Since its invention, cellular communication has dramatically transformed personal lifes and the evolution of mobile networks is still ongoing. Evergrowing demand for higher data rates has driven development of 3G and 4G systems, but foreseen 5G requirements also address diverse characteristics such as low latency or massive connectivity. It is speculated that the 4G plain cyclic prefix (CP)-orthogonal frequency division multiplexing (OFDM) cannot sufficiently fulfill all requirements and hence alternative waveforms have been in-vestigated, where generalized frequency division multiplexing (GFDM) is one popular option. An important aspect for any modern wireless communication system is the application of multi-antenna, i.e. MIMO techiques, as MIMO can deliver gains in terms of capacity, reliability and connectivity. Due to its channel-independent orthogonality, CP-OFDM straightforwardly supports broadband MIMO techniques, as the resulting inter-antenna interference (IAI) can readily be resolved. In this regard, CP-OFDM is unique among multicarrier waveforms. Other waveforms suffer from additional inter-carrier interference (ICI), inter-symbol interference (ISI) or both. This possibly 3-dimensional interference renders an optimal MIMO detection much more complex. In this thesis, weinvestigate how GFDM can support an efficient multiple-input multiple-output (MIMO) operation given its 3-dimensional interference structure. To this end, we first connect the mathematical theory of time-frequency analysis (TFA) with multicarrier waveforms in general, leading to theoretical insights into GFDM. Second, we show that the detection problem can be seen as a detection problem on a large, banded linear model under Gaussian noise. Basing on this observation, we propose methods for applying both space-time code (STC) and spatial multiplexing techniques to GFDM. Subsequently, we propose methods to decode the transmitted signals and numerically and theoretically analyze their performance in terms of complexiy and achieved frame error rate (FER). After showing that GFDM modulation and linear demodulation is a direct application of Gabor expansion and transform, we apply results from TFA to explain singularities of the modulation matrix and derive low-complexity expressions for receiver filters. We derive two linear detection algorithms for STC encoded GFDM signals and we show that their performance is equal to OFDM. In the case of spatial multiplexing, we derive both non-iterative and iterative detection algorithms which base on successive interference cancellation (SIC) and minimum mean squared error (MMSE)-parallel interference cancellation (PIC) detection, respectively. By analyzing the error propagation of the SIC algorithm, we explain its significantly inferior performance compared to OFDM. Using feedback information from the channel decoder, we can eventually show that near-optimal GFDM detection can outperform an optimal OFDM detector by up to 3dB for high SNR regions. We conclude that GFDM, given the obtained results, is not a general-purpose replacement for CP-OFDM, due to higher complexity and varying performance. Instead, we can propose GFDM for scenarios with strong frequency-selectivity and stringent spectral and FER requirements.

When considering the addition of a mobile presentation channel to an existing web-based application, project managers should know how the mobile channel|s characteristics will impact the user experience and the cost of using the application, even before development begins. The PETTICOAT (Performance Tuning and cost discovery of mobile web-based Applications) approach presented here provides decision-makers with indicators on the economical feasibility of mobile channel development. In a nutshell, it involves analysing interaction patterns on the existing stationary channel, identifying key business processes among them, measuring the time and data volume incurred in their execution, and then simulating how the same interaction patterns would run when subjected to the frame conditions of a mobile channel. As a result of the simulation, we then gain time and volume projections for those interaction patterns that allow us to estimate the costs incurred by executing certain business processes on different mobile channels.

