Impact of Scheduling in the Return-Link of Multi-Beam Satellite MIMO Systems

The utilization of universal frequency reuse in multi-beam satellite systems introduces a non-negligible level of co-channel interference (CCI), which in turn penalizes the quality of service experienced by users. Taking this as starting point, the paper focuses on resource management performed by the gateway (hub) on the return-link, with particular emphasis on a scheduling algorithm based on bipartite graph approach. The study gives important insights into the achievable per-user rate and the role played by the number of users and spot beams considered for scheduling. More interestingly, it is shown that a free-slot assignment strategy helps to exploit the available satellite resources, thus guaranteeing a max-min rate requirement to users. Remarks about the trade-off between efficiency-loss and performance increase are finally drawn at the end of the paper.Comment: Submitted and accepted to IEEE GLOBECOM 2012 Conference, 6 pages, 10 figure

Aerial base stations with opportunistic links for next generation emergency communications

Rapidly deployable and reliable mission-critical communication networks are fundamental requirements to guarantee the successful operations of public safety officers during disaster recovery and crisis management preparedness. The ABSOLUTE project focused on designing, prototyping, and demonstrating a high-capacity IP mobile data network with low latency and large coverage suitable for many forms of multimedia delivery including public safety scenarios. The ABSOLUTE project combines aerial, terrestrial, and satellites communication networks for providing a robust standalone system able to deliver resilience communication systems. This article focuses on describing the main outcomes of the ABSOLUTE project in terms of network and system architecture, regulations, and implementation of aerial base stations, portable land mobile units, satellite backhauling, S-MIM satellite messaging, and multimode user equipments

Anaesth Crit Care Pain Med

PURPOSE: To provide recommendations for the anaesthetic and peri-operative management for thrombectomy procedure in stroke patients DESIGN: A consensus committee of 15 experts issued from the French Society of Anaesthesia and Intensive Care Medicine (Société Française d'Anesthésie et Réanimation, SFAR), the Association of French-language Neuro-Anaesthetists (Association des Neuro-Anesthésistes Réanimateurs de Langue Francaise, ANARLF), the French Neuro-Vascular Society (Société Francaise de Neuro-Vasculaire, SFNV), the French Neuro-Radiology Society (Société Francaise de Neuro-Radiologie, SFNR) and the French Study Group on Haemostasis and Thrombosis (Groupe Français d'Études sur l'Hémostase et la Thrombose, GFHT) was convened, under the supervision of two expert coordinators from the SFAR and the ANARLF. A formal conflict-of-interest policy was developed at the outset of the process and enforced throughout. The entire guideline elaboration process was conducted independently of any industry funding. The authors were required to follow the principles of the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system to guide their assessment of quality of evidence. METHODS: Four fields were defined prior to the literature search: (1) Peri-procedural management, (2) Prevention and management of secondary brain injuries, (3) Management of antiplatelet and anticoagulant treatments, (4) Post-procedural management and orientation of the patient. Questions were formulated using the PICO format (Population, Intervention, Comparison, and Outcomes) and updated as needed. Analysis of the literature was then conducted and the recommendations were formulated according to the GRADE methodology. RESULTS: The SFAR/ANARLF/SFNV/SFNR/GFHT guideline panel drew up 18 recommendations regarding anaesthetic management of mechanical thrombectomy procedures. Due to a lack of data in the literature allowing to conclude with high certainty on relevant clinical outcomes, the experts decided to formulate these guidelines as "Professional Practice Recommendations" (PPR) rather than "Formalized Expert Recommendations". After two rounds of rating and several amendments, a strong agreement was reached on 100% of the recommendations. No recommendation could be formulated for two questions. CONCLUSIONS: Strong agreement among experts was reached to provide a sizable number of recommendations aimed at optimising anaesthetic management for thrombectomy in patients suffering from stroke

A Tool for Satellite Communications: Advanced DVB-RCS / DVB-S2 System and Protocol Simulator

