Satellite Communications Edited by Nazzareno Diodato Satellite Communications edited by Nazzareno Diodato SCIYO Satellite Communications http://dx.doi.org/10.5772/253 Edited by Nazzareno Diodato © The Editor(s) and the Author(s) 2010 The moral rights of the and the author(s) have been asserted. All rights to the book as a whole are reserved by INTECH. The book as a whole (compilation) cannot be reproduced, distributed or used for commercial or non-commercial purposes without INTECH’s written permission. Enquiries concerning the use of the book should be directed to INTECH rights and permissions department (permissions@intechopen.com). Violations are liable to prosecution under the governing Copyright Law. 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For more information visit www.intechopen.com 4,200+ Open access books available 151 Countries delivered to 12.2% Contributors from top 500 universities Our authors are among the Top 1% most cited scientists 116,000+ International authors and editors 125M+ Downloads We are IntechOpen, the world’s leading publisher of Open Access books Built by scientists, for scientists Meet the editor Nazzareno Diodato was born in Benevento, Italy in 1966 and was educated at the University of Naples \”Fed- erico II\” where he received five years of education in Urban and Landscape Planning. Thereafter he conduct- ed graduate studies at the several International Schools on GIS and Earth Sciences. Between 2008 and 2010 he was titled to the Fellow degree by Royal Meteorological Society. On 2009 Mr Diodato was regarded Member of the Scientific and Technical Committees-Editorial Review Boards at the World Academy of Science, Engineering and Technology. Currently Mr Diodato is a Geoscien- tist at the Met European Research Observatory (MetEROBS). Established in 1986, MetEROBS is an accredited observational supersite, awarded in 2011 as Laureate by the ComputerWorld Honors Program Computer- World Honors Program. Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Preface XI About QoS in DVB-S2/RCS Systems 1 Baptiste Jacquemin, Pascal Berthou, Thierry Gayraud and Lionel Bertaux Antenna System for Land Mobile Satellite Communications 33 Basari, Kazuyuki Saito, Masaharu Takahashi and Koichi Ito Cooperative Strategies for Satellite Access 59 Luca Simone Ronga, Rosalba Suffritti and Enrico Del Re MIMO Channel Models for Satellite Communications 79 Abbas Mohammed and Asad Mehmood Analysis of Uses and Metrology : an Experiment in Telecommunications by Satellite and Wireless Network Solution for Rural Areas 93 Fautrero Valérie, Fernandez Valérie and Puel Gilles Design and Implementation of Satellite-Based Networks and Services for Ubiquitous Access to Healthcare 115 Georgi Graschew, Theo A. Roelofs, Stefan Rakowsky and Peter M. Schlag Characterisation and Channel Modelling for Satellite Communication Systems 133 Asad Mehmood and Abbas Mohammed Combining satellite and geospatial technologies for exploring rainstorm hazard over Mediterranean Central Area 153 Nazzareno Diodato Design and Simulation of a DVB-S2-like Adaptive Air interface Designed for Low Bit Rate Emergency Communications Satellite Link in Ku/Ka/Q/V Bands 163 Ponia Pech, Marie Robert, Alban Duverdier and Michel Bousquet Mapping and Estimation of Chemical Concentrations in Surface Soils Using LANDSAT TM Satellite Imagery 183 B.B. Maruthi Sridhar and Robert K. Vincent Contents X Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 OLFISH - A complete, paperless solution for the collection, management and dissemination of marine data 203 Dr. Amos Barkai, Fatima Felaar, Karl Geggus, Zahrah Dantie and Arno Hayes Vegetation Mapping of the Mond Protected Area of Bushehr Province (SW Iran) 239 Ahmadreza Mehrabian, Alireza Naqinezhad, Abdolrassoul Salman Mahiny, Hossein Mostafavi, Homan Liaghati and Mohsen Kouchekzadeh Earth to space link 253 Mandeep Jit Singh, Mardina Abdullah, Baharudin Yatim, Mahamod Ismail and Wayan Suparta Guidelines for Satellite Tracking 283 Dusan Vuckovic, Petar Rajkovic and Dragan Jankovic Interference in Cellular Satellite Systems 299 Ozlem Kilic and Amir I. Zaghloul Beyond life-cycle utilization of geostationary communication satellites in end-of-life 323 Shi Hu-Li, Han Yan-Ben, Ma Li-Hua, Pei Jun, Yin Zhi-Qiang and Ji Hai-Fu Planar Antennas For Satellite Communications 367 Jorge Sosa-Pedroza, Fabiola Martínez-Zúniga and Mauro Enciso-Aguilar Power and Spectral Efficient Multiuser Broadband Wireless Communication System 395 Santi P. Maity Quantum Based Information Transfer in Satellite Communication 421 Laszlo Bacsardi and Sandor Imre Satellite coverage optimization problems with shaped reflector antennas 437 Adriano C. Lisboa, Douglas A. G. Vieira and Rodney R. Saldanha