FALCON: A New Approach for the Evaluation of Opportunistic Networks

[EN] Evaluating the performance of opportunistic networks with a high number of nodes is a challenging problem. Analytical models cannot provide a realistic evaluation of these networks, and simulations can be very time-consuming, sometimes requiring even weeks only to provide the results of a single scenario. In this paper, we present a fast evaluation model called FALCON (Fast Analysis, using a Lattice Cell model, of Opportunistic Networks) that is computationally very efficient and precise. The model is based on discretising space and time in order to reduce the computation complexity, and we formalised it as a discrete dynamic system that can be quickly solved. We describe some validation experiments showing that the precision of the obtained results is equivalent to the ones obtained with standard simulation approaches. The experiments also show that computation time is reduced by two orders of magnitude (from hours to seconds), allowing for a faster evaluation of opportunistic networks. Finally, we show that the FALCON model is easy to adapt and expand to consider different scenarios and protocols.This work was partially supported by Ministerio de Economia y Competitividad, Spain, grant TEC2014-52690-R.Hernández-Orallo, E.; Cano, J.; Tavares De Araujo Cesariny Calafate, CM.; Manzoni, P. (2018). FALCON: A New Approach for the Evaluation of Opportunistic Networks. Ad Hoc Networks. 81:109-121. https://doi.org/10.1016/j.adhoc.2018.07.004S1091218

New approaches for characterizing inter-contact times in opportunistic networks

Characterizing the contacts between nodes is of utmost importance when evaluating mobile opportunistic networks. The most common characterization of inter-contact times is based on the study of the aggregate distribution of contacts between individual pairs of nodes, assuming an homogenous network, where contact patterns between nodes are similar. The problem with this aggregate distribution is that it is not always representative of the individual pair distributions, especially in the short term and when the number of nodes in the network is high. Thus, deriving results from this characterization can lead to inaccurate performance evaluation results. In this paper, we propose new approaches to characterize the inter-contact times distribution having a higher representativeness and, thus, increasing the accuracy of the derived performance results. Furthermore, these new characterizations require only a moderate number of contacts in order to be representative, thereby allowing to perform a temporal modelization of traffic traces. This a key issue for increasing accuracy, since real-traces can have a high variability in terms of contact patterns along time. The experiments show that the new characterizations, compared with the established one, are more precise, even using short time contact traces. © 2016 Elsevier B.V. All rights reserved.Hernández Orallo, E.; Cano Escribá, JC.; Tavares De Araujo Cesariny Calafate, CM.; Manzoni, P. (2016). New approaches for characterizing inter-contact times in opportunistic networks. Ad Hoc Networks. 52:160-172. doi:10.1016/j.adhoc.2016.04.003S1601725

DROiD: Adapting to Individual Mobility Pays Off in Mobile Data Offloading

International audienceCellular operators count on the potentials of offloading techniques to relieve their overloaded data channels. Beyond standard access point-based offloading strategies, a promising alternative is to exploit opportunistic direct communication links between mobile devices. Nevertheless, achieving efficient device- to-device offloading is challenging, as communication opportunities are, by nature, dependent on individual mobility patterns. We propose, design, and evaluate DROiD (Derivative Reinjection to Offload Data), an original method to finely control the distribution of popular contents throughout a mobile network. The idea is to use the infrastructure resources as seldom as possible. To this end, DROiD injects copies through the infrastructure only when needed: (i) at the beginning, in order to trigger the dissemination, (ii) if the evolution of the opportunistic dissemination is below some expected pace, and (iii) when the delivery delay is about to expire, in order to guarantee 100% diffusion. Our strategy is particularly effective in highly dynamic scenarios, where sudden creation and dissolution of clusters of mobile nodes prevent contents to diffuse properly.We assess the performance of DROiD by simulating a traffic information service on a realistic large-scale vehicular dataset composed of more than 10,000 nodes. DROiD substantially outperforms other offloading strategies, saving more than 50% of the infrastructure traffic even in the case of tight delivery delay constraints. DROiD allows terminal- to-terminal offloading of data with very short maximum reception delay, in the order of minutes, which is a realistic bound for cellular user acceptance

A delay and cost balancing protocol for message routing in mobile delay tolerant networks

The increasing pervasiveness of mobile devices with networking capabilities has led to the emergence of Mobile Delay Tolerant Networks (MDTNs). The characteristics of MDTNs, which include frequent and long-term partitions, make message routing a major challenge in these networks. Most of the existing routing protocols either allocate an unlimited number of message copies or use a xed number of message copies to route a message towards its destination. While the first approach unnecessarily oods the network, the rigidity of the second approach makes it ine cient from the viewpoint of message replication. Hence, the question that we address in this paper is: "How to dynamically allocate message copies in order to strike a balance between the delay and cost of message delivery?". We present a novel adaptive multi-step routing protocol for MDTNs. In each routing step, our protocol reasons on the remaining time-tolive of the message in order to allocate the minimum number of copies necessary to achieve a given delivery probability. Experiment results demonstrate that our protocol has a higher delivery ratio and a lower delivery cost compared to the state-of-the-art Spray-and-Wait and Bubble protocols

