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Satellite and Space Communications, 2007. IWSSC '07. International Workshop on

Date 13-14 Sept. 2007

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Displaying Results 1 - 25 of 56
  • [Society related material]

    Page(s): 1 - 44
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    Freely Available from IEEE
  • Applicability of Fade Mitigation Techniques to Mobile DVB-S2/RCS Satellite Systems: Accent on Railway Scenario

    Page(s): 1 - 5
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    This paper addresses the applicability of fade mitigation techniques (FMTs) to mobile DVB-S2/RCS based broadband interactive satellite systems. Emphasis is put on the railway scenario, where quite a few pilot projects and demonstration initiatives have already been launched and even (pre-) commercial activities have already commenced. A useful methodology to transform rain fading statistics from a fixed to a mobile satellite communication system is described. Particular attention is paid to the second order rain fading statistics and, specifically, to the rain fade slope, whose accurate knowledge is essential to the design and performance of the FMT control loop. The FMT control loop margin required due to mobility is estimated in line-of-sight (LOS) conditions for different train speeds and rain attenuation levels. In addition, the impact of non-LOS effects, such as long blockages due to tunnels, on the performance of FMT control loop is examined and the possible use of short-term rain fade prediction methods is analyzed. Numerical results obtained through computer simulations are provided and useful conclusions are drawn. View full abstract»

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  • Indoor fading distributions for GPS-based pseudolite signals

    Page(s): 6 - 10
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    During the past few years, accurate positioning of terminals has received much attention in wireless communication. One reason is that of the requirement for emergency call positioning imposed by the authorities. The positioning algorithms based on the Navstar satellites have limitations in the indoor environment because the signal experiences severe attenuation in the indoor environment. The characteristics of the indoor propagation is still not well understood. In many cases, it is assumed that with the deployment of pseudolites, indoor navigation can show better performance. In this paper we analyze the indoor channel propagation using pseudolites, based on the measurement data collected in different scenarios. View full abstract»

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  • Simple Digital Satellite Channel Modeling with Bandwidth, Capacity and Efficiency Evaluations

    Page(s): 11 - 14
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    Digital satellite network is modeled by a set of discrete memoryless channels (DMCs), which reduce to three simple cascade binary symmetric channels (BSCs) for information transmission. The results of channel improvement due to specific error correction are asymptotically or numerically demonstrated in terms of channel capacity, transmission efficiency, message delay, bandwidth conservation and ease message traffic congestion. View full abstract»

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  • On the Optimization of Signal Constellations for Satellite Channels

    Page(s): 17 - 21
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    A gradient method is used to obtain the signal constellation that yields to the minimum error probability over a channel affected by non-linear amplification and additive noise. The results show the dominance of phase shift keying when the amplifier is driven near saturation, and the better performance given by amplitude-phase shift keying if the amplifier is operated in its linear region. View full abstract»

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  • Scintillation Time Series Synthesis for Satellite Links with Hidden Markov Model

    Page(s): 22 - 25
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    This paper introduces a method to model the rapid attenuation fluctuations (the scintillation) on satellite links with generating the time series of attenuation levels. The applied model is a hidden Markov model which is parameterized from an appropriate filtered Gaussian white noise signal. For the parameterization of the Markov chain the Baum-Welch expectation-maximization algorithm has been used. The resulting Markov model is applicable to generate scintillation time series for any desired duration with the time and amplitude resolution of the original training data. From the synthesized time series the statistical properties like the cumulative distribution and the dynamics of the scintillation can be also determined. To prove the accuracy of the model at first the cumulative distribution function of the original and synthesized time series are compared. A further test of the model validity is the comparison with real scintillation measurement on a land mobile satellite link. Finally, the spectral test of the filtered Gaussian model, the hidden Markov model and the satellite link measurement shows that the constant and decreasing parts in the periodograms are showing similarities what confirms the good quality of the model. View full abstract»

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  • On the Relation between Mobility and Rainfall Effects in Ku/Ka-band Line-of-Sight Land Mobile Satellite Channels: An Analytical Statistical Approach

