Supporting emerging mobile applications in densely populated environments requires connecting mobile users and their devices with the surrounding digital landscape. Specifically, the volume of digitally-available data in such computing spaces presents an imminent need for expressive mechanisms that enable humans and applications to share and search for relevant information within their digitally accessible physical surroundings. Device-to-device communications will play a critical role in facilitating transparent access to proximate digital resources. A wide variety of approaches exist that support device-to-device dissemination and query-driven data access. Very few, however, capitalize on the contextual history of the shared data itself to distribute additional data or to guide queries. This dissertation presents Gander, an application substrate and mobile middleware designed to ease the burden associated with creating applications that require support for sharing and searching of hyper-localized data in situ. Gander employs a novel trajectory-driven model of spatiotemporal provenance that enriches shared data with its contextual history -- annotations that capture data's geospatial and causal history across a lifetime of device-to-device propagation. We demonstrate the value of spatiotemporal data provenance as both a tool for improving ad hoc routing performance and for driving complex application behavior. This dissertation discusses the design and implementation of Gander's middleware model, which abstracts away tedious implementation details by enabling developers to write high-level rules that govern when, where, and how data is distributed and to execute expressive queries across proximate digital resources. We evaluate Gander within several simulated large-scale environments and one real-world deployment on the UT Austin campus. The goal of this research is to provide formal constructs realized within a software framework that ease the software engineering challenges encountered during the design and deployment of several applications in emerging mobile environments. / text

Abstract Mobile peer-to-peer (P2P) networks have emerged as a substrate for distributed wireless Internet applications. With P2P systems, it is possible to share resources such as data storage space, media files, network bandwidth, or computing power among the devices, which participate in the network, without large and expensive centralised server machines. However, the special characteristics of the mobile environment such as the low computational power, changing network conditions, and limited battery life pose several challenges for the fluent operation of mobile devices in P2P networks; this is also in part affected by the complexity of distributed P2P systems. Software development for mobile devices and the design of mobile networking systems are challenging due to the limited device resources and heterogeneous software platforms. Moreover, the energy consumption of a mobile device, and the network-wide routing efficiency that affects for example the resource lookup performance, depend on multiple variable parameters. P2P application development can be facilitated, however, by using middleware, which hides the complexity of networking from the application programmers. The research contributions of this thesis can be classified into three categories: (1) Novel functionalities of mobile middleware are proposed. One of these is a cross-layer connectivity management framework, which aims to select the best combination of network technology entities in a specific usage situation; the selection is made by logic contained in a replaceable state machine. Another new functionality is a system, which installs a missing application for the user, when the user receives a session request from another user. A signalling system based on the cellular USSD protocol is also presented; the system facilitates the establishment of a P2P connection with a mobile device, whose IP-based network connection is off. Moreover, the suitability of the P2PSIP protocol for implementing wireless distributed services is analysed. (2) P2P-related measurement studies are presented. In them, the message routing efficiency of a P2PP protocol implementation and the network traffic load caused by the messaging are observed, and the energy consumption incurred by the same implementation in a mobile device is measured. In addition, a server-based testbed system used in these measurements is described. (3) Experience-backed guidelines for mobile middleware development are presented. These include practical instructions for software development on a restricted mobile platform, and guidelines and observations related to cross-platform software development. / Tiivistelmä Mobiilit vertaisverkot (P2P) ovat uusi alusta hajautetuille langattomille Internet-sovelluksille. P2P-järjestelmien avulla on mahdollista jakaa resursseja kuten tiedon tallennustilaa, mediatiedostoja, verkon kaistanleveyttä tai laskentatehoa laitteiden kesken, jotka osallistuvat verkkoon, ilman suuria ja kalliita keskitettyjä palvelinkoneita. Mobiiliympäristön erityispiirteet kuten vähäinen laskentateho, vaihtelevat verkko-olosuhteet ja rajallinen akkukesto asettavat kuitenkin useita haasteita sujuvalle mobiililaitteiden vertaisverkkokäytölle; tähän vaikuttaa osaltaan myös hajautettujen P2P-järjestelmien monimutkaisuus. Mobiililaitteiden ohjelmistokehitys ja mobiiliverkkojärjestelmien suunnittelu on haastavaa rajallisten laiteresurssien ja epäyhtenäisten ohjelmistoalustojen vuoksi. Lisäksi mobiililaitteen energiankulutus ja koko P2P-verkon reititystehokkuus, joka vaikuttaa esimerkiksi resurssien hakutehokkuuteen, riippuvat useista muuttuvista