This thesis explores the use of virtual reality as a prototyping tool for designpractitioners to utilize when designing artifacts situated in physical places.Methods used in the study are qualitative and derive from the field ofinteraction design. The topic is explored through literature review on theattributes of virtual reality and sense of place, presented in the theorychapter, and is connected to the empirical research throughout the designprocess chapter. The theories presented strongly indicate that places affecthuman behavior, making them a substantial part of the user experience wheninteracting with designed artifacts in specific locations, which is echoedthough the target audience who voice the need to prototype design conceptsin the context of place. The study culminates in two kinds of virtual realityprototypes, dubbed contextual prototypes, that are suggested to havedifferent use cases depending on what the purpose for prototyping is.

Device-to-device (D2D) communication is a promising new feature in LTE-Advanced networks. It is brought up to enable efficient discovery and communication between proximate devices. With D2D capability, devices in physical proximity could be able to discover each other using LTE radio technology and to communicate with each other via a direct data path. This thesis is concerned with the design, coordination and testing of a hybrid D2D and cellular network. Design requirements and choices in physical and MAC layer functions to support D2D discovery and communication underlaying LTE networks are analyzed. In addition, a centralized scheduling strategy in base station is proposed to coordinate D2D data communication operating in LTE spectrum. The scheduling strategy combines multiple techniques, including mode selection, resource and power allocation, to jointly achieve an overall user performance improvement in a cell. Finally the performances of D2D data communication underlaying LTE system are calibrated in a multi-link scenario via system-level simulation.

Abstract Cognitive radio (CR) is becoming a promising tool for solving the problem of the scarce radio resource and spectrum inefficiency. Spectrum sensing (signal detection) enables real-time detection of spectrum holes by unlicensed secondary users (SUs) in cognitive radio networks (CRNs). In this thesis, performance analysis of CRNs and radio resource allocation are considered. A continuous time Markov chain (CTMC) based analytical model taking into account all relevant elements as well as addressing the issue of the false alarm rate (FAR) associated with the continuous sensing is developed. In some cases, the PU can be modeled as time-slotted with constant state (transmitting or not) in each slot. In this case, assuming SU can synchronize to the slots, its intuitive to use beginning of a slot for sensing and rest (possibly) for communication. For this model, M/D/1 priority queueing scheme has been applied in this thesis to find waiting time and queue length for PU and SU. Multiple access among SUs in a time-slotted channel is considered next. A conventional method is e.g. using a channel access probability ψ in each slot similar to the slotted ALOHA. A radically new idea is introduced in this thesis: why not increase the false alarm probability PFA of each SU and use it as a multiple access method? A game theoretic approach to radio resource allocation for the downlink capacity providing fair resource sharing among mobile nodes located along a multihop link is presented. Furthermore, the problem of resource allocations in heterogeneous wireless networks is also studied. Finally, device-to-device (D2D) communication - with localized distribution, where users tend to gather around some areas (clusters/hot-spots) within the cell such as buildings is studied. Theoretical analysis with two dimensional clustering is presented including cases with correlated clusters. Correlation in cluster selection is shown to significantly improve performance. / Tiivistelmä Kognitiivinen radio (CR) on nousemassa lupaavaksi työkaluksi niukkojen radioresurssien ja spektrin käytön tehottomuuden ratkaisemisessa. Spektrin nuuskiminen (signaalin ilmaisu) mahdollistaa spektriaukkojen reaaliaikaisen tunnistamisen toissijaisten käyttäjien (SU) toimesta kognitiivisissa radioverkoissa (CRN). Tässä väitöskirjassa painotus on CRN verkkojen suorituskykyanalyysissa ja radioresurssien hallinnassa. Työssä kehitetään jatkuva-aikaiseen Markov ketjuun (CTMC) perustuva analyyttinen malli joka ottaa huomioon kaikki olennaiset asiat mukaan lukien jatkuva-aikaiseen spektrin nuuskimiseen liittyvän väärien hälytysten tiheyden (FAR). Joissakin tapauksissa PU:ta voidaan mallintaa aikajaoteltuna siten että PU:n tila on vakio kussakin aikavälissä. Olettaen että SU voi synkronoitua aikaväleihin, on intuitiivista käyttää aikavälin alkua nuuskimiselle ja loppuosaa (mahdollisesti) viestintää varten. M/D/1:n ensisijaisuus-jonotus-suunnitelmaa soveltamalla tässä väitöskirjassa saadaan tuloksia odotusajalle ja jonon pituudelle sekä SU:lle että PU:lle. Seuraavaksi käsitellään monikäyttöä SU:den joukossa aikajaotellussa kanavassa. Tavanomainen menetelmä käyttää esimerkiksi kanavapääsytodennäköisyyttä ψ kussakin aikavälissä vastaten aikajaoteltua ALOHA protokollaa. Tässä väitöskirjassa esitetään radikaali uusi idea: miksei lisätä väärän hälytyksen todennäköisyyttä kussakin SU:ssa ja käytetä sitä moniliittymämenetelmänä? Työssä esitetään peliteoreettinen lähestymistapa radioresurssien allokointiin siten että resurssit jaetaan oikeudenmukaisesti monen yhteysvälin linkeissä. Lisäksi tutkitaan myös resursoinnin ongelmaa heterogeenisissa langattomissa verkoissa. Lopuksi tutkitaan laitteiden välistä suoraa viestintää (D2D) paikallisen jakauman kanssa, jossa käyttäjillä on tapana kasaantua solun sisällä esim. rakennuksiin. Esitetään teoreettinen analyysi kaksiulotteisella klusteroinnilla myös korreloitujen ryhmien kanssa. Osoitetaan että korrelaatio ryhmän valinnassa parantavaa merkittävästi suorituskykyä.

