Total order in opportunistic networks

Data dissemination in opportunistic networks poses a series of challenges, since there is no central entity aware of all the nodes' subscriptions. Each individual node is only aware of its own interests and those of a node that it is contact with, if any. Thus, dissemination is generally performed using epidemic algorithms that flood the network, but they have the disadvantage that the network overhead and congestion are very high. In this paper, we propose ONSIDE, an algorithm that leverages a node's online social connections (i.e. friends on social networks such as Facebook or Google+), its interests and the history of contacts, in order to decrease congestion and required bandwidth, while not affecting the overall network's hit rate and the delivery latency. We present the results of testing our algorithm using an opportunistic network emulator and three mobility traces taken in different environments.

Opportunistic networks are usually formed spontaneously by mobile devices equipped with short range wireless communication interfaces. The idea is that an end-to-end connection may never be present. Designing and implementing a routing protocol to support both service discovery and delivery in such kinds of networks is a challenging problem on account of frequent disconnections and topology changes. In this network one of the most important issues relies on the selection of the best intermediate node to forward the messages towards the destination. This paper presents a trust framework for opportunistic network where the nodes in the network follow the trace based mobility model. The selection of next hop to forward the data packets is based on the trust value as well as the direction of movement of node towards the destination. The trust value is obtained from the trust framework of the data forwarding node. The direction of destination is obtained from the movement trace file that is maintained by the nodes in the network. In this proposed framework, the message is encrypted to secure both the data and path information. The effectiveness of this proposed framework is shown using simulation.

An increasing number of mobile users (MUs) share common interests in general information, such as traffic information, weather forecast, and domestic/international news. However, the centralized infrastructure-based system has not been designed for efficiently disseminating the information of common interest (IoCI) to numerous requesters. Thanks to the rapid development of mobile devices equipped with large storage and multiple communication modes, opportunistic communication between a pair of MUs can be readily realized. With the aid of opportunistic networks formed by MUs, we can improve the connectivity of cellular networks in the rural areas, we can offload the tele-traffic from the overloaded cellular networks, and we can efficiently disseminate the IoCI in the densely populated areas. We commence with a detailed survey on the cross-disciplinary research area of social network analysis aided telecommunication networking. We continue by focusing our attention on the family of integrated cellular and large-scale opportunistic networks, whose performance is dominated by the inter-contact duration as well as the contact duration between any pairs of MUs. A continuous-time-pure-birth Markov chain is invoked for analyzing the relevant performance. We demonstrate that the delivery ratio of the IoCI before it expires becomes higher than 90% with the aid of opportunistic networks consisting of 20 MUs. Moreover, our experiments based on the InfoCom 2006 mobility trace show that the opportunistic networks are capable of offloading 58% of the tele-traffic from the cellular networks. Thereafter, we propose a hybrid information dissemination scheme for the integrated cellular and small-scale opportunistic networks, which is comprised of two main stages: 1) the base station-aided single-hop multicast (BSSHM) stage and 2) the cooperative multicast aided spontaneous dissemination stage. In contrast to their large-scale counterparts, in small-scale opportunistic networks, the information dissemination is mainly affected by the mobility of the MUs, by the wireless channel attenuation and by the resource scheduling, where a discrete-time-pure-birth Markov chain is utilized for characterizing the relevant performance. We demonstrate that our hybrid information dissemination scheme outperforms the traditional BSSHM in terms of various delay metrics, despite consuming less energy.

Barter trade improves message delivery in opportunistic networks

This paper investigates the optimization of Automatic Identification System (AIS) message transmission for Virtual Aids to Navigation (VATONs) in maritime communication networks under challenging environmental conditions. The study addresses critical network bottlenecks by analysing the impact of path loss (α = 2 to 4.0) on communication reliability and evaluating opportunistic networking solutions, specifically Epidemic routing protocols, for enhanced message delivery. Using OMNeT++ simulations with 40 vessels across a 100km × 100km maritime area, we demonstrate that traditional shore-to-ship communication suffers significant degradation when path loss exponents exceed 2.8, with packet reception rates dropping below 20% at α > 3.2. Our research reveals that Epidemic routing can effectively address these connectivity gaps through ship-to-ship relay mechanisms, maintaining critical VATON position updates even when direct shore-based communication fails. The findings indicate that opportunistic networking achieves substantial improvements in message delivery rates under adverse conditions. This work presents a proof-of-concept demonstration of opportunistic networking principles in maritime environments, establishing a foundation for future field validation studies.