A tool has been designed to simulate broadband satellite communication systems and techniques: a system and protocol simulator based on advanced DVB-RCS and DVB-S2 standards. As a powerful and flexible tool, it can be used to investigate and optimize current and future satellite communication systems, mainly to develop resource management algorithms and assess system performances. It is capable of simulating a satellite system using Ka-Band with multi-beam European coverage. It integrates rain attenuation and interference models and respects the complete DVB-RCS/DVB-S2 protocol stack and an evolution of DVB-RCS with adaptive coding and modulation (ACM). The simulator supports different quality of services (QoS)/service level agreements (SLA), ACM, several encapsulation schemes, congestion control mechanisms, call admission control and resource management. This paper gives an overview of the possibilities offered by the tool and presents some results

A System Simulator for Advanced DVB-S2/RCS Multibeam Systems

Satellite communication systems play an increasing role for broadband communication in the customer, as well as in specialized segments. They can be used as gap-fillers for areas not covered and not likely to be covered by broadband DSL, they have their advantages for some kinds of applications (massive multicast) and can help closing the digital divide without having to invest into terrestrial infrastructure in challenging territories. The peculiarities of satellite systems – high initial costs, complexity or impossibility of updates – make it especially important to obtain a correct evaluation of the performance of the system before installing it. It is also a major necessity to be able to invent new algorithms and techniques, to tune system parameters, without having to use a real, expensive satellite system. This paper presents a simulator representing a complete satellite communication system based on DVB-S2 and advanced DVB-RCS techniques, including simulation of atmospheric effects, user behavior and all major protocols needed in transparent as well as regenerative systems. This simulator allows developing new algorithms and protocols, tuning satellite systems and analyzing system stability and performance. The paper also presents an advanced forward link scheduling algorithm as well as some results obtained with the simulator

Performance Assessment using ACM in DVB-S2/Advanced DVB-RCS Satellite Systems

This paper presents the benefits of using adaptive coding and modulation in DVB-S2/advanced DVB-RCS satellite systems. The results are based on a satellite system simulator which was developed during an ESA study. Such a simulator aims at making performance assessments before implementing a system, at developing and evaluating new algorithms like schedulers, encapsulators or resource managers. The simulator is capable of reproducing DVB-S2 and advanced DVB-RCS standards and techniques so that system performance can be analysed and optimized without the need of using a real satellite system

Subset Optimization of Adaptive Coding and Modulation Schemes for Broadband Satellite Systems

The number of Coding and Modulation Schemes suggested for the two standards DVB-S2 and DVB-RCS (in its "advanced" version) is clearly overdimensioned; a subset of schemes can be used by reducing the overall system performance negligibly. This paper presents the investigations performed on this rain fading mitigation technique, called Adaptive Coding and Modulation (ACM), supported by the DVB-S2 standard and shows how the sets of modulation and coding schemes, considered in the forward- and in the return-links, can be changed to reduce terminal complexity and how this affects the overall system performance. It is shown that, by a careful selection of the ACM schemes, already with less than one fourth (7 or 5 out of 28) of the total number of schemes it is possible to get performance close to the optimum, but with a much lower terminal complexity

On the Achievable Rates for the Return-Link of Multi-Beam Satellite Systems Using Successive Interference Cancellation

This paper investigates the theoretically reachable rates in the return-link of multi-user multi-beam satellite systems. The return-link can actually be analyzed by means of multiple-input multiple-output signal processing techniques. While MIMO inspired multi-user detection for the return-link of satellite systems has been partly investigated in the past, a fundamental look at the achievable gains by these advanced signal processing techniques for satellite communications is missing. Depending on the number of colors used in the system, the available bandwidth per beam can be traded off against the level of co-channel interference. This paper explores the fundamental limits dictated by information theory to the communication rates on satellite multi-beam scenarios, and the impact of a realistic beam patterns on these data rates

Development of Integrated and Transportable Communication Terminal Using GSM and WiFi over Satellite for Emergency Communications

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