Los sistemas de comunicaciones con múltiples antenas o sistemas MIMO (multiple-input multiple-output) se presentan como una de las tecnologías más prometedoras en el campo de las comunicaciones inalámbricas, ya que permiten aprovechar la dimensión espacial además de las dimensiones de frecuencia y tiempo. De esta forma, se pueden obtener tasas de transmisión más elevadas usando el mismo ancho de banda, que es un recurso escaso, y manteniendo una potencia de transmisión baja, lo cual es crucial para dispositivos alimentados por baterías. Por estas razones, la tecnología MIMO ha sido adoptada en muchos estándares como Long-Term Evolution (LTE), LTE Advanced y Worldwide Interoperability for Microwave Access (WiMAX). Las técnicas MIMO también pueden se pueden emplear en un escenario multiusuario, donde varios usuarios comparten la dimensión espacial provocando una interferencia multiusuario. A través de la precodificación y del uso de múltiples antenas en el transmisor, la señal de los diferentes usuarios puede ser multiplexada espacialmente de forma que se mitigue la interferencia multiusuario incluso con usuarios de una sola antena. Estos sistemas, conocidos como sistemas MU-MISO (multiuser multiple-input single-output), han atraído mucho la atención en los últimos años ya que permiten el desarrollo de terminales pequeños y baratos, manteniendo así el equipamiento más caro en el transmisor. Sin embargo, estos beneficios conllevan un sistema más complejo. Por una parte, el multiplexado espacial requiere una carga de procesado considerable, que depende del tamaño del sistema: número de antenas transmisoras, número de receptores y ancho de banda. Por otra parte, las técnicas MIMO requieren un conocimiento del canal en transmisión o CSIT (channel state information at the transmitter) preciso. En sistemas con duplexación por división en frecuencia o FDD (frequency-division duplex), la información de canal o CSI (channel state information) debe ser estimada en el receptor y proporcionada al transmisor a través del enlace de realimentación, reduciendo así la eficiencia del sistema. Por lo tanto, esta tesis se centra en la mejora de la eficiencia de las implementaciones de precodificación y en el rendimiento de los esquemas de realimentación de canal en sistemas MU-MISO. El problema de la precodificación se aborda en primer lugar. Se ha llevado a cabo un análisis de algunas de las técnicas de precodificación más usadas, prestando especial atención a su rendimiento y a su complejidad. Este análisis revela que aquellas técnicas que hacen uso de lattice reduction (LR) obtienen un mejor rendimiento. Sin embargo, la complejidad computacional de la técnica LR dificulta su implementación en la práctica. El análisis también revela que las técnicas zero-forcing (ZF), Tomlinson-Harashima precoding (THP) y LR-THP son las técnicas más adecuadas para cubrir todo el rango de rendimiento y complejidad computacional. Asimismo, se ha llevado a cabo un análisis de estas técnicas bajo CSIT imperfecto. Dicho análisis ha demostrado que LR es una técnica muy importante también para el caso de CSIT imperfecto. A continuación, se han presentado implementaciones paralelas de técnicas de precodificación sobre unidades de procesamiento gráfico o GPUs (graphic processing unit), comparándose con implementaciones en unidades de procesamiento central o CPU (central processing unit). Dado que las implementaciones de THP y LR-THP han demostrado ser las que mejor se adaptan a la arquitectura de la GPU y ya que tienen muchas operaciones comunes, se ha propuesto una implementación sobre GPU de un esquema THP reconfigurable combinado con LR. La reconfigurabilidad de las GPUs permite desactivar la etapa de LR cuando los requisitos de los usuarios están garantizados por el esquema THP, combinando complejidad computacional con rendimiento. Aunque esta implementación consigue una mejora significativa respecto a la implementación sobre CPU, su paralelismo viene limitado por la naturaleza secuencial del problema LR. Por ello, se han propuesto varias estrategias para la paralelización del problema LR que han sido evaluadas en distintas plataformas: CPU multi-núcleo, GPU y plataforma heterogénea que consiste en CPU+GPU. Los resultados revelan que la arquitectura GPU permite reducir considerablemente el tiempo de computación del problema LR, especialmente en la plataforma heterogénea. La segunda parte de la tesis trata el problema de la realimentación de canal en sistemas FDD. En estos sistemas, los receptores normalmente proporcionan una versión cuantificada del canal a través del canal de realimentación. Con el objetivo de mantener una eficiencia alta, el canal debe ser cuantificado con los mínimos bits posibles. En primer lugar, se explora el uso de la correlación en frecuencia para reducir el volumen de información de realimentación. Se han presentado dos esquemas diferentes basados en cuantificación vectorial o VQ (vector