    Page(s): 26 - 30
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (590 KB) |  | HTML iconHTML  

    The candidate frequency bands for the extension of the DVB-S2/RCS broadband satellite systems to fully support mobility are the Ku (12/14 GHz) and Ka (20/30 GHz). At these frequencies, rainfall is a significant propagation impairment which has to be taken into account together with other propagation effects due to mobility, such as multipath, shadowing and blockage. Experimental measurement campaigns conducted so far for Ku/Ka-band land mobile satellite (LMS) channels have mainly focused on the characterization of the mobility effects and have not considered any possible relation between the mobility and rainfall effects. However, recent limited work has indicated that these two fading sources are not independent. The present analysis represents a first approximation addressing this open problem. Emphasis is put on the line-of-sight (LOS) state of a Ku/Ka-band LMS channel, which can be modeled by the Ricean distribution and a high K-factor. A novel analytical model relating the Ricean K-factor with the rain fading effects is presented based on which, an analytical prediction model for the distribution of the Ricean K-factor is derived. The proposed analysis is flexible, can be applied on a global scale and incorporate the impact of several important operational, climatic and geometrical parameters of a mobile satellite system on its channel multipath behavior. Useful numerical results are provided, the need for further experimental verification data is pointed out and specific future planned work is also mentioned. View full abstract»

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  • Capacity Dimensioning for Air Traffic Management (ATM) Services in a Spot Beam Satellite System

    Page(s): 33 - 37
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    Eurocontrol and FAA have jointly produced a roadmap document for future development of Air Traffic Management (ATM) systems, which is called the Communications Operating Concepts and Requirements (COCR) for Future Radio Systems (FRS) [1]. The document (COCR) is written as a general guideline, without taking into account any technological implementation. In this work we are interested in estimating the capacity requirements for a satellite system for ATM. The bit rate requirement per spot beam is determined using the same approach as in the COCR, with some parameters adjusted to fit in a satellite system scenario. Furthermore, the criticality of one particular service message, the A-EXEC, is verified by comparing the required bit rate when it is excluded from the computation. A condition when this criticality applies is also determined. View full abstract»

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  • QoS Support in Hybrid WiFi and DVB-S Networks

    Page(s): 38 - 42
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    The aim of this paper is to investigate QoS in a hybrid satellite-WiFi network and to study mapping issues in the interconnection of these two segments. We have considered both a DVB-RCS-based satellite network and a wireless system based on IEEE 802.11e. Both TCP-based and UDP-based traffic flows are considered. In the satellite network, a dynamic bandwidth allocation scheme is used that is managed by a network control center: differentiated QoS support is guaranteed by the use of separate queues at the Gateway for distinct traffic classes. An ns-2-based simulator has been implemented to study the hybrid scenario. We have been able to show the impact of both different traffic mapping solutions in the interconnection of the network segment and different channel condition on the TCP performance. View full abstract»

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  • Optimal Beam Management in Earth-fixed Satellite Systems

    Page(s): 43 - 47
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1761 KB) |  | HTML iconHTML  

    In this paper we investigate the beam management issue for providing optimal mapping between ground and space terminals in earth-fixed satellite systems. We take the non-homogeneity of the traffic demands into account and define an optimal beam management problem for supplying more bandwidth to denser areas. We model the problem as a network flow problem and propose a feasible solution approach. Performance results show that significant improvement in system availability can be achieved at the expense of acceptable increase in the system cost. View full abstract»

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  • Exact Analysis of Different Detector Algorithms for NDA Carrier Phase Recovery of 16-APSK Signals

    Page(s): 51 - 55
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4114 KB) |  | HTML iconHTML  

