Opportunistic communication, off-loading, and decentrlaized distribution have been proposed as a means of cost efficient disseminating content when users are geographically clustered into communities. Despite its promise, none of the proposed systems have not been widely adopted due to unbounded high content delivery latency, security, and privacy concerns. This paper, presents a novel hybrid content storage and distribution system addressing the trust and privacy concerns of users, lowering the cost of content distribution and storage, and shows how they can be combined uniquely to develop mobile social networking services. The system exploit the fact that users will trust their friends, and by replicating content on friends' devices who are likely to consume that content it will be possible to disseminate it to other friends when connected to low cost networks. The paper provides a formal definition of this content replication problem, and show that it is NP hard. Then, it presents a community based greedy heuristic algorithm with novel dynamic centrality metrics that replicates the content on a minimum number of friends' devices, to maximize availability. Then using both real world and synthetic datasets, the effectiveness of the proposed scheme is demonstrated. The practicality of the proposed system, is demonstrated through an implementation on Android smartphones.

Distributed social networking services show promise to solve data ownership and privacy problems associated with centralized approaches. Smartphones could be used for hosting and sharing users data in a distributed manner, if the associated high communication costs and battery usage issues of the distributed systems could be mitigated. We propose a novel mechanism for reducing these costs to a level comparable with centralized systems by using a connectivity aware replication strategy. We develop an algorithm for grouping devices into tribes for content replication among intended content consumers and serve it using low-cost network connections. We evaluate the performance of the algorithm using three real world trace data sets. The results show that a persistent low-cost network availability can be achieved with an average of two replicas per content. Additionally, cellular bandwidth consumption and energy consumption of users are evaluated analytically using user content creation and consumption modeling. The results show that the proposed mechanism lowers monetary and energy costs for users compared to non-mobile-optimized distributed systems irrespective of the content demand model.

We focus on dissemination of content for delay tolerant applications, (i.e. content sharing, advertisement propagation, etc.) where users are geographically clustered into communities. We propose a novel architecture that addresses the issues of lack of trust, delivery latency, loss of user control, and privacy-aware distributed mobile social networking by combining the advantages of decentralized storage and opportunistic communications. The content is to be replicated on friends' devices who are likely to consume the content. The fundamental challenge is to minimize the number of replicas whilst ensuring high and timely availability. We propose a greedy heuristic algorithm for computationally hard content replication problem to replicate content in well-selected users, to maximize the content dissemination with limited number of replication. Using both real world and synthetic traces, we show the viability of the proposed scheme.

We proposed MobiTribe which enables device centric social networking on smart mobile devices while reducing high communication costs and battery usage normally associated with mobile distributed systems. In this paper, we demonstrate the feasibility of MobiTribe by integrating the service with the popular social networking application Facebook. We show that it is possible to provide the benefits of distributed content sharing on top of the existing centralized social networking services with minimal changes to the content sharing process.

Distributed social networking services show promise to solve data ownership and privacy problems associated with centralised approaches. Smartphones could be used for hosting and sharing users data in a distributed manner, if the associated high communication costs and battery usage issues of the distributed systems could be mitigated. We propose a novel mechanism for reducing these costs to a level comparable with centralised systems by using a connectivity aware replication strategy. To this end, we develop an algorithm based on a combination of bipartite b-matching and a greedy heuristics for grouping devices into tribes among intended content consumers. The tribes replicate content and serve it using low-cost network connections by exploiting time elasticity of user generated content sharing. The performance is evaluated using three real world trace data sets. The results show that a persistent low-cost network availability can be achieved with an average of two replicas per content. Additionally, a content creator can reduce 3G traffic by up to 43% and device energy use by up to 41% on average compared to content sharing in non-mobile-optimised distributed social networking approaches. Moreover, the results show that the proposed mechanism can provide the benefits of a distributed content sharing system for monetary and energy costs comparable to those of a centralised server based system.

An increasing portion of traffic in mobile networks conies from users creating content and uploading it to the Internet to share it. The capacity of mobile networks is a limited resource and uploading high resolution content consumes a large part of it. We introduce MobiTribe, a distributed storage cloud consisting of mobile devices for storing the content created on the phones. It can serve requests for content and take advantage of networks with spare capacity to deliver the content at a lower cost. We propose a content distribution and replication algorithm which achieves this goal. The performance of the algorithm is evaluated using empirical data traces of WLAN availability patterns of mobile devices, showing that it is possible to achieve 99.98% availability of a content via WLAN while minimising content distribution to an average of 2.69 replicas.

The rate at which the Internet is becoming mobile is unprecedented. This has increased the demand for continuous connectivity even while moving from one network to another at very high speeds. Moving from one network to another gives rise to a handoff process which often incurs packet losses and severe end to end transport protocol performance degradations for the Mobile Node. Most research on IP mobility has focused on minimizing the delays of the handoff process with network infrastructure based approaches. A different way of minimizing the impact of the handoff is to enable the Mobile Node to connect to multiple access networks simultaneously, allowing it to perform Make-Before-Break handoffs. In this paper, we compare the performance of these two alternatives, focusing on the use of Fast Handovers for Mobile IPv6 framework on the infrastructure side and on the other hand Make-Before-Break handoffs using two network interfaces. Both of these schemes require proactive handoffs for optimal performance. The results show that the use of two interfaces for Make-Before-Break handoffs provides increased handoff performance over Fast Handovers for Mobile IPv6.

Measuring the performance of an implementation of a set of protocols and analyzing the results is crucial to understanding the performance and limitations of the protocols in a real network environment. Based on this information, the protocols and their interactions can be improved to enhance the performance of the whole system. To this end, we have developed a network mobility testbed and implemented the network mobility (NEMO) basic support protocol and have identified problems in the architecture which affect the handoff and routing performance. To address the identified handoff performance issues, we have proposed the use of make-before-break handoffs with two network interfaces for NEMO. We have carried out a comparison study of handoffs with NEMO and have shown that the proposed scheme provides near-optimal performance. Further, we have extended a previously proposed route optimization (RO) scheme, OptiNets. We have compared the routing and header overheads using experiments and analysis and shown that the use of the extended OptiNets scheme reduces these overheads of NEMO to a level comparable with Mobile IPv6 RO. Finally, this paper shows that the proposed handoff and RO schemes enable NEMO protocol to be used in applications sensitive to delay and packet loss

The inherent difficulty in faithfully modeling wireless channel characteristics in simulators has prompted researchers to build wireless network testbeds for realistic testing of protocols. While previous testbeds are mostly designed to provide a research environment of static wireless networks, our work is aimed to assess protocols used for mobile wireless networks (such as an on-board network on public transport vehicles). In this work, we describe our on-going efforts in designing and implementing a network mobility testbed for network mobility (NEMO) protocol. This paper attempts to provide an initial reference to identify the feature set necessary for a network mobility testbed. We first describe the architecture of our testbed. Next, we present some preliminary results to demonstrate the use of our testbed in evaluating the performance of NEMO protocol under different scenarios.