Hybrid routing in delay tolerant networks

This work addresses the integration of today\\u27s infrastructure-based networks with infrastructure-less networks. The resulting Hybrid Routing System allows for communication over both network types and can help to overcome cost, communication, and overload problems. Mobility aspect resulting from infrastructure-less networks are analyzed and analytical models developed. For development and deployment of the Hybrid Routing System an overlay-based framework is presented

Hybrid Routing in Delay Tolerant Networks

This work addresses the integration of today\u27s infrastructure-based networks with infrastructure-less networks. The resulting Hybrid Routing System allows for communication over both network types and can help to overcome cost, communication, and overload problems. Mobility aspect resulting from infrastructure-less networks are analyzed and analytical models developed. For development and deployment of the Hybrid Routing System an overlay-based framework is presented

LSSTCS- A Social-Based DTN Routing in Cooperative Vehicular Sensor Networks

As a cooperative information system, vehicles in Vehicular Sensor Networks delivery messages based on collaboration. Due to the high speed of vehicles, the topology of the network is highly dynamic, and the network may be disconnected frequently. So how to transfer large files in such network is worth considering. In case that the encountering nodes which never meet before flood messages blindly to cause tremendous network overhead. We address this challenge by introducing the Encounter Utility Rank Router(EURR) based on social metrics. EURR includes three cases: Utility Replication Strategy, Lifetime Replication Strategy and SocialRank Replication Strategy. The Lifetime Replication is promising complement to Utility Replication. It enhances the delivery ratio by relaying the copy via the remaining lifetime. Considering network overhead, the SocialRank Replication replicates a copy according to the SocialRank when two communicating nodes do not meet before. The routing mechanism explores the utility of history encounter information and social opportunistic forwarding. The results under the scenario show an advantage of the proposed Encounter Utility Rank Router (EURR) over the compared algorithms in terms of delivery ratio, average delivery latency and overhead ratio

How Human Mobility Models Can Help to Deal with COVID-19

[EN] One of the key factors for the spreading of human infections, such as the COVID-19, is human mobility. There is a huge background of human mobility models developed with the aim of evaluating the performance of mobile computer networks, such as cellular networks, opportunistic networks, etc. In this paper, we propose the use of these models for evaluating the temporal and spatial risk of transmission of the COVID-19 disease. First, we study both pure synthetic model and simulated models based on pedestrian simulators, generated for real urban scenarios such as a square and a subway station. In order to evaluate the risk, two different risks of exposure are defined. The results show that we can obtain not only the temporal risk but also a heat map with the exposure risk in the evaluated scenario. This is particularly interesting for public spaces, where health authorities could make effective risk management plans to reduce the risk of transmission.Hernández-Orallo, E.; Armero-Martínez, A. (2021). How Human Mobility Models Can Help to Deal with COVID-19. Electronics. 10(1):1-24. https://doi.org/10.3390/electronics1001003312410

From MANET to people-centric networking: Milestones and open research challenges

In this paper, we discuss the state of the art of (mobile) multi-hop ad hoc networking with the aim to present the current status of the research activities and identify the consolidated research areas, with limited research opportunities, and the hot and emerging research areas for which further research is required. We start by briefly discussing the MANET paradigm, and why the research on MANET protocols is now a cold research topic. Then we analyze the active research areas. Specifically, after discussing the wireless-network technologies, we analyze four successful ad hoc networking paradigms, mesh networks, opportunistic networks, vehicular networks, and sensor networks that emerged from the MANET world. We also present an emerging research direction in the multi-hop ad hoc networking field: people centric networking, triggered by the increasing penetration of the smartphones in everyday life, which is generating a people-centric revolution in computing and communications

Flexible Application-Layer Multicast in Heterogeneous Networks

This work develops a set of peer-to-peer-based protocols and extensions in order to provide Internet-wide group communication. The focus is put to the question how different access technologies can be integrated in order to face the growing traffic load problem. Thereby, protocols are developed that allow autonomous adaptation to the current network situation on the one hand and the integration of WiFi domains where applicable on the other hand