    In the new digital video broadcasting standard for satellite communications (DVB-S2), 16-ary amplitude-phase shift keying (APSK) is recommended as modulation scheme, together with 2/4/8-PSK and 32-APSK as alternatives. For carrier phase recovery with feedback loops, decision-directed (DD) and non- data aided (NDA) detector algorithms are basically applicable to 16-APSK schemes. In a recent paper, however, a hybrid NDA/DD solution has been suggested although not analyzed in detail. Motivated by this fact, the latter is to be investigated in terms of open-loop detector characteristic (S-curve) and jitter variance as the main figures of merit in this respect, but with an additional design parameter introduced for optimization purposes. On the other hand, for comparison reasons, results of power-law and monomial-based Viterbi and Viterbi trackers, as classical NDA solutions, are considered as well. View full abstract»

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  • Comparison of SC-FDMA and HSUPA in the Return-Link of Evolved S-UMTS Architecture

    Page(s): 56 - 60
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    Single carrier frequency division multiple access (SC-FDMA), a multiple access technique similar to orthogonal frequency division multiple access (OFDMA), presently features as a strong candidate in the return link of the long time evolution (LTE) of T-UMTS. In the satellite domain there is an emerging research interest in extending mobile broadcasting system architectures that include complementary ground components, in providing bi-directional data services to mobile users. In such 'evolved S-UMTS' architecture, compatibility with current (CDMA based) and future (OFDMA/SC-FDMA) based) T-UMTS physical layer techniques is of high relevance, if satellite networks are to assume a complementary role to terrestrial ones. In this paper, we first give an overview of SC-FDMA and then compare, via simulations, the performance of the technique with that of the WCDMA-based high speed uplink packet access (HSUPA) that has been defined in release 6 of T-UMTS. The performance evaluations are performed over channels that are representative of the evolved S-UMTS architectures. Emphasis in the study is also given to realistic channel estimation and taking into account the effects of the amplifier's non-linearity. Other elements addressed in this paper are the impact of linearization techniques, and the pilot channel design in order to achieve robust estimation in the presence of non-linear channels. View full abstract»

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  • Non-Linear Interference Mitigation for Broadband Multimedia Satellite Systems

    Page(s): 61 - 65
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    This contribution explores the use of interference mitigation techniques applied to broadband satellite systems with co-channel interference. In particular, our focus is on nonlinear precoding techniques, borrowing ideas from the theory of broadcast MIMO channels. A number of schemes are compared, including several implementations of Tomlinson-Harashima precoding and their linear precoding counterparts. Simulations on realistic scenarios show potential improvements of non-linear precoding with respect to linear interference mitigation and classical countermeasures based on frequency division among beams. Also, we identify several practical issues related to the implementation of Tomlinson-Harashima Precoding in satellite communication systems. View full abstract»

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  • Time Synchronization Issues for Quasi-Orthogonal Space-Time Block Codes

    Page(s): 66 - 70
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (441 KB) |  | HTML iconHTML  

    This paper deals with some of the problems arising in multiple-input multiple-output (MIMO) antenna systems, when the receiver's clock is not synchronized to the modulator. Considering that the spatial diversity is exploited through quasi-orthogonal space-time block codes (QOSTBC), we examine the influence of the remaining timing offset on the performance of the system, after coarse timing acquisition has been carried out at the receiver. Specifically, by utilizing the statistical properties of the channel paths and simulating the time error as a uniformly distributed random variable, we show that the average trace of the diversity gain matrix (DGM) undergoes a decrease with respect to the ideal case of zero intersymbol interference (ISI). View full abstract»

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  • Satellite Communications: Research Trends and Open Issues

    Page(s): 71 - 75
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (644 KB) |  | HTML iconHTML  

    A panoramic view on the study and design of digital satellite communication links is the focus of this paper. Starting from the characterization of satellite propagation channel in different application environments (from broadcast to fixed terminals, to broadband mobile satellite access), we address physical layer aspects related to satellite communications in the attempt of providing the reader with an overview of the new trends and open issues in this field. View full abstract»

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  • Joint Symbol Timing and Carrier Frequency Recovery for DVB-SH System

