Delivering Live Multimedia Streams to Mobile Hosts in a Wireless Internet with Multiple Content Aggregators

We consider the distribution of channels of live multimedia content (e.g., radio or TV broadcasts) via multiple content aggregators. In our work, an aggregator receives channels from content sources and redistributes them to a potentially large number of mobile hosts. Each aggregator can offer a channel in various configurations to cater for different wireless links, mobile hosts, and user preferences. As a result, a mobile host can generally choose from different configurations of the same channel offered by multiple alternative aggregators, which may be available through different interfaces (e.g., in a hotspot). A mobile host may need to handoff to another aggregator once it receives a channel. To prevent service disruption, a mobile host may for instance need to handoff to another aggregator when it leaves the subnets that make up its current aggregator�s service area (e.g., a hotspot or a cellular network).\ud In this paper, we present the design of a system that enables (multi-homed) mobile hosts to seamlessly handoff from one aggregator to another so that they can continue to receive a channel wherever they go. We concentrate on handoffs between aggregators as a result of a mobile host crossing a subnet boundary. As part of the system, we discuss a lightweight application-level protocol that enables mobile hosts to select the aggregator that provides the �best� configuration of a channel. The protocol comes into play when a mobile host begins to receive a channel and when it crosses a subnet boundary while receiving the channel. We show how our protocol can be implemented using the standard IETF session control and description protocols SIP and SDP. The implementation combines SIP and SDP�s offer-answer model in a novel way

Integrated context management for multi-domain pervasive environments

An important part of the value of ubiquitous computing environments is in their ability to interact with external domains. This paper addresses the issue of cross-domain context management in a scenario of seamless integration between a user home domain and a ubiquitous computing environment. The work is based on the broader concept of Value ADded Environment (Vade), where multiple integration possibilities are explored. This paper is focused on location context management issues and describes two integration paths for sharing context data: the possibility to provide local applications with access to the context of a visiting user, and the possibility to provide global applications with access to context sources that are specific to the visited location.(undefined

Systems-Level Support for Mobile Device Connectivity.

The rise of handheld computing devices has inspired a great deal of research aimed at addressing the unique problems posed by their mobile, "always-on" nature. In order to help mobile devices navigate a complex world of overlapping, uneven public wireless coverage, one must be mindful of the distinction between nomadic usage and true mobility. Accordingly, systems research must move beyond simply optimizing for a set of local conditions (e.g., finding the best access point for a laptop user in a stationary location) to considering the "derivative of connectivity" when network conditions are constantly in flux. This dissertation presents a new paradigm for networking support on mobile devices. This project has several complementary aspects. As devices encounter network connectivity our system both evaluates the application-level quality of WiFi access points and updates a device-centric mobility model. Together, this mobility model and AP quality database yield "connectivity forecasts," which let applications optimize not just for current network conditions but for the expected big picture to come. Results of a prototype deployment in several cities shows that considering the application-level quality of APs (rather than just signal strength) significantly boosts the success rate of finding a usable access point. Furthermore, this dissertation shows how connectivity forecasts---even with minimal model training time---allow several applications commonly found on mobile devices to reap significant benefits, such as extended battery life. Mobile devices are often within range of multiple connectivity options, however, and choosing just one therefore ignores potential connectivity. This dissertation describes a virtual link layer for Linux, called Juggler, that uses one network card to simultaneously associate with many WiFi APs, ad hoc groups or mesh networks. The results show how Juggler can boost effective bandwidth by striping data across multiple APs, enable seamless 802.11 handoff by preemptively associating with the "next" AP before the current one become unusable, and maintain a modest side-channel to the user's personal area network or mesh network without impacting foreground bandwidth to infrastructure.Ph.D.Computer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/61718/1/tonynich_1.pd

JANUS: A Framework for Distributed Management of Wireless Mesh Networks

Abstract — Wireless Mesh Networks (WMNs) are emerging as a potentially attractive access architecture for metropolitan-scale networks. While research on WMNs has been up to a large extent confined to the study of efficient routing protocols, there is a clear need to envision new network management tools, able to sufficiently exploit the peculiarities of WMNs. In particular, a new generation of middleware tools for network monitoring and profiling must be introduced in order to speed up development and testing of novel protocol architectures. Currently, manage-ment functionalities are developed using conventional central-ized approaches. The distributed and self-organizing nature of WMNs suggest a transition from network monitoring to network sensing. In this work, we propose JANUS, a novel framework for distributed monitoring of WMNs. We describe the JANUS architecture, present a possible implementation based on open-source software and report some experimental measurements carried out on a small-scale testbed. Index Terms — wireless mesh networks, network management, distributed hash table, overlay networks, publish-subscribe sys-tems I

