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Wide-band CDMA for the UMTS/IMT-2000 satellite component

This paper describes the main aspects relevant to the development of a third-generation radio transmission technology (RTT) concept identified as satellite wide-band CDMA (SW-CDMA), which has been accepted by the International Telecommunications Union (ITU) as one of the possible RTTs for the satellite component of International Mobile Telecommunications-2000 (IMT-2000). The main outcomes of the extensive system engineering effort that has led to the above ITU RTT are described. In particular, we address propagation channel characteristics, satellite diversity, power control, pilot channel, code acquisition, digital modulation and spreading format, interference mitigation, and resource allocation. Due to its similarity with respect to the terrestrial W-CDMA proposal from which it is derived, the SW-CDMA open air interface solution is described briefly, with emphasis only on the major adaptation required to best cope with the satellite environment. Quantitative results concerning the physical-layer performance over realistic channel conditions, for both forward and reverse link, are reported. A system capacity study case for a low-Earth-orbit constellation is also provided.

A survey of architectures and scenarios in satellite‐based wireless sensor networks: system design aspects

This paper is not a survey related to generic wireless sensor networks (WSNs), which have been largely treated in a number of survey papers addressing more focused issues; rather, it specifically addresses architectural aspects related to WSNs in some way connected with a satellite link, a topic that presents challenging interworking aspects. The main objective is to provide an overview of the potential role of a satellite segment in future WSNs. In this perspective, requirements of the most meaningful WSN applications have been drawn and matched to characteristics of various satellite/space systems in order to identify suitable integrated configurations. Copyright

Analysis and performance evaluation of a burst-based TCP for satellite DVB RCS links

ESA Satlabs proposed a splitting architecture, named Interoperable-Performance Enhancing Proxy (I-PEP), which defines a protocol stack for the edges of a Digital Video Broadcasting-Return Channal over Satellite (DVB-RCS) link with the aim of improving performance of Transmission Control Protocol (TCP)-based applications. At the transport layer of I-PEPs, the Space Communications Protocols Standards-Transport Protocol (SCPS-TP) provides a reliable connection to upper layers, although resulting in very poor performance in tests. In fact, standard congestion-control mechanisms under-perform mainly due to long latency and Demand Assignment Multiple Access (DAMA) access schemes, especially in the case of short transfers, as for Web traffic, when optimum window may not be reached. In this paper, a burst-based TCP, named TCP Noordwijk (TCPN), is introduced to improve on these aspects. To evaluate performance, the protocol has been implemented on the Network Simulator NS-2. Definitively, details on the protocol design, implementation, and a vast gamut of results coming from simulations are reported.

Large‐scale site diversity for satellite communication networks

The utilization of high frequencies, such as Ka-band and beyond, necessary to avoid the highly congested lower satellite frequencies and to get larger bandwidth availability is considered for many developing satellite systems. The new satellite low-margin systems in Ka-band will need to be designed using fade countermeasures to counteract rain attenuation. One of these techniques foresees the possibility of switching the communication link among different Earth stations spread on a very large territory to reduce the system outage time to the joint outage time of all the stations. The design of such systems depends on the probability that the Earth stations simultaneously exceed their margins. In this paper, a well-assessed model is utilized for the prediction of joint statistics of rain attenuation in multiple locations, using Monte Carlo simulation. The model is based on a pair of multi-variate normal processes whose parameters are related to those characterizing the single-location statistics and whose covariance matrices are assumed to depend only on the distances between locations. The main results concerning both the probability and margin improvement will be presented and discussed. Copyright

Dynamic resource allocation based on a TCP‐MAC cross‐layer approach for DVB‐RCS satellite networks

Satellite communication networks can provide multimedia broadband services to fixed and mobile users in several scenarios where terrestrial networks are not present or where they need to be complemented. Moreover, satellite links can be useful to bypass crowded terrestrial networks, thus helping in reducing congestion. In such a scenario, characterized by a high propagation delay and a radio channel affected by losses, standard bandwidth allocation schemes prove to be inefficient when Transmission Control Protocol (TCP) is running. Hence, we propose a novel resource allocation scheme based on the cross-layer interaction between TCP and Medium Access Control (MAC) layers. The interest is here in achieving an efficient transfer of files by means of the FTP application protocol. Our scheme permits to avoid network congestion, to reduce the average file transfer time and to achieve a fair sharing of resources among competing flows. The allocation technique has been applied to an Interactive Satellite Network (ISN) based on the DVB-RCS standard with a group of fixed satellite terminals, which communicate with a Netivork Control Center (NCC) through a geostationary bent-pipe satellite, according to a classical star topology. Results are obtained through a network simulator. Copyright (c) 2006 John Wiley & Sons, Ltd.