Satellite Laser Communication With Widely Dispersed Ground Stations 453 Paul Christopher Satellite Motion 475 Miljenko Solarić System Aspects of Active Phased Arrays 513 Amir I. Zaghloul, Ozlem Kilic and Eric C. Kohls The title of this study incorporates two currently very popular concepts: satellite and communication . In an era where geoinformation demand are growing at worldwide scale, remote sensing and telecommunication around digital and electronic networks are seriously challenged by the diverse applications of novel digital and information communication technologies. The omnipresence of personal computers and, especially, the introduction of the World Wide Web and the enormous growth of Internet use that has followed, has concretized the possibility to exchange information. The massive amount of writing on the information society has been very much a result of sociologic, philosophic, and political discussion. It is generally accepted that the currently ongoing transition, resulting in a knowledge-based information society, can bring enormous benefits to societies. Decisions made and actions taken today may affect the evolution considerably. Therefore individuals active in various fields need to have a basic understanding of the topics, their relation to each other and the factors influencing their combined evolution. This study is motivated by the need to give the reader a broad view of the developments, key concepts, and technologies related to information society evolution, with a focus on the wireless communications and geoinformation technologies and their role in the environment. Giving perspective, it aims at assisting people active in the industry, the public sector, and Earth science fields as well, by providing a base for their continued work and thinking. Questions addressed in the study are developed within 23 chapters which can be enclosed in four main thematic areas: ♣ System and Models for Satellite Access and Communications ♣ Emergency Communications in social areas ♣ Mapping Communication in Earth Sciences ♣ Optimization Problems and Develop of New Technologies In the first issue System and models for satellite access and communications are presented five chapters: 1) About-QoS in DVB-S2/RCS systems that deals with design and evaluation of Quality of Service Architecture to be implemented in DVB-S2/RCS systems. In this way, geostationary satellite networks are expected to play a decisive role in bridging the existing digital divide through providing broadband access to multimedia services in low terrestrial infrastructure areas. 2) Antenna system for land mobile satellite communications describes an antenna system for land mobile satellite communications particularly in design, development and chamber measurement as well as realization in field experiment using the geostationary satellite. The developed antenna system is simple, compact and promising in low cost production. 3) Cooperative strategies for satellite access can be seen as a new form of spatial Preface XII diversity in which the diversity gain can be achieved through the cooperation of different users, opportunely grouped in clusters. In this way a new class of communications, called cooperative communications, has been proposed as a valuable alternative to spatial diversity techniques which require the deployment of additional antennas in order to mitigate fading effects. 4) In MIMO channel modelling is presented an overview and analytical analysis of standard MIMO channel models for satellite communication systems. In order to further test the channel models and the effect of the propagation environment, was investigated a novel application of using satellite diversity in conjunction with compact MIMO antenna array configurations (exploiting the polarization and pattern diversity features provided by these compact MIMO antennas) in order to enhance the capacity of satellite communication links. In the second issue Emergency Communications in social areas are presented four chapters: 1) Experiment in telecommunications by satellite and wireless network solution for rural areas , where the TWISTER project (2005/2007) responses to the European Commission’s call for tenders, dedicated to satellite solutions. This analysis has enabled to confirm the relevance such as the ‘applications-territories’ coupling, certain territorial stakeholders want to develop more particularly structuring applications, such as, for example, e-administration services (for citizens), telemedicine (for retirement homers, ski resorts, etc.). 