    Page(s): 79 - 83
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    In this paper, we present a novel joint symbol timing and carrier frequency synchronization algorithm for orthogonal frequency division multiplexing (OFDM) system with very low hardware complexity. Although we developed the proposed algorithm with reference to the DVB-SH standard, it is easily adaptable to other OFDM based systems. A well-known problem in OFDM modulation is its vulnerability to synchronization errors. In particular, accurate recovery of carrier frequency and symbol timing is crucial for the proper demodulation of the received packets. The proposed algorithm has low hardware complexity, and at the same time achieves very good performance in both AWGN and multipath channels. Finally, the paper includes also a detailed comparison of the proposed technique with several time and frequency synchronization algorithms already presented in the scientific literature and compliant with the DVB-SH physical layer. View full abstract»

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  • Use of Optical Amplifiers in GEO-HAP free space links

    Page(s): 84 - 88
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    By the use of optical Erbium Doped Fiber Amplifiers (EDFA) in space communications it is possible to exploit the large capacity offered by the optical link, with a considerable reduction of transmitted power. A novel optical system for stratospheric communications is proposed. The link from a stratospheric platform to another one is carried out within the optical domain, thanks to the presence of a GEO that ensure the optical amplification. The optical preamplifier on the receiver end, is the key point for the system design: it must ensure the proper gain to the signal without introducing limitative Spontaneous Emission Noise. View full abstract»

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  • Improved Self-noise Performance of Gardner Synchronizers for Bandwidth-efficient M-PSK Signals

    Page(s): 89 - 91
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    Raised cosines represent more or less the de facto standard for baseband shaping in satellite communications. However, any pulse function satisfying the first Nyquist criterion could be used for this purpose. As reported in a recent paper, some of them exhibit considerably less self-noise jitter than raised cosines if they are employed for non-data-aided recovery of the symbol timing with Gardner detectors. With an extended version of the latter, it is shown analytically and by simulation results that the self-noise floor can be decreased significantly in the medium-to-low range of the excess bandwidth, if the corresponding synchronizer is applied to M-PSK signals shaped by a linear instead of a raised cosine pulse function. View full abstract»

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  • Soft Demapping and Turbo Decoding for Satellite Broadcasting Communications

    Page(s): 92 - 96
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    In this paper an original detection strategy for satellite digital broadcasting communications is defined; particularly, we consider a system derived from the DVB-S2 standard, which has been proposed as a development of the DVB-S system and exploits an iterative decoding and higher order modulations. The proposed approach relies on the use of the information which can be obtained by proper soft demapping schemes and on the use of the turbo codes instead of the LDPC (low density parity check) codes required by the standard. Moreover, an original receiver which is based on iterative demapping and decoding, is introduced. The adoption of this strategy can permit a remarkable performance gain and an improvement of the system throughput. View full abstract»

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  • Ubiquitous and Multifunctional Mobile Satellite all-IP over DVB-S Networking Technology 4G with Radically Distributed Architecture for RRD Regions

    Page(s): 99 - 103
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    The recent broadband satellite systems are based mainly on centralized low-meshed architecture. It predetermines very high traffics concentration. Such structure is not adequate in context of the traffic topology for rural, remote, and difficult for access (RRD) regions. Therefore the cost of these systems is unacceptably large for deployment of future mass broadband communications in RRD regions, which are characterized by poor terrestrial core infrastructures. This paper presents a novel concept of the space-based cost-effective networking technology of future 4G communications with radically distributed (grid-like), mesh, and scalable all-IP/ATM integrated satellite/mobile/wireless architecture for RRD areas. The proposed architecture based on novel QoS-oriented multi-functional access control technology to long-delay space medium (MFMAC), and also on MFMAC-based next generations of wireless ATM (ATM- MFMAC) and multi-protocol label switching (MPLS-MFMAC) technologies. This networking technology will allow an effective support and integration of mobile satellite and terrestrial cellullar, personal, WLAN, WiFi, WiMax, and other wireless systems of future generations 4G for such RRD territories, as BRIC (Brasilia, Russia, India, and China), Sea and Ocean's Archipelago, North Canada, Alaska, Central and South-East Asia, South America, Africa, Australia, etc. View full abstract»