parametreista. P2P-sovelluskehitystä voidaan kuitenkin helpottaa käyttämällä välikerrosohjelmistoja, jotka kätkevät verkon käytön monimutkaisuuden sovellusohjelmoijilta. Tämän väitöskirjan tutkimuksellinen uutuusarvo voidaan jakaa kolmeen osa-alueeseen: (1) Uusia toiminnallisuuksia mobiileihin välikerrosohjelmistoihin esitellään. Eräs näistä on verkkokerrosten välinen yhteydenhallintajärjestelmä, jossa pyritään valitsemaan tietyssä käyttötilanteessa paras verkkotekniikoiden yhdistelmä; valinnan tekee vaihdettavien tilakoneiden sisältämä logiikka. Toinen uusi toiminnallisuus on järjestelmä, joka asentaa puuttuvan sovelluksen käyttäjälle, kun käyttäjä saa toiselta käyttäjältä pyynnön ryhtyä yhteysjaksoon tämän kanssa. Myös soluverkkojen USSD-protokollaan perustuva signalointijärjestelmä esitellään; järjestelmän avulla helpotetaan P2P-yhteydenmuodostusta sellaisen mobiililaitteen kanssa, jonka IP-pohjainen verkkoyhteys on poissa päältä. Lisäksi P2PSIP-protokollan soveltuvuutta langattomien hajautettujen palvelujen toteuttamiseen analysoidaan. (2) Esitellään P2P-mittaustutkimuksia. Näissä havainnoidaan P2PP-protokollatoteutuksen viestien reititystehokkuutta ja viestien aiheuttamaa verkkoliikennekuormaa sekä mitataan saman toteutuksen aiheuttamaa energiankulutusta mobiililaitteessa. Lisäksi kuvaillaan mittauksissa hyödynnetty palvelinpohjainen testausjärjestelmä. (3) Esitetään kokemuksiin perustuvia neuvoja mobiilien välikerrosohjelmistojen kehitystyötä varten. Nämä sisältävät käytännöllisiä ohjeita rajoitetulla mobiilialustalla tapahtuvaan ohjelmistokehitykseen sekä neuvoja ja havaintoja liittyen yhtäaikaiseen useiden kohdealustojen ohjelmistokehitykseen.

Abstract The popularity of social networking services emphasises the importance of user communities. As the next evolutionary step, social networking will evolve towards user communities that are dynamically established according to contextual aspects such as the shared location and/or activities of people. In this vision, distributed peer-to-peer (P2P) technologies provide a respectable alternative to the centralised client-server technologies for implementing the upcoming community-centric mobile services. This thesis focuses on the development of enabling techniques and methods for a community-centric mobile service environment and on the evaluation of users’ perceptions and user acceptance of novel community-centric mobile services. The research was carried out by first examining the applicability of different P2P system architectures for implementing the management of user communities. Next, an experimental prototype of a community-centric mobile service environment was implemented. The experimental prototype was used for evaluating the performance of the community-centric mobile service environment and for conducting the user studies of novel community-centric mobile services. The evaluation was conducted in a real deployment environment with test users. The main results are the following: (1) a conceptual analysis of the advantages and disadvantages of P2P group management systems that are implemented using architecturally distinct P2P system architectures; (2) a performance evaluation of a P2P community management system, in which each community is implemented as an independent structured P2P overlay network; (3) a novel community-centric mobile service environment and its core component, a mobile middleware, which enables the use of P2P technologies and context information as part of Web-based applications running on a Web browser; (4) an evaluation of users’ perceptions and user acceptance of novel community-centric mobile services that are related to making a selection of an entertainment premise based on its music style and voting for music in a user community. / Tiivistelmä Käyttäjäyhteisöiden tärkeys on korostunut sosiaalista verkottumista edistävien palveluiden suosion kautta. Seuraavaksi sosiaalinen verkottuminen tulee laajentumaan yhteisöihin, jotka perustetaan dynaamisesti muun muassa ihmisten yhteisen sijainnin ja/tai toiminnan perusteella. Tulevaisuuden yhteisöllisten mobiilipalveluiden toteutuksessa hajautetut vertaisverkkoteknologiat tarjoavat varteenotettavan vaihtoehdon keskitetyille asiakas-palvelin -teknologioille. Tämä väitöskirjatyö keskittyy kehittämään tarvittavia tekniikoita ja menetelmiä yhteisöllisen mobiilipalveluympäristön toteuttamiseen sekä arvioimaan käyttäjien kokemuksia uusista yhteisöllisistä mobiilipalveluista. Tutkimuksessa tarkasteltiin aluksi arkkitehtuurillisesti erilaisten vertaisverkkojärjestelmien sopivuutta käyttäjäyhteisöjen hallinnan toteutettamiseksi. Seuraavaksi tutkimuksessa toteutettiin kokeellinen prototyyppi yhteisöllisestä mobiilipalveluympäristöstä. Kokeellista prototyyppiä hyödynnettiin sekä yhteisöllisen mobiilipalveluympäristön suorituskyvyn että uusien yhteisöllisten mobiilipalveluiden käyttäjäkokemuksen arvioinnissa. Arviointi suoritettiin aidossa käyttöympäristössä testikäyttäjien avulla. Väitöskirjatyön keskisimmät tulokset ovat seuraavat: (1) käsitteellinen analyysi arkkitehtuurillisesti erilaisten vertaisverkkojärjestelmien vahvuuksista ja heikkouksista ryhmänhallintajärjestelmän toteuttamisessa; (2) sellaisen yhteisönhallintajärjestelmän arviointi, jossa jokainen yhteisö on toteutettu erillisen ja itsenäisen rakenteellisen vertaisverkon avulla; (3) uusi yhteisöllinen mobiilipalveluympäristö, jonka keskeisin osa mobiili välikerrosohjelmisto mahdollistaa vertaisverkkoteknologioiden ja kontekstitiedon käyttämisen selaimessa toimivissa Web-sovelluksissa; (4) sellaisten uusien yhteisöllisten mobiilipalveluiden käyttäjäkokemuksen arviointi, jotka liittyvät vapaa-ajan viettopaikan valitaan musiikin perusteella ja soitettavan musiikin äänestämiseen käyttäjäyhteisöissä.

