Recent trends in wireless communication systems show a significant demand for the delivery of multimedia services and applications over mobile networks - mobile multimedia - like video telephony, multimedia messaging, mobile gaming, interactive and streaming video, etc. However, despite the ongoing development of key communication technologies that support these applications, the communication resources and bandwidth available to wireless/mobile radio systems are often severely limited. It is well known, that these bottlenecks are inherently due to the processing capabilities of mobile transmission systems, and the time-varying nature of wireless channel conditions and propagation environments. Therefore, new ways of processing and transmitting multimedia data over mobile radio channels have become essential which is the principal focus of this thesis. In this work, the performance and suitability of various signal processing techniques and transmission strategies in the application of multimedia data over wireless/mobile radio links are investigated. The proposed transmission systems for multimedia communication employ different data encoding schemes which include source coding in the wavelet domain, transmit diversity coding (space-time coding), and adaptive antenna beamforming (eigenbeamforming). By integrating these techniques into a robust communication system, the quality (SNR, etc) of multimedia signals received on mobile devices is maximised while mitigating the fast fading and multi-path effects of mobile channels. To support the transmission of high data-rate multimedia applications, a well known multi-carrier transmission technology known as Orthogonal Frequency Division Multiplexing (OFDM) has been implemented. As shown in this study, this results in significant performance gains when combined with other signal-processing techniques such as spa ce-time block coding (STBC). To optimise signal transmission, a novel unequal adaptive modulation scheme for the communication of multimedia data over MIMO-OFDM systems has been proposed. In this system, discrete wavelet transform/subband coding is used to compress data into their respective low-frequency and high-frequency components. Unlike traditional methods, however, data representing the low-frequency data are processed and modulated separately as they are more sensitive to the distortion effects of mobile radio channels. To make use of a desirable subchannel state, such that the quality (SNR) of the multimedia data recovered at the receiver is optimized, we employ a lookup matrix-adaptive bit and power allocation (LM-ABPA) algorithm. Apart from improving the spectral efficiency of OFDM, the modified LM-ABPA scheme, sorts and allocates subcarriers with the highest SNR to low-frequency data and the remaining to the least important data. To maintain a target system SNR, the LM-ABPA loading scheme assigns appropriate signal constella tion sizes and transmit power levels (modulation type) across all subcarriers and is adapted to the varying channel conditions such that the average system error-rate (SER/BER) is minimised. When configured for a constant data-rate load, simulation results show significant performance gains over non-adaptive systems. In addition to the above studies, the simulation framework developed in this work is applied to investigate the performance of other signal processing techniques for multimedia communication such as blind channel equalization, and to examine the effectiveness of a secure communication system based on a logistic chaotic generator (LCG) for chaos shift-keying (CSK).

This thesis covers topic of mobile application development for Android and iOS. It also points out differences between Android and iOS programming. The main goal is to de-scribe the whole process of development which starts by choosing suitable mobile plat-forms and ends by distribution of finished application. The theory is shown on video streaming application. The first part of this thesis covers choosing of suitable platforms for development. Next chapter focuses on different development methods of mobile applica-tions. The rest of thesis is dedicated to Android and iOS development. There is one chapter covering software development kit and one chapter covering mobile user interface - its principles and creation methods. The last theoretical chapter covers fundamentals of each Android and iOS application. The whole development process of sample application is described in the seventh chapter. It includes functional and non-functional application re-quirements, analysis, design of user interface, implementation, testing and distribution of finished application. This thesis is supposed to be jump start for all new developers, who consider mobile application development.