2) Design and implementation of satellite-based networks and services for ubiquitous access to healthcare was explicited by different projects that provided satellite-based trans-European competence network for telemedicine, telemedical support in cases of disaster emergencies, support on-board of cruise ships, and the EMISPHER project that enabled an equal access for most of the Euro- Mediterranean countries to online services for healthcare in the required quality of service. 3) In rate emergency communications satellite link in Ku/Ka/Q/V bands is expounded the link budget dimensioning and a customized, enhanced DVB-S2-like air interface proposed to support minimum emergency communications in a severely impaired channel environment in high frequencies. The paper then outlines the combined Excel//Juzzle/Matlab high-level transmission link software simulation platform that was developed in order to assess the performance of theproposed transmission scheme. In the third issue Mapping in Earth Sciences are presented six chapters: 1) Combining satellite and geospatial technologies for exploring rainstorm hazard where a set of sequential GIScience rules was utilized for converting coding data of a Rainstorm Hazard Index ( RHI ) from point record to spatial information using TRMM–NASA satellite rain data as covariate. Examples of probability estimation for different precipitation durations, ranging from 3 to 48 hours and the quantification of hydrological hazard fields were used with probability maps of damaging rainstorms prone-areas for the test-region of Southern Italy. 2) In design and simulation of a DVB-S2-like adaptive air interface designed for low bit , a DVB-S2-based adaptive air interface was proposed and simulated to meet the performance constraints of bidirectional satellite communication links to be established in a post-disaster emergency situation in Ku/Ka and Q/V bands where strong channel impairments occur. So that this chapter expounds the link budget dimensioning and a customized, enhanced DVB-S2-like air interface proposed to support minimum emergency communications in a severely impaired channel environment in high frequencies. 3) Mapping and estimation of chemical concentrations in surface soils has used LANDSAT TM satellite imagery as an alternative method for determining and mapping the physical and chemical characteristics of the soil. Consequently, the focus of this study was to determine the use of remote sensing XIII to map chemical variability in bare soils in elemental concentrations of soils amended with biosolids, and in to use LANDSAT TM data to map these elemental concentrations of the soils when they are not covered by vegetation. 4) In paperless solution for the collection, management and dissemination of marine data were addressed many of the problems related to the complexity of the logical linkages between the different types of data in fisher management, Olrac (www.olrac.com) a South African company, that has developed a data collection and management system it has named Olfish (www.olfish.com) for the specific use of operators and managers in the marine environment with a special focus on the commercial fishing industry. 5) In Vegetation mapping and management was studied the vegetation types in the semiarid to arid region of Mond Protected Area, south-west Iran, based on unsupervised classification of the Spot XS bands and then produced updated maps. Based on field observation and supported by satellite maps, three major habitat zones in the study area, namely, the coastal, riverine and inland zones, were recognized. Twelve vegetation types were recognized in the field that showed a good compatibility with the satellite image. 6) Earth to space link describes how to calculate link-power budget in order to relate to two quantities, the transmitted power and the received power, and show in detail how the difference between these two powers is accounted. To arrive at an accurate answer, factors such as the uplink power amplifier gain and noise factors, transmit antenna gain, slant angles and corresponding atmospheric loss over distance and climatic attenuation factors must be taken into account. In the fourth issue Optimization problems and develop of new technologies are presented with ten chapters: 1) Guidelines for satellite tracking raise the need to know where to look for the artificial and natural satellites in the evening sky has been the obsession for many. So that mathematical models and positioning mechanisms were explained in this chaper to paint the picture of satellite tracking and give the brief insight in when to use what mathematical model to pinpoint the object in sky, even if the final goal is just a view through a telescope. 