Waldir Moreira

Virtual currency and reputation-based cooperation incentives in user-centric networks

Cooperation incentives are essential in user-centric networks to motivate users to share services and resources (including bandwidth, computational power, and storage space) and to avoid selfish nodes to hinder the functioning of the entire system. Virtual currency and reputation mechanisms are commonly adopted in online communities to boost participation, but their joint application has not been deeply explored, especially in the context of wireless communities, where not only the services, but even the enabling infrastructure is opportunistically built by community members. This paper investigates the combined use of virtual currency and reputation-based incentives in the specific context of a community of users with Wi-Fi enabled devices capable of establishing ad-hoc connections.

Social-Aware Opportunistic Routing: The New Trend

Since users move around based on social relationships and interests, their movement patterns represent how nodes are socially connected (i.e., nodes with strong social ties, nodes that meet occasionally by sharing the same working environment). This means that social interactions reflect personal relationships (e.g., family, friends, co-workers, and passers-by) that may be translated into statistical contact opportunities within and between social groups over time. Such contact opportunities may be exploited to ensure good data dissemination and retrieval, even in the presence of intermittent connectivity. Thus, in the last years, a new routing trend based on social similarity emerged where social relationships, interests, popularity, and among other social characteristics are used to improve opportunistic routing (i.e., routing able to take advantage on intermittent contacts). In this chapter, the reader will learn about the different approaches related to opportunistic routing, focusing on social-aware approaches, and how such approaches make use of social information derived from opportunistic contacts to improve data forwarding. Additionally, a brief overview on the existing taxonomies for opportunistic routing as well as a new one, based on the new social trend, are provided along with a set of experiments in scenarios based on synthetic mobility models and human traces to show the potential of social-aware solutions.

Impact of Human Behavior on Social Opportunistic Forwarding

Abstract The current Internet design is not capable of supporting communications in environments characterized by very long delays and frequent network partitions. To allow devices to communicate in such environments, delay-tolerant networking solutions have been proposed by exploiting opportunistic message forwarding, with limited expectations of end-to-end connectivity and node resources. Such solutions envision non-traditional communication scenarios, such as disaster areas and development regions. Several forwarding algorithms have been investigated, aiming to offer the best trade-off between cost (number of message replicas) and rate of successful delivered message. Among such proposals, there has been an effort to employ social similarity, inferred from users’ mobility patterns, to improve opportunistic forwarding solutions. However, such proposals present two major drawbacks: first, they focus on distribution of intercontact times over the complete network structure, ignoring the impact that human behavior has on the dynamics of the network; and second, most of the proposed solutions look at challenging networking environments where networks have low density, ignoring the potential use of delay-tolerant networking to support low cost communications in networks with higher density, such as urban scenarios. This paper presents a study of the impact that human behavior has on opportunistic forwarding. Our goal is twofold: (i) to show that performance in low and high density networks can be improved by taking the dynamics of the network into account; and (ii) to show that delay-tolerant networking can be used to reduce communication costs in networks with high density by considering the users’ behavior.

Study on the effect of network dynamics on opportunistic routing

There has been an effort to employ social similarity inferred from user mobility patterns in opportunistic routing solutions to improve forwarding. However, the dynamics of the networks are still not fully considered when devising solutions based on social similarity metrics. To address this issue, we propose two utility functions which consider the daily life routines of users and the intensity of their social interactions to take forwarding decisions: Time-Evolving Contact Duration (TECD) that weights social interactions among nodes considering the duration of contacts; and TECD Importance (TECDi) which estimates the importance of nodes. We compare our utility functions against contact- and social-based solutions, and we show that the use of daily life routines information (i.e., using TECD and TECDi) has a positive effect on opportunistic routing.

Social-Aware Opportunistic Routing Protocol Based on User’s Interactions and Interests

Nowadays, routing proposals must deal with a panoply of heterogeneous devices, intermittent connectivity, and the users’ constant need for communication, even in rather challenging networking scenarios. Thus, we propose a Social-aware Content-based Opportunistic Routing Protocol, SCORP, that considers the users’ social interaction and their interests to improve data delivery in urban, dense scenarios. Through simulations, using synthetic mobility and human traces scenarios, we compare the performance of our solution against other two social-aware solutions, dLife and Bubble Rap, and the social-oblivious Spray and Wait, in order to show that the combination of social awareness and content knowledge can be beneficial when disseminating data in challenged networks.