Performance evaluation of TCP-based applications over DVB-RCS DAMA schemes

Transmission Control Protocol (TCP) performance over Digital Video Broadcasting-Return Channel via Satellite (DVB-RCS) standard is greatly affected by the total delay, which is mainly clue to two components, propagation delay and access delay. Both are significant because they are dependent oil the long propagation path of the satellite link. I-lie former is intrinsic and due to radio wave propagation over the satellite channel for both TCP packets and acknowledgements. It is regulated by the control loop that governs TCP. The latter is due to the control loop that governs the demand assignment Multiple access (DAMA) signalling exchange between satellite terminals and the network control center. necessary to manage return link resources. DAMA is adopted in DVB-RCS standard to achieve flexible and efficient use of the shared resources. Therefore, performance of TCP over DVB-RCS may degrade due to the exploitation of two nested control loops also depending oil both file selected DAMA algorithm and the traffic profile. This paper analyses the impact of basic DAMA implementation oil TCP-based applications over a DVB-RCS link for a large Set Of study Cases. To provide a detailed overview of TCP performance in DVB-RCS environment, the analysis includes both theoretical approach and simulation campaign. Copyright (C) 2009 John Wiley & Sons, Ltd.

Dynamic Resource Allocation based on a TCP-MAC Cross-Layer Approach for Interactive Satellite Networks

DVB-RCS is an open standard for interactive broadband satellite services. According to the standard, interactive terminals communicate with the network control center through the return channel adopting MF-TDMA. In this scenario, classical bandwidth allocation schemes do not take into account TCP evolution, leading to sub-optimal performance when TCP-based traffic share the return link. A cross-layer approach, based on exchange of information between not-adjacent layers, can help to improve efficiency. This paper presents an innovative allocation algorithm based on a cross-layer interaction between TCP and MAC layers. Such an algorithm aims to synchronize the requests of resources with the TCP transmission window trend. The obtained results show that our scheme permits both to reduce the delay, to increase the utilization of air interface resource and to achieve a fair share of resources among competing flows

Interworking between MANET and satellite systems for emergency applications

SUMMARY This paper presents the main achievements of a project, focused on the design of an integrated system composed of a satellite segment and a MANET to provide telecommunication services in emergency scenarios, in terms of network design, focusing in particular on the development of the interface between the two systems and showing the results of field trials. Copyright # 2007 John Wiley & Sons, Ltd. Accepted 23 June 2007

Satellite coverage in urban areas using unmanned airborne vehicles (UAVs)

In case of emergency, when fixed infrastructures collapse, access to satellite resources might represent the only means of communication, even though, especially in an urban environment, shadowing can strongly reduce the visibility time. In addition, TCP based applications suffer from well know problems due to long latency. To improve performance we can act both at the architectural and protocol level. This paper considers an innovative architecture using HAPS (high altitude platforms station)/UAV connected to the satellite, thereby reducing the impairment of shadowing and introducing a short-range link with the user terminal; efficient TCP solutions allow use of standard equipment and applications without sacrificing performance. The combined use of both can greatly improve overall performance. The paper investigates how this innovative system architecture can be usefully employed in critical scenarios and provides a performance evaluation of TCP based applications using high data rate links.

Intersegment handover between terrestrial and satellite segments: analysis and performance evaluation through simulation

In future generation communication systems, integration among different segments (terrestrial indoor, terrestrial outdoor and satellite) will be necessary if aiming at providing real global and contiguous coverage without interruption. To achieve integrated or interworking systems efficient algorithms to perform intersegment handover (ISHO) must be implemented. In this way, the switching among different segments can occur without dropping of the call. The paper aims at analyzing some ISHO procedures developed in the frame of some European projects and at evaluating their performance for different system configurations utilizing a dynamic constellation simulator in the time domain. On the basis of the above procedures, aiming at optimizing resources, a new procedure is proposed and analyzed. For each procedure the execution delay and its range of variation have been evaluated for different constellation geometry. Finally, a performance comparison among the various procedures is shown.