Socially-Aware Networking: A Survey
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paper_title: A framework for mobile and context-aware applications applied to vehicular social networks

paper_content:

The notion of context has become very important in computer science, especially when users are highly mobile. In a short period of time the environment changes; communication networks can become available or unavailable, user communities can appear or disappear, etc. The work presented in this paper focuses on the transportation domain and more particularly on applications which accompany and assist the user in transportation activities (e.g., driving, visiting a city, etc.) through the use of ad hoc social networks. We present a case study related to the VESPA system, designed to help drivers by providing them with diverse information (e.g., traffic information, available parking spaces, etc.); we show how the framework we propose can help the system deal with context issues. In the last part, we analyze different mechanisms of changing application behavior through the use of services, an important step towards making our devices reactive to new situations.
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paper_title: Opportunistic IoT: Exploring the social side of the internet of things

paper_content:

The Internet of Things (IoT) is a technical revolution that represents the future of computing and communications. Under its vision, the next-generation Internet will promote the harmonious interaction between human, society, and smart things. The current research in IoT is mainly from the perspective of connecting and managing things. The humanized, social side of IoT, however, is still not explored. In this article, we intend to present the IoT from the human-centric perspective. By analyzing the tight-coupled relationship between human and opportunistic connection of smart things (e.g., mobile phones, vehicles), we propose Opportunistic IoT. It enables information sharing and dissemination within/among opportunistic communities that are formed with the movement and opportunistic contact nature of human. We characterize the bi-directional effect between human and opportunistic IoT, present the innovative application areas, and discuss the challenges raised by this new computing paradigm.
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paper_title: A survey and challenges in routing and data dissemination in vehicular ad-hoc networks

paper_content:

In this paper, we survey recent results in VANET data dissemination. We structure the survey into three broad categories: geocast/broadcast, multicast, and unicast approaches; and describe key ideas of representative technologies in each category. In addition, we consider location service and security issues that are crucial for data dissemination in VANET. We conclude by sharing our thoughts on further challenges.
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paper_title: Mobile social networks: state-of-the-art and a new vision

paper_content:

Social networks have attracted much attention and are gaining increasing momentum in communities, academia and industries. The mobilization of social networks, thus mobile social networks (MSNs), has equally been widely used, driven by the rapid advancement of both wireless network technologies and mobile devices. In light of the many works on MSNs focusing on its various different aspects, this paper aims to provide an overall view of this young and exciting field by summarizing its key research activities/categories and analyzing their interrelationships. Furthermore, the paper goes one step further by presenting a new vision of MSNs, which brings its other equally important arm, that is, mobile communication networks, into the horizon of MSN research. This new vision advocates the seamless integration of both arms, each located at different layers, that is, social networks at the application layer and mobile wireless networks at the network and communication layers. This integration calls for a cross-layer information exchange of the two layers for the benefit of the MSN as a whole. The methodologies that shall be adopted by this new vision of MSN and the upcoming research challenges faced by this new field are discussed. It is hoped that this paper can serve as a seed to spark wider and deeper discussions and research activities on this new field of MSNs, where social computing activities and mobile wireless network researches embrace each other to create an era where all stakeholders in the MSN supply chain and in particular end-users benefit. Copyright © 2011 John Wiley & Sons, Ltd.
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paper_title: Handbook of Wireless Networks and Mobile Computing

paper_content:

If you want to get Handbook of Internet Computing pdf eBook copy write by good Handbook of Wireless Networks and Mobile Computing Google Books. Mobile Computing General. Handbook of Algorithms for Wireless Networking and Mobile Computing by Azzedine Boukerche (Editor). Call Number: TK 5103.2. CITS4419 Mobile and Wireless Computing software projects related to wireless networks, (2) write technical reports and documentation for complex computer.
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paper_title: Beyond Traditional DTN Routing: Social Networks for Opportunistic Communication

paper_content:

This article examines the evolution of routing protocols for intermittently connected ad hoc networks and discusses the trend toward socialbased routing protocols. A survey of current routing solutions is presented, where routing protocols for opportunistic networks are classified based on the network graph employed. The need to capture performance trade-offs from a multi-objective perspective is highlighted.
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paper_title: Opportunistic networking: data forwarding in disconnected mobile ad hoc networks

paper_content:

Opportunistic networks are one of the most interesting evolutions of MANETs. In opportunistic networks, mobile nodes are enabled to communicate with each other even if a route connecting them never exists. Furthermore, nodes are not supposed to possess or acquire any knowledge about the network topology, which (instead) is necessary in traditional MANET routing protocols. Routes are built dynamically, while messages are en route between the sender and the destination(s), and any possible node can opportunistically be used as next hop, provided it is likely to bring the message closer to the final destination. These requirements make opportunistic networks a challenging and promising research field. In this article we survey the most interesting case studies related to opportunistic networking and discuss and organize a taxonomy for the main routing and forwarding approaches in this challenging environment. We finally envision further possible scenarios to make opportunistic networks part of the next-generation Internet
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paper_title: Pocket switched networking: Challenges, feasibility, and implementation issues

paper_content:

The Internet is built around the assumption of contemporaneous end-to-end connectivity. This is at odds with what typically happens in mobile networking, where mobile devices move between islands of connectivity, having opportunity to transmit packets through their wireless interface or simply carrying the data toward a connectivity island. We propose Pocket Switched Networking, a communication paradigm which reflects the reality faced by the mobile user. Pocket Networking falls under DTN. We describe the challenges that this approach entails and provide evidence that it is feasible with today's technology.
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paper_title: Opportunities in Opportunistic Computing

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When two devices come into contact, albeit opportunistically, it provides a great opportunity to match services to resources, exchange information, cyberforage, execute tasks remotely, and forward messages.
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paper_title: The Emergence of Social and Community Intelligence

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Social and community intelligence research aims to reveal individual and group behaviors, social interactions, and community dynamics by mining the digital traces that people leave while interacting with Web applications, static infrastructure, and mobile and wearable devices.
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paper_title: Collective dynamics of ‘small-world’ networks

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Networks of coupled dynamical systems have been used to model biological oscillators1,2,3,4, Josephson junction arrays5,6, excitable media7, neural networks8,9,10, spatial games11, genetic control networks12 and many other self-organizing systems. Ordinarily, the connection topology is assumed to be either completely regular or completely random. But many biological, technological and social networks lie somewhere between these two extremes. Here we explore simple models of networks that can be tuned through this middle ground: regular networks ‘rewired’ to introduce increasing amounts of disorder. We find that these systems can be highly clustered, like regular lattices, yet have small characteristic path lengths, like random graphs. We call them ‘small-world’ networks, by analogy with the small-world phenomenon13,14 (popularly known as six degrees of separation15). The neural network of the worm Caenorhabditis elegans, the power grid of the western United States, and the collaboration graph of film actors are shown to be small-world networks. Models of dynamical systems with small-world coupling display enhanced signal-propagation speed, computational power, and synchronizability. In particular, infectious diseases spread more easily in small-world networks than in regular lattices.
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paper_title: Social Network Analysis

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Power no longer resides exclusively (if at all) in states, institutions, or large corporations. It is located in the networks that structure society. Social network analysis seeks to understand networks and their participants and has two main focuses: the actors and the relationships between them in a specific social context.
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paper_title: Habit: Leveraging human mobility and social network for efficient content dissemination in Delay Tolerant Networks

paper_content:

This paper proposes Habit, an efficient multi-layered approach to content dissemination in Delay Tolerant Networks (DTN) that leverages information about nodes' colocation (physical layer) and their social network (application layer). More precisely, the regularity of users' colocation is learned based on historical colocation observations; also, the users' social network (or ‘network of interest’) is dynamically propagated during periods of colocation; finally, these distinct pieces of information are locally combined and used to compute the paths that content should follow, in a way that maximises both precision (i.e., nodes receive only content they are interested in) and recall (i.e., all relevant content is received by interested nodes).
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paper_title: Social Network Analysis for Information Flow in Disconnected Delay-Tolerant MANETs

paper_content:

Message delivery in sparse mobile ad hoc networks (MANETs) is difficult due to the fact that the network graph is rarely (if ever) connected. A key challenge is to find a route that can provide good delivery performance and low end-to-end delay in a disconnected network graph where nodes may move freely. We cast this challenge as an information flow problem in a social network. This paper presents social network analysis metrics that may be used to support a novel and practical forwarding solution to provide efficient message delivery in disconnected delay-tolerant MANETs. These metrics are based on social analysis of a node's past interactions and consists of three locally evaluated components: a node's "betweenness" centrality (calculated using ego networks) and a node's social 'similarity' to the destination node and a node's tie strength relationship with the destination node. We present simulations using three real trace data sets to demonstrate that by combining these metrics delivery performance may be achieved close to epidemic routing but with significantly reduced overhead. Additionally, we show improved performance when compared to PRoPHET routing.
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paper_title: A socio-aware overlay for publish/subscribe communication in delay tolerant networks

paper_content:

The emergence of Delay Tolerant Networks (DTNs) has culminated in a new generation of wireless networking. We focus on a type of human-to-human communication in DTNs, where human behaviour exhibits the characteristics of networks by forming a community. We show the characteristics of such networks from extensive study of real-world human connectivity traces. We exploit distributed community detection from the trace and propose a Socio-Aware Overlay over detected communities for publish/subscribe communication. Centrality nodes have the best visibility to the other nodes in the network. We create an overlay with such centrality nodes from communities. Distributed community detection operates when nodes (i.e. devices) are in contact by gossipping, and subscription propagation is performed along with this operation. We validate our message dissemination algorithms for publish/subscribe with connectivity traces.
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paper_title: LocalCom: A Community-based Epidemic Forwarding Scheme in Disruption-tolerant Networks

paper_content:

In disruption-tolerant networks (DTNs), network topology constantly changes and end-to-end paths can hardly be sustained. However, social network properties are observed in many DTNs and tend to be stable over time. To utilize the social network properties to facilitate packet forwarding, we present LocalCom, a community-based epidemic forwarding scheme that efficiently detects the community structure using limited local information and improves the forwarding efficiency based on the community structure. We define similarity metrics according to nodes' encounter history to depict the neighboring relationship between each pair of nodes. A distributed algorithm, which only utilizes local information, is then applied to detect communities and the formed communities have strong intra-community connections. We also present two schemes to first select and then prune gateways that connect communities to control redundancy and facilitate efficient intercommunity packet forwarding. Extensive real-trace-driven simulation results are presented to support the effectiveness of our scheme.
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paper_title: LocalCom: A Community-based Epidemic Forwarding Scheme in Disruption-tolerant Networks

paper_content:

In disruption-tolerant networks (DTNs), network topology constantly changes and end-to-end paths can hardly be sustained. However, social network properties are observed in many DTNs and tend to be stable over time. To utilize the social network properties to facilitate packet forwarding, we present LocalCom, a community-based epidemic forwarding scheme that efficiently detects the community structure using limited local information and improves the forwarding efficiency based on the community structure. We define similarity metrics according to nodes' encounter history to depict the neighboring relationship between each pair of nodes. A distributed algorithm, which only utilizes local information, is then applied to detect communities and the formed communities have strong intra-community connections. We also present two schemes to first select and then prune gateways that connect communities to control redundancy and facilitate efficient intercommunity packet forwarding. Extensive real-trace-driven simulation results are presented to support the effectiveness of our scheme.
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paper_title: Impact of social structure on forwarding algorithms in opportunistic networks

paper_content:

Opportunistic networks are formed among mobile wireless devices based on spontaneous connectivity such as mobile phone networks using short range radio. Different setting of social structure in such networks gives significant impact on the feasibility and performance. In this paper we aim at understanding how social structure affects forwarding algorithm in various opportunistic network configurations. Having human mobility traces from the real world, we focus on the social structure in terms of centrality and community. We exploit different community detection and centrality calculation from the trace to present the features of such networks. We study a collection of Social-based Forwarding algorithms, such as LABEL, RANK, and BUBBLE [10]. Furthermore, we implement those forwarding algorithms over a Xen-based Haggle testbed [9]. We investigate the impact of community structure and centrality on performance and demonstrate that social structure influences the performance of the social-based Forwarding algorithms. Our result demonstrates that it is important to find appropriate centrality and communities for social networks with complex structure in the design of the social-based data dissemination algorithms.
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paper_title: BUBBLE Rap: Social-Based Forwarding in Delay-Tolerant Networks

paper_content:

The increasing penetration of smart devices with networking capability form novel networks. Such networks, also referred as pocket switched networks (PSNs), are intermittently connected and represent a paradigm shift of forwarding data in an ad hoc manner. The social structure and interaction of users of such devices dictate the performance of routing protocols in PSNs. To that end, social information is an essential metric for designing forwarding algorithms for such types of networks. Previous methods relied on building and updating routing tables to cope with dynamic network conditions. On the downside, it has been shown that such approaches end up being cost ineffective due to the partial capture of the transient network behavior. A more promising approach would be to capture the intrinsic characteristics of such networks and utilize them in the design of routing algorithms. In this paper, we exploit two social and structural metrics, namely centrality and community, using real human mobility traces. The contributions of this paper are two-fold. First, we design and evaluate BUBBLE, a novel social-based forwarding algorithm, that utilizes the aforementioned metrics to enhance delivery performance. Second, we empirically show that BUBBLE can substantially improve forwarding performance compared to a number of previously proposed algorithms including the benchmarking history-based PROPHET algorithm, and social-based forwarding SimBet algorithm.
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paper_title: Social network analysis for routing in disconnected delay-tolerant MANETs

paper_content:

Message delivery in sparse Mobile Ad hoc Networks (MANETs) is difficult due to the fact that the network graph is rarely (if ever) connected. A key challenge is to find a route that can provide good delivery performance and low end-to-end delay in a disconnected network graph where nodes may move freely. This paper presents a multidisciplinary solution based on the consideration of the so-called small world dynamics which have been proposed for economy and social studies and have recently revealed to be a successful approach to be exploited for characterising information propagation in wireless networks. To this purpose, some bridge nodes are identified based on their centrality characteristics, i.e., on their capability to broker information exchange among otherwise disconnected nodes. Due to the complexity of the centrality metrics in populated networks the concept of ego networks is exploited where nodes are not required to exchange information about the entire network topology, but only locally available information is considered. Then SimBet Routing is proposed which exploits the exchange of pre-estimated "betweenness' centrality metrics and locally determined social "similarity' to the destination node. We present simulations using real trace data to demonstrate that SimBet Routing results in delivery performance close to Epidemic Routing but with significantly reduced overhead. Additionally, we show that SimBet Routing outperforms PRoPHET Routing, particularly when the sending and receiving nodes have low connectivity.
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paper_title: Social network analysis concepts in the design of wireless Ad Hoc network protocols

paper_content:

This article presents a survey of ad hoc networking protocols that have used concepts such as centrality metrics and community formation from the area of social network analysis, which is seen as a network measurement task that deals with structural properties of the network graph. We recognize the synergy among social network analysis and ad hoc networking as a fertile research area that can provide significant advances for the design of network protocols, especially in environments where the communication is opportunistic in nature and therefore cannot be easily or efficiently described as an optimization problem, and other systematic approaches like cross-layer optimization are more difficult to apply.
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paper_title: Social network analysis on data diffusion in delay tolerant networks

paper_content:

Different from existing mobility-assisted data access techniques, we propose to use data diffusion to reduce the query delay in DTNs. We use social network analysis to classify and study four diffusion schemes based on the "homophily" phenomenon in social network. Theoretical models are further developed to analyze the data diffusion process and compare the performance of the four proposed diffusion schemes in terms of diffusion speed and query delay.
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paper_title: The Emergence of Social and Community Intelligence

paper_content:

Social and community intelligence research aims to reveal individual and group behaviors, social interactions, and community dynamics by mining the digital traces that people leave while interacting with Web applications, static infrastructure, and mobile and wearable devices.
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paper_title: Are you moved by your social network application?

paper_content:

This paper studies a Bluetooth-based mobile social network application deployed among a group of 28 participants collected during a computer communication conference. We compare the social graph containing friends, as defined by participants, to the contact graph, that is the temporal network created by opportunistic contacts as owners of devices move and come into communication range. Our contribution is twofold: first, we prove that most properties of nodes, links, and paths correlate among the social and contact graphs. Second, we describe how the structure of the social graph helps build forwarding paths in the contact graph, allowing two nodes to communicate over time using opportunistic contacts and intermediate nodes. Efficient paths can be built using only pairs of nodes that are socially close (i.e. connected through a few pairs of friends). Our results indicate that opportunistic forwarding complies with the requirement of social network application.
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paper_title: Social network analysis for routing in disconnected delay-tolerant MANETs

paper_content:

Message delivery in sparse Mobile Ad hoc Networks (MANETs) is difficult due to the fact that the network graph is rarely (if ever) connected. A key challenge is to find a route that can provide good delivery performance and low end-to-end delay in a disconnected network graph where nodes may move freely. This paper presents a multidisciplinary solution based on the consideration of the so-called small world dynamics which have been proposed for economy and social studies and have recently revealed to be a successful approach to be exploited for characterising information propagation in wireless networks. To this purpose, some bridge nodes are identified based on their centrality characteristics, i.e., on their capability to broker information exchange among otherwise disconnected nodes. Due to the complexity of the centrality metrics in populated networks the concept of ego networks is exploited where nodes are not required to exchange information about the entire network topology, but only locally available information is considered. Then SimBet Routing is proposed which exploits the exchange of pre-estimated "betweenness' centrality metrics and locally determined social "similarity' to the destination node. We present simulations using real trace data to demonstrate that SimBet Routing results in delivery performance close to Epidemic Routing but with significantly reduced overhead. Additionally, we show that SimBet Routing outperforms PRoPHET Routing, particularly when the sending and receiving nodes have low connectivity.
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paper_title: Social Network Analysis for Information Flow in Disconnected Delay-Tolerant MANETs

paper_content:

Message delivery in sparse mobile ad hoc networks (MANETs) is difficult due to the fact that the network graph is rarely (if ever) connected. A key challenge is to find a route that can provide good delivery performance and low end-to-end delay in a disconnected network graph where nodes may move freely. We cast this challenge as an information flow problem in a social network. This paper presents social network analysis metrics that may be used to support a novel and practical forwarding solution to provide efficient message delivery in disconnected delay-tolerant MANETs. These metrics are based on social analysis of a node's past interactions and consists of three locally evaluated components: a node's "betweenness" centrality (calculated using ego networks) and a node's social 'similarity' to the destination node and a node's tie strength relationship with the destination node. We present simulations using three real trace data sets to demonstrate that by combining these metrics delivery performance may be achieved close to epidemic routing but with significantly reduced overhead. Additionally, we show improved performance when compared to PRoPHET routing.
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paper_title: Understanding individual human mobility patterns

paper_content:

Despite their importance for urban planning, traffic forecasting and the spread of biological and mobile viruses, our understanding of the basic laws governing human motion remains limited owing to the lack of tools to monitor the time-resolved location of individuals. Here we study the trajectory of 100,000 anonymized mobile phone users whose position is tracked for a six-month period. We find that, in contrast with the random trajectories predicted by the prevailing Lévy flight and random walk models, human trajectories show a high degree of temporal and spatial regularity, each individual being characterized by a time-independent characteristic travel distance and a significant probability to return to a few highly frequented locations. After correcting for differences in travel distances and the inherent anisotropy of each trajectory, the individual travel patterns collapse into a single spatial probability distribution, indicating that, despite the diversity of their travel history, humans follow simple reproducible patterns. This inherent similarity in travel patterns could impact all phenomena driven by human mobility, from epidemic prevention to emergency response, urban planning and agent-based modelling.
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paper_title: Modeling Time-Variant User Mobility in Wireless Mobile Networks

paper_content:

Realistic mobility models are important to understand the performance of routing protocols in wireless ad hoc networks, especially when mobility-assisted routing schemes are employed, which is the case, for example, in delay-tolerant networks (DTNs). In mobility-assisted routing, messages are stored in mobile nodes and carried across the network with nodal mobility. Hence, the delay involved in message delivery is tightly coupled with the properties of nodal mobility. Currently, commonly used mobility models are simplistic random i.i.d. model that do not reflect realistic mobility characteristics. In this paper we propose a novel time-variant community mobility model. In this model, we define communities that are visited often by the nodes to capture skewed location visiting preferences, and use time periods with different mobility parameters to create periodical re-appearance of nodes at the same location. We have clearly observed these two properties based on analysis of empirical WLAN traces. In addition to the proposal of a realistic mobility model, we derive analytical expressions to highlight the impact on the hitting time and meeting times if these mobility characteristics are incorporated. These quantities in turn determine the packet delivery delay in mobility-assisted routing settings. Simulation studies show our expressions have error always under 20%, and in 80% of studied cases under 10%.
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paper_title: Writing on the clean slate: Implementing a socially-aware protocol in Haggle

paper_content:

Developing protocols and applications for opportunistic networking can represent a daunting task given the many aspects that must be taken into consideration, such as intermittent connectivity, smart choice among multiple interfaces and intelligent data storage. The implementation of these protocols can be based on generic layer-less communication frameworks that provide programming abstractions for the extraction and analysis of social, colocation and mobility information and allows data exchange by means of heterogeneous devices. We propose Gently, a novel fully implemented solution which combines techniques of context awareness and social knowledge to concretely solve issues related to opportunistic forwarding. More precisely, Gently is born as the combination of the Context-aware Adaptive Routing (CAR) and the socially aware LABEL protocol. We discuss the implementation of our solution on top of the layer-less Haggle framework presenting the key design choices and the lessons learnt.
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paper_title: PeopleRank: Social Opportunistic Forwarding

paper_content:

In opportunistic networks, end-to-end paths between two communicating nodes are rarely available. In such situations, the nodes might still copy and forward messages to nodes that are more likely to meet the destination. The question is which forwarding algorithm offers the best trade off between cost (number of message replicas) and rate of successful message delivery. We address this challenge by developing the PeopleRank approach in which nodes are ranked using a tunable weighted social information. Similar to the PageRank idea, PeopleRank gives higher weight to nodes if they are socially connected to important other nodes of the network. We develop centralized and distributed variants for the computation of PeopleRank. We present an evaluation using real mobility traces of nodes and their social interactions to show that PeopleRank manages to deliver messages with near optimal success rate (close to Epidemic Routing) while reducing the number of message retransmissions by 50% compared to Epidemic Routing.
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paper_title: Social network analysis for routing in disconnected delay-tolerant MANETs

paper_content:

Message delivery in sparse Mobile Ad hoc Networks (MANETs) is difficult due to the fact that the network graph is rarely (if ever) connected. A key challenge is to find a route that can provide good delivery performance and low end-to-end delay in a disconnected network graph where nodes may move freely. This paper presents a multidisciplinary solution based on the consideration of the so-called small world dynamics which have been proposed for economy and social studies and have recently revealed to be a successful approach to be exploited for characterising information propagation in wireless networks. To this purpose, some bridge nodes are identified based on their centrality characteristics, i.e., on their capability to broker information exchange among otherwise disconnected nodes. Due to the complexity of the centrality metrics in populated networks the concept of ego networks is exploited where nodes are not required to exchange information about the entire network topology, but only locally available information is considered. Then SimBet Routing is proposed which exploits the exchange of pre-estimated "betweenness' centrality metrics and locally determined social "similarity' to the destination node. We present simulations using real trace data to demonstrate that SimBet Routing results in delivery performance close to Epidemic Routing but with significantly reduced overhead. Additionally, we show that SimBet Routing outperforms PRoPHET Routing, particularly when the sending and receiving nodes have low connectivity.
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paper_title: On Exploiting Transient Social Contact Patterns for Data Forwarding in Delay-Tolerant Networks

paper_content:

Unpredictable node mobility, low node density, and lack of global information make it challenging to achieve effective data forwarding in Delay-Tolerant Networks (DTNs). Most of the current data forwarding schemes choose the nodes with the best cumulative capability of contacting others as relays to carry and forward data, but these nodes may not be the best relay choices within a short time period due to the heterogeneity of transient node contact characteristics. In this paper, we propose a novel approach to improve the performance of data forwarding with a short time constraint in DTNs by exploiting the transient social contact patterns. These patterns represent the transient characteristics of contact distribution, network connectivity and social community structure in DTNs, and we provide analytical formulations on these patterns based on experimental studies of realistic DTN traces. We then propose appropriate forwarding metrics based on these patterns to improve the effectiveness of data forwarding. When applied to various data forwarding strategies, our proposed forwarding metrics achieve much better performance compared to existing schemes with similar forwarding cost.
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paper_title: Time Critical Content Delivery Using Predictable Patterns in Mobile Social Networks

paper_content:

In Mobile Social Networks (MSN) individuals with similar interests or commonalities connect to each other using the mobile phones. MSN are special kind of Ad-hoc Networks in which wireless connectivity (i.e. encounters and re-encounters) with social peers is predictable. Most of the recent research proposes routing framework to exploit these predictable patterns to identify the best information carriers. The best information carriers are selected based on the high probability of encounter with potential information recipients. In these approaches an important variable is ignored i.e. time of encounter. Considering encounter time in the protocol gives time assurance of message delivery for time critical application. Therefore in this paper we address the research question, how to exploit people's predictable social patterns to improve the content delivery performance and lower end-to-end delay in time critical applications? Our assumption is that the people follow similar mobility patterns daily (i.e. Monday to Friday). In this paper we verify our research question and assumption using real trace data of 100 users carrying Nokia 6600 smart phones over the course of nine months. Furthermore we model, analyze and propose algorithms for social encounter based content delivery system for time critical applications. The simple heuristics and initial study presented in this paper achieve a timely content delivery using predictable patterns while lowering system wide traffic flooding.
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paper_title: Impact of Human Mobility on the Design of Opportunistic Forwarding Algorithms

paper_content:

Studying transfer opportunities between wireless devices carried by humans, we observe that the distribution of the inter-contact time, that is the time gap separating two contacts of the same pair of devices, exhibits a heavy tail such as one of a power law, over a large range of value. This observation is confirmed on six distinct experimental data sets. It is at odds with the exponential decay implied by most mobility models. In this paper, we study how this new characteristic of human mobility impacts a class of previously proposed forwarding algorithms. We use a simplified model based on the renewal theory to study how the parameters of the distribution impact the delay performance of these algorithms. We make recommendation for the design of well founded opportunistic forwarding algorithms, in the context of human carried devices.
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paper_title: Diverse Routing: Exploiting Social Behavior for Routing in Delay-Tolerant Networks

paper_content:

Delay tolerant network (DTN) is an emerging research area that exploits user mobility for transporting information. While user mobility connects disconnected network components, it causes a large end to end communicationlatency. Towards reducing this latency, the habitual nature of human movements have been widely exploited for prediction-based routing protocols. We observe that while habitual mobility is useful in reducing the average communication latency, irregular deviation from habits canseriously affect worst-case performance. This paper motivates the need to address such deviations, characterizes their impact on latency, and addresses them through a protocol called Diverse Routing (DR). Evaluation of our protocol on a variety of real-life traces offers promising results. Experimental results reveal that DR provides efficient handling on worst-case latency, i.e., DR’s delivery delay is hardly affected by those irregular deviations, while it only incurs a moderate communication overhead. Moreover, DR can be easily tuned to meet different requirements of delivery delay and communication overhead.
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paper_title: Social Network Analysis for Information Flow in Disconnected Delay-Tolerant MANETs

paper_content:

Message delivery in sparse mobile ad hoc networks (MANETs) is difficult due to the fact that the network graph is rarely (if ever) connected. A key challenge is to find a route that can provide good delivery performance and low end-to-end delay in a disconnected network graph where nodes may move freely. We cast this challenge as an information flow problem in a social network. This paper presents social network analysis metrics that may be used to support a novel and practical forwarding solution to provide efficient message delivery in disconnected delay-tolerant MANETs. These metrics are based on social analysis of a node's past interactions and consists of three locally evaluated components: a node's "betweenness" centrality (calculated using ego networks) and a node's social 'similarity' to the destination node and a node's tie strength relationship with the destination node. We present simulations using three real trace data sets to demonstrate that by combining these metrics delivery performance may be achieved close to epidemic routing but with significantly reduced overhead. Additionally, we show improved performance when compared to PRoPHET routing.
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paper_title: MV routing and capacity building in disruption tolerant networks

paper_content:

Disruption-tolerant networks (DTNs) differ from other types of networks in that capacity is exclusively created by the movements of participants. This implies that understanding and influencing the participants' motions can have a significant impact on network performance. In this paper, we introduce the routing protocol MV, which learns structure in the movement patterns of network participants and uses it to enable informed message passing. We also propose the introduction of autonomous agents as additional participants in DTNs. These agents adapt their movements in response to variations in network capacity and demand. We use multi-objective control methods from robotics to generate motions capable of optimizing multiple network performance metrics simultaneously. We present experimental evidence that these strategies, individually and in conjunction, result in significant performance improvements in DTNs.
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paper_title: MobiID: a user-centric and social-aware reputation based incentive scheme for delay/disruption tolerant networks

paper_content:

Delay/Disruption tolerant networks (DTNs) are wireless ad-hoc networks, where end-to-end connectivity can not be guaranteed and communications rely on the assumption that the nodes are willing to store-carry-and-forward bundles in an opportunistic way. However, this assumption would be easily violated due to the selfish nodes which are unwilling to consume precious wireless resources by serving as bundle relays. Incentive issue in DTNs is extraordinarily challenging due to the unique network characteristics. To tackle this issue, in this paper, we propose MobiID, a novel user-centric and social-aware reputation based incentive scheme for DTNs. Different from conventional reputation schemes which rely on neighboring nodes to monitor the traffic and keep track of each other's reputation, MobiID allows a node to manage its reputation evidence and show to demonstrate its reputation whenever necessary. We also define the concepts of self-check and community-check to speed up reputation establishment and allow nodes to form consensus views towards targets in the same community, which is based on our social metric by forwarding willingness. Performance simulation are given to demonstrate the security, effectiveness and efficiency of the proposed scheme.
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paper_title: Using social network theory for modeling human mobility

paper_content:

Human mobility modeling plays an essential role in accurately understanding the performance of data forwarding protocols in mobile networks and has been attracting increasing research interest in recent years. People's movement behaviors are strongly affected by their social interactions with each other, which, however, are not sufficiently considered in most existing mobility models. Recent studies in social network theory have provided many theoretical and experimental results, which are useful and powerful for modeling the realistic social dimension of human mobility. In this article we present a novel human mobility model based on heterogeneous centrality and overlapping community structure in social networks. Instead of extracting communities from artificially generated social graphs, our model manages to construct the k-clique overlapping community structure which satisfies the common statistical features observed from distinct real social networks. This approach achieves a good trade-off between complexity and reality. The simulation results of our model exhibit characteristics observed from real human motion traces, especially heterogeneous human mobility popularity, which has significant impact on data forwarding schemes but has never been considered by existing mobility models.
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paper_title: DTN routing in a mobility pattern space

paper_content:

Routing in Delay Tolerant Networks (DTNs) benefits considerably if one can take advantage of knowledge concerning node mobility. The main contribution of this paper is the definition of a generic routing scheme for DTNs using a high-dimensional Euclidean space constructed upon nodes' mobility patterns. For example, nodes are represented as points having as coordinates their probability of being found in each possible location. We present simulation results indicating that such a scheme can be beneficial in a scenario inspired by studies done on real mobility traces. This work should open the way to further use of the virtual space formalism in DTN routing.
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paper_title: Probabilistic routing in intermittently connected networks

paper_content:

We consider the problem of routing in intermittently connected networks. In such networks there is no guarantee that a fully connected path between source and destination exist at any time, rendering traditional routing protocols unable to deliver messages between hosts. We propose a probabilistic routing protocol for such networks.
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paper_title: LocalCom: A Community-based Epidemic Forwarding Scheme in Disruption-tolerant Networks

paper_content:

In disruption-tolerant networks (DTNs), network topology constantly changes and end-to-end paths can hardly be sustained. However, social network properties are observed in many DTNs and tend to be stable over time. To utilize the social network properties to facilitate packet forwarding, we present LocalCom, a community-based epidemic forwarding scheme that efficiently detects the community structure using limited local information and improves the forwarding efficiency based on the community structure. We define similarity metrics according to nodes' encounter history to depict the neighboring relationship between each pair of nodes. A distributed algorithm, which only utilizes local information, is then applied to detect communities and the formed communities have strong intra-community connections. We also present two schemes to first select and then prune gateways that connect communities to control redundancy and facilitate efficient intercommunity packet forwarding. Extensive real-trace-driven simulation results are presented to support the effectiveness of our scheme.
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paper_title: Opportunities in Opportunistic Computing

paper_content:

When two devices come into contact, albeit opportunistically, it provides a great opportunity to match services to resources, exchange information, cyberforage, execute tasks remotely, and forward messages.
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paper_title: Friendship Based Routing in Delay Tolerant Mobile Social Networks

paper_content:

Routing in delay tolerant networks (DTN) have attracted a great interest recently. Increasingly popular type of DTNs are mobile social networks (MSN) also called pocket switched networks. Hence, analyzing accurately social network properties has become an important issue in designing efficient routing protocols for MSNs. In this paper, we first introduce a new metric for detecting the quality of friendships accurately. Using the introduced metric, each node defines its friendship community as the set of nodes having close friendship with itself either directly or indirectly. Then, we present Friendship Based Routing in which temporally differentiated friendships are used to make the forwarding decisions of messages. Real trace-driven simulation results show that the introduced algorithm achieves better delivery rate while forwarding fewer messages than the existing algorithms.
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paper_title: Predict and relay: an efficient routing in disruption-tolerant networks

paper_content:

Routing is one of the most challenging open problems in disruption-tolerant networks (DTNs) because of the short-lived wireless connectivity environment. To deal with this issue, researchers have investigated routing based on the prediction of future contacts, taking advantage of nodes' mobility history. However, most of the previous work focused on the prediction of whether two nodes would have a contact, without considering the time of the contact. This paper proposes predict and relay (PER), an efficient routing algorithm for DTNs, where nodes determine the probability distribution of future contact times and choose a proper next hop in order to improve the end-to-end delivery probability. The algorithm is based on two observations: one is that nodes usually move around a set of well-visited landmark points instead of moving randomly; the other is that node mobility behavior is semi-deterministic and could be predicted once there is sufficient mobility history information. Specifically, our approach employs a time-homogeneous semi-markov process model that describes node mobility as transitions between landmarks. Landmark transition and sojourn time probability distributions are determined from nodes' mobility history. A simulation study shows that this approach improves the delivery ratio and also reduces the delivery latency compared to traditional DTN routing schemes.
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paper_title: Adaptive routing for intermittently connected mobile ad hoc networks

paper_content:

The vast majority of mobile ad hoc networking research makes a very large assumption - that communication can only take place between nodes that are simultaneously accessible within the same connected cloud (i.e., that communication is synchronous). In reality, this assumption is likely to be a poor one, particularly for sparsely or irregularly populated environments. We present the context-aware routing (CAR) algorithm. CAR is a novel approach to the provision of asynchronous communication in partially-connected mobile ad hoc networks, based on the intelligent placement of messages. We discuss the details of the algorithm, and then present simulation results demonstrating that it is possible for nodes to exploit context information in making local decisions that lead to good delivery ratios and latencies with small overheads.
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paper_title: BUBBLE Rap: Social-Based Forwarding in Delay-Tolerant Networks

paper_content:

The increasing penetration of smart devices with networking capability form novel networks. Such networks, also referred as pocket switched networks (PSNs), are intermittently connected and represent a paradigm shift of forwarding data in an ad hoc manner. The social structure and interaction of users of such devices dictate the performance of routing protocols in PSNs. To that end, social information is an essential metric for designing forwarding algorithms for such types of networks. Previous methods relied on building and updating routing tables to cope with dynamic network conditions. On the downside, it has been shown that such approaches end up being cost ineffective due to the partial capture of the transient network behavior. A more promising approach would be to capture the intrinsic characteristics of such networks and utilize them in the design of routing algorithms. In this paper, we exploit two social and structural metrics, namely centrality and community, using real human mobility traces. The contributions of this paper are two-fold. First, we design and evaluate BUBBLE, a novel social-based forwarding algorithm, that utilizes the aforementioned metrics to enhance delivery performance. Second, we empirically show that BUBBLE can substantially improve forwarding performance compared to a number of previously proposed algorithms including the benchmarking history-based PROPHET algorithm, and social-based forwarding SimBet algorithm.
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paper_title: MaxProp: Routing for Vehicle-Based Disruption-Tolerant Networks

paper_content:

Disruption-tolerant networks (DTNs) attempt to route network messages via intermittently connected nodes. Routing in such environments is difficult because peers have little information about the state of the partitioned network and transfer opportunities between peers are of limited duration. In this paper, we propose MaxProp, a protocol for effective routing of DTN messages. MaxProp is based on prioritizing both the schedule of packets transmitted to other peers and the schedule of packets to be dropped. These priorities are based on the path likelihoods to peers according to historical data and also on several complementary mechanisms, including acknowledgments, a head-start for new packets, and lists of previous intermediaries. Our evaluations show that MaxProp performs better than protocols that have access to an oracle that knows the schedule of meetings between peers. Our evaluations are based on 60 days of traces from a real DTN network we have deployed on 30 buses. Our network, called UMassDieselNet, serves a large geographic area between five colleges. We also evaluate MaxProp on simulated topologies and show it performs well in a wide variety of DTN environments.
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paper_title: How Small Labels Create Big Improvements

paper_content:

It is widely believed that identifying communities in an ad hoc mobile communications system, such as a pocket switched network, can reduce the amount of traffic created when forwarding messages, but there has not been any empirical evidence available to support this assumption to date. In this paper, we show through use of real experimental human mobility data, how using a small label, identifying users according to their affiliation, can bring a large improvement in forwarding performance, in term of both delivery ratio and cost
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paper_title: A Qualitative Survey on Multicast Routing in Delay Tolerant Networks

paper_content:

Delay Tolerant Networks (DTNs) are a class of networks that make communication in stressed and challenging environments possible. DTN is characterized with a number of unique features by virtue of which a working environment is achieved in situations where traditional networking paradigms fail to deliver satisfactorily or entirely. The utility of multicasting in DTNs extends to numerous potential DTN applications i.e., crisis environments, battlefield situations, deep space communications, dynamic data size management, etc. In this paper, we propose taxonomy for the different multicast routing strategies and thereafter, we present a comprehensive up to date survey of these strategies. Further, we perform a qualitative comparison between the different multicast strategies with respect to important performance issues in DTN. We also highlight some unexplored areas in DTN multicasting that could inspire research in the near future.
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paper_title: Social-Aware Multicast in Disruption-Tolerant Networks

paper_content:

Node mobility and end-to-end disconnections in disruption-tolerant networks (DTNs) greatly impair the effectiveness of data forwarding. Although social-based approaches can address the problem, most existing solutions only focus on forwarding data to a single destination. In this paper, we study multicast with single and multiple data items in DTNs from a social network perspective, develop analytical models for multicast relay selection, and furthermore investigate the essential difference between multicast and unicast in DTNs. The proposed approach selects relays according to their capabilities, measured by social-based metrics, for forwarding data to the destinations. The design of social-based metrics exploits social network concepts such as node centrality and social community, and the selected relays ensure achieving the required data delivery ratio within the given time constraint. Extensive trace-driven simulations show that the proposed approach has similar data delivery ratio and delay to that of Epidemic routing, but significantly reduces data forwarding cost, measured by the number of relays used.
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paper_title: Efficient and adaptive congestion control for heterogeneous delay-tolerant networks

paper_content:

Detecting and dealing with congestion in delay-tolerant networks (DTNs) is an important and challenging problem. Current DTN forwarding algorithms typically direct traffic towards more central nodes in order to maximise delivery ratios and minimise delays, but as traffic demands increase these nodes may become saturated and unusable. We propose CafRep, an adaptive congestion aware protocol that detects and reacts to congested nodes and congested parts of the network by using implicit hybrid contact and resources congestion heuristics. CafRep exploits localised relative utility based approach to offload the traffic from more to less congested parts of the network, and to replicate at adaptively lower rate in different parts of the network with non-uniform congestion levels. We extensively evaluate our work against benchmark and competitive protocols across a range of metrics over three real connectivity and GPS traces such as Sassy 44], San Francisco Cabs 45] and Infocom 2006 33]. We show that CafRep performs well, independent of network connectivity and mobility patterns, and consistently outperforms the state-of-the-art DTN forwarding algorithms in the face of increasing rates of congestion. CafRep maintains higher availability and success ratios while keeping low delays, packet loss rates and delivery cost. We test CafRep in the presence of two application scenarios, with fixed rate traffic and with real world Facebook application traffic demands, showing that regardless of the type of traffic CafRep aims to deliver, it reduces congestion and improves forwarding performance.
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paper_title: A Qualitative Survey on Multicast Routing in Delay Tolerant Networks

paper_content:

Delay Tolerant Networks (DTNs) are a class of networks that make communication in stressed and challenging environments possible. DTN is characterized with a number of unique features by virtue of which a working environment is achieved in situations where traditional networking paradigms fail to deliver satisfactorily or entirely. The utility of multicasting in DTNs extends to numerous potential DTN applications i.e., crisis environments, battlefield situations, deep space communications, dynamic data size management, etc. In this paper, we propose taxonomy for the different multicast routing strategies and thereafter, we present a comprehensive up to date survey of these strategies. Further, we perform a qualitative comparison between the different multicast strategies with respect to important performance issues in DTN. We also highlight some unexplored areas in DTN multicasting that could inspire research in the near future.
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paper_title: Fair Routing in Delay Tolerant Networks

paper_content:

The typical state-of-the-art routing algorithms for delay tolerant networks are based on best next hop hill-climbing heuristics in order to achieve throughput and efficiency. The combination of these heuristics and the social network structure leads the routing to direct most of the traffic through a small subset of good users. For instance, in the SimBet algorithm, the top 10% of users carry out 54% of all the forwards and 85% of all the handovers. This unfair load distribution is not sustainable as it can quickly deplete constraint resources in heavily utilized mobile devices (e.g. storage, battery, budget, etc.). Moreover, because a small number of users carry a significant amount of the traffic, the system is not robust to random failures and attacks. To overcome these inefficiencies, this paper introduces Fair-Route, a routing algorithm for delay tolerant networks inspired by the social processes of perceived interaction strength, where messages are preferably forwarded to users that have a stronger social relation with the target of the message; and assortativity, that limits the exchange of messages to those users with similar "social status". We compare the performance of FairRoute to the state-of-the-art algorithms by extensive simulations on the MIT reality mining dataset. The results show that our algorithm outperforms existing algorithms in the de facto benchmark of throughput vs. forwards. Furthermore, it distributes better the load; the top 10% carry out 26% of the forwards and 28% of the handovers without any loss in performance.
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paper_title: Message Duplication Reduction in Dense Mobile Social Networks

paper_content:

NA
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paper_title: Congestion aware forwarding in delay tolerant and social opportunistic networks

paper_content:

We propose an approach for opportunistic forwarding that supports optimization of multipoint high volume data flow transfer while maintaining high buffer availability and low delays. This paper explores a number of social, buffer and delay heuristics to offload the traffic from congested parts of the network and spread it over less congested parts of the network in order to keep low delays, high success ratios and high availability of nodes. We conduct an extensive set of experiments for assessing the performance of four newly proposed heuristics and compare them with Epidemic, Prophet, Spay and Wait and Spay and Focus protocols over real connectivity driven traces (RollerNet) and with a realistic publish subscribe filecasting application. We look into success ratio of answered queries, download times (delays) and availability of buffer across eight protocols for varying congestion levels in the face of increasing number of publishers and topic popularity. We show that all of our combined metrics perform better than Epidemic protocol, Prophet, Spray and Wait, Spray and Focus and our previous prototype across all the assessed criteria.
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paper_title: Delegation forwarding

paper_content:

Mobile opportunistic networks are characterized by unpredictable mobility, heterogeneity of contact rates and lack of global information. Successful delivery of messages at low costs and delays in such networks is thus challenging. Most forwarding algorithms avoid the cost associated with flooding the network by forwarding only to nodes that are likely to be good relays, using a quality metric associated with nodes. However it is non-trivial to decide whether an encountered node is a good relay at the moment of encounter. Thus the problem is in part one of online inference of the quality distribution of nodes from sequential samples, and has connections to optimal stopping theory. Based on these observations we develop a new strategy for forwarding, which we refer to as delegation forwarding. We analyse two variants of delegation forwarding and show that while naive forwarding to high contact rate nodes has cost linear in the population size, the cost of delegation forwarding is proportional to the square root of population size. We then study delegation forwarding with different metrics using real mobility traces and show that delegation forwarding performs as well as previously proposed algorithms at much lower cost. In particular we show that the delegation scheme based on destination contact rate does particularly well.
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paper_title: On Exploiting Few Strangers for Data Forwarding in Delay Tolerant Networks

paper_content:

Routing is one of the challenging tasks in Delay Tolerant Networks (DTNs), due to the lack of global knowledge and sporadic contacts between nodes. Most existing works take greedy mechanism to forward messages, i.e., only nodes which have higher quality metrics than current carriers can be selected as relays to final destinations. In this work, we explore the influence of strangers on routing performance under a more challenging scenario of pure darkness. We first present a method to identify the relationship between nodes (i.e., stranger or friend). Second, we explore the optimized number of strangers we can employ. Third, we propose a novel routing scheme which are called STRON in this paper by taking both the STRangers and their Optimized Number into account. We finally compare our routing scheme with the greedy mechanism through synthetical and trace-driven simulations, the results show that our routing strategy achieves a better performance, especially in terms of combined overhead/packet delivery ratio and the average number of hops per message.
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paper_title: Routing in Socially Selfish Delay Tolerant Networks

paper_content:

Existing routing algorithms for Delay Tolerant Networks(DTNs) assume that nodes are willing to forward packets for others. In the real world, however, most people are socially selfish; i.e., they are willing to forward packets for nodes with whom they have social ties but not others, and such willingness varies with the strength of the social tie. Following the philosophy of design for user, we propose a Social Selfishness Aware Routing (SSAR) algorithm to allow user selfishness and provide better routing performance in an efficient way. To select a forwarding node, SSAR considers both users' willingness to forward and their contact opportunity, resulting in a better forwarding strategy than purely contact-based approaches. Moreover, SSAR formulates the data forwarding process as a Multiple Knapsack Problem with Assignment Restrictions (MKPAR) to satisfy user demands for selfishness and performance. Trace-driven simulations show that SSAR allows users to maintain selfishness and achieves better routing performance with low transmission cost.
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paper_title: Evaluating the effects of node cooperation on DTN routing

paper_content:

a b s t r a c t Due to the uncertainty of transmission opportunities between mobile nodes, delay tolerant networks (DTN) routing exploits the opportunistic forwarding mechanism. This mechanism requires nodes to forward messages in a cooperative way. However, in the real word, most of the nodes exhibit noncooperation behaviors such as dropping and not relaying messages. In this letter, we investigate the problem of how the non-cooperation behaviors of nodes influence the performance of DTN routing algorithms of two-hop relay and epidemic routing. First, we model the message delivery process with noncooperation behaviors by a two dimensional continuous time Markov chain. Then, we obtain the system performance of message delivery delay and delivery cost by explicit expressions. Numerical results show that different non-cooperation behaviors may have opposite impacts on different routing algorithms. Specifically, dropping message increases the message delivery delay and delivery cost in the two-hop relay, while increases the delay but does not affect the delivery cost in the epidemic routing, and not relaying message increases the delivery delay but decreases the delivery cost for both the two-hop and epidemic routing.
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paper_title: The Impact of Node Selfishness on Multicasting in Delay Tolerant Networks

paper_content:

Due to the uncertainty of transmission opportunities between mobile nodes, delay tolerant networks (DTNs) exploit the opportunistic forwarding mechanism. This mechanism requires nodes to forward messages in a cooperative and selfish way. However, in the real word, most of the nodes exhibit selfish behaviors, such as individual and social selfishness. In this paper, we are the first to investigate how the selfish behaviors of nodes affect the performance of DTN multicast. We consider two typical multicast relaying schemes, namely, two-hop relaying and epidemic relaying, and study their performance in terms of average message transmission delay and transmission cost. Specifically, we model the message delivery process under selfish behaviors by a 3-D continuous time Markov chain; under this model, we derive closed-form formulas for the message transmission delay and cost. Then, we evaluate the accuracy of the proposed Markov chain model by comparing the theoretical results with the simulation results obtained by simulating the message dissemination under both two-hop and epidemic relaying with different network sizes and mobility models. Our study shows that different selfish behaviors may have different impacts on different performance metrics. In addition, selfish behaviors influence epidemic relaying more than two-hop relaying. Furthermore, our results show that the performance of multicast with selfish nodes depends on the multicast group size.
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paper_title: On the Effects of Cooperation in DTNs

paper_content:

In a delay tolerant network (DTN) the nodes may behave autonomously deciding on their own whether to implement or not the rules of a routing algorithm. In this paper, the effects of node cooperation (or lack of it) are explored for three well-known routing algorithms proposed for DTNs with respect to the message delivery delay and the transmission overhead incurred until message delivery or the termination of the message spreading process. The results show that the sensitivity of the algorithms to the cooperation degree can be high, to the point of making them inferior to algorithms they typically outperform under a fully cooperative environment. Finally, it is demonstrated how a simple mechanism that incorporates the cooperation degree can help improve effectiveness.
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paper_title: Trust Management for Encounter-Based Routing in Delay Tolerant Networks

paper_content:

We propose and analyze a class of trust management protocols for encounter-based routing in delay tolerant networks (DTNs). The underlying idea is to incorporate trust evaluation in the routing protocol, considering not only quality-of-service (QoS) trust properties (connectivity) but also social trust properties (honesty and unselfishness) to evaluate other nodes encountered. Two versions of trust management protocols are considered: an equal-weight QoS and social trust management protocol (called trust-based routing) and a QoS only trust management protocol (called connectivity-based routing). By utilizing a stochastic Petri net model describing a DTN behavior, we analyze the performance characteristics of these two routing protocols in terms of message delivery ratio, latency, and message overhead. We also perform a comparative performance analysis with epidemic routing for a DTN consisting of heterogeneous mobile nodes with vastly different social and networking behaviors. The results indicate that trust-based routing approaches the ideal performance of epidemic routing in delivery ratio, while connectivity-based routing approaches the ideal performance in message delay of epidemic routing, especially as the percentage of selfish and malicious nodes present in the DTN system increases. By properly selecting weights associated with QoS and social trust metrics for trust evaluation, our trust management protocols can approximate the ideal performance obtainable by epidemic routing in delivery ratio and message delay without incurring high message overhead.
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paper_title: The Sybil Attack

paper_content:

Large-scale peer-to-peer systems face security threats from faulty or hostile remote computing elements. To resist these threats, many such systems employ redundancy. However, if a single faulty entity can present multiple identities, it can control a substantial fraction of the system, thereby undermining this redundancy. One approach to preventing these "Sybil attacks" is to have a trusted agency certify identities. This paper shows that, without a logically centralized authority, Sybil attacks are always possible except under extreme and unrealistic assumptions of resource parity and coordination among entities.
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paper_title: IRONMAN: Using Social Networks to Add Incentives and Reputation to Opportunistic Networks

paper_content:

Opportunistic networks enable users to communicate in the absence of network infrastructure. But forwarding messages in such a network incurs costs for nodes in terms of energy and storage. This may lead to nodes being selfish and not forwarding messages for other nodes, resulting in degraded network performance. This paper presents a novel incentive mechanism for opportunistic networks that uses pre-existing social-network information to detect and punish selfish nodes, incentivising them to participate in the network. Trace-driven simulations demonstrate that our mechanism performs better than existing mechanisms, and that social-network information can also be used to improve existing incentive mechanisms.
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paper_title: MobiID: a user-centric and social-aware reputation based incentive scheme for delay/disruption tolerant networks

paper_content:

Delay/Disruption tolerant networks (DTNs) are wireless ad-hoc networks, where end-to-end connectivity can not be guaranteed and communications rely on the assumption that the nodes are willing to store-carry-and-forward bundles in an opportunistic way. However, this assumption would be easily violated due to the selfish nodes which are unwilling to consume precious wireless resources by serving as bundle relays. Incentive issue in DTNs is extraordinarily challenging due to the unique network characteristics. To tackle this issue, in this paper, we propose MobiID, a novel user-centric and social-aware reputation based incentive scheme for DTNs. Different from conventional reputation schemes which rely on neighboring nodes to monitor the traffic and keep track of each other's reputation, MobiID allows a node to manage its reputation evidence and show to demonstrate its reputation whenever necessary. We also define the concepts of self-check and community-check to speed up reputation establishment and allow nodes to form consensus views towards targets in the same community, which is based on our social metric by forwarding willingness. Performance simulation are given to demonstrate the security, effectiveness and efficiency of the proposed scheme.
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paper_title: RADON: reputation-assisted data forwarding in opportunistic networks

paper_content:

In opportunistic networks, the probability of encountering a destination node is popularly used to select a qualified forwarder; however, it can not represent the competency of delivering data in a hostile wireless environment, because a malicious node can bloat its such probability to intercept data from others. In this paper, we design a reputation-based framework to more accurately evaluate an encounter's competency of delivering data, which can be integrated with a large family of existing data forwarding protocols in opportunistic networks. In particular, a special message, called Positive Feedback Message (PFM), is proposed to help monitor the forwarding behavior of a node. We also design a Reputation-Assisted Data forwarding protocol for Opportunistic Networks (RADON), which integrates our reputation framework with a bare-bone data forwarding protocol using the number of times of previous encounters as the metric to select the next qualified forwarder. Through simulation experiments, we demonstrate that RADON effectively improves the network performance (e.g., data delivery ratio) against "black hole" attacks.
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paper_title: SReD: A Secure REputation-based Dynamic Window Scheme for disruption-tolerant networks

paper_content:

Disruption-tolerant networks (DTNs) provide a promising low-cost solution to transfer data in network environment where the connectivity is sporadic and unpredictable. Many existing methods for opportunistic data forwarding depend on the hypothesis that every node forwards messages regardless of the identities of the senders or receivers, however, the networks based on such methods are fragile under baleful attacks, such as black hole, denial of service (DoS), and wormhole. In this paper, we present a security strategy, namely SReD, to mitigate a number of known routing layer attacks. Our solution is a localized, link-state-based and multi-path routing protocol. We employ dynamic window mechanism to switch between reputation-based routing generation mode and probabilistic routing generation mode, and the proposed SReD is particularly suitable for resource-constrained DTNs. The proposed scheme has been compared with Epidemic and Prophet protocols in terms of efficiency and effectiveness against three common attacks. The results show that SReD is robust to these attacks and is more efficient under different metrics.
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paper_title: Distributed Maintenance of Cache Freshness in Opportunistic Mobile Networks

paper_content:

Opportunistic mobile networks consist of personal mobile devices which are intermittently connected with each other. Data access can be provided to these devices via cooperative caching without support from the cellular network infrastructure, but only limited research has been done on maintaining the freshness of cached data which may be refreshed periodically and is subject to expiration. In this paper, we propose a scheme to efficiently maintain cache freshness. Our basic idea is to let each caching node be only responsible for refreshing a specific set of caching nodes, so as to maintain cache freshness in a distributed and hierarchical manner. Probabilistic replication methods are also proposed to analytically ensure that the freshness requirements of cached data are satisfied. Extensive trace driven simulations show that our scheme significantly improves cache freshness, and hence ensures the validity of data access provided to mobile users.
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paper_title: The Social Cost of Cheap Pseudonyms

paper_content:

We consider the problems of societal norms for cooperation and reputation when it is possible to obtain cheap pseudonyms, something that is becoming quite common in a wide variety of interactions on the Internet. This introduces opportunities to misbehave without paying reputational consequences. A large degree of cooperation can still emerge, through a convention in which newcomers "pay their dues" by accepting poor treatment from players who have established positive reputations. One might hope for an open society where newcomers are treated well, but there is an inherent social cost in making the spread of reputations optional. We prove that no equilibrium can sustain significantly more cooperation than the dues-paying equilibrium in a repeated random matching game with a large number of players in which players have finite lives and the ability to change their identities, and there is a small but nonvanishing probability of mistakes. Although one could remove the inefficiency of mistreating newcomers by disallowing anonymity, this is not practical or desirable in a wide variety of transactions. We discuss the use of entry fees, which permits newcomers to be trusted but excludes some players with low payoffs, thus introducing a different inefficiency. We also discuss the use of free but unreplaceable pseudonyms, and describe a mechanism that implements them using standard encryption techniques, which could be practically implemented in electronic transactions. Copyright (c) 2001 Massachusetts Institute of Technology.
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paper_title: MobiCent: a Credit-Based Incentive System for Disruption Tolerant Network

paper_content:

When Disruption Tolerant Network (DTN) is used in commercial environments, incentive mechanism should be employed to encourage cooperation among selfish mobile users. Key challenges in the design of an incentive scheme for DTN are that disconnections among nodes are the norm rather than exception and network topology is time varying. Thus, it is difficult to detect selfish actions that can be launched by mobile users or to pre-determine the routing path to be used. In this paper, we propose MobiCent, a credit-based incentive system for DTN. While MobiCent allows the underlying routing protocol to discover the most efficient paths, it is also incentive compatible. Therefore, using MobiCent, rational nodes will not purposely waste transfer opportunity or cheat by creating non-existing contacts to increase their rewards. MobiCent also provides different payment mechanisms to cater to client that wants to minimize either payment or data delivery delay.
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paper_title: MobiCent: a Credit-Based Incentive System for Disruption Tolerant Network

paper_content:

When Disruption Tolerant Network (DTN) is used in commercial environments, incentive mechanism should be employed to encourage cooperation among selfish mobile users. Key challenges in the design of an incentive scheme for DTN are that disconnections among nodes are the norm rather than exception and network topology is time varying. Thus, it is difficult to detect selfish actions that can be launched by mobile users or to pre-determine the routing path to be used. In this paper, we propose MobiCent, a credit-based incentive system for DTN. While MobiCent allows the underlying routing protocol to discover the most efficient paths, it is also incentive compatible. Therefore, using MobiCent, rational nodes will not purposely waste transfer opportunity or cheat by creating non-existing contacts to increase their rewards. MobiCent also provides different payment mechanisms to cater to client that wants to minimize either payment or data delivery delay.
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paper_title: Pi: A practical incentive protocol for delay tolerant networks

paper_content:

Delay Tolerant Networks (DTNs) are a class of networks characterized by lack of guaranteed connectivity, typically low frequency of encounters between DTN nodes and long propagation delays within the network. As a result, the message propagation process in DTNs follows a store-carryand- forward manner, and the in-transit bundle messages can be opportunistically routed towards the destinations through intermittent connections under the hypothesis that each individual DTN node is willing to help with forwarding. Unfortunately, there may exist some selfish nodes, especially in a cooperative network like DTN, and the presence of selfish DTN nodes could cause catastrophic damage to any well designed opportunistic routing scheme and jeopardize the whole network. In this paper, to address the selfishness problem in DTNs, we propose a practical incentive protocol, called Pi, such that when a source node sends a bundle message, it also attaches some incentive on the bundle, which is not only attractive but also fair to all participating DTN nodes. With the fair incentive, the selfish DTN nodes could be stimulated to help with forwarding bundles to achieve better packet delivery performance. In addition, the proposed Pi protocol can also thwart various attacks, which could be launched by selfish DTN nodes, such as free ride attack, layer removing and adding attacks. Extensive simulation results demonstrate the effectiveness of the proposed Pi protocol in terms of high delivery ratio and lower average delay.
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paper_title: SMART: A Secure Multilayer Credit-Based Incentive Scheme for Delay-Tolerant Networks

paper_content:

Delay-tolerant networks (DTNs) provide a promising solution to support wide-ranging applications in the regions where end-to-end network connectivity is not available. In DTNs, the intermediate nodes on a communication path are expected to store, carry, and forward the in-transit messages (or bundles) in an opportunistic way, which is called opportunistic data forwarding. Such a forwarding method depends on the hypothesis that each individual node is ready to forward packets for others. This assumption, however, might easily be violated due to the existence of selfish or even malicious nodes, which may be unwilling to waste their precious wireless resources to serve as bundle relays. To address this problem, we propose a secure multilayer credit-based incentive scheme to stimulate bundle forwarding cooperation among DTN nodes. The proposed scheme can be implemented in a fully distributed manner to thwart various attacks without relying on any tamperproof hardware. In addition, we introduce several efficiency optimization techniques to improve the overall efficiency by exploiting the unique characteristics of DTNs. Extensive simulations demonstrate the efficacy and efficiency of the proposed scheme.
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paper_title: Barter trade improves message delivery in opportunistic networks

paper_content:

In opportunistic networks, selfish nodes can exploit the services provided by other nodes by downloading messages that interest them, but refusing to store and distribute messages for the benefit of other nodes. We propose a mechanism to discourage selfish behavior based on the principles of barter. We develop a game-theoretic model in which we show that the proposed approach indeed stimulates cooperation of the nodes. The results show that, in practical scenarios, the message delivery rate considerably increases, if the mobile nodes follow the Nash Equilibrium strategy in the proposed mechanism compared to the data dissemination protocol when no encouraging mechanism is present.
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paper_title: RELICS: In-network realization of incentives to combat selfishness in DTNs

paper_content:

In this paper, we develop a cooperative mechanism, RELICS, to combat selfishness in DTNs. In DTNs, nodes belong to self-interested individuals. A node may be selfish in expending resources, such as energy, on forwarding messages from others, unless offered incentives. We devise a rewarding scheme that provides incentives to nodes in a physically realizable way in that the rewards are reflected into network operation. We call it in-network realization of incentives. We introduce explicit ranking of nodes depending on their transit behavior, and translate those ranks into message priority. Selfishness drives each node to set its energy depletion rate as low as possible while maintaining its own delivery ratio above some threshold. We show that our cooperative mechanism compels nodes to cooperate and also achieves higher energy-economy compared to other previous results.
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paper_title: Incentive-aware routing in DTNs

paper_content:

Disruption tolerant networks (DTNs) are a class of networks in which no contemporaneous path may exist between the source and destination at a given time. In such a network, routing takes place with the help of relay nodes and in a store-and-forward fashion. If the nodes in a DTN are controlled by rational entities, such as people or organizations, the nodes can be expected to behave selfishly and attempt to maximize their utilities and conserve their resources. Since routing is an inherently cooperative activity, system operation will be critically impaired unless cooperation is somehow incentivized. The lack of end-to-end paths, high variation in network conditions, and long feedback delay in DTNs imply that existing solutions for mobile ad-hoc networks do not apply to DTNs. In this paper, we propose the use of pair-wise tit-for-tat (TFT) as a simple, robust and practical incentive mechanism for DTNs. Existing TFT mechanisms often face bootstrapping problems or suffer from exploitation. We propose a TFT mechanism that incorporates generosity and contrition to address these issues. We then develop an incentive-aware routing protocol that allows selfish nodes to maximize their own performance while conforming to TFT constraints. For comparison, we also develop techniques to optimize the system-wide performance when all nodes are cooperative. Using both synthetic and real DTN traces, we show that without an incentive mechanism, the delivery ratio among selfish nodes can be as low as 20% as what is achieved under full cooperation; in contrast, with TFT as a basis of cooperation among selfish nodes, the delivery ratio increases to 60% or higher as under full cooperation. We also address the practical challenges involved in implementing the TFT mechanism. To our knowledge, this is the first practical incentive-aware routing scheme for DTNs.
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paper_title: Social-Based Trust in Mobile Opportunistic Networks

paper_content:

The fundamental challenge in opportunistic networking, regardless of the application, is enabling node cooperation in order to forward a message. While node cooperation is considered as a fundamental property in such networks, ensuring such a property between two devices in mobile opportunistic networks remains largely unexplored. In this paper, we investigate the potential impact of the lack of trust on node cooperation. We adopt a real-trace driven approach to study and analyze the trade-off between trust and success delivery rates in opportunistic networks. We first explore leveraging social information to establish trustworthy communication for mobile opportunistic networks. We then propose six trust based filters that use three social-based estimators of trust including common interests, common friends, and the distance in the social graph, coupled with two major techniques of trust establishment including Relay-to-Relay, and Source-to-Relay. We finally show that our trust filters yield a fair trade-off between trust and success rate by achieving more than 35\% success rate compared to an untrusted environment where 10% of the nodes refuse to cooperate in the absence of trust.
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paper_title: Social Trust in Opportunistic Networks

paper_content:

Opportunistic networks enable mobile users to participate in various social interactions with applications such as content distribution and micro-blogs. Because of their distributed nature, securing user interactions relies rather on trust than hard cryptography. Trust is often based on past user interactions such as in reputation systems relying on ratings. Yet, a more fundamental trust, social trust - assessing a user is genuine with honest intentions - must be established beforehand as many identities can be created easily (i.e., sybils). By leveraging the social network structure and its dynamics (conscious secure pairing and wireless contacts), we propose two complementary approaches for social trust establishment: explicit social trust and implicit social trust. Complexity, trust propagation and security issues are evaluated using real world complex graphs, synthetic mobility models and mobility traces. We show how our approach limits the maximum number of sybils independently of the network size and is more robust against manipulation attacks compared to state-of-the-art approaches such as PGP- like certification chains and distributed community detection algorithms.
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paper_title: Routing in Socially Selfish Delay Tolerant Networks

paper_content:

Existing routing algorithms for Delay Tolerant Networks(DTNs) assume that nodes are willing to forward packets for others. In the real world, however, most people are socially selfish; i.e., they are willing to forward packets for nodes with whom they have social ties but not others, and such willingness varies with the strength of the social tie. Following the philosophy of design for user, we propose a Social Selfishness Aware Routing (SSAR) algorithm to allow user selfishness and provide better routing performance in an efficient way. To select a forwarding node, SSAR considers both users' willingness to forward and their contact opportunity, resulting in a better forwarding strategy than purely contact-based approaches. Moreover, SSAR formulates the data forwarding process as a Multiple Knapsack Problem with Assignment Restrictions (MKPAR) to satisfy user demands for selfishness and performance. Trace-driven simulations show that SSAR allows users to maintain selfishness and achieves better routing performance with low transmission cost.
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paper_title: Trust Management for Encounter-Based Routing in Delay Tolerant Networks

paper_content:

We propose and analyze a class of trust management protocols for encounter-based routing in delay tolerant networks (DTNs). The underlying idea is to incorporate trust evaluation in the routing protocol, considering not only quality-of-service (QoS) trust properties (connectivity) but also social trust properties (honesty and unselfishness) to evaluate other nodes encountered. Two versions of trust management protocols are considered: an equal-weight QoS and social trust management protocol (called trust-based routing) and a QoS only trust management protocol (called connectivity-based routing). By utilizing a stochastic Petri net model describing a DTN behavior, we analyze the performance characteristics of these two routing protocols in terms of message delivery ratio, latency, and message overhead. We also perform a comparative performance analysis with epidemic routing for a DTN consisting of heterogeneous mobile nodes with vastly different social and networking behaviors. The results indicate that trust-based routing approaches the ideal performance of epidemic routing in delivery ratio, while connectivity-based routing approaches the ideal performance in message delay of epidemic routing, especially as the percentage of selfish and malicious nodes present in the DTN system increases. By properly selecting weights associated with QoS and social trust metrics for trust evaluation, our trust management protocols can approximate the ideal performance obtainable by epidemic routing in delivery ratio and message delay without incurring high message overhead.
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paper_title: Wireless Ad Hoc Podcasting

paper_content:

Podcasting has become popular for dissemination of streaming contents over the Internet. It is based on software clients that query servers for updates of subscribed content feeds. Podcasting may be used for any media content, but it is most commonly associated with audio streams. It provides a simple, no-frills broadcasting system for delay tolerant contents. A main limitation with this system is the inflexible separation of downloading to a docked media player and expending of the data when on the move. We herein present how podcast could be supported by our previously proposed delay-tolerant broadcasting system in order to reduce the expected times between updates and to provide a new ad hoc podcasting mode among mobile nodes. Our system substitutes the client-server paradigm inherent in present podcasting by a peer-to-peer paradigm where mobile nodes provide each other with contents. We present the protocol for this, and an evaluation of solicitation and caching strategies that greatly affect the application-level throughput. Our design is aiming at simplicity in order to enable implementation in mobile phones with media players and other devices that communicate over short ranges by means of Bluetooth or wireless LAN.
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paper_title: A socio-aware overlay for publish/subscribe communication in delay tolerant networks

paper_content:

The emergence of Delay Tolerant Networks (DTNs) has culminated in a new generation of wireless networking. We focus on a type of human-to-human communication in DTNs, where human behaviour exhibits the characteristics of networks by forming a community. We show the characteristics of such networks from extensive study of real-world human connectivity traces. We exploit distributed community detection from the trace and propose a Socio-Aware Overlay over detected communities for publish/subscribe communication. Centrality nodes have the best visibility to the other nodes in the network. We create an overlay with such centrality nodes from communities. Distributed community detection operates when nodes (i.e. devices) are in contact by gossipping, and subscription propagation is performed along with this operation. We validate our message dissemination algorithms for publish/subscribe with connectivity traces.
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paper_title: Cooperative Content Dissemination in Intermittently Connected Networks

paper_content:

Over the last few years, the popularity of multimedia content sharing among the Internet users has promoted a new kind of networking where the content dissemination is determined by the interests of users rather than pre-specified destinations. Development of wireless mobile devices has further enhanced the trend of content exchange among the mobile users. However, such mobile nodes based content dissemination may suffer the underlying intermittent connectivity due to the inherent limitations such as short radio transmission range, sporadic node densities and constrained power. To this effect, some solutions have been proposed in the literature that exploit the mobility and storage space of the nodes to distribute contents even if a route never exists. In all these mechanisms, whenever two mobile nodes encounter each other, each node only focuses on making independent disseminating decisions to improve the overall performance. However, even though each node can get its own optimized decisions, it may not be an optimized decision between the two encountering nodes. With this in mind, this paper presents a cooperative content dissemination framework (CCDF) with an analytical model to select and store the contents that maximizes the overall content delivery probability in the future. Simulation results demonstrate the enhanced delivery performance offered by the proposed CCDF over existing schemes.
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paper_title: Cooperative User Centric Information Dissemination in Human Content-Based Networks

paper_content:

Powerful wireless devices carried by humans can form human contact-based networks. Such networks often suffer from intermittent connectivity. Thus, providing an effective information dissemination feature in such networks is very important. In this paper, we explore a cooperative user centric information dissemination scheme which allows published data items to be delivered to interested nodes efficiently. Our scheme uses fewer relays and allows each node to operate distributedly using locally gathered information. Our scheme is more effective than the epidemic scheme since it achieves comparable success ratio with a 45-60% reduction in storage requirement and 47-53% reduction in transmissions. We also compare our scheme with an ideal scheme which assumes one can analyze contact traces apriori to determine their dominating sets, and show that our scheme can be more efficient than this ideal scheme.
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paper_title: Social-Based Trust in Mobile Opportunistic Networks

paper_content:

The fundamental challenge in opportunistic networking, regardless of the application, is enabling node cooperation in order to forward a message. While node cooperation is considered as a fundamental property in such networks, ensuring such a property between two devices in mobile opportunistic networks remains largely unexplored. In this paper, we investigate the potential impact of the lack of trust on node cooperation. We adopt a real-trace driven approach to study and analyze the trade-off between trust and success delivery rates in opportunistic networks. We first explore leveraging social information to establish trustworthy communication for mobile opportunistic networks. We then propose six trust based filters that use three social-based estimators of trust including common interests, common friends, and the distance in the social graph, coupled with two major techniques of trust establishment including Relay-to-Relay, and Source-to-Relay. We finally show that our trust filters yield a fair trade-off between trust and success rate by achieving more than 35\% success rate compared to an untrusted environment where 10% of the nodes refuse to cooperate in the absence of trust.
---
paper_title: A socio-aware overlay for publish/subscribe communication in delay tolerant networks

paper_content:

The emergence of Delay Tolerant Networks (DTNs) has culminated in a new generation of wireless networking. We focus on a type of human-to-human communication in DTNs, where human behaviour exhibits the characteristics of networks by forming a community. We show the characteristics of such networks from extensive study of real-world human connectivity traces. We exploit distributed community detection from the trace and propose a Socio-Aware Overlay over detected communities for publish/subscribe communication. Centrality nodes have the best visibility to the other nodes in the network. We create an overlay with such centrality nodes from communities. Distributed community detection operates when nodes (i.e. devices) are in contact by gossipping, and subscription propagation is performed along with this operation. We validate our message dissemination algorithms for publish/subscribe with connectivity traces.
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paper_title: Design and performance evaluation of ContentPlace, a social-aware data dissemination system for opportunistic networks

paper_content:

In this paper we present and evaluate ContentPlace, a data dissemination system for opportunistic networks, i.e., mobile networks in which stable simultaneous multi-hop paths between communication endpoints cannot be provided. We consider a scenario in which users both produce and consume data objects. ContentPlace takes care of moving and replicating data objects in the network such that interested users receive them despite possible long disconnections, partitions, etc. Thanks to ContentPlace, data producers and consumers are completely decoupled, and might be never connected to the network at the same point in time. The key feature of ContentPlace is learning and exploiting information about the social behaviour of the users to drive the data dissemination process. This allows ContentPlace to be more efficient both in terms of data delivery and in terms of resource usage with respect to reference alternative solutions. The performance of ContentPlace is thoroughly investigated both through simulation and analytical models.
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paper_title: Context and resource awareness in opportunistic network data dissemination

paper_content:

Opportunistic networks are challenging mobile ad hoc networks characterised by frequent disconnections and partitioning. In this paper we focus on data dissemination services, i.e. cases in which data should be disseminated in the network without a priori knowledge about the set of intended destinations. We propose a general autonomic data dissemination framework that exploits information about the userspsila context and social behaviour, to decide how to replicate and replace data on nodespsila buffers. Furthermore, our data dissemination scheme explicitly takes into account resource constraints, by jointly considering the expected utility of data replication and the associated costs. The results we present show that our solution is able to improve data availability, provide fairness among nodes, and reduce the network load, with respect to reference proposals available in the literature.
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paper_title: Cache-Based Content Delivery in Opportunistic Mobile Ad Hoc Networks

paper_content:

Over the last few years, multimedia content sharing through different service providers have gained popularity among the Internet users. The development of wireless mobile devices with enhanced features have further fueled this phenomenon. While such content sharing in Internet is accommodated through an overlay architecture, for infrastructure-less environment such as wireless mobile ad hoc networks (MANETs) experiencing intermittent connectivity, the distribution mechanism is not that straightforward. Arising from inherent MANET limitations such as short radio transmission range, sporadic node densities and constrained power, intermittent connectivity limits the ability of the network to provide successful content delivery. Although some solutions have been proposed in literature, they fail to consider the mobility characteristics of nodes for making decisions regarding the caching of contents for future delivery. Moreover, user-centric service requirements are also not addressed where different subscribers prefer different content profiles. To address this issue, a novel content sharing framework with optimized caching strategy is proposed in this paper. Based on the cached subscription profiles, the framework exploits two decision-making technologies namely analytic hierarchy process (AHP) and grey relational analysis (GRA) to evaluate all possible content requests between two meeting nodes and subsequently request the preferred contents for future encounters. Simulation results validate the improved performance of the proposed distribution framework in comparison to the existing schemes.
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paper_title: A cooperative cache-based content delivery framework for intermittently connected mobile ad hoc networks

paper_content:

For an infrastructure-less wireless environment, content dissemination among mobile users can be facilitated by self-organizing mobile ad hoc networks (MANETs) through low cost wireless connections. However, due to limited radio transmission range, sporadic node densities and power limitations, MANETs can become intermittently connected. As a result, some proposed solutions exploit mobility and storage space of the nodes to distribute contents even if a route never exists. In all these mechanisms, whenever two mobile nodes encounter each other, each node only focuses on making independent disseminating decisions to improve the overall performance. With this in mind, this paper presents a cooperative cache-based content dissemination framework (CCCDF) to carry out the cooperative soliciting and caching strategies for the two encountering nodes. Two cooperative strategies are investigated: CCCDF (Optimal) is to maximize the overall content delivery performance while CCCDF (Max-Min) is to share the limited network resources among the contents in a Max-Min fairness manner. Simulation results demonstrated the enhanced delivery performance offered by the proposed CCCDF over existing schemes.
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paper_title: MOPS: Providing Content-Based Service in Disruption-Tolerant Networks

paper_content:

Content-based service, which dynamically routes and delivers events from sources to interested users, is extremely important to network services. However, existing content-based protocols for static networks will incur unaffordable maintenance costs if they are applied directly to the highly mobile environment that is featured in disruption-tolerant networks (DTNs). In this paper, we propose a unique publish/subscribe scheme that utilizes the long-term social network properties, which are observed in many DTNs, to facilitate content-based services in DTNs. We distributively construct communities based on the neighboring relationships from nodes' encounter histories. Brokers are deployed to bridge the communities, and they adopt a locally prioritized pub/sub scheme which combines the structural importance with subscription interests, to decide what events they should collect, store, and propagate. Different trade-offs for content-based service can be achieved by tuning the closeness threshold in community formation or by adjusting the broker-to-broker communication scheme. Extensive real-trace and synthetic-trace driven simulation results are presented to support the effectiveness of our scheme.
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paper_title: Habit: Leveraging human mobility and social network for efficient content dissemination in Delay Tolerant Networks

paper_content:

This paper proposes Habit, an efficient multi-layered approach to content dissemination in Delay Tolerant Networks (DTN) that leverages information about nodes' colocation (physical layer) and their social network (application layer). More precisely, the regularity of users' colocation is learned based on historical colocation observations; also, the users' social network (or ‘network of interest’) is dynamically propagated during periods of colocation; finally, these distinct pieces of information are locally combined and used to compute the paths that content should follow, in a way that maximises both precision (i.e., nodes receive only content they are interested in) and recall (i.e., all relevant content is received by interested nodes).
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paper_title: Socially-aware routing for publish-subscribe in delay-tolerant mobile ad hoc networks

paper_content:

Applications involving the dissemination of information directly relevant to humans (e.g., service advertising, news spreading, environmental alerts) often rely on publish-subscribe, in which the network delivers a published message only to the nodes whose subscribed interests match it. In principle, publish- subscribe is particularly useful in mobile environments, since it minimizes the coupling among communication parties. However, to the best of our knowledge, none of the (few) works that tackled publish-subscribe in mobile environments has yet addressed intermittently-connected human networks. Socially-related people tend to be co-located quite regularly. This characteristic can be exploited to drive forwarding decisions in the interest-based routing layer supporting the publish-subscribe network, yielding not only improved performance but also the ability to overcome high rates of mobility and long-lasting disconnections. In this paper we propose SocialCast, a routing framework for publish-subscribe that exploits predictions based on metrics of social interaction (e.g., patterns of movements among communities) to identify the best information carriers. We highlight the principles underlying our protocol, illustrate its operation, and evaluate its performance using a mobility model based on a social network validated with real human mobility traces. The evaluation shows that prediction of colocation and node mobility allow for maintaining a very high and steady event delivery with low overhead and latency, despite the variation in density, number of replicas per message or speed.
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paper_title: A socio-aware overlay for publish/subscribe communication in delay tolerant networks

paper_content:

The emergence of Delay Tolerant Networks (DTNs) has culminated in a new generation of wireless networking. We focus on a type of human-to-human communication in DTNs, where human behaviour exhibits the characteristics of networks by forming a community. We show the characteristics of such networks from extensive study of real-world human connectivity traces. We exploit distributed community detection from the trace and propose a Socio-Aware Overlay over detected communities for publish/subscribe communication. Centrality nodes have the best visibility to the other nodes in the network. We create an overlay with such centrality nodes from communities. Distributed community detection operates when nodes (i.e. devices) are in contact by gossipping, and subscription propagation is performed along with this operation. We validate our message dissemination algorithms for publish/subscribe with connectivity traces.
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paper_title: Geography-aware active data dissemination in mobile social networks

paper_content:

In mobile social networks (MSNets), data dissemination is an important topic, which has not been widely investigated yet. Active data dissemination is a networking paradigm where a superuser intentionally facilitates the connectivity in the network. One of the key challenges under this paradigm is how to design the most efficient superuser route to achieve certain properties of end-to-end connectivity. Most existing solutions only focus on the network with stationary users or strongly constrained node mobility, and assume the superuser always moves with a fixed route. In this paper, we propose a flexible approach to design the superuser routes, considering the realistic user movements in MSNets. To the best of our knowledge, this work is the first to study active data dissemination from the social network perspective. We explore the geographic regularity of human mobility in the network, employ a semi-Markov analytical model to describe such mobility pattern, and hence formulate the superuser route design as a combinational optimization problem of Convex Optimization and Traveling Salesman Problem by exploiting social network concepts including communities and centrality. Extensive trace-driven simulations show that our approach consistently outperforms other existing superuser route design algorithms in terms of delivery ratio and energy efficiency.
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paper_title: Spray and wait: an efficient routing scheme for intermittently connected mobile networks

paper_content:

Intermittently connected mobile networks are sparse wireless networks where most of the time there does not exist a complete path from the source to the destination. These networks fall into the general category of Delay Tolerant Networks. There are many real networks that follow this paradigm, for example, wildlife tracking sensor networks, military networks, inter-planetary networks, etc. In this context, conventional routing schemes would fail.To deal with such networks researchers have suggested to use flooding-based routing schemes. While flooding-based schemes have a high probability of delivery, they waste a lot of energy and suffer from severe contention, which can significantly degrade their performance. Furthermore, proposed efforts to significantly reduce the overhead of flooding-based schemes have often be plagued by large delays. With this in mind, we introduce a new routing scheme, called Spray and Wait, that "sprays" a number of copies into the network, and then "waits" till one of these nodes meets the destination.Using theory and simulations we show that Spray and Wait outperforms all existing schemes with respect to both average message delivery delay and number of transmissions per message delivered; its overall performance is close to the optimal scheme. Furthermore, it is highly scalable retaining good performance under a large range of scenarios, unlike other schemes. Finally, it is simple to implement and to optimize in order to achieve given performance goals in practice.
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paper_title: Mitigating Routing Misbehavior in Disruption Tolerant Networks

paper_content:

In disruption tolerant networks (DTNs), selfish or malicious nodes may drop received packets. Such routing misbehavior reduces the packet delivery ratio and wastes system resources such as power and bandwidth. Although techniques have been proposed to mitigate routing misbehavior in mobile ad hoc networks, they cannot be directly applied to DTNs because of the intermittent connectivity between nodes. To address the problem, we propose a distributed scheme to detect packet dropping in DTNs. In our scheme, a node is required to keep a few signed contact records of its previous contacts, based on which the next contacted node can detect if the node has dropped any packet. Since misbehaving nodes may misreport their contact records to avoid being detected, a small part of each contact record is disseminated to a certain number of witness nodes, which can collect appropriate contact records and detect the misbehaving nodes. We also propose a scheme to mitigate routing misbehavior by limiting the number of packets forwarded to the misbehaving nodes. Trace-driven simulations show that our solutions are efficient and can effectively mitigate routing misbehavior.
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paper_title: CPMC: An Efficient Proximity Malware Coping Scheme in Smartphone-based Mobile Networks

paper_content:

Smartphones are envisioned to provide promising applications and services. At the same time, smartphones are also increasingly becoming the target of malware. Many emerging malware can utilize the proximity of devices to propagate in a distributed manner, thus remaining unobserved and making detections substantially more challenging. Different from existing malware coping schemes, which are either totally centralized or purely distributed, we propose a Community-based Proximity Malware Coping scheme, CPMC. CPMC utilizes the social community structure, which reflects a stable and controllable granularity of security, in smartphone-based mobile networks. The CPMC scheme integrates short-term coping components, which deal with individual malware, and long-term evaluation components, which offer vulnerability evaluation towards individual nodes. A closeness-oriented delegation forwarding scheme combined with a community level quarantine method is proposed as the short-term coping components. These components contain a proximity malware by quickly propagating the signature of a detected malware into all communities while avoiding unnecessary redundancy. The long-term components offer vulnerability evaluation towards neighbors, based on the observed infection history, to help users make comprehensive communication decisions. Extensive real- and synthetic-trace driven simulation results are presented to to evaluate the effectiveness of CPMC.
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paper_title: Trust Management for Encounter-Based Routing in Delay Tolerant Networks

paper_content:

We propose and analyze a class of trust management protocols for encounter-based routing in delay tolerant networks (DTNs). The underlying idea is to incorporate trust evaluation in the routing protocol, considering not only quality-of-service (QoS) trust properties (connectivity) but also social trust properties (honesty and unselfishness) to evaluate other nodes encountered. Two versions of trust management protocols are considered: an equal-weight QoS and social trust management protocol (called trust-based routing) and a QoS only trust management protocol (called connectivity-based routing). By utilizing a stochastic Petri net model describing a DTN behavior, we analyze the performance characteristics of these two routing protocols in terms of message delivery ratio, latency, and message overhead. We also perform a comparative performance analysis with epidemic routing for a DTN consisting of heterogeneous mobile nodes with vastly different social and networking behaviors. The results indicate that trust-based routing approaches the ideal performance of epidemic routing in delivery ratio, while connectivity-based routing approaches the ideal performance in message delay of epidemic routing, especially as the percentage of selfish and malicious nodes present in the DTN system increases. By properly selecting weights associated with QoS and social trust metrics for trust evaluation, our trust management protocols can approximate the ideal performance obtainable by epidemic routing in delivery ratio and message delay without incurring high message overhead.
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paper_title: Working day movement model

paper_content:

Abstract movement models, such as Random Waypoint, do not capture reliably the properties of movement in the real life scenarios. We present and analyse a movement model for delay-tolerant network simulations that is able to produce inter-contact time and contact time distributions that follow closely the ones found in the traces from the real-world measurement experiments. We validate the movement model using the ONE simulator.
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paper_title: CPMC: An Efficient Proximity Malware Coping Scheme in Smartphone-based Mobile Networks

paper_content:

Smartphones are envisioned to provide promising applications and services. At the same time, smartphones are also increasingly becoming the target of malware. Many emerging malware can utilize the proximity of devices to propagate in a distributed manner, thus remaining unobserved and making detections substantially more challenging. Different from existing malware coping schemes, which are either totally centralized or purely distributed, we propose a Community-based Proximity Malware Coping scheme, CPMC. CPMC utilizes the social community structure, which reflects a stable and controllable granularity of security, in smartphone-based mobile networks. The CPMC scheme integrates short-term coping components, which deal with individual malware, and long-term evaluation components, which offer vulnerability evaluation towards individual nodes. A closeness-oriented delegation forwarding scheme combined with a community level quarantine method is proposed as the short-term coping components. These components contain a proximity malware by quickly propagating the signature of a detected malware into all communities while avoiding unnecessary redundancy. The long-term components offer vulnerability evaluation towards neighbors, based on the observed infection history, to help users make comprehensive communication decisions. Extensive real- and synthetic-trace driven simulation results are presented to to evaluate the effectiveness of CPMC.
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paper_title: Applications, Architectures, and Protocol Design Issues for Mobile Social Networks: A Survey

paper_content:

The mobile social network (MSN) concept combines social science and communications science and has created a new research area that is relevant for content publishing, data exchange, sharing, and delivery services. This paper starts with a brief overview of MSNs. The major applications of MSNs are then reviewed. Architectures of MSNs for different data exchange, sharing, and delivery services are described. Issues related to the design and analysis of MSNs are presented, and related work in the literature is reviewed. Finally, several major open research issues are discussed, and future research directions are outlined.
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paper_title: Reclaiming Location Privacy in Mobile Telephony Networks—Effects and Consequences for Providers and Subscribers

paper_content:

Mobile telephony (e.g., Global System for Mobile Communications [GSM]) is today's most common communication solution. Due to the specific characteristics of mobile communication infrastructure, it can provide real added value to the user and various other parties. Location information and mobility patterns of subscribers contribute not only to emergency planning, general safety, and security, but are also a driving force for new commercial services. However, there is a lack of transparency in today's mobile telephony networks regarding location disclosure. Location information is generated, collected, and processed without being noticed by subscribers. Hence, by exploiting subscriber location information, an individual's privacy is threatened. We develop a utility-based opponent model to formalize the conflict between the additional utility of mobile telephony infrastructure being able to locate subscribers and the individual's privacy. Based on these results, measures were developed to improve an individual's location privacy through a user-controllable GSM software stack. To analyze and evaluate the effects of specific subscriber provider interaction, a dedicated test environment will be presented, using the example of GSM mobile telephony networks. The resulting testbed is based on real-life hardware and open-source software to create a realistic and defined environment that includes all aspects of the air interface in mobile telephony networks and thus, is capable of controlling subscriber–provider interaction in a defined and fully controlled environment.
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paper_title: Self-Organized Cooperation Policy Setting in P2P Systems Based on Reinforcement Learning

paper_content:

In this paper, we have developed a self-organized approach to cooperation policy setting in a system of rational peers that have only partial views of the whole system in order to improve the overall welfare as a system-wide performance metric. The proposed approach is based on distributed reinforcement learning and sets cooperation policies of the peers through their self-organized interactions. We have analyzed this approach to demonstrate that it results in Pareto optimality in the system by disseminating the local value functions of the peers among the neighbors. We have also experimentally verified that this approach outperforms the other commonly used approaches in the literature, in terms of the performance of the system.
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paper_title: Scalable Routing Modeling for Wireless Ad Hoc Networks by Using Polychromatic Sets

paper_content:

Graph theory is a traditional mathematical method to analyze computer networks, including intelligent wireless networks, such as ad hoc networks, sensor networks, and wireless mesh networks. Because of the variety of the network nodes and wireless links, conventional graph theory and set theory used to describe the element of the network (node and link) are not suitable to model the modern complex wireless networks. Recent research in weighted graph and random graph theories that place a weight on the links and a probability to decide the existence of the link or not is a further step to model the wireless network in a near real-life scenario. However, it lacks the ability to describe the properties of the network node. In this paper, a new mathematical tool, polychromatic sets (PS-sets), is introduced in modeling the complex wireless networks. PS-sets have the ability to describe the property of each element, which we believe will be a perfect tool to describe the network nodes and links of wireless networks. This paper demonstrates a scalable network modeling using PS-sets theory and a routing scheme based on this model. Evaluation results show that it is simple and scalable, and its performance is superior to other conventional routing schemes. The PS-sets theory could become a new tool in studying modern complex wireless networks.
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Title: Socially-Aware Networking: A Survey
Section 1: INTRODUCTION
Description 1: Introduce the development of wireless communications and networking technologies, the emergence of mobile devices, and explain the introduction of the concept of socially-aware networking (SAN).

Section 2: ARCHITECTURE OF SOCIALLY-AWARE NETWORKING
Description 2: Describe the simple architecture of SAN, emphasizing social awareness by sensing and analyzing data using intelligent technologies.

Section 3: SOCIAL PROPERTIES
Description 3: Explain various social properties such as social graph, community, centrality, similarity, tie strength, and human mobility pattern that are pivotal in SAN.

Section 4: SOCIALLY-AWARE ROUTING AND FORWARDING PROTOCOLS
Description 4: Review unicast and multicast routing protocols based on social properties and also address the congestion problem in SAN.

Section 5: ROUTING AND FORWARDING WITH SELFISHNESS
Description 5: Discuss the challenge of dealing with non-cooperative nodes and outline the incentive mechanisms to stimulate nodes' cooperation, including reputation-based, credit-based, TFT, and trust-based strategies.

Section 6: SOCIALLY-AWARE DATA DISSEMINATION
Description 6: Cover the methods for efficient data dissemination in SAN, classified into solicitation and cache-based approaches, and forwarding-based approaches.

Section 7: OPEN ISSUES
Description 7: Outline several open issues in SAN such as mobile social sensing and learning, privacy, node selfishness, and scalability.

Section 8: CONCLUSION
Description 8: Summarize the survey and emphasize the potential of SAN as an emerging field, while highlighting the challenges that need to be addressed for practical implementation.