quantization) y en la transformación Karhunen-Loève, respectivamente, y se han comparado con esquemas existentes en términos de rendimiento y complejidad computacional. Los resultados muestran que ambas técnicas son capaces de reducir significativamente el volumen de información de realimentación aprovechando la correlación en frecuencia. Finalmente, la correlación espacial también se aprovecha para reducir la información de realimentación. Se ha presentado una caracterización espacial estadística del modelo de canal SCM (spatial channel model) del 3GPP (3rd Generation Partnership Project) para un entorno de alta correlación. Basado en esta caracterización, se propone un esquema de cuantificación de canal para entornos de alta correlación. Con el objetivo de obtener una caracterización para alta y baja correlación, se considera un modelo de correlación más sencillo como el modelo de Kronecker. Basado en esta caracterización, se proponen dos esquemas de cuantificación y se evalúan con un modelo de canal realista como el SCM. Los resultados muestran que ambos esquemas son capaces de reducir la información de realimentación en ambientes con correlación alta y moderada. / Multiple-input multiple-output (MIMO) communication systems have emerged as one of the most promising technologies in the field of wireless communications, allowing to exploit the spatial dimension as well as the time and frequency dimensions. Thus, higher rates can be obtained by using the same bandwidth, which is a scarce resource, and keeping a low transmit power, which is crucial in battery-operated devices. For these reasons, MIMO technologies have been adopted by many standards such as Long-Term Evolution (LTE), LTE advanced (LTE-A) and Worldwide Interoperability for Microwave Access (WiMAX). MIMO techniques can also be used in a multiuser scenario, where several usersshare the spatial dimension causing multiuser interference. By means of precoding and the use of multiple antennas at the transmitter, the signal of the different users can be spatially multiplexed so that multiuser interference is mitigated even for single-antenna users. These systems, known as multiuser multiple-input singular-output (MU-MISO) systems, have attracted much attention in recent years since they allow the development of small and inexpensive terminals, keeping the most expensive hardware at the transmitter. However, these benefits come at the cost of having a more complex system. On the one hand, spatial multiplexing requires a considerable processing load that depends on the size of the system: number of transmit antennas, number of receivers and bandwidth. On the other hand, MIMO techniques require accurate channel state information at the transmitter (CSIT). In frequency-division duplex (FDD) systems, channel state information (CSI) has to be estimated at the receiver and provided to the transmitter through the feedback link, hence reducing the efficiency of the system. Therefore, this thesis is primarily focused on improving the efficiency of precoding implementations and the performance of feedback schemes in MU-MISO systems. First, the problem of precoding is addressed. An analysis of some of the most utilized precoding techniques is conducted, paying special attention to their performance and computational complexity. The analysis reveals that those techniques that make use of lattice reduction (LR) achieve the best performance. However, the computational complexity of LR makes its implementation difficult for practical systems. The analysis reveals that zero-forcing (ZF), Tomlinson-Harashima precoding (THP) and lattice reduction Tomlinson-Harashima precoding (LR-THP) are the most suitable techniques for covering the entire range of performance and computational complexity. An analysis of these techniques with imperfect CSIT has also been performed. In this analysis, LR has proven to be a key technique also when imperfect CSIT is available. Next, parallel implementations of the precoding techniques on a graphic processing unit (GPU) are presented and compared to implementations that use a central processing unit (CPU). Since the implementations of THP and LR-THP have shown to best fit the GPU architecture and since they also share many operations, a GPU implementation of a reconfigurable THP scheme combined with LR has been proposed. The reconfigurable nature of GPUs allows gating the LR stage off when the user requirements are sufficiently guaranteed by the THP scheme, trading computational cost and performance. Although this implementation achieves a significant speed-up compared to its CPU implementation, its parallelism is limited by the sequential nature of LR. Therefore, several strategies for the parallelization of the LR problem are proposed and evaluated on different platforms: multicore CPU, GPU and a heterogeneous platform consisting of CPU+GPU. Results reveal that a GPU architecture allows a considerable reduction of