Assessment model for opportunistic routing

Due to the increased capabilities of mobile devices and through wireless opportunistic contacts, users can experience new ways to share and retrieve content anywhere and anytime, even in the presence of link intermittency. Due to the significant number of available routing solutions, it is difficult to understand which one has the best performance, since all of them follow a different evaluation method. This paper proposes an assessment model, based on a new taxonomy, which comprises an evaluation guideline with performance metrics and experimental setup to aid designers in evaluating solutions through fair comparisons. Simulation results based on the proposed model revisit the performance results published by Epidemic, PROPHET, and BubbleRap, showing how they perform under the same set of metrics and scenario.

Towards next-generation routing protocols for pocket switched networks

A pocket switched network (PSN) is dynamically formed by people who carry portable handheld devices. Interest in PSNs is driven by the increasing number of handheld devices, the several wireless interfaces they possess, as well as their ability to store, carry and forward data. The lack of fixed network topology distinguishes PSNs from traditional networks, and unlike other types of mobile networks, nodes in PSNs closely follow human movement patterns. As a result, PSNs are faced with new challenges especially in the aspect of routing. Although various routing protocols have been proposed, most of them focus on optimizing the performance of networking primitives for traditional networks such as unicast, broadcast and multicast. However, these primitives themselves appear to be insufficient due to new application opportunities presented by PSNs. This paper adopts a user scenario based approach to determine the current state of PSN routing protocols. Specifically, four modes of data transfer are established from six generalized PSN user scenarios. Due to the wide range of existing routing proposals, a new taxonomy is proposed to facilitate analysis of their compatibility with the established modes of data transfer. The analysis provides new insights into application based routing approaches for realizing next-generation PSN routing protocols. A detailed characterization of PSN user scenarios and respective data transfer modes.An exhaustive analysis of existing PSN routing solutions.A novel classification for PSN routing complementing gaps of existing taxonomies.A scenario-driven set of design guidelines for next-generation PSN routing solutions.An instructive list of future directions towards real-world PSN implementations.

Social-aware forwarding in opportunistic wireless networks: Content awareness or obliviousness?

Information-Centric Networking (ICN) has gained increasing attention from the research community as it is able to improve content dissemination by releasing the dependency on content location. With the current host-based Internet architecture, networking faces limitations in dynamic scenarios, due mostly to host mobility. The ICN paradigm mitigates such problems by releasing the need to have an end-to-end transport session established during the life time of the data transfer. Moreover, the ICN concept solves the mismatch between the Internet architecture and the way users would like to use it: currently a user needs to know the topological location of the hosts involved in the communication when he/she just wants to get the data, independently of its location. Most of the research efforts aim to come up with a stable ICN architecture in fixed networks, with few examples in ad-hoc and vehicular networks. However, the Internet is becoming more pervasive with powerful personal mobile devices that allow users to form dynamic networks in which content may be exchanged at all times and with low cost. Such pervasive wireless networks suffer with different levels of disruption given user mobility, physical obstacles, lack of cooperation, intermittent connectivity, among others. This paper discusses the combination of content knowledge (e.g., type and interested parties) and social awareness within opportunistic networking as to drive the deployment of ICN solutions in disruptive networking scenarios. With this goal in mind, we go over few examples of social-aware content-based opportunistic networking proposals that consider social awareness to allow content dissemination independently of the level of network disruption. To show how much content knowledge can improve social-based solutions, we illustrate by means of simulation some content-oblivious/oriented proposals in scenarios based on synthetic mobility patterns and real human traces.

LatinCon14 - Providing QoE and QoS in Wireless Mesh Networks Through Dynamic Choice of Routing Metrics

The increasing demand of multimedia applications requires a new behavior of routing protocols for wireless mesh networks (WMNs). It is necessary to support the minimum requirements for quality of service (QoS), but WMNs also need to support the minimum requirements for quality of experience (QoE). This paper is an additional analysis of the proposed routing protocol OLSR-DC, from a perspective of the network (QoS) and from a perspective of the user (QoE). The simulations were performed to demonstrate the performance of OLSR-DC compared against original OLSR and its ETX and MD versions considering different performance evaluation metrics and the quality of the video received by the user.

Trust Management in ULOOP

This White Paper provides an insight on Trust Management within the context of the User-centric Wireless Local Loop (ULOOP) project, depicting the main principles and the overall trust management framework, and also describing its main individual components. It has as motivation to disseminate ULOOP concepts and to raise awareness towards trust management in user-centric wireless networks.