Mobility intertwines with routing protocols play a vital role in opportunistic networks. First and foremost, mobility creates opportunities for mobile nodes to connect and communicate when they encounter. A series of encounter opportunities can spread a message among many nodes and to a large area until eventual delivery. Further, mobility properties, when utilized by routing protocols, can greatly improve performance. This chapter will trace the research on mobility and mobility enabled message dissemination approaches, and will present a survey over mobility models, analytical results on motion characteristics, and routing strategies that largely rely on mobility. These three components intertwine and show a strong research agenda in opportunistic networks. The survey shows that analytical mobility properties and abstracted graphic features are significant to the success of some routing protocols. By emphasizing on the three components, the survey will help in developing novel integrated mobility and message dissemination solutions for opportunistic networks.

Opportunistic networks are a kind of Ad Hoc networks that make use of meeting opportunities from mobile nodes to realize the network communication which doesn't need a full path between the source nodes and destination nodes. It’s tolerant in latency and network division. It’s a great challenge to design routing protocols in opportunistic networks in that the movements of nodes are uncertain leading to intermittent connection which make it hard to transmit message to its destination. However, the problems have also attracted more and more attention from researchers. Firstly, in this paper, we introduced the basic concept of opportunistic networks. Secondly we classified and interpreted routing protocols according to the infrastructure, scenario, forwarding mechanism etc. Thirdly, we carried out the computer simulation and analysis for opportunistic network routing protocols in aspect of message delivery ratio, network latency, routing overhead and the number of lost packets. Then we summarized the advantages and disadvantages of routing protocol and discussed its applicability. Finally we looked ahead the hotspot of recent routing protocols under opportunistic networks.

How to shorten time delay and enhance delivery ratio is still an open problem in the study of opportunistic networks. Most proposals are trying to deal with this issue by introducing infrastructures. Although related research has been proven to be useful in improving the routing performance of the network, there is still room for further improvement. In this article, inspired by the powerful message synchronization capability of wireless sensor networks (WSNs), we propose a new opportunistic network framework called WON that introduces WSNs into opportunistic network. With the support of WSNs, fast message delivery and high success ratio can be achieved. We specifically present the layered architecture of WON and compare WON to existing architectures in opportunistic networking. The simulation results concerning delivery delay and success ratio are highly encouraging. Finally, open issues are outlined.

Past research on opportunistic communications has demonstrated the power of mobile phones as information mediators and content providers to co-located devices. As an extension of opportunistic communication paradigm, opportunistic computing and services research leverages the powerful capabilities and pervasive nature of modern smartphones to provision services to nearby nodes. When an opportunistic network is viewed as a provider of services rather than as a simple message routing system, node and service discovery come to play a critical role. This paper discusses several factors that affect the discover ability of pervasive services with current existing devices in light of their practical limitations. Moreover, the impact of these limitations to pervasive service discovery is studied in evaluation results.

A geo-temporal mobility prediction method for cooperative time-validity-constrained content delivery in opportunistic networks

A pioneering body of work in the area of mobile opportunistic networks has shown that characterizing aggregated inter-contact time between mobile nodes is crucial. The most common approaches to study aggregated inter-contact time (ICT) in literatures are focused on a certain type of mobile wireless networks. Up to now, it still lacks a general approach to model the aggregated ICT effectively in different type of networks. This paper proposes a new approach to model aggregated ICT based on extreme value theory (EVT), which uses the generalized Pareto distribution as the unique asymptotic model of the tail distribution. Mean excess function is proposed to choose the threshold value and also other parameter estimation methods to the statistical model are discussed and applied to real mobility traces collected from different opportunistic networks, such as social pocket switched networks and vehicular ad hoc network. A decision rule based on confidence level of parameter is proposed to determine the statistical characteristics of aggregated ICT. By performing extensive experiments using EVT-based model, the aggregated ICT distributions for different type of networks are obtained. To show how well the EVT-based model actually fits the data in the tails, the complementary cumulative distribution function in a logarithmic scale is used to validate the model. Also according to the Kolmogorov---Smirnov test, it illustrates that EVT-based distributions with different parameter values fit the tails well at the desired significance level 0.05 for the taxi mobility in VANET and the human node in the other type of opportunistic networks. Finally, some prospective applications based on the statistical model are discussed in designing new network protocols.