2) Interference studies in cellular satellite systems accounts to reduce the array antenna aperture on board the satellite for multiple-spot-beam cellular coverage. The reduction in the antenna aperture with this approach translates into significant reductions in number of array elements, RF components, and A/D and D/A converters. Analysis has shown that in spite of the smaller aperture and the broader beams of the sub-beams, the co-channel interference between sub-beams using the same frequency segment is not adversely affected. 3) In Ultra- life cycle utilization of GEO have proposed and verified practical development plan for satellites navigation based on GEO satellites. Particularly was introduced one kind of satellite communication techniques with micro-terminal low-information rate developed in this section. This technique can satisfy some communications and positioning requirements such as unattended measurement and short-message emergency communications. 4) Planar antennas for satellite communications was devoted to planar antennas not only for that already in use but proposing other kind that could be used for satellite applications. In this way was described actual planar antennas used in satellite communications systems and finished with a proposal of new developments of planar antennas that authors think could be used in the near future. 5) Power and spectral efficient multiuser broadband wireless communication system focuses on different aspects of the communication system, namely PAPR reduction and power control in transmitter, channel estimation for design of adaptive and optimized system, multiuser detection at the receiver for increase in user capacity. The newly proposed CI/MC-CDMA system discussed in this chapter may become an efficient multiple access scheme for XIV Satellite communication used for long distance broadband signal transmission in conjunction with cellular system. 6) In Quantum based information transfer was introduced the quantum communication to help to establish a secure communication link, and present solutions with zero redundancy error correction. 7) Satellite coverage optimization problems with shaped reflector antennas was devoted to optimization formulations of satellite coverage problems and their solution which are specially useful in satellite broadcasting applications, and where the information goes from one to many. 8) In Satellite Laser Communication is used a cloud attenuation model derived from key Italsat results to find laser cloud attenuation for satellite- ground links with gaseous attenuation included for 2-10 micron attenuation. Link availability is raised with suitable Northern Latitude satellites, such as Earth Observation Satellites. Soviet cloud correlation results indicate that link availability would be raised to acceptable levels with ground sites separated by 100-290 km. 9) In Satellite motion is described a little history on the satellite motion and its mathematical formulation. This includes the dimensions of orbit and the position of satellite on its orbits, and what velocity for a satellite is requested. 10) System aspects of active phased arrays concluded this book by reviewing early developments of phased arrays for multiple-beam satellite communications applications. A key component in these developments is the modular monolithic microwave integrated circuit (MMIC) beam-forming matrices that generate a number of simultaneous and independently digitally controlled beams. Editor Nazzareno Diodato MetEROBS – Met European Research Observatory, GEWEX-CEOP Network, World Climate Research Programme, via Monte Pino snc, 82100 Benevento Italy About QoS in DVB-S2/RCS Systems 1 X About QoS in DVB-S2/RCS Systems Baptiste Jacquemin 1,2 , Pascal Berthou 1,2 , Thierry Gayraud 1,2 and Lionel Bertaux 1,2 1 CNRS; LAAS; 7 avenue du Colonel Roche, F-31077 Toulouse, France 2 Université de Toulouse; UPS, INSA, INP, ISAE; LAAS; F-31077 Toulouse, France 1. Introduction The standardization of a Return Channel via Satellite and the satellite community efforts in term of interoperability over the last few years stands for major milestones in the development of reliable, efficient and low cost satellite equipments. It leads to quite a positive outcome: geostationary satellite networks are expected to play a decisive role in bridging the existing digital divide through providing broadband access to multimedia services in low terrestrial infrastructure areas. However, unlike cable or 3GPP access networks, a lot of work on IP over satellite has been needed, especially about Quality of Service (QoS). The QoS architecture takes benefits from DVB-RCS dynamic allocation schemes and IP QoS architecture to cope with the satellite delay and the scarce uplink resources. This chapter deals with design and evaluation of Quality of Service Architecture to be implemented in DVB-S2/RCS systems. The first section of this chapter