Christian Kissling

Sliding window-based Contention Resolution Diversity Slotted ALOHA

Contention Resolution Diversity Slotted ALOHA (CRDSA) and its burst degree optimizations (CRDSA++, IRSA) make use of MAC burst repetitions and Interference Cancellation (IC) making possible to reach throughput values as high as T ≃ 0.8 in practical implementations, whereas for the traditional slotted ALOHA T ≃ 0.37. However, these new techniques introduce a frame-based access to the channel that limits the performance in terms of throughput and packet delivery delay. In this paper, a new technique named Sliding Window CRDSA (SW-CRDSA) and its counterpart for irregular repetitions (SW-IRSA) are introduced in order to exploit the advantages of MAC burst repetition and Interference Cancellation (IC) with an unframed access scheme. Numerical results are also provided in order to validate the statement of better performance.

On the Stability of Contention Resolution Diversity Slotted ALOHA (CRDSA)

The stability of Random Access protocols is of high importance to ensure an efficient usage of resources and good service perception by the users. In this paper the stability region for the recently proposed Contention Resolution Diversity Slotted ALOHA random access protocol is discussed for finite user populations. The system dynamics of a CRDSA Random Access channel are described and a mathematical model is formulated, which allows predicting the stability of the system. From the derived model quantitative approximations of the stability regions and parameter selection for stable operation are provided. Numerical results are derived by means of simulations for validating the mathematical model and the quantitative approximations of the stability region

Architecture of an IP-based aeronautical network

The International Civil Aviation Organization (ICAO) has defined a mobile IPv6-based Aeronautical Telecommunications Network (ATN/IPS) as a next generation communication network for future Air Traffic Management (ATM). The ATN/IPS will be used with different terrestrial and satellite link technologies for supporting future ATM. In parallel, non-operational services will use different link technologies as well. In such an environment, the main challenge is to design a network architecture that integrates all link technologies in a way that mobile users (be it a cockpit user or a passenger) can make use of them in a seamless way. This paper presents the core functionalities developed within the NEWSKY project of such an integrated IP network architecture.

The operation of TCP over aeronautical networks

Future initiatives on enhancing the current air traffic management (ATM) system aim at the integration of various communication systems enabling network centric operations. Therefore, reliable communication protocols and capable communication systems have to be provided in order to realize the eager goals of programs like SESAR and NextGen. Theoretically there are several possibilities where to place the reliable communication protocol but a main idea of the future aeronautical communication network is to use commercial of the shelf products (COTS). Thus, as it seems, there remains only a single candidate protocol, which TCP - a protocol in widespread use over the whole planet, used by millions of internet users from day to day. It seems reasonable to consider the use of TCP in aeronautical networks as well however, there is one major drawback when using TCP over lossy, narrow band, and slow wireless communication links - it does not perform as well as over high-speed broadband interconnected wired networks. This paper investigates several possible options to TCP use in the aeronautical environment.

On the integration of random access and DAMA channels for the return link of satellite networks

Recent advances in Random Access (RA), improving throughput and loss rates, make the usage of such technique particularly interesting to complement Demand Assigned Multiple Access (DAMA) channels for the return link of satellite systems. In this paper, a novel approach for the integration of the two access strategies aimed at transmission delay optimization is presented. An algorithm for DAMA and RA delay estimation is presented, and its accuracy shown by simulations. Furthermore, the benefits of the proposed integration concept are demonstrated with significant gains in delay and throughput in moderate to high load operating regions.

A delay model for satellite constellation networks with inter-satellite links

Within this paper we examine a non-geostationary satellite constellation network with inter-satellite links (ISLs) for global air traffic control (ATC) and air passenger communication (APC). More specifically, an analysis is done to investigate the impacts of different routing policies on the end-to-end delay, and a general model describing the delays is developed. All considerations are based on a Galileo-like satellite constellation network and real global flight data of all commercial flights during one day

Functional building blocks for an integrated aeronautical IP-network

Within the next 10-15 years, air-traffic management (ATM) will be primarily based on data communications and voice communication will be mostly used as fallback solution. Furthermore, it is foreseen that IP-based networking solutions for A/G communication will be deployed for cost savings, high reliability and an optimal alignment with the evolution of communication and security technologies. Such an efficient and sustainable data network for aeronautical communications is required to enable the implementation of a range of operational improvements needed to support the expected growth in air transportation. An IP-based global aeronautical communication network is currently being developed within the NEWSKY project, co-funded by the European Commission and in close collaboration with Eurocontrol and ICAO ACP WG-I (Specification of ATN/IPS). NEWSKY pursues the vision of Networking the Sky by integrating different data link technologies (long range A/G links, airport links, satellite links) and different services (ATS, AOC/AAC, APC) in a single, seamless network. Key functionalities have been identified, namely resource management, mobility, security and end-to-end data transport. In this paper, the raw functional architecture and the ongoing activities towards the specification of the functional modules are investigated.

Capacity versus bit error rate trade-off in the DVB-S2 forward link

The paper presents an approach to optimize the use of satellite capacity in DVB-S2 forward links. By reducing the so-called safety margins, in the adaptive coding and modulation technique, it is possible to increase the spectral efficiency at expenses of an increased BER on the transmission. The work shows how a system can be tuned to operate at different degrees of this trade-off, and also the performance which can be achieved in terms of BER/PER, spectral efficiency, and interarrival, duration, strength of the error bursts. The paper also describes how a Markov chain can be used to model the ModCod transitions in a DVB-S2 system, and it presents results for the calculation of the transition probabilities in two cases.

Satellite constellation networks for aeronautical communication: traffic modelling and link load analysis

The authors examine two different non-geostationary satellite constellation networks with inter-satellite links for global air traffic control and air passenger communication. After developing a traffic model for aeronautical communication services, the authors derive bandwidth requirements for such a global system. The influence of different routing policies is discussed and they show that link loads are comparable for both medium earth orbit and low earth orbit constellations. All considerations are based on real global flight data of all commercial flights during 1 day.

Protocol Stack Options in Heterogeneous Aeronautical Networks

In the future the amount of air traffic as well as the total data traffic volume of aeronautical communication will significantly increase. A single terrestrial technology alone will likely not be able to manage this challenge but satellite communication systems will serve as complement to direct air to ground data links. The future air traffic management (ATM) will thus consist of highly heterogeneous networks consisting of diverse technologies. It is highly important to design the network protocol stack in a way that allows interoperability of all involved networks while being transparent to the end users and providing the required levels of QoS performance, especially in the presence of transport layer protocols like TCP. This paper presents three different protocol stack alternatives dealing with the mentioned issues, investigates their advantages and disadvantages and proposes a protocol stack fitting the needs of ATM communications.