The Impact of Rogue Nodes on the Dependability of Opportunistic Networks

Opportunistic Networks (OppNets) are an extension to the classical Mobile Ad hoc Networks (MANETs) where the network is not dependent on any infrastructure (e.g. Access Points or centralized administrative nodes). OppNets can be more flexible than MANETs because an end to end path does not exist and much longer delays can be expected. Whereas a Rogue Access Point is typically immobile in the legacy infrastructure based networks and can have considerable impact on the overall connectivity, the research question in this project evaluates how the pattern and mobility of a rogue nodes impact the dependability and overall "Average Latency" in an Opportunistic Network Environment. We have simulated a subset of the mathematical modeling performed in a previous publication in this regard. Ad hoc networks are very challenging to model due to their mobility and intricate routing schemes. We strategically started our research by exploring the evolution of Opportunistic networks, and then implemented the rogue behavior by utilizing The ONE (Opportunistic Network Environment, by Nokia Research Centre) simulator to carry out our research over rogue behavior. The ONE simulator is an open source simulator developed in Java, simulating the layer 3 of the OSI model. The Rogue behavior is implemented in the simulator to observe the effect of rogue nodes. Finally we extracted the desired dataset to measure the latency by carefully simulating the intended behavior, keeping rest of the parameters (e.g. Node Movement Models, Signal Range and Strength, Point of Interest (POI) etc) unchanged. Our results are encouraging, and coincide with the average latency deterioration patterns as modeled by the previous researchers, with a few exceptions. The practical implementation of plug-in in ONE simulator has shown that only a very high degree of rogue nodes impact the latency, making OppNets more resilient and less vulnerable to malicious attacks

Assessing the Vulnerability of DTN Data Relaying Schemes to Node Selfishness

The main principle behind the working of delay tolerant networks (DTN) is the mobility of the nodes along with their contact sequences for exchanging data. Nodes which are a part of the DTN network can behave selfishly due to network reservation policy, especially when constrained to energy or storage space. Several forwarding protocols exist for spreading data but our focus is on the performance of popular data relaying protocols namely epidemic routing and two hop routing protocol in a situation where nodes exhibit various degrees of selfishness. Results of an analytical model show the performance advantage of epidemic routing over two hop routing decreases as the number of selfish nodes and intensity of the selfishness increases either deterministically or probabilistically. We practically asses the vulnerability of the above mentioned protocols using ONE simulator. We find that our result coincides with analytical results with some variations in the graph

Assessing the Vulnerability of DTN Data Relaying Schemes to Node Selfishness

The main principle behind the working of delay tolerant networks (DTN) is the mobility of the nodes along with their contact sequences for exchanging data. Nodes which are a part of the DTN network can behave selfishly due to network reservation policy, especially when constrained to energy or storage space. Several forwarding protocols exist for spreading data but our focus is on the performance of popular data relaying protocols namely epidemic routing and two hop routing protocol in a situation where nodes exhibit various degrees of selfishness. Results of an analytical model show the performance advantage of epidemic routing over two hop routing decreases as the number of selfish nodes and intensity of the selfishness increases either deterministically or probabilistically. We practically asses the vulnerability of the above mentioned protocols using ONE simulator. We find that our result coincides with analytical results with some variations in the graph

Assessing the Vulnerability of DTN Data Relaying Schemes to Node Selfishness

The main principle behind the working of delay tolerant networks (DTN) is the mobility of the nodes along with their contact sequences for exchanging data. Nodes which are a part of the DTN network can behave selfishly due to network reservation policy, especially when constrained to energy or storage space. Several forwarding protocols exist for spreading data but our focus is on the performance of popular data relaying protocols namely epidemic routing and two hop routing protocol in a situation where nodes exhibit various degrees of selfishness. Results of an analytical model show the performance advantage of epidemic routing over two hop routing decreases as the number of selfish nodes and intensity of the selfishness increases either deterministically or probabilistically. We practically asses the vulnerability of the above mentioned protocols using ONE simulator. We find that our result coincides with analytical results with some variations in the graph

Performance evaluation of cooperation strategies for m-health services and applications

Health telematics are becoming a major improvement for patients’ lives, especially for disabled, elderly, and chronically ill people. Information and communication technologies have rapidly grown along with the mobile Internet concept of anywhere and anytime connection. In this context, Mobile Health (m-Health) proposes healthcare services delivering, overcoming geographical, temporal and even organizational barriers. Pervasive and m-Health services aim to respond several emerging problems in health services, including the increasing number of chronic diseases related to lifestyle, high costs in existing national health services, the need to empower patients and families to self-care and manage their own healthcare, and the need to provide direct access to health services, regardless the time and place. Mobile Health (m- Health) systems include the use of mobile devices and applications that interact with patients and caretakers. However, mobile devices have several constraints (such as, processor, energy, and storage resource limitations), affecting the quality of service and user experience. Architectures based on mobile devices and wireless communications presents several challenged issues and constraints, such as, battery and storage capacity, broadcast constraints, interferences, disconnections, noises, limited bandwidths, and network delays. In this sense, cooperation-based approaches are presented as a solution to solve such limitations, focusing on increasing network connectivity, communication rates, and reliability. Cooperation is an important research topic that has been growing in recent years. With the advent of wireless networks, several recent studies present cooperation mechanisms and algorithms as a solution to improve wireless networks performance. In the absence of a stable network infrastructure, mobile nodes cooperate with each other performing all networking functionalities. For example, it can support intermediate nodes forwarding packets between two distant nodes. This Thesis proposes a novel cooperation strategy for m-Health services and applications. This reputation-based scheme uses a Web-service to handle all the nodes reputation and networking permissions. Its main goal is to provide Internet services to mobile devices without network connectivity through cooperation with neighbor devices. Therefore resolving the above mentioned network problems and resulting in a major improvement for m-Health network architectures performances. A performance evaluation of this proposal through a real network scenario demonstrating and validating this cooperative scheme using a real m-Health application is presented. A cryptography solution for m-Health applications under cooperative environments, called DE4MHA, is also proposed and evaluated using the same real network scenario and the same m-Health application. Finally, this work proposes, a generalized cooperative application framework, called MobiCoop, that extends the incentive-based cooperative scheme for m-Health applications for all mobile applications. Its performance evaluation is also presented through a real network scenario demonstrating and validating MobiCoop using different mobile applications