José Radzik

Next generation High Throughput Satellite system

This paper aims at presenting an overview of the state-of-the-art in High Throughput Satellite (HTS) systems for Fixed Satellite Services (FSS) and High Density-FSS. Promising techniques and innovative strategies that can enhance system performance are reviewed and analyzed aiming to show what to expect for next generation ultra-high capacity satellite systems. Potential air interface evolutions, efficient frequency plans, feeder link dimensioning strategies and interference cancellation techniques are presented to show how Terabit/s satellite myth may turn into reality real soon.

Smart gateways for terabit/s satellite

To reach the terabit per second of throughput, telecommunication satellites cannot make use of frequency below Ka band only. Therefore, the use of broad portion of the spectrum available at Q/V (40/50 GHz) band is foreseen for the feeder link. This study presents the evaluation of performances of different macro-diversity schemes that may allow mitigating the deep fades experienced at Q/V bands by introducing cooperation and a limited redundancy between the different gateways of the system. Two different solutions are firstly described. The performances resulting from the use of those assumptions are derived in a second stage.

Aeronautical Ad Hoc Network for Civil Aviation

Aeronautical communication systems are constantly evolving in order to handle the always increasing flow of data generated by civil aviation. In this article we first present communication systems currently used for en-route aircraft. We then propose Aeronautical Ad hoc NETwork (AANET) as a complementary communication system and demonstrate its connectivity and assess the throughput by simulations based on real aircraft trajectories over the French sky and over the Atlantic ocean.

Wireless Ad Hoc Networks Access For Aeronautical Communications

There is an increasing interest in the current aeronautical context to offer new services for civil aircraft passengers. For example, airlines want to offer their customers the opportunity to access the Internet, to manage their mails, to watch video on demand, to access corporate VPNs.... All these services represent a new type of air-ground communications called APC (Aeronautical Passenger Communications) in the ATN (Aeronautical Telecommunication Network) context. In this paper, we will show how an aeronautical ad hoc access network and satellite links can be used simultaneously for these communications.

Interference estimation in an aeronautical ad hoc network

Recent research have considered aeronautical ad hoc networks as a possible mean for future aeronautical communications. By introducing inter-aircraft links, they are supposed to become an alternative to existing solutions based on direct air-ground or satellite links. In this paper, we propose the use of asynchronous Code Division Multiple Access (CDMA) in aeronautical ad hoc networks. We then present a simulation model developed with OPNET Modeler that estimates the impact of Multiple Access Interference (MAI) on packets delivery. Finally, we give the results of some simulations made with an ATC/AOC traffic model, and with real aircraft positions over the French sky.

DVB-RCS return link Radio Resource Management for Broadband Satellite systems using fade mitigation techniques at Ka band

Current broadband satellite systems supporting DVB-RCS at Ku band have static physical layer in order not to complicate their implementation. However at Ka band frequencies and above an adaptive physical layer wherein the physical layer parameters are dynamically modified on a per user basis is necessary to counteract atmospheric attenuation. Satellite radio resource management (RRM) at the medium access control (MAC) layer has become an important issue given the emphasis placed on quality of service (QoS) provided to the users. The work presented here tackles the problem of Satellite RRM for broadband satellite systems using DVB-RCS where a fully adaptive physical layer is envisaged at Ka band frequencies. The impact of adaptive physical layer and user traffic conditions on the MAC layer functions is analyzed and an algorithm is proposed for the RRM process. Various physical layer issues associated with the resource management problem are also analyzed.

Channel and Traffic based Adaptive Radio Resource Management strategies for the return link of Ka/Q/V band Communication Satellite systems employing Fade Mitigation Techniques

Efficient utilization of the satellite radio resource is of paramount importance to a satellite systems performance and economic competitiveness. The likely use of Ka band and above frequencies for future satellite systems and the need for a better quality of service (QoS) complicate the radio resource management process especially in the return link of a satellite system, one that connects the user to the Gateway or Hub. This paper discusses the research themes that are part of the PhD research, carried out at SUPAERO, aimed at developing radio resource management algorithms that will ultimately improve the resource utilization and the QoS for the return link of interactive broadband satellite systems employing fade mitigation techniques at Ka/Q/V band frequencies. The inputs and optimization criteria for the resource management process are identified. Various physical layer issues that confront the process are also identified. The duration of the research is about 3 years from March 2007 to end of 2009.

On the trade-off between spectrum efficiency with dedicated access and short end-to-end transmission delays with random access in DVB-RCS2

This paper analyses the performance of TCP over random and dedicated access methods in the context of DVB-RCS2. Random access methods introduce a lower connection delay compared to dedicated methods. We investigate the potential to improve the performance of short flows in regards to transmission delay, over random access methods for DVB-RCS2 that is currently under development. Our simulation experiments show that the transmission of the first ten IP datagrams of each TCP flow can be 500\,ms faster with random access than with dedicated access making the former of interest to carry Internet traffic. Such methods, however, are less efficient in regards to bandwidth usage than dedicated access mecanisms and less reliable in overloaded network conditions. Two aspects of channel usage optimization can be distinguished: reducing the duration of ressource utilization with random access methods, or increasing the spectrum efficiency with dedicated access methods. This article argues that service providers may let low-cost users exploit the DVB-RCS2 to browse the web by introducing different services, which choice is based on the channel access method.

Physical Channel Access (PCA): Time and Frequency Access Methods Simulation in NS-2

We present an NS-2 module, Physical Channel Access (PCA), to simulate different access methods on a link shared with Multi-Frequency Time Division Multiple Access (MF-TDMA). This technique is widely used in various network technologies, such as satellite communication. In this context, different access methods at the gateway induce different queuing delays and available capacities, which strongly impact transport layer performance. Depending on QoS requirements, design of new congestion and flow control mechanisms and/or access methods requires evaluation through simulations.

Broadband Access Terabit/s Satellite Concepts

This paper aims at presenting different concepts for a broadband access satellite. A hybrid system using Q/V-bands on the feeder links and Ka-band on the user links has been considered. European coverage with a large number of beams allows a large frequency reuse factor depending on the number of colors of the cluster pattern. The use of Q/V band for the feeder links requires site diversity to counteract the strong tropospheric fading occurring at Q/V band and to obtain acceptable link availability. The paper gives an overview of the various trade-offs for frequency-reuse scenarios, size and number of beams, number of gateways, site diversity options and gateway handover.