Vinicius F. S. Mota

Protocols, mobility models and tools in opportunistic networks: A survey

Abstract In opportunistic networks, instead of assuming an end-to-end path as in the traditional Internet model, messages are exchanged opportunistically when an encounter happens between two nodes. In the last years, several forwarding algorithms to efficiently decide when to forward messages were proposed. Those protocols are commonly suitable to a specific scenario, which has led to the creation of new subtypes of networks. Two different examples are pocket switched networks – PSN and vehicular networks – VANETs, since those networks have different features like a specific mobility pattern and intermittent connectivity. In this article we present an overview of opportunistic networks, proposing a taxonomy which encompasses those new types of network. We discuss the commonly used tools, simulators, contact traces, mobility models and applications available. Moreover, we analyzed a set of forwarding protocols to map the approach used by the research community to evaluate their proposals in terms of mobility, contacts and traffic pattern, reliability of simulations and practical projects. We show that although researchers are making efforts to use more realistic contact models (e.g., using real traces) the traffic pattern is generally disregarded, using assumptions that may not fit real applications.

On the feasibility of WiFi offloading in urban areas: The Paris case study

With the increasing number of users subscribing to mobile Internet such as 3G and 4G networks, the Wireless Internet Services providers (WISP) aim to offer a good service for customers while elevating the number of clients. Several proposals to offload the traffic of 3G networks have been made in the past few years, including the use of femtocells,WiFi offloading and more recently mobile-to-mobile opportunistic offloading. In this paper, we measure the public WiFi hotspots provided by the government and private WiFi access points (AP) scanned during several bus routes in Paris in order to evaluate the feasibility of offloading data traffic through WiFi. We compare the AP positions with the positions of mobile clients provided publicly in Location Sharing Services, such as Foursquare. Our main findings are that, on average, an access point is available up to 60m of range, during 30 seconds, and the already deployed WiFi infrastructure could offload up to 30% of mobile traffic in the scenario analyzed.

Managing the decision-making process for opportunistic mobile data offloading

With the increasing number of users subscribing to mobile Internet such as 3G and 4G networks, Wireless Internet Services providers (WISP) aim to provide a good service for customers while elevating the number of clients. Several proposals to offload the traffic of 3G networks were made in the last few years, including the use of femtocells, WiFi offloading and more recently mobile-to-mobile opportunistic offloading. In this paper, we propose a multi-criteria decision-making framework to manage the offload of data from 3G networks using mobile-to-mobile opportunistic communications. Primarily, we focus on building a decision framework that employs only user knowledge to select which users should handover from infrastructure to mobile-to-mobile network, avoiding changes in the infrastructure. Next, we evaluate our proposal and demonstrate its feasibility through trace-driven simulations, achieving 6% of data offload when there is no delay tolerance in the application and up to 36% when application can tolerate 20 minutes of delay.

Users in the urban sensing process: Challenges and research opportunities

The popularization of portable devices such as smartphones and the worldwide adoption of social media services make it increasingly possible to be connected and share data anywhere and at any time. Data from this process represent a new source of sensing, which is called participatory sensor network (PSN). In this scenario, people participate as social sensors voluntarily providing data that capture their experiences of daily life. This large amount of social data can provide valuable new forms of information to be obtained that are currently not available within the same global reach and that can be used to improve the decision-making processes of different entities (eg, people, groups, services, and applications). The objective of this chapter is to discuss PSNs, presenting an overview of the area, challenges, and opportunities. We aim to show that PSNs (eg, Instagram, Foursquare, and Waze) can act as valuable sources of large-scale sensing, providing access to important characteristics of city dynamics and urban social behavior, more quickly and comprehensively. This chapter starts by studying the properties of PSN. Next, it discusses how to work with PSN, showing its applicability in the development of more sophisticated applications. In addition, it discusses several research challenges and opportunities in this area.The popularization of portable devices such as smartphones and the worldwide adoption of social media services make it increasingly possible to be connected and share data anywhere and at any time. Data from this process represent a new source of sensing, which is called participatory sensor network (PSN). In this scenario, people participate as social sensors voluntarily providing data that capture their experiences of daily life. This large amount of social data can provide valuable new forms of information to be obtained that are currently not available within the same global reach and that can be used to improve the decision-making processes of different entities (eg, people, groups, services, and applications). The objective of this chapter is to discuss PSNs, presenting an overview of the area, challenges, and opportunities. We aim to show that PSNs (eg, Instagram, Foursquare, and Waze) can act as valuable sources of large-scale sensing, providing access to important characteristics of city dynamics and urban social behavior, more quickly and comprehensively. This chapter starts by studying the properties of PSN. Next, it discusses how to work with PSN, showing its applicability in the development of more sophisticated applications. In addition, it discusses several research challenges and opportunities in this area.

Real-time monitoring of transmission lines using wireless sensor networks

This paper presents the conception and development of a management system for power transmission lines based on wireless sensor networks (WSNs). In the operation of power transmission lines, there is a real need for this kind of system to help the identification of problems and fault diagnoses in reduced time. The system uses multiple sensor technologies, such as vision, acceleration and magnetic induction, integrated in elements of the WSN for real-time data collection and processing regarding the status of the monitored power transmission lines. The collected data is transmitted to a control and supervision center through the nodes of the WSN. The source of energy of the nodes is independent of the power of the lines. This article presents the general idea, the architecture, and the implementation.

An hierarchical routing protocol for opportunistic emergency networks

In critical and emergency scenarios such as disasters, first responders must setup mobile networks in order to address the lack of a functioning network infrastructure. Communication in such scenarios may be susceptible to long interruptions, and as a consequence we must employ DTN-based (Delay/Disruption Tolerant Networks) communication protocols. Existing routing approaches suitable for emergency scenarios tend to consume a large amount of resources, due to the stochastic behavior of node movement. This paper has two contributions. First, we propose a resource-efficient DTN routing protocol, called HIerarquical Group ROuting Protocol (HIGROP). HIGROP aims to reduce the forwarding overhead by the use of node clusters, while maximizing the message delivery rate. The second contribution is the definition of a new mobility model, called MME, which emulates the movement patterns of first responders in search and rescue scenarios. We compared HIGROP against Epidemic and Prophet protocols and noticed that it is scalable and has a lower communication overhead.