth allocation algorithms and satellite link impairment mitigation techniques.

In this paper, a QoS framework for satellite IP networks including requirements, objectives and mechanisms are described. To fully understand end-to-end QoS at each layer, QoS parameters and the current research are surveyed. For example at physical layer (modulation, adaptive coding), link layer (bandwidth allocation), network layer (IntServ/DiffServ, MPLS traffic engineering), transport layer (TCP enhancements, and alternative transport protocols) and security issues are discussed. Some planned system examples, QoS simulations and experimental results are provided. The paper also includes the current status of the standardization of satellite IP by ETSI, ITU and IETF organizations. Copyright © 2003 John Wiley & Sons, Ltd.

Quality of service for satellite IP networks: a survey

Impairment of radio wave signal by rainfall on fixed satellite service on earth-space path at 37 stations in Nigeria

Future satellite communications systems operating in Ka-band frequency band are subject to degradation produced by the troposphere which is much more severe than those found at lower frequency bands. These impairments include signal absorption by rain, clouds and gases, and amplitude scintillation's arising from refractive index irregularities. For example, rain attenuation at 20 GHz is almost three times that at 11 GHz. Although some of these impairments can be overcome by oversizing the ground station antennas and high power amplifiers, the current trend is using small (less than 20 inches apertures), low-cost ground stations (less than $1000) that can be easily deployed at user premises. As a consequence, most Ka-band systems are expected to employ different forms of fade mitigation that can be implemented relatively easily and at modest cost. The rain fade mitigation approaches are defined by three types of Ka-band communications systems - a low service rate (less than 1.5 Mb/s), a moderate service rate (1.5 to 6 Mb/s) system and a high service rate (greater than 43 Mb/s) system. The ACTS VSAT network, which includes an adaptive rain fade technique, is an example of a moderate service rate.

/pdf/rain-fade-compensation-alternatives-for-ka-band-4tt35wewk4.pdf

Roberto J. Acosta

Papers

Rain Fade Compensation Alternatives for Ka Band Communication Satellites