Realistic mobility models are crucial for the simulation of Delay Tolerant and Opportunistic Networks. The long standing benchmark of reproducing realistic pairwise statistics (e.g., contact and inter-contact time distributions) is today mastered by state-of-the-art models. However, mobility models should also reflect the macroscopic community structure of who meets whom. While some existing models reproduce realistic community structure - reflecting groups of nodes who work or live together - they fail in correctly capturing what happens between such communities: they are often connected by few bridging links between nodes who socialize outside of the context and location of their home communities. In a first step, we analyze the bridging behavior in mobility traces and show how it differs to that of mobility models. By analyzing the context and location of contacts, we then show that it is the social nature of bridges which makes them differ from intra-community links. Based on these insights, we propose a Hypergraph to model time-synchronized meetings of nodes from different communities as a social overlay. Applying this as an extension to two existing mobility models we show that it reproduces correct bridging behavior while keeping other features of the original models intact.

There are many cities where urbanization occurs at a faster rate than that of communication infrastructure deployment. Mobile users with sophisticated devices are often dissatisfied with this lag in infrastructure deployment; their Internet connection is via opportunistic open Access Points for short durations, or via weak, unreliable, and costly 3G connections. With increased demands on network infrastructure, we believe that opportunistic networking, where user mobility is exploited to increase capacity and augment Internet reachability, can play an active role as a complimentary technology to improve user experience, particularly with delay insensitive data. Opportunistic forwarding solutions were mainly designed using a set of assumptions that have grown in complexity, rendering them unusable outside their intended environment. Figure 1 categorizes sample state-of-the-art opportunistic forwarding solutions based on their assumption complexity. Most of these solutions however are not designed for large scale urban environments. In this work, we believe to be the first to exploit the space syntax paradigm to better guide forwarding decisions in large scale urban environments. Space syntax, initially proposed in the field of architecture to model natural mobility patterns by analyzing spacial configurations, offers a set of measurable metrics that quantify the effect of road maps and architectural configurations on natural movement. By interacting with the pre-built static environment, space syntax predicts natural movement patterns in a given area. Our goal is to leverage space syntax concepts to create efficient opportunistic forwarding distributed solutions for large scale urban environments. We address two communication themes: (1) Mobile-to-Infrastructure: We propose a set of space syntax based algorithms that adapt to a spectrum of simplistic assumptions in urban environments. As depicted in Figure 1, our goal is to gain performance improvement across the spectrum, within each assumption category, when compared to other state-of-the-art solutions. We adopt a data driven approach to evaluate the space syntax based forwarding algorithms we propose, within each of three assumption categories, based on large scale mobility traces capturing vehicle mobility. Overall, our results show that our space syntax based algorithms perform more efficiently within each assumption category. (2) Infrastructure-to-Mobile: We propose a new algorithm, Select&Spray, which leverages space syntax, and enables data transfers to mobile destinations reached directly through the infrastructure or opportunistically via other nodes. This architecture consists of: (i) a select engine that identifies a subset of directly connected nodes with a higher probability to forward messages to destinations, and (ii) a spray engine residing on mobile devices that guide the opportunistic dissemination of messages towards destination devices. We evaluate our algorithm using several mobility traces. Our results show that Select&Spray is more efficient in guiding messages towards their destinations. It helps extend the reach in data dissemination to more than 20% of the interested destinations within very short delays, and successfully reaches almost 90% of the destinations in less than 5 minutes.

In this paper we examine opportunistic content distribution. We design and evaluate a caching strategy where a node will fetch and share contents on behalf of other nodes, although the contents are not of its own interest. We propose three caching options for improving the use of network resources: relay request on demand, hop-limit, and greedy relay request. The proposed strategies are implemented in the OMNeT++ simulator and evaluated on mobility traces from Legion Studio that have churn. We also compare our strategies with a strategy from the literature. The results are analyzed and they show that the use of opportunistic caching for a community of nodes may enhance the performance marginally while overhead increases significantly.

Opportunistic networks are a new evolution of mobile ad hoc networks composed of intermittently connected nodes, in which the routing for the dynamic topology is a challenging issue. In opportunistic networks, the mobile nodes with common interest or close relationship may form into groups and move together, which brings us a good feature to employ when designing the routing protocol for opportunistic networks under resource constraints. Our main idea in this paper is to maximize the message delivery probability in a group-aware opportunistic network under the constraints of bandwidth and buffer space. Embedded this idea, we propose a cooperative routing protocol using the group feature, which includes the cooperative message transfer scheme and the buffer management strategy. In the cooperative message transfer scheme, the limited bandwidth is considered and the message transfer priorities are designed to maximize the delivery probability. In the buffer management strategy, by considering the constraint of buffer space, we propose the cooperative message caching scheme and the dropping order of the messages is designed to minimize the reduced delivery probability. Finally, we conduct the simulations to demonstrate the effectiveness of our proposed routing protocol.