aims at introducing DVB-S2/RCS Systems. The long term efforts to optimize the DVB-S standard to lower the price of satellite access networks led to a new evolution of the standard: DVB-S2. A better encapsulation mechanism of IP packets and a new adaptative transmission scheme are the main concerns for the QoS architecture. The encapsulation of IP packets in DVB-S has always been a complex problem. This section presents the evolution of the standard from the Multiprotocol Encapsulation (MPE) and the Ultra Lightweight Protocol (ULE) to the Generic Stream Encapsulation (GSE). The Adaptive Coding and Modulation (ACM) technique that increase the network efficiency according to the weather conditions is a major evolution. The variable transmission rate impacts the QoS management and offers new perspectives for future system evolution. DVB-S Satellite Terminals can only receive frames from the satellite. The need for a return link rapidly becomes essential so as to support emerging Internet services via satellite. The return link access scheme in DVB-S/RCS systems is MF-TDMA. The return link is segmented into portions of time and frequency (“superframes. A Network Control Center (NCC) performs the entire satellite system control, especially Satellite Terminals synchronization and resource allocation. It periodically broadcasts a signaling frame, the TBTP (Terminal Burst Time Plan), which updates the timeslot allocation within a 1 Satellite Communications 2 superframe between every competing ST. This allocation can be dynamically modified on STs demand thanks to a bandwidth on demand protocol called Demand Assignment Multiple Access (DAMA). This system is presented here. The next section rapidly overviews the concepts and mechanisms of Quality of Service management in basic architectures such as IETF Intserv and IETF / Diffserv. Others mechanisms such as Traffic shaping / conditioning, SLA, Scheduling and Admission control that have a main impact on the QoS are also described. The next part aims at describing what means QoS in satellite networks thanks to the DVB- S2/RCS QoS Architecture example. From the very first system only based on MPLS, a first architecture based on Diffserv was proposed. It was then enhanced to better fit to the DVB-RCS system in the IST project Satsix. The next part will answer a main question related to the satellite networking systems that is: How to develop new services with Satellite Systems? Based on our research work and results in the field, we’ll explain how to use Simulation (using NS-2 or NS-3), Basic Emulation (using Linux TC/Simnet) and Advanced Emulation testbed like the one that was developed in various projects we were involved in. And we’ll conclude that part with our skill on Real Deployed Systems. The last part deals with Performance Evaluation of the described proposals. We first evaluated DVB-S/RCS NS-2 emulation model with QoS. The next way used to evaluate the proposed architecture was done through the PLATINE emulation testbed coming as the main result of the Satsix project. Our last experiment was done in the OURSES project, labeled in the Aerospace Valley research center with the following main devices from Astra (satellite), Thales Alenia Space (Gateway) and Advantech (Satellite Terminal). To conclude this chapter, results summary and lessons learned will be given and future work will be described. 2. DVB-S2/RCS main features 2.1 First overview of DVB-S/RCS systems Started in 1993, the international European DVB Project published, in the end-nineties, a family of digital transmission specifications, based upon MPEG-2 (Motion Picture Expert Group) video compression and transmission techniques. Data are transported within MPEG-2 transport streams (MPEG2-TS) which are identified through DVB Service Information Tables. Adapted for satellite systems, DVB-S defines one of the most widespread formats used for Digital TV over the last years and still nowadays. However, DVB-S Satellite Terminals can only receive frames from the satellite. The need for a return link rapidly becomes essential so as to support emerging Internet services via satellite, leading to 3 solutions: UDLR (UniDirectional Link Routing) which emulates a cheap bidirectional solution through a terrestrial return link, DVB-S system with low speed terrestrial return link, superframe between every competing ST. This allocation can be dynamically modified on STs demand thanks to a bandwidth on demand protocol called Demand Assignment Multiple Access (DAMA). This system is presented here. The next section rapidly overviews the concepts and mechanisms of Quality of Service management in basic architectures such as IETF Intserv and IETF / Diffserv. Others mechanisms such as Traffic