Design of a web-based LBS framework addressing usability, cost, and implementation constraints

This research investigates barriers that prevent Location Based Services (LBS) from reaching its full potential. The different constraints, including poor usability, lack of positioning support, costs, and integration difficulties are highlighted. A framework was designed incorporating components based on existing and new technologies that could help address the constraints of LBS and increase end-user acceptance. This research proposes that usability constraints can be addressed by adapting a system to user characteristics which are inferred on the basis of captured user context and interaction data. A prototype LBS system was developed to prove the feasibility and benefit of the framework design, demonstrating that constraints of positioning, cost, and integration can be overcome. Volunteers were asked to use the system, and to answer questions in relation to their proficiency and experience. User-feedback showed that the proposed combination of functionality was well-received, and the prototype was appealing to many users. Ground-truths from the survey were related back to data captured with a user monitoring component in order to investigate whether users can be classified according to their context and how they interact. The results have shown that statistically significant relationships exist, and that by using the C4.5 decision-tree, computer proficiency can be estimated within one class-width in 76.7% of the cases. These results suggest that it may be possible to build a user-model to estimate computer proficiency on the basis of user-interaction data. The user model could then used to improve usability through adaptive user-specific customisations

Feasibility of Using Passive Monitoring Techniques in Mesh Networks for the Support of Routing

In recent years, Wireless Mesh Networks (WMNs) have emerged as a promising solution to provide low cost access networks that extend Internet access and other networking services. Mesh routers form the backbone connectivity through cooperative routing in an often unstable wireless medium. Therefore, the techniques used to monitor and manage the performance of the wireless network are expected to play a significant role in providing the necessary performance metrics to help optimize the link performance in WMNs. This thesis initially presents an assessment of the correlation between passive monitoring and active probing techniques used for link performance measurement in single radio WMNs. The study reveals that by combining multiple performance metrics obtained by using passive monitoring, a high correlation with active probing can be achieved. The thesis then addresses the problem of the system performance degradation associated with simultaneous activation of multiple radios within a mesh node in a multi-radio environment. The experiments results suggest that the finite computing resource seems to be the limiting factor in the performance of a multi-radio mesh network. Having studied this characteristic of multi-radio networks, a similar approach as used in single radio mesh network analysis was taken to investigate the feasibility of passive monitoring in a multi-radio environment. The accuracy of the passive monitoring technique was compared with that of the active probing technique and the conclusion reached is that passive monitoring is a viable alternative to active probing technique in multi-radio mesh networks

Opportunity Knocks: A System to Provide Cognitive Assistance with Transportation Services

We present an automated transportation routing system, called “Opportunity Knocks,” whose goal is to improve the efficiency, safety and independence of individuals with mild cognitive disabilities. Our system is implemented on a combination of a Bluetooth sensor beacon that broadcasts GPS data, a GPRS-enabled cell-phone, and remote activity inference software. The system uses a novel inference engine that does not require users to explicitly provide information about the start or ending points of their journeys; instead this information is learned from users’ past behavior. Futhermore, we demonstrate how route errors can be detected and how the system helps to correct the errors with real-time transit information. In addition we present a novel solution to the problem of labeling positions with place names.Engineering and Applied Science

Integration of the Captive Portal paradigm with the 802.1X architecture

In a scenario where hotspot wireless networks are increasingly being used, and given the amount of sensitive information exchanged on Internet interactions, there is the need to implement security mechanisms that guarantee data confidentiality and integrity in such networks, as well as the authenticity of the hotspot providers. However, many hotspots today use Captive Portals, which rely on authentication through Web pages (thus, an application-level authentication approach) instead of a link-layer approach. The consequence of this is that there is no security in the wireless link to the hotspot (it has to be provided at upper protocol layers), and is cumbersome to manage wireless access profiles (we need special applications or browsers' add-ons to do that). This work exposes the weaknesses of the Captive Portals' paradigm, which does not follow a unique nor standard approach, and describes a solution that intends to suppress them, based on the 802.1X architecture. This solution uses a new EAP-compliant protocol that is able to integrate an HTTP-based registration or authentication with a Captive Portal within the 802.1X authentication framework