Wireless operators adopting third-generation (3G) technologies and those migrating from second-generation (2G) to 3G face a number of challenges related to traffic modeling, demand characterization, and performance analysis, which are key elements in the processes of designing, dimensioning and optimizing their network infrastructure. Traditional traffic modeling assumptions used for circuit-switched voice traffic no longer hold true with the convergence of voice and data over packet-switched infrastructures. Self-similar models need to be explored to appropriately account for the burstiness that packet traffic is expected to exhibit in all time scales. The task of demand characterization must include an accurate description of the multiple user profiles and service classes the network is expected to support, with their distinct geographical distributions, as well as forecasts of how the market should evolve over near and medium terms. The appropriate assessment of the quality of service becomes a more complex issue as new metrics and more intricate dependencies have to be considered when providing a varying range of services and applications that include voice, real-time, and non-real time data. All those points have to be considered by the operator to obtain a proper dimensioning, resource allocation, and rollout plan for system deployment. Additionally, any practical optimization strategy has to rely on accurate estimates of expected demand and growth in demand. In this research, we propose a practical framework to characterize the traffic offered to multimedia wireless systems that allows proper dimensioning and optimization of the system for a particular demand scenario. The framework proposed includes a methodology to quantitatively and qualitatively describe the traffic offered to multimedia wireless systems, solutions to model that traffic as practical inputs for simulation analysis, and investigation of demand-sensitive techniques for system dimensioning and performance optimization. We consider both theoretical and practical aspects related to the dimensioning of hybrid traffic (voice and data) for mobile wireless networks. We start by discussing wireless systems and traffic theory, with characterization of the main metrics and models that describe the users’ voice and data demand, presenting a review of the most recent developments in the area. The concept of service class is used to specify parameters that depend on the application type, performance requirements and traffic characteristics for a given service. Then we present the concept of “user profile,“ which ties together a given combination of service class, propagation environment and terminal type. Next, we propose a practical approach to explore the dynamics of user geographical distribution in creating multi-service, multi-class traffic layers that serve as input for network traffic simulation algorithms. The concept of quality-of-service (QoS) is also discussed, focusing on the physical layer for 3G systems. We explore system simulation as a way to dimension a system given its traffic demand characterization. In that context, we propose techniques to translate geographical distributions of user profiles into the actual number of active users of each layer, which is the key parameter to be used as input in simulations. System level simulations are executed for UMTS systems, with the purpose of validating the methodology proposed here. We complete the proposed framework by applying all elements together in the process of dimensioning and optimization of 3G wireless networks using the demand characterization for the system as input. We investigate the effects of modifying some elements in the system configuration such as network topology, radio-frequency (RF) configuration, and radio resource management (RRM) parameters, using strategies that are sensitive to traffic geographical distribution. Case study simulations are performed for Universal Mobile Telecommunications System (UMTS) networks, and multiple system variables (such as antenna tilts, pilot powers, and RRM parameters) are optimized using traffic sensitive strategies, which result in significant improvements in the overall system capacity and performance. Results obtained in the case studies, allied to a generic discussion of the trade-offs involved in the proposed framework, demonstrate the close dependence between the processes of system dimensioning and optimization with the accurate modeling of traffic demand offered to the system. / Ph. D.

I avhandlingen beskrivs ett hypotetiskt system som kan användas av mobila användare, bland andra taxichaufförer, som exempelvis vill följa en viktig fotbollsmatch. Flera faktorer ställer till problem: Ibland står bilen still och föraren har inget annat att tänka på än matchen. Ibland kör denne runt med en kund som inte vill bli störd av matchen. Dessutom kan det vara svårt att titta på rörliga bilder och köra bil samtidigt. I och med att bilen körs runt har man också olika bra anslutning till Internet vid olika tillfällen – det kan variera mellan inget alls, en dålig GSM/GPRS förbindelse (8 kbps) och en snabb WLAN anslutning (100 Mbps). I avhandlingen presenteras en tre-lagers modell som kan användas för att beskriva den här typen av applikationers kvalitet. Modellen delas in i tre lager: nätverk, applikation och användare/använding. Det sistnämnda lagret ligger utanför det tekniska systemet och