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SUMMARYThis paper presents the detailed architecture of the WISECOM system, which can quickly re-establish and provide telecommunication services after a disaster by integrating terrestrial mobile radio networks, such as GSM, WiFi, WiMAX and TETRA, with satellite technologies. The system aims to be a useful tool to be deployed in the early hours after a disaster event, for both the victims and the rescue services who will be able to communicate in a reliable and robust way, improving the coordination of the different teams and reducing the time needed to provide victims with the proper treatment. The paper presents in detail the different services provided by the system taking into account its two different versions, based on two different satellite technologies, Inmarsat BGAN and DVB-RCS. Together with the presentation of the system capabilities, a business model is also proposed. Thereafter, the architecture of the general system and the demonstrators that have been developed are detailed, according to the two versions of the system. The work also presents the outcomes of the tests conducted with a prototype of the system, and of the final project demonstration, which was held in Germany in May 2008 with the involvement of real end-users (fire brigades and civil protection authorities).

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This paper presents the development of a compact, ruggedized satellite terminal, to be used for communications in emergency situation. The terminal provides GSM coverage in disaster area, where existing communication infrastructure is destroyed or overloaded. It uses GSM backhauling over satellite to transport GSM signalling and data traffic to the core GSM network infrastructure in the disaster-safe area. Additionally, basic data services such as HTTP web browsing and email are also provided via WiFi access. Issues related to the terminal design and the tests that have been undertaken are presented in the paper.

Earth-observation (EO) satellite missions produce a large amount of data using high-resolution optical or radar sensors. During the last decades the amount of data has steadily increased due to improved sensor technologies with increased temporal resolution, sensor resolution, and pixel count. As a consequence EO satellite missions have become limited by the downlink data rates of microwave communication systems, which are inhibited by spectrum restrictions, manageable antenna sizes, and available transmit power. Optical downlinks from EO satellites with data rates of several Gbps mitigate the limiting effects of microwave communication systems; however optical links do not provide the necessary link availability through the atmosphere due to cloud blockage above the ground station. Apart from diversity concepts with several ground stations or satellite networks, a stratospheric High Altitude Platform (HAP) could act as a relay station to forward the optical communication beam over the last 20km through the atmosphere to the ground station, where short-range, high data-rate microwave systems are feasible. This paper will discuss the capabilities of HAP and GEO relay stations to increase the downlink capacities of LEO satellites. Environmental aspects for the deployment of HAP relays and regulatory/technology issues for a microwave downlink on the last 20km to the ground will be discussed.

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SUMMARYThe next generation of satellite systems will likely use some on-board switching techniques enabling the direct transmission of data from any up-link spot-beam to any down-link spot-beam. If the switch used in the payload of the system is an ATM-based shared buffer switch, some losses and delays can occur. Fortunately, these drawbacks can be fought thanks to some buffer management policies (HSPO, SMXQ, EPD) that either ensure low delay or low loss ratio.Real-time (voice or MPEG video streams) and non-real-time applications (file transfer, email, web browsing using TCP/IP protocols) should be carried over these satellite systems with different quality of service (QoS) requirements. Different combinations of buffer management policies are presented to guaranty the QoS required by the user. Especially, special emphasis is put on the way to transmit efficiently layer 3 messages (IP datagrams) within a mix of traffic in order to avoid some high layer retransmission techniques (provided in TCP for instance) wasting both time and bandwidth. Copyright The aim of this paper is to study the optimization of the transmission of layer 3 messages over an ATM UBR-like service provided by a geo-stationary satellite system with ATM-based onboard switching. This optimization will be performed while using different management schemes for the shared buffer of the ATM-like on-board switch. To achieve the transmission of data over the satellite system, all the layer 3 messages}potentially IP datagrams}and data streams are split into several layer 2 cells whose format is fixed (length, payload, addresses, etc.). The switch then handles these cells. If the buffer of the switch becomes overloaded, this kind of switch will react with the drop of some cells inside the buffer in order to avoid the congestion. If a dropped cell belongs to a sequence of cells that makes up a layer 3 message, its loss causes the definitive damage of the entire layer 3 message. This also implies the inefficient transmission of the remaining cells belonging to the same sequence of cells and often the use of a high layer retransmission policy (for example TCP). In Section 1, the ATM-like shared buffer switch will be detailed together with the buffer management policies we can implement to improve its performance. We have assumed in this

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