Este trabalho explora a gerência de segurança e cooperação de aplicações em sistemas distribuídos móveis. Neste contexto, é feito um estudo sobre os diferentes middlewares para ambientes móveis (mobile middleware): suas capacidades de enfrentar os desafios da mobilidade e da segurança. As análises do estudo mostram que esses middlewares devem possuir características que lhes permitem uma melhor adaptação às necessidades das aplicações e à natureza dos ambientes móveis. Os middlewares existentes pouco abordam a questão da segurança. A segurança ainda é um problema complexo que deve ser gerido em todos os níveis de um sistema distribuído móvel, incluindo novos mecanismos. Com base nessa análise, foi desenvolvido um modelo de gerência de segurança que implementa um mecanismo de autenticação mútua, confidencialidade, detecção de intruso e controle de acesso em ambientes móveis. O objetivo é garantir a confiabilidade, a disponibilidade de serviços e a privacidade do usuário através da tecnologia PET - Privacy-Enhancing Tecnologies. A idéia é fundamentada em agentes interceptadores e autoridades de segurança que distribuem tíquetes de segurança e controlam o acesso a recursos e espaços de tuple do ambiente. O estudo de caso apresentou resultados satisfatórios que permitem julgar a pertinência do modelo proposto. O modelo será integrado a um sistema de e-saúde. / The work exploits the security management and the cooperation of applications in mobile distributed systems. In this context a study of different mobile middleware is made. The study examines their capacities to face the challenges of mobility and security issues. The analysis shows that the existing middleware has very few approaches on security problems; security is still a complex issue to be managed in all the levels of mobile distributed system including new mechanisms. Based on this analysis, a security management model is developed that implements a mechanism for mutual authentication, confidentiality, intrusion detection, access control of mobile agents in mobile environments, ensures services availability and user privacy, through technology PET (Privacy-Enhancing Technologies). The idea is based on interceptor agents and security authorities that distribute security tickets and control the access to resources and Tuple spaces in mobile environment. The proposed model presents good performance and is integrated to an e-health system: Relationship Management with Chronic Patient GRPC.

Este trabalho explora a gerência de segurança e cooperação de aplicações em sistemas distribuídos móveis. Neste contexto, é feito um estudo sobre os diferentes middlewares para ambientes móveis (mobile middleware): suas capacidades de enfrentar os desafios da mobilidade e da segurança. As análises do estudo mostram que esses middlewares devem possuir características que lhes permitem uma melhor adaptação às necessidades das aplicações e à natureza dos ambientes móveis. Os middlewares existentes pouco abordam a questão da segurança. A segurança ainda é um problema complexo que deve ser gerido em todos os níveis de um sistema distribuído móvel, incluindo novos mecanismos. Com base nessa análise, foi desenvolvido um modelo de gerência de segurança que implementa um mecanismo de autenticação mútua, confidencialidade, detecção de intruso e controle de acesso em ambientes móveis. O objetivo é garantir a confiabilidade, a disponibilidade de serviços e a privacidade do usuário através da tecnologia PET - Privacy-Enhancing Tecnologies. A idéia é fundamentada em agentes interceptadores e autoridades de segurança que distribuem tíquetes de segurança e controlam o acesso a recursos e espaços de tuple do ambiente. O estudo de caso apresentou resultados satisfatórios que permitem julgar a pertinência do modelo proposto. O modelo será integrado a um sistema de e-saúde. / The work exploits the security management and the cooperation of applications in mobile distributed systems. In this context a study of different mobile middleware is made. The study examines their capacities to face the challenges of mobility and security issues. The analysis shows that the existing middleware has very few approaches on security problems; security is still a complex issue to be managed in all the levels of mobile distributed system including new mechanisms. Based on this analysis, a security management model is developed that implements a mechanism for mutual authentication, confidentiality, intrusion detection, access control of mobile agents in mobile environments, ensures services availability and user privacy, through technology PET (Privacy-Enhancing Technologies). The idea is based on interceptor agents and security authorities that distribute security tickets and control the access to resources and Tuple spaces in mobile environment. The proposed model presents good performance and is integrated to an e-health system: Relationship Management with Chronic Patient GRPC.