definieras av att det är där de verkliga informationsutbytet sker. På applikationsnivån samlas data in, packas och packas upp i samband med nätverkstransport och visas sedan för användaren. Det är också här som eventuell interaktion sker med användaren. Nätverkslagret är ansvarigt för ändamålsenlig transport av data. De tre lagren är ömsesidigt beroende av varandra. Dålig prestanda på ettlager påverkar de andra lagren och tvärtom. Tre studier har genomförts av hur problem på nätverkslagret i form av begränsad bandbredd och hög fördöjning påverkar användarna. Låg bandbredd ger låg videokvalitet vilket inte uppskattas av användarnamnen genom att skifta till animeringar som fungerar med lägre bandbredd kan man ändå få användarna nöjda. Om användarna måste välja mellandålig videokvalitet och animeringar väljer de som ser sig som fotbollskunniga det förstnämnda och de som ser sig som okunniga men dock fotbollsfans väljer det sistnämnda. Men i en annan studie där användarna spelade bluffstopp mot varandra över ett datanätverk fick vi ett annat resultat. Där var det negativt med högre videokvalitet (bilder per sekund). En förklaring kan vara att användarna distraherades mer av högre bildfrekvens. I den tredje studien studerades vad som händer i Pong om man läggerin fördröjningar i spelet. Sedan tidigare visste man att det blir svårare attspela med fördröjningar – särskilt om man inte märker dem. Vi ställde ossfrågan om man kan kompensera för dem genom att informera användarna om dem. Det visade sig att användare som får information med i vårtfall en prediktiv visning lättare anpassar sin mentala insats till uppgiftens svårighetsgrad. Det är alltså inte bara möjligt utan ibland också önskvärt att utnyttja en lägre bandbredd från användarens perspektiv. Med det sagt finns det ändå i långt fler situationer där det är bättre med bättre nätverksprestanda. Pongspelet var roligare med lägre delay. Videon uppfattades som bättre medhögre bandbredd i den förstnämnda studien. Multicast, där ett paket skickas till flera användare i stället för att de skafå varsin, identiska paket, är ett viktigt verktyg för att få bättre prestanda i videoapplikationer. Tyvärr är det inbyggda stödet för multicast i den viktiga IEEE 802.11 standardfamiljen för trådlösa nätverk mycket outvecklat. Ettstort problem är att det inte går att veta om ett paket har kommit fram eller om det har försvunnit i en, mycket trolig, krock. Vi har vidareutvecklat och anpassat en föga känd krockdetektionsmekanism från 80-talet för använding i IEEE 802.11 nätverk. Den anpassade algoritmen kallar vi EMCD vilket är en förkortning för ‘‘Early Multicast Collision Detection’’ eller tidig krockupptäckt för multicast. Vi har presenterat en nysannolikhetsbaserad modell för att beräkna algoritmens prestanda undermaximal belastning. Modellen som har verifierats genom simuleringar kanäven användas för att beräkna optimala parametrar för algoritmen. Algoritmen har visats kraftigt reducera risken för oupptäckta kollisioner och reducerar den tid som går åt för dem. EMCD-algoritmen inspirerade till att utveckla en ytterligare algoritm som inte bara kan upptäcka utan också undvika kollisioner: PREMA som står för ‘‘Prioritized Repeated Eliminations Multiple Access’’ eller prioriterad kanal-åtkomst med upprepade eliminationer. Det finns två viktiga skillnader mellanhur de fungerar. I EMCD bygger kollisionsdetektionen på rektangelfördelade slumptal och en enda upptäcktsomgång. I PREMA används i stället geometriskt fördelade slumptal och upprepade omgångar. Effekten blir att man med stor säkerhet får en enda vinnare. även för PREMA presenteras en sannolikhetskalkylsbaserad prestandaanalys för maxlastfallet vilken stöds av simuleringar. Samma formler kan användas för att approximativt skatta prestanda i EY-NPMA som är en närliggande algoritm. Den var tänkt att använda i Hiperlan/1; en standard som aldrig fick något kommersiellt genombrott. Använder man den modell som vi presenterar i avhandlingens sista studiekan man med ganska god noggrannhet beräkna optimala parametrar för EY-NPMA med en beräkningsinsats O(mY S) mot O(mES×mY S) för tidigare kända algoritmer. / Imagine a taxi driver wanting to watch a football game while working. Events in the game cannot be predetermined, the driver's available attentional resources vary and network connections change from non-existing to excellent, so it will be necessary to develop a viewing application that can adapt to circumstances. This thesis presents a system model and sketches a framework for design and run time adaptations. The model has three layers: user/usage, application and network. Quality of service metrics are proposed for each layer. A particular emphasis is placed on the difference between the user/usage layer and the application layer. Satisfaction at the former means a job well done, a match played to your liking etc. Satisfaction at the latter means good picture quality, nice colours etc. The thesis continues by identifying and describing elements required to build the system used by the taxi driver. Three studies are presented where either bandwidth or delay are varied at the network level. Video is better the higher the bandwidth; animations can be used as a complement. They are shown to be better than low quality video but worse than high quality video for watching a football game. Better video in the form of higher frame rates turned out to be worse for playing a card game over the