shaping / conditioning, SLA, Scheduling and Admission control that have a main impact on the QoS are also described. The next part aims at describing what means QoS in satellite networks thanks to the DVB- S2/RCS QoS Architecture example. From the very first system only based on MPLS, a first architecture based on Diffserv was proposed. It was then enhanced to better fit to the DVB-RCS system in the IST project Satsix. The next part will answer a main question related to the satellite networking systems that is: How to develop new services with Satellite Systems? Based on our research work and results in the field, we’ll explain how to use Simulation (using NS-2 or NS-3), Basic Emulation (using Linux TC/Simnet) and Advanced Emulation testbed like the one that was developed in various projects we were involved in. And we’ll conclude that part with our skill on Real Deployed Systems. The last part deals with Performance Evaluation of the described proposals. We first evaluated DVB-S/RCS NS-2 emulation model with QoS. The next way used to evaluate the proposed architecture was done through the PLATINE emulation testbed coming as the main result of the Satsix project. Our last experiment was done in the OURSES project, labeled in the Aerospace Valley research center with the following main devices from Astra (satellite), Thales Alenia Space (Gateway) and Advantech (Satellite Terminal). To conclude this chapter, results summary and lessons learned will be given and future work will be described. 2. DVB-S2/RCS main features 2.1 First overview of DVB-S/RCS systems Started in 1993, the international European DVB Project published, in the end-nineties, a family of digital transmission specifications, based upon MPEG-2 (Motion Picture Expert Group) video compression and transmission techniques. Data are transported within MPEG-2 transport streams (MPEG2-TS) which are identified through DVB Service Information Tables. Adapted for satellite systems, DVB-S defines one of the most widespread formats used for Digital TV over the last years and still nowadays. However, DVB-S Satellite Terminals can only receive frames from the satellite. The need for a return link rapidly becomes essential so as to support emerging Internet services via satellite, leading to 3 solutions: UDLR (UniDirectional Link Routing) which emulates a cheap bidirectional solution through a terrestrial return link, DVB-S system with low speed terrestrial return link, DVB-RCS, which provides a full bidirectional satellite architecture [Fig. 1]. A good overview of DVB-S/RCS satellite networks architecture is given in Fig. 1, compliant with the architecture adopted within the ETSI BSM [3] group and the DVB-RCS standards. It consists in a geostationary satellite network with Ka MF-TDMA (Multiple Frequency Time Division Multiple Access) uplinks and Ku TDM (Time Division Multiplexed) downlinks. a) transparent satellite b) regenerative satellite Fig. 1. DVB-S/RCS architecture Satellite Terminals (RCST) provide single PC or LANs with the access to the network, while Gateways (GWs) allow the connection with Internet core networks. The uplink access from each RCST is managed through DVB-RCS interfaces. On the 2 topologies, the end-user side of the platform is on the right. On the left is shown the provider/enterprise/Internet side of the platform. It can be distinguished also between the satellite network side (in the middle) and the IP network sides (on left and right ends), interconnected by RCSTs. So, the 3 main components in the satellite network side (middle) are the Satellite, the Return Channel by Satellite Terminals (RCST) and the Network Control Center (NCC). In Fig. 1–a, the architecture relies on a transparent satellite offering a star topology. All the forward links from GW to the RCSTs are DVB-S links and all the return links are DVB-RCS links. This allows the satellite payload to work in a simple transparent way without any computation to be made on the received frames before resending. Such a payload is easier to design and was the first implemented in such GEO satellites. But the main constraints of such architecture are due to the mandatory double hop to be done to go from one RCST to another one as it is needed to go through the GW to access to an RCST. On the opposite, this problem is solved in the second kind of architecture shown in Fig. 1–b. In this topology, the uplinks (to the satellite) are DVB-RCS links only and the downlinks (to the RCST) are DVB-S. The complexity of this solution is located in the satellite where the payload has to be regenerative to translate incoming frames in DVB-RCS in outgoing frames in DVB-S. More complex to implement, the regenerative payload was designed later than the transparent