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.
Random Access (RA) Medium Access (MAC) protocols are simple and effective when the nature of the traffic is unpredictable and random. In the following paper, a novel RA protocol called Enhanced ...Contention Resolution ALOHA (ECRA) is presented. This evolution, based on the previous Contention Resolution ALOHA (CRA) protocol, exploits the nature of the interference in unslotted Aloha-like channels for trying to resolve most of the partial collision that can occur there. In the paper, the idea behind ECRA is presented together with numerical simulations and a mathematical analysis of its performance gain. It is shown that relevant performance increases in both throughput and Packet Error Rate (PER) can be reached by ECRA with respect to CRA. A comparison with Contention Resolution Diversity Slotted ALOHA (CRDSA) is also provided.
Safe flying in a future, crowded airspace will require significantly increased volumes of information exchanges, as well as reliable and adequate transfer mechanisms for both the air/ground and the ...air/air segments. However, current communications systems will not be able to support the estimated traffic growth using today's operational data links or the upcoming data links already under development. A new Air Traffic Management communications infrastructure is hence required. A very likely scenario for forthcoming aircraft communication includes satellite links as an essential component in order to meet the QoS requirements in terms of coverage, availability, priority and integrity. This work evaluates the suitability of DVB-S2/RCS for the provision of Air Traffic Management services and discusses possible designs for network architecture, resource management concepts and security issues.
The EU SANDRA (Seamless Aeronautical Networking through integration of Data-Links, Radios and Antennas) project 1 aims to design, specify and develop an integrated aircraft communication system to ...improve efficiency and cost-effectiveness by ensuring a high degree of flexibility, scalability, modularity and reconfigurability. SANDRA aims at the definition of an access to an open system resulting in a collection of communications technologies targeted at specific operational settings. Within the paper the main ideas of this envisaged communications concept are addressed. Furthermore, quality of service management strategies are assessed with respect to their applicability and efficiency in the ATM (Air Traffic Management) context. Additionally, techniques for the selection of links for data transmission and the interaction between technology independent and technology dependent components in the networking architecture are covered by means of standardized communication protocols such as IEEE 802.21 and ETSI BSM extensions.
NEWSKY is a project aiming at the integration of various communication links into an all-IP based network. This network shall be based on IPv6 and commercial of the shelf products (COTS). Technical ...work packages have defined solutions for quality of service, mobility, inter- and intra- network handover, and security. In order to validate the derived concepts a realistic topology has been built which facilitates simulating the NEWSKY functions on the participating entities of that topology. In a further step various simulation scenarios shall provide insight of advantages and disadvantages of different protocol solutions, respectively.
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.
The aim of this study was to evaluate the possible risk of impaired bone metabolism following augmentation cystoplasties with different gastrointestinal segments.
60 young rats underwent augmentation ...cystoplasties using gastric, ileal or sigma segments, or sham operations. An additional group undergoing sigma-cystoplasty received the bisphosphonate ibandronate to inhibit osteoclast-mediated bone resorption. Bone mass in the lumbar spine and tibia was analyzed monthly by in vivo densitometry. Bone turnover was assessed monthly using current bone metabolism markers for a period of 16 weeks. Bone ashing and serum analyses of the osteotropic hormones parathyroid hormone (PTH), and 25-OH vitamin D3 were performed at study conclusion.
Following ileocystoplasty, reduced bone mineral density (BMD) was seen throughout the observation period; this was pronounced in the trabecular bone. The decline in BMD was associated with decreased serum 25-OH vitamin D3 levels. Following sigmacystoplasty, bone calcium content was significantly decreased; this could be prevented by ibandronate. No skeletal changes occurred in the gastrocystoplasty group. Serum pH was not altered in any group, and markers of bone resorption indicated normal bone resorption rates.
There is a significant correlation between impaired bone metabolism and the type of segment used for bladder augmentation. While the use of the ileum (and probably the colon too) causes osteopenia, gastrocystoplasties seem to have little influence on bone turnover.
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 \(T \simeq 0.8\) in practical implementations, whereas for the traditional slotted ALOHA \(T \simeq 0.37\). 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.
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