Experimentation and Characterization of Mobile Broadband Networks

The Internet has brought substantial changes to our life as the main tool to access a large variety of services and applications. Internet distributed nature and technological improvements lead to new challenges for researchers, service providers, and network administrators. Internet traffic measurement and analysis is one of the most trivial and powerful tools to study such a complex environment from different aspects. Mobile BroadBand (MBB) networks have become one of the main means to access the Internet. MBB networks are evolving at a rapid pace with technology enhancements that promise drastic improvements in capacity, connectivity, and coverage, i.e., better performance in general. Open experimentation with operational MBB networks in the wild is currently a fundamental requirement of the research community in its endeavor to address the need for innovative solutions for mobile communications. There is a strong need for objective data relating to stability and performance of MBB (e.g., 2G, 3G, 4G, and soon-to-come 5G) networks and for tools that rigorously and scientifically assess their performance. Thus, measuring end user performance in such an environment is a challenge that calls for large-scale measurements and profound analysis of the collected data. The intertwining of technologies, protocols, and setups makes it even more complicated to design scientifically sound and robust measurement campaigns. In such a complex scenario, the randomness of the wireless access channel coupled with the often unknown operator configurations makes this scenario even more challenging. In this thesis, we introduce the MONROE measurement platform: an open access and flexible hardware-based platform for measurements on operational MBB networks. The MONROE platform enables accurate, realistic, and meaningful assessment of the performance and reliability of MBB networks. We detail the challenges we overcame while building and testing the MONROE testbed and argue our design and implementation choices accordingly. Measurements are designed to stress performance of MBB networks at different network layers by proposing scalable experiments and methodologies. We study: (i) Network layer performance, characterizing and possibly estimating the download speed offered by commercial MBB networks; (ii) End users’ Quality of Experience (QoE), specifically targeting the web performance of HTTP1.1/TLS and HTTP2 on various popular web sites; (iii) Implication of roaming in Europe, understanding the roaming ecosystem in Europe after the "Roam like Home" initiative; and (iv) A novel adaptive scheduler family with deadline is proposed for multihomed devices that only require a very coarse knowledge of the wireless bandwidth. Our results comprise different contributions in the scope of each research topic. To put it in a nutshell, we pinpoint the impact of different network configurations that further complicate the picture and hopefully contribute to the debate about performance assessment in MBB networks. The MBB users web performance shows that HTTP1.1/TLS is very similar to HTTP2 in our large-scale measurements. Furthermore, we observe that roaming is well supported for the monitored operators and the operators using the same approach for routing roaming traffic. The proposed adaptive schedulers for content upload in multihomed devices are evaluated in both numerical simulations and real mobile nodes. Simulation results show that the adaptive solutions can effectively leverage the fundamental tradeoff between the upload cost and completion time, despite unpredictable variations in available bandwidth of wireless interfaces. Experiments in the real mobile nodes provided by the MONROE platform confirm the findings

Περί κοινωνιοκεντρικών προσεγγίσεων στο πρόβλημα δρομολόγησης σε ασύρματα οπορτουνιστικά δίκτυα

Τα τελευταία χρόνια, το ενδιαφέρον της δρομολόγησης στα οπορτουνιστικά δίκτυα επικεντρώνεται στην εξαγωγή των κοινωνικών χαρακτηριστικών που θα μπορούσαν να περιγράψουν τα συγκεκριμένα δίκτυα. Κάποιες μετρικές κεντρικότητας, όπως το Betweenness Centrality, που αντιστοιχεί στο βαθμό που ένας κόμβος βρίσκεται στη διαδρομή που συνδέει άλλους κόμβους, παρουσιάζουν τη σπουδαιότητα κάθε κόμβου στην αναμετάδοση ενός μηνύματος προς κάποιον προορισμό, συνεισφέροντας σε μία καλύτερη δρομολόγηση, συγκριτικά με τις πιο απλοϊκές τεχνικές. Ωστόσο, η ανωτέρω προσέγγιση παρουσιάζει τρεις αδυναμίες: α) Η δρομολόγηση είναι ανεξάρτητη του προορισμού του μηνύματος. β) Η απόδοση καθορίζεται άμεσα από το γράφο των επαφών μεταξύ των κόμβων, στους οποίους υπολογίζονται οι τιμές κεντρικότητας. γ) Η συνολική κεντρικότητα του δικτύου πρέπει πρακτικά να υπολογιστεί με χρήση των εγωκεντρικών δικτύων. Η παρούσα εργασία εξετάζει πειραματικά την επίδραση αυτών των τριών παραγόντων στη δρομολόγηση που εκμεταλλεύεται την κεντρικότητα. Πέντε διαφορετικές τεχνικές δρομολόγησης συγκρίνονται μεταξύ τους και με δύο εξαιρετικές περιπτώσεις πολύπλοκης δρομολόγησης στα DTN: το απλό πρωτόκολλο δρομολόγησης με πιθανότητες και ένα ιδεατό σχήμα, με πλήρη γνώση των μελλοντικών επαφών, που υπολογίζει τη βέλτιστη χωροχρονική διαδρομή σε έναν πρωτότυπο γράφο, με κόμβους τις επαφές και ακμές με χρονικά βάρη. Τα αποτελέσματα αποδεικνύουν ότι η δρομολόγηση με βάση την κεντρικότητα περικλείει εγγενείς αδυναμίες.The exploitation of social context for routing data in opportunistic networks is a relatively recent trend. Node centrality metrics, such as the betweenness centrality, quantify the relaying utility of network nodes and inform routing decisions,resulting in better performance than more naive routing approaches. Nevertheless, centrality-based routing is far from optimal for three main reasons: a) routing decisions are greedy and message destination-agnostic; b) its performance is highly sensitive to the contact graph over which the node centrality values are computed; c) the global network centrality values have for practical reasons to be approximated by their egocentric counterparts. Our paper experimentally assesses the impact of these three factors on the efficacy of centrality-based routing. Five centrality-based routing variants are compared with each other and against two schemes representing extreme instances of DTN routing complexity:the simple probabilistic forwarding protocol and an ideal scheme with perfect knowledge of future contacts that computes optimal message space-time paths over a novel graph construct with contacts as vertices and time-weighted edges.The results of this comparison are not always inline with intuition and indicate inherent weaknesses of centrality-based routing