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  • TCP Throughput Enhancement via Link Layer Relay in Multi-hop Satellite IP Networks

    Page(s): 104 - 108
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    Due to the high bit error rate and varying propagation delay over satellite channels, transmission control protocol (TCP)'s performance degrades considerably. In this work, we propose a novel hop-by-hop link layer relay mechanism to enhance TCP throughput in multi-hop satellite IP networks, e.g., Low Earth Orbit (LEO) satellite networks, Medium Earth Orbit (MEO) satellite networks or hierarchical LEO/MEO satellite networks. Analytical methodology is used to estimate the performance of this mechanism first. Then simulations have been carried out to prove it. Numerical results show TCP throughput increases significantly when channel is in poor condition with link layer relay mechanism deployed. View full abstract»

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  • Experimental Evaluation of PDU Concatenation in ULE with IP Telephony

    Page(s): 109 - 113
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    Efficient encapsulation of IP and other network packets is an important issue for wireless links. The Unidirectional Lightweight Encapsulation has been designed to be efficient, yet flexible in providing means to add new header extensions for developing requirements. One of the recently proposed extensions allows for wrapping several network packets into one SubNetwork Data Unit, the PDU-Concat mode. In this paper we give some first results on both the efficiency of this mode, but also critically analyze impacts of the concatenation on real-time audio traffic for IP telephony. For the tests a combination of a laboratory set-up with a DVB-C chain for the PDU-Concat processing and the Astra2connect network for the real satellite networking part has been utilized. View full abstract»

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  • Analytical and Experimental IP Encapsulation Efficiency Comparison of GSE, MPE, and ULE over DVB-S2

    Page(s): 114 - 118
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    Transmitting variable-length network layer (IP) packets over satellite links with fixed frame lengths (or lengths depending on the ACM transmission mode) requires (IP) encapsulation. For DVB-S links with fixed-size 188-byte TS packets, MPE and ULE encapsulations are available. DVB-S2 provides a compatibility mode to pack TS packets into the longer base band frames (BBFrames). Thus MPE and ULE are also available for S2, as well as a native generic stream encapsulation (GSE), avoiding the double overhead of TS and BBFrame encapsulation. The present paper gives a short overview on the available encapsulation protocols for DVB-S2, and then provides a mathematical efficiency calculation model for these encapsulations, in order to allow for performing theoretical efficiency simulations. Comparison graphs of the efficiency values are presented, using both the efficiency models and measurements from real satellite traffic. View full abstract»

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  • Joint DAMA-TCP protocol optimization through multiple cross layer interactions in DVB RCS scenario

    Page(s): 121 - 125
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    Two aspects of DVB-RCS standard can worsen performance of TCP data connections: DAMA access scheme, since it introduces additional and variable delay to the already significant propagation delay and the adoption of Adaptive Coding on the return link to maximize bandwidth efficiency to face variable weather conditions, because it results in variable bandwidth allocation. Both aspects can severely impact TCP performance, especially for what concerns flow adaptation to varying channel conditions and channel usage efficiency. To optimize performance, in this paper cross-layer signaling among transport, MAC and physical layers of a DVB-RCS system is addressed. In particular MAC-TCP cross-layer is analyzed through the use of NS2 network simulator, showing the possible benefit in a DVB-RCS scenario. View full abstract»

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  • Evaluation of a Generic Unidirectional Header Compression Protocol

    Page(s): 126 - 130
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    Header compression techniques are now widely used in wireless and satellite communications. The main drawback of these techniques is to weaken the transmission against bit error or packet losses. Indeed, a corrupted or missing header can lead to a non-decompression of consecutive packets and then to a disconnection until the reception of a non-compressed packet. The parameters of the header compression system should then be carefully determined. In this paper, we first review the main header compression protocols standardized for a unidirectional link. This analysis allows us to build a simple generic header compression model depending on few parameters characterizing a header compression protocol. The evaluation of this model in cases corresponding to particular applications allows us to draw some first lessons for the use of header compression in Satellite communications. View full abstract»

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