one. It has to be noticed that it is now time to implement hybrid payload including two parts one transparent and the other one regenerative inducing more complexity of the payload, but nothing new in the architecture components where the two kinds of network components coexist, but in separated configurations. About QoS in DVB-S2/RCS Systems 3 DVB-RCS, which provides a full bidirectional satellite architecture [Fig. 1]. A good overview of DVB-S/RCS satellite networks architecture is given in Fig. 1, compliant with the architecture adopted within the ETSI BSM [3] group and the DVB-RCS standards. It consists in a geostationary satellite network with Ka MF-TDMA (Multiple Frequency Time Division Multiple Access) uplinks and Ku TDM (Time Division Multiplexed) downlinks. a) transparent satellite b) regenerative satellite Fig. 1. DVB-S/RCS architecture Satellite Terminals (RCST) provide single PC or LANs with the access to the network, while Gateways (GWs) allow the connection with Internet core networks. The uplink access from each RCST is managed through DVB-RCS interfaces. On the 2 topologies, the end-user side of the platform is on the right. On the left is shown the provider/enterprise/Internet side of the platform. It can be distinguished also between the satellite network side (in the middle) and the IP network sides (on left and right ends), interconnected by RCSTs. So, the 3 main components in the satellite network side (middle) are the Satellite, the Return Channel by Satellite Terminals (RCST) and the Network Control Center (NCC). In Fig. 1–a, the architecture relies on a transparent satellite offering a star topology. All the forward links from GW to the RCSTs are DVB-S links and all the return links are DVB-RCS links. This allows the satellite payload to work in a simple transparent way without any computation to be made on the received frames before resending. Such a payload is easier to design and was the first implemented in such GEO satellites. But the main constraints of such architecture are due to the mandatory double hop to be done to go from one RCST to another one as it is needed to go through the GW to access to an RCST. On the opposite, this problem is solved in the second kind of architecture shown in Fig. 1–b. In this topology, the uplinks (to the satellite) are DVB-RCS links only and the downlinks (to the RCST) are DVB-S. The complexity of this solution is located in the satellite where the payload has to be regenerative to translate incoming frames in DVB-RCS in outgoing frames in DVB-S. More complex to implement, the regenerative payload was designed later than the transparent one. It has to be noticed that it is now time to implement hybrid payload including two parts one transparent and the other one regenerative inducing more complexity of the payload, but nothing new in the architecture components where the two kinds of network components coexist, but in separated configurations. Satellite Communications 4 2.2 Specific DVB-RCS features DVB-RCS systems involve lots of specific techniques, but only a few of them impact the QoS of such a satellite network. So this section is dedicated to the 2 main ones that are DAMA and Encapsulation. 2.2.1 DVB-RCS Demand Assignment Multiple Access (DAMA) Furthermore, DVB-RCS requires a Medium Access Control (MAC) protocol because Satellite Terminals (ST) is able to simultaneously access the return channel capacity. The standard method relies on a Multi-Frequency Time Division Multiple Access (MF-TDMA). It basically relies on the availability of several TDMA channels (corresponding to different carrier frequencies), each subdivided into frames and further into timeslots of fixed length (bursts) during which the STs are able to transmit data through MPEG2-TS or ATM traffic bursts. The entity responsible for this timeslot allocation within the Superframe shared by competing STs is the NCC (Network Control Center) that centralizes the satellite resources management. Thus it periodically broadcasts a signaling frame, the TBTP (Terminal Burst Time Plan) that contains the information on which STs relies to know when to transmit their bursts. This allocation can be dynamically modified by STs requests so as to prevent from wasting satellite resources that would be otherwise statically allocated. The implementation of such a mechanism is generally known as bandwidth on demand (BoD) algorithm. In order to dynamically manage the bandwidth allocation, a bandwidth on demand protocol called Demand Assignment Multiple Access (DAMA) is defined. It relies on the STs ability to request frequently “capacities” to the NCC which enables a regular update of the TBTP to fit to the STs respective traffic load [Fig. 2]. The latter provides