Paulo Mendes

User-provided networks: consumer as provider

This article describes and characterizes an emerging type of user-centric wireless network model, here named a user-provided network, where the end user is at the same time a consumer and a provider of Internet access. A discussion of challenges these new models face is also provided.

Context-aware handover using active network technology

Context-aware computing can play a major role to improve the services of mobile networking systems. In this paper, we focus on optimizing handover decisions in heterogeneous environments, where the user has a choice among different mobile networks and access points. In our approach, the decision is not only based on the signal quality, but also on the knowledge about the context of mobile devices and networks. Since context information and context processing evolves fast, we propose a flexible, integrated approach for context management, which can adapt in several ways. Our architecture encompasses programmable platforms and distributed context management components in network nodes and mobile devices, as well as a service deployment scheme for network services. This flexible architecture is able to actively deploy different handover services. It manages dynamic context information and allows mobile devices to be always connected to the most suitable access network. Our architecture is validated in a prototype implementation and performance results are discussed.

A framework for self-organized network composition

This paper discusses a framework for a flexible, self-organized control plane for future mobile and ubiquitous networks. The current diversification of control planes requires a manual configuration of network interworking. The problem will increase in the future, with more dynamic topologies and integration of heterogeneous networks in a ubiquitous, reactive environment. In this paper we introduce the concept of network composition, a basic, scalable and dynamic network operation to achieve autonomic control plane interworking between Ambient Networks - our approach for next generation networks. We show the architectural components of a generic control plane and its flexible interfaces. With an example on seamless mobility we illustrate how composition can simplify and improve the interworking of future networks.

A Resource Reservation Protocol Supporting QoS-aware Multicast Trees for Next Generation Networks

It is expected that next generation of networks will handle new types of services which are destined to large audiences and have different QoS requirements. From the transport point of view, multicast is the most suitable technology for the required group communication services, since it avoids packets duplication and saves network resources. However, QoS-aware multicast content deliver raises several problems, such as the control of QoS trees in environments with asymmetric routing. This paper presents Multi-service Resource Allocation (MIRA), a multicast-aware resource reservation protocol for class-based networks that consider routing asymmetries. MIRA controls the resources of network classes associated to multicast sessions considering the QoS characteristics of the latter and network conditions of the available classes in the source-to-receivers path. A detailed description of the functionalities of MIRA and a conceptual analysis against RSVP and RMD-QoSM are presented. Finally, the session setup time, and the signalling and state overheard in comparison with RSVP are analyzed based on simulations.

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.

Scalable Resource Provisioning for Multi-User Communications in Next Generation Networks

The great demand for real-time multimedia sessions encompassing groups of users (multi-user), associated with the limitations of the current Internet in providing quality assurance, has raised challenges for defining the best mechanisms to deploy the next generation of networks (NGN). There is a consensus that an efficient and scalable provisioning of network resources is crucial for the success of the NGN, mainly in what concerns access networks. Previous solutions for the control of multi-user sessions rely mostly on uncoordinated actions to allocate per-flow bandwidth and multicast trees. This paper introduces a multiuser aggregated resource allocation mechanism (MARA) that coordinates the control of class-based bandwidth and multicast resources in a scalable manner. In comparison with previous work, MARA significantly reduces signaling, state and processing overhead. The performance benefits of MARA are analyzed though simulations, which successfully demonstrated the significant optimization in the network performance.

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.

MMC04-3: A Unifying Architecture for Publish-Subscribe Services in the Next Generation IP Networks

Next generation IP networks are envisioned to be heterogeneous, to provide a wide variety of services, and to support mobility of users with distinct requirements. Moreover, mobile communications are expected to expand from telephony to publish-subscribe services, such as real-time multimedia. With this goal, the University of Coimbra is working with DoCoMo Euro-Labs on a unifying control architecture for multimedia publish-subscribe services over an IP-based mobile system, where our proposal aims to control the quality of service and mobility across heterogeneous networks with no perceived service degradation to the users. This article highlights the requirements of a control architecture for publish-subscribe services, and presents our proposal, called QoS Architecture for Multi-user Mobile Multimedia (Q3M). The main components and functionality of the Q3M architecture are analysed from the user and network perspectives, and some simulation results concerning the analysis of the session setup times are presented.

Relay selection approaches for wireless cooperative networks

Wireless networks are characterized by having limited resources accessed by a large number of mobile stations with distinct capabilities. In such challenged environment the dynamic control of resources is of major importance to mitigate the limitations of wireless networks, such as the impact of low data rate stations and wireless channel oscillations. Such augmented usage of wireless resources can be implemented based upon cooperative relaying schemes, which have the potential to support the desired system performance and network lifetime. However, the introduction of cooperative relay raises several problems such as the issue for relay selection and resource allocation. Due to the significant number of different cooperative relaying approaches, this article aims to provide a systematic analysis and classification of major relay selection procedures, and to identify open research directions as well as the most suitable evaluation methods for an efficient analysis of different approaches.