Internet. A possible explanation is the distraction experienced when the image is updated constantly. Another result of our studies is that users can adapt their mental effort to the actual load when given feedback on the network delay affecting a computer game. The results mentioned above show that it is possible to compensate for poor network performance. For the user, improved network performance is generally more satisfactory. Early multicast collision detection is a method for improved multicast performance in high load IEEE 802.11 networks. Prioritised repeated eliminations multiple access is a method for multicast and other traffic which can be used alone or in an IEEE 802.11 network. Probabilistic performance analysis and simulations show that both protocols drastically reduce the time spent in collisions and improve throughput compared to IEEE 802.11. Some of the formulae are applied to EY-NPMA as well; they are used to estimate performance and to estimate optimal operating parameters more efficiently than with previously known methods.

With camera, smart phone, and wireless connection to a worldwide distribution source on a single device that fits in your pocket, now billions of citizens are able to become sousveillant micro-media activist – in real time. This case study investigates purposive texts in detail from over 50 hours of live and archived streaming video webcasts taken from geographically diverse sites. The goal is to explore how this tool is being used by videographers in a complex 21st century social movement. My sample video texts were gathered in late February and early March 2012 as the Occupy Movement stirred to life after a relatively quiet winter (from the corporate media’s point-of-view). In this project, I examine how Occupy’s use of live-streaming video combines “mediated co-presence” (Giddens 1984; Ito 2005) with “networked autonomy” (Castells 2011) to represent the ambivalent face of a complex, postmodern movement for social justice. / text

In the world of high mobility, there is a growing need for people to communicate with each other and have timely access to information regardless of the location of the individuals or the information. This need is supported by the advances in the technologies of networking, wireless communications, and portable computing devices with reduction in the physical size of computers, lead to the rapid development in mobile communication infrastructure. Hence, mobile and wireless networks present many challenges to application, hardware, software and network designers and implementers. One of the biggest challenge is to provide a secure mobile environment. Security plays a more important role in mobile communication systems than in systems that use wired communication. This is mainly because of the ubiquitous nature of the wireless medium that makes it more susceptible to security attacks than wired communications. The aim of the thesis is to develop an integrated dynamic security and authentication system for mobile transactions. The proposed system operates at the transactions-level of a mobile application, by intelligently selecting the suitable security technique and authentication protocol for ongoing transaction. To do this, we have designed two schemes: the transactions-based security selection scheme and the transactions-based authentication selection scheme. These schemes use transactions sensitivity levels and the usage context, which includes users behaviors, network used, device used, and so on, to decide the required security and authentication levels. Based on this analysis, requisite security technique, and authentication protocols are applied for the trans-action in process. The Behaviors-Observations-Beliefs (BOB) model is developed using cognitive agents to supplement the working of the security and authentication selection schemes. A transaction classification model is proposed to classify the transactions into various sensitivity levels. The BOB model The BOB model is a cognitive theory based model, to generate beliefs over a user, by observing various behaviors exhibited by a user during transactions. The BOB model uses two types of Cognitive Agents (CAs), the mobile CAs (MCAs) and the static CAs (SCAs). The MCAs are deployed over the client devices to formulate beliefs by observing various behaviors of a user during the transaction execution. The SCA performs belief analysis, and identifies the belief deviations w.r.t. established beliefs. We have developed four constructs to implement the BOB model, namely: behaviors identifier, observations generator, beliefs formulator, and beliefs analyser. The BOB model is developed by giving emphasis on using the minimum computation and minimum code size, by keeping the resource restrictiveness of the mobile devices and infrastructure. The knowledge organisation using cognitive factors, helps in selecting the rational approach for deciding the legitimacy of a user or a session. It also reduces the solution search space by consolidating the user behaviors into an high-level data such as beliefs, as a result the decision making time reduces considerably. The transactions classification model This model is proposed to classify the given set of transactions of an application service into four sensitivity levels. The grouping of transactions is based on the operations they perform, and the amount of risk/loss involved if they are misused. The four