signaling schemes as well as MAC QoS Classes and their mapping on capacity types. S IG NALLI NG F RAME DA TA F RA ME 1 DA TA F RA ME 2 DA TA F RA ME 3 DA TA F RA ME 4 DA TA F RA ME 5 DA TA F RA ME 6 DA TA F RA ME 7 DA TA F RA ME 8 S U P E R - F R A M E k - 1 T F B 1 = T R T D + T N C C = 1 9 D A T A F R A M E S N CC STs t T N C C S IG NALLI NG F RAME DA TA F RA ME 1 DA TA F RA ME 2 DA TA F RA ME 3 DA TA F RA ME 4 DA TA F RA ME 5 DA TA F RA ME 6 DA TA F RA ME 7 DA TA F RA ME 8 S IG NALLI NG F RAME DA TA F RA ME 1 DA TA F RA ME 2 T FB 1 F ee d ba ck D el ay T R TD Ro u nd Tr ip D e la y T N CC N C C a lg o r it h m r u nt i m e DA TA F RA ME 3 DA TA F RA ME 4 DA TA F RA ME 5 T N C C S U P E R - F R A M E S U P E R - F R A M E k r IN [ k ] = num be r of pa cke ts re c ei ved in supe r-fra m e k -1 Fig. 2. DAMA algorithm: TBTP computed from RCST requests Thus, the norm defines 5 Capacity Categories to fit the applications needs that will be detailed further in this paper. Capacity types are vital to return path QoS support at MAC layer; therefore they will be described in more details in the following. Any given ST can be 2.2 Specific DVB-RCS features DVB-RCS systems involve lots of specific techniques, but only a few of them impact the QoS of such a satellite network. So this section is dedicated to the 2 main ones that are DAMA and Encapsulation. 2.2.1 DVB-RCS Demand Assignment Multiple Access (DAMA) Furthermore, DVB-RCS requires a Medium Access Control (MAC) protocol because Satellite Terminals (ST) is able to simultaneously access the return channel capacity. The standard method relies on a Multi-Frequency Time Division Multiple Access (MF-TDMA). It basically relies on the availability of several TDMA channels (corresponding to different carrier frequencies), each subdivided into frames and further into timeslots of fixed length (bursts) during which the STs are able to transmit data through MPEG2-TS or ATM traffic bursts. The entity responsible for this timeslot allocation within the Superframe shared by competing STs is the NCC (Network Control Center) that centralizes the satellite resources management. Thus it periodically broadcasts a signaling frame, the TBTP (Terminal Burst Time Plan) that contains the information on which STs relies to know when to transmit their bursts. This allocation can be dynamically modified by STs requests so as to prevent from wasting satellite resources that would be otherwise statically allocated. The implementation of such a mechanism is generally known as bandwidth on demand (BoD) algorithm. In order to dynamically manage the bandwidth allocation, a bandwidth on demand protocol called Demand Assignment Multiple Access (DAMA) is defined. It relies on the STs ability to request frequently “capacities” to the NCC which enables a regular update of the TBTP to fit to the STs respective traffic load [Fig. 2]. The latter provides signaling schemes as well as MAC QoS Classes and their mapping on capacity types. S IG NALLI NG F RAME DA TA F RA ME 1 DA TA F RA ME 2 DA TA F RA ME 3 DA TA F RA ME 4 DA TA F RA ME 5 DA TA F RA ME 6 DA TA F RA ME 7 DA TA F RA ME 8 S U P E R - F R A M E k - 1 T F B 1 = T R T D + T N C C = 1 9 D A T A F R A M E S N CC STs t T N C C S IG NALLI NG F RAME DA TA F RA ME 1 DA TA F RA ME 2 DA TA F RA ME 3 DA TA F RA ME 4 DA TA F RA ME 5 DA TA F RA ME 6 DA TA F RA ME 7 DA TA F RA ME 8 S IG NALLI NG F RAME DA TA F RA ME 1 DA TA F RA ME 2 T FB 1 F ee d ba ck D el ay T R TD Ro u nd Tr ip D e la y T N CC N C C a lg o r it h m r u nt i m e DA TA F RA ME 3 DA TA F RA ME 4 DA TA F RA ME 5 T N C C S U P E R - F R A M E S U P E R - F R A M E k r IN [ k ] = num be r of pa cke ts re c ei ved in supe r-fra m e k -1 Fig. 2. DAMA algorithm: TBTP computed from RCST requests Thus, the norm defines 5 Capacity Categories to fit the applications needs that will be detailed further in this paper. Capacity types are vital to return path QoS support at MAC layer; therefore they will be described in more details in the following. Any given ST can be assigned one or a mix of the four capacity types. Generally, higher priority classes of service are associated with guaranteed capacity (CRA, RBDC), while lower priority classes are predominantly given best effort capacity (VBDC, FCA). The DVB-RCS standard has left many issues open, e.g. how capacity requests are triggered, how and when certain parameters are negotiated (CRA), and if they can be re-negotiated, etc. It defines that when the NCC assigns timeslots to a certain RCST through the TBTP table, it can indicate a “channel” to which the timeslots are assigned. It is obvious that this DAMA mechanism has great impact on what we will discuss later in this paper. 2.2.2 Encapsulation: from MPE to ULE The multipro