Publications
Publications from UMOBILE activities
We propose a quality assessment framework for crowdsourced media streaming in urban railway networks. We assume that commuters either “tune in” to some TV/radio channel, or submit requests for content they desire to watch or listen to, which eventually forms a playlist of videos/podcasts/tunes. Given that connectivity is challenged by the movement of trains and the disconnection that this movement causes, users collaboratively download (through cellular and WiFi connections) and share content, in order to maintain undisrupted playback. We model collaborative media streaming for the case of the London Underground train network. The proposed quality assessment framework comprises a utility function which characterises the Quality of Experience (QoE) that users (subjectively) perceive and takes into account all the necessary parameters that affect smooth playback. The framework can be used to assess the media streaming quality in any railway network, after adjusting the related parameters.
To the best of our knowledge, this is the first study to quantify the perceptual quality of collaborative media streaming in (underground) railway networks from a modelling perspective, as opposed to a systems perspective. Based on real commuter traces from the London Underground network, we evaluate whether audio and video can be streamed to commuters with acceptable QoE. Our results show that even with very highspeed Internet connection, users still experience disruptions, but a carefully designed collaborative mechanism can result in high levels of perceived QoE even in such disruptive scenarios.
We exploit the traffic shaping potential of network storage and improve energy efficiency for mobile devices through the creation of idle communication intervals. We model the activity patterns between the WIRED/wireless gateway and the wireless battery-powered receiver, and employ a rendezvous mechanism that utilizes periods of inactivity created by the traffic shaping function of the network. In case multiple receivers are simultaneously active, a scheduling algorithm limits overlaps of buffer flushes. Our scenarios are based on the DTN paradigm, however, our approach is not DTN-specific. The presented simulation study involves three main types of Internet traffic (i.e. file transfer, streaming and web browsing) and demonstrates that our proposed scheme achieves significant energy conservation for mobile receivers involving, under most circumstances, only mild performance cost.
In the era of big data, the Internet engineering community is searching for solutions to alleviate the issues caused by the constantly increasing data traffic. In this paper, we at-tempt to revive the sneakernet paradigm as a possible solution for non-real-time bulk data transfers. We propose a sample net-work architecture that takes advantage of the existing worldwide airline infrastructure, and leverages Delay-Tolerant Networking architecture to transfer data over the air in an automated way. We exploit Contact Graph Routing algorithm, which utilizes flight schedules to route bundles based on delivery delay or cost minimization. We examine the applicability of our proposal in a scenario that includes bulk space-data transfers between ESA data centers. Through simulations, we illustrate that the pro-posed scheme can deliver data efficiently between connected data centers, while the achieved throughput increases with the amount of data transmitted.
This demo presents Oi!, an opportunistic data transmission tool. Implemented on Android and available as open-source, Oi! relies on social interaction, device-to-device short range wireless transmission, as well as on history of contact duration to perform opportunistic data transmission. In this demo we show how Oi! can be used with intermittent Internet access between sources and destinations, to transmit data in a reliable and yet opportunistic way.
Community networks owned and operated by local communities have recently gained popularity as a low cost solution for Internet access. In this paper, we seek to understand the characteristics of Internet usage in community networks and provide useful insights on designing and improving community networks in rural areas. We report the results of a socio-technical study carried out during a three month measurement of a community wireless mesh network (CWMN) which has been operating for two years in a rural area of northern Thailand. An on-site social interview was also conducted to supplement our analysis. The results reveal several interesting findings: rural users do use online social networks, instant messaging applications and online games similarly to urban users; they install unnecessary applications on their mobile phones and are completely obvious to their side effects – the traffic from these applications accounts for a major share of the traffic leading to numerous network anomalies. Finally our analysis uncovers the characteristic of locality in community networks where users in close geographical proximity interact with each other.
Scoped-flooding is a technique for content discovery in a broad networking context. This paper investigates the effects of scoped-flooding on various topologies in informationcentric networking. Using the proposed ring model, we show that flooding can be constrained within a very small neighbourhood to achieve most of the gains which come from areas where the growth rate is relatively low, i.e., the network edge. We also study two flooding strategies and compare their behaviours. Given that caching schemes favour more popular items in competition for cache space, popular items are expected to be stored in diverse parts of the network compared to the less popular items. We propose to exploit the resulting divergence in availability along with the routers’ topological properties to fine tune the flooding radius. Our results shed light on designing e!cient content discovery mechanism for future information-centric networks.
Today, users can use their personal devices for a wide range of applications and services, such as controlling other devices, monitoring human physiological signals, or accessing information while on the move. Due to the communication and sensing capability of personal devices as well as embedded devices, their pervasive deployment and use may lead to an improvement of social and personal welfare by exploiting novel mobile citizen sensing applications. However, the pervasiveness of such large-scale sensing systems is only possible if devices are able to share sensing data independently of the available communication infrastructure, their location, and applications making use of the collected data. Hence, this paper describes a set of paradigms that should be considered to allow pervasive data sharing for the support mobile citizen sensing systems.
This paper proposes the HURRy (HUman Routines used for Routing) protocol, which infers and benefits from the social behaviour of nodes in disruptive networking environments. HURRy incorporates the contact duration to the information retrieved from historical encounters among neighbours, so that smarter routing decisions can be made. The specification of HURRy is based on the outcomes of a thorough experiment, which highlighted the importance of distinguishing between short and long contacts and deriving mathematical relations in order to optimally prioritize the available routes to a destination. HURRy introduces a novel and more meaningful rating system to evaluate the quality of each contact and overcome the limitations of other routing approaches in social environments.
The capability of a mobility model to detect certain patterns of user behavior (e.g., favorite walks or walking habits) enables solutions for a number of challenging networking problems, including efficient opportunistic communications and handoff / cellular planning. We argue that the limited viewpoint of a single mobile node and its scarce resources (e.g., energy, memory or processing) are major obstacles for accurate estimations. Targeting at hybrid network environments, we offload prediction capabilities to the fixed nodes that may be available in the area, offering a global view and the capability of resource-demanding calculations. Here, we introduce a solution running on top of the infrastructure nodes that: (i) implements a mobility model which provides a number of mobility forecasts to the mobile users in the area, (ii) supports proactively the routing decisions of opportunistic mobile devices being taken at times there is not connectivity. We introduce the corresponding semi-Markov model and demonstrate its efficiency using scenarios deployed in a pre-selected city center, where a number of mobile nodes seek for Internet access.
Do-It-Yourself (DIY) networks are decentralised networks built by an (often) amateur community. As DIY networks do not rely on the need for backhaul Internet connectivity, these networks are mostly a mix of both offline and online networks. Although DIY networks have their own home- grown services, the current Internet-based cloud services are often useful, and access to some services could be benefi- cial to the community (e.g. Google Maps). Considering that most DIY networks have challenged Internet connectiv- ity, migrating current service virtualisation instances could face great challenges. Service Centric Networking (SCN) has been recently proposed as a potential solution to manag- ing services more efficiently using Information Centric Net- working (ICN) principles. In this position paper, we present our arguments for the need for a resilient SCN architecture, propose a strawman SCN architecture that combines mul- tiple transmission technologies for providing resilient SCN in challenged DIY networks and, finally, identify key chal- lenges that needs to be explored further to realise the full potential of our architecture.
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