1,720,981 research outputs found
QoS Optimisation of eMBB Services in Converged 5G-Satellite Networks
No full textThe integration of satellite communications into 5G ecosystem is pivotal to boost enhanced mobile broadband (eMBB) services in highly dynamic scenarios and in areas not optimally supported by terrestrial infrastructures. Given the heterogeneity of the networks involved, network slicing is key networking paradigm to ensure different grades of quality of service (QoS) based on the users' and verticals' requirements. In this light, this paper proposes an optimisation framework able to exploit the available resources allocated to the defined network slices so as to meet the diverse QoS/QoE requirements exposed by the network actors. Resource allocation schemes built upon neural network algorithms are validated through extensive simulation campaigns that have shown the superiority of the proposed concepts with respect to other solution candidates available from the literature
Reliable data delivery over deep space networks: Benefits of long erasure codes over arq strategies
No full textMulticolor Licklider Transmission Protocol: An LTP Version for Future Interplanetary Links
Full text linkThe Licklider Transport Protocol (LTP) is the "convergence layer" of choice in Interplanetary networks based on Delay-/Disruption-Tolerant architecture. It was designed for long-delay scheduled-intermittent links, offering either a reliable or an unreliable service, with "red" and "green" parts, respectively. The aim of this article is to present multicolor LTP, an LTP version consisting in a series of enhancements of which the most significant are the use of monochrome sessions, the introduction of an additional orange color offering a "notified" service, and the definition of default link colors. After a thorough examination of basic LTP mechanisms for all color variants, this article discusses two scenarios where orange seems particularly appealing: video streaming and optical interplanetary links. Numerical results offer further insight into the complex LTP mechanisms and also highlight the difference between LTP retransmissions and bundle protocol retransmissions, the latter benefitting from routing reprocessing. Multicolor LTP has already been implemented as an interplanetary overlay network (ION) plug-in and its enhancements have been proposed to Consultative Committee for Space Data Systems Space Internetworking Services Delay-/Disruption-Tolerant Networking working group for a possible inclusion in the next version of LTP specifications (LTPv2)
Local or Edge/Cloud Processing for Data Freshness
No full textSeveral actuation choices in the Internet of things (IoT) require state information to be up-to-date. In this context, the choice between local processing and offloading to a more powerful remote server can have a significant impact on data freshness. Local processing is indeed typically less reliable due to limited computing power and may require multiple attempts, which can result in data becoming stale. Conversely, remote (i.e., edge/cloud) processing can be more reliable, yet entail longer response times due to data transmission to an external server, possibly performing processor sharing with other tasks. The optimal balance depends on the specific system conditions, especially on the congestion at the remote server, and is in general non-trivial. We explore this tradeoff through a mathematical model, and argue about the derivation of a freshness-efficient local vs. remote split of requests, providing insights on the role played by reliability and latency in selecting the optimal strategy
A DTN-oriented protocol design for satellite based architectures
No full textSeveral communication environments, supporting important operational scenarios such as deep space communications, Earth observation and mobile terrestrial communications, are extremely challenging for traditional TCP/IP protocols because of their intrinsic characteristic to not guarantee continuously an end-to-end path. An attractive application scenario is concerned the presence of terminals moving on a large area requiring handovers among different networks. This paper addresses mobility management through a DTN-based architecture, focusing on both routing and application level issues. In addition, a preliminary analysis of performance of a TCPbased convergence layer is carried out within satellite segment, highlighting implications on the overall architecture. Finally, TCP Noordwijk is proposed as a DTN convergence layer over satellite links and validated through NS-2 simulations
HSLTP - An LTP Variant for High Speed Links and Memory Constrained Nodes
Full text linkDelay/disruption-tolerant networking architecture relies on the use of Licklider Transmission Protocol (LTP) on interplanetary links. LTP loss recovery is based on automatic repeat request retransmissions, which, when the propagation delay is very long, are costly. Alternatively, losses could be recovered by using Packet Layer Forward Error Correcting codes, as done by the authors in ECLSA (error Coding Link Service Adapter), recently presented in a companion paper, where LTP segment retransmissions are limited to the unlikely case of decoding failures. However, on high bandwidth-delay-product links, the very possibility of segment retransmission requires that a huge number of Rx buffers be available. To resolve this problem, high-speed LTP, presented here, has a more disruptive approach than ECLSA: it enforces almost one-to-one correspondence between LTP blocks and FEC codewords, and never requires LTP segment retransmissions. In the unlikely case of a FEC failure, the partially received block is discarded and its bundles are resent directly by the bundle protocol. The advantages and disadvantages of this approach are explored in the article. On nodes limited in memory, the results are significantly improved
LTP Performance on Near Earth Optical Links
Full text linkThe Licklider Transport Protocol (LTP) has been designed to cope with long-delay and error-prone scheduled-intermittent links, and thus is envisaged as the Bundle Protocol (BP) “convergence layer” of choice in future Inter-planetary networks (IPN) based on the Delay-/Disruption-Tolerant architecture. Moreover, LTP's remarkable ability to cope with multiple losses when operating in “red” reliable mode also makes it potentially appealing when coupled with Near Earth optical links. The aim of this paper is to assess LTP performance in this scenario, so we have developed a test bed based on real machines, real implementations of BP and LTP, and a channel emulator; this is based on “erasure vectors”, i.e. time series describing the on/off state of the optical link, derived from real data measurements conducted by DLR. Our results show that, when properly configured, LTP is able to use all available bandwidth even under the most severe conditions, which makes it a perfect match to Near Earth Optical links
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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