levels are namely, transactions who’s execution may cause no-damage (level-0), minor-damage (level-1), significant-damage (level-2) and substantial-damage (level-3). A policy-based transaction classifier is developed and incorporated in the SCA to decide the transaction sensitivity level of a given transaction. Transactions-based security selection scheme (TBSS-Scheme) The traditional security schemes at application-level are either session or transaction or event based. They secure the application-data with prefixed security techniques on mobile transactions or events. Generally mobile transactions possesses different security risk profiles, so, empirically we may find that there is a need for various levels of data security schemes for the mobile communications environment, which face the resource insufficiency in terms of bandwidth, energy, and computation capabilities. We have proposed an intelligent security techniques selection scheme at the application-level, which dynamically decides the security technique to be used for a given transaction in real-time. The TBSS-Scheme uses the BOB model and transactions classification model, while deciding the required security technique. The selection is purely based on the transaction sensitivity level, and user behaviors. The Security techniques repository is used in the proposed scheme, organised under three levels based on the complexity of security techniques. The complexities are decided based on time and space complexities, and the strength of the security technique against some of the latest security attacks. The credibility factors are computed using the credibility module, over transaction network, and transaction device are also used while choosing the security technique from a particular level of security repository. Analytical models are presented on beliefs analysis, security threat analysis, and average security cost incurred during the transactions session. The results of this scheme are compared with regular schemes, and advantageous and limitations of the proposed scheme are discussed. A case study on application of the proposed security selection scheme is conducted over mobile banking application, and results are presented. Transactions-based authentication selection scheme (TBAS-Scheme) The authentication protocols/schemes are used at the application-level to authenticate the genuine users/parties and devices used in the application. Most of these protocols challenges the user/device to get the authentication information, rather than deploying the methods to identify the validity of a user/device. Therefore, there is a need for an authentication scheme, which intelligently authenticates a user by continuously monitoring the genuinity of the activities/events/ behaviors/transactions through out the session. Transactions-based authentication selection scheme provides a new dimension in authenticating users of services. It enables strong authentication at the transaction level, based on sensitivity level of the given transaction, and user behaviors. The proposed approach intensifies the procedure of authentication by selecting authentication schemes by using the BOB-model and transactions classification models. It provides effective authentication solution, by relieving the conventional authentication systems, from being dependent only on the strength of authentication identifiers. We have made a performance comparison between transactions-based authentication selection scheme with session-based authentication scheme in terms of identification of various active attacks, and average authentication delay and average authentication costs are analysed. We have also shown the working of the proposed scheme in inter-domain and intra-domain hand-off scenarios, and discussed the merits of the scheme comparing it with mobile IP authentication scheme. A case study on application of the proposed authentication selection scheme for authenticating personalized multimedia services is presented. Implementation of the TBSS and the TBAS schemes for mobile commerce application We have implemented the integrated working of both the TBSS and TBAS schemes for a mo-bile commerce application. The details on identifying vendor selection, day of purchase, time of purchase, transaction value, frequency of purchase behaviors are given. A sample list of mobile commerce transactions is presented along with their classification into various sensitivity levels. The working of the system is discussed using three cases of purchases, and the results on trans-actions distribution, deviation factor generation, security technique selection, and authentication challenge generation are presented. In summary, we have developed an integrated dynamic security and authentication system using, the above mentioned selection schemes for mobile transactions, and by incorporating the BOB model, transactions classification model, and credibility modules. We have successfully implemented the proposed schemes using cognitive agents based middleware. The results of experiments suggest that incorporating user behaviors, and transaction sensitivity levels will bring dynamism and adaptiveness to security and authentication system. Through which the mobile communication security could be made more robust to attacks, and resource savvy in terms of reduced bandwidth and computation requirements by using an appropriate security and authentication technique/protocol.