Avec la croissance des familles binationales, les divorces et séparations des époux donnent souvent lieu aux problèmes d’enlèvement parental d’enfant : l'un d’eux décide de déplacer l'enfant à l'étranger sans le consentement de l'autre afin de se faire accorder le droit de garde par un juge étranger plus clément. Des instruments juridiques internationaux tendent à résoudre ce problème d’enlèvement international d’enfants par le mécanisme de retour immédiat. La Convention de La Haye du 25 octobre 1980 sur les aspects civils de l'enlèvement international d'enfants est l'instrument principal qui est ratifié par un grand nombre d'États. Son effectivité dépend de la conformité de l'application par les États. Autrement dit, il est important d'interpréter des termes principaux et des exceptions de la Convention de manière conforme, voire similaire. Pour ce faire, le principe est l'interprétation autonome des notions de la Convention. Outre que la question d'interprétation de la Convention, l'attention est aussi portée sur l'exécution de l'ordonnance de retour. Cette exécution est en effet encadrée par l'obligation de célérité et elle requiert en même temps une forte coopération entre les autorités judiciaires et administratives entre les deux États concernés. Les États sont donc invités à donner effet aux ordonnances de retour à travers les différentes mesures, y compris les mesures coercitives. Cependant, la remise volontaire de l'enfant reste la meilleure solution qui doit être favorisée, notamment à travers le recours à une procédure amiable telle que la médiation familiale internationale. / With the increase of binational families, the divorces and separations between the married couple always give rise to problems of parental child kidnapping: one of them decides to remove the couple's child abroad, without consent of the other, with a view to having the child custody awarded by more clement foreign judges. International legal instruments tend to solve this problem of international child abduction through the summary return mechanism. The Hague Convention of 25 October 1980 on the Civil Aspects of International Child Abduction, as the main instrument, is now ratified by a great number of States. Its effectiveness depends on the compliance of the application of the Convention by member States. In other words, it is important for member States to interpret the Convention terms in the way to comply with the other. In doing so, the proposed principle must be the autonomous interpretation of the Convention terms. In addition to the issue of interpretation, attention must also be placed on the enforcement of return orders. This enforcement must be guided by the celerity obligation. At the same time, the enforcement of return orders requires a strong cooperation between judicial and administrative authorities of the States involved in each abduction case. The States are, thus, invited to give effect to return orders by taking different measures, including coercive ones. However, voluntary return of the abducted child is always the best solution that must be favored, especially through the use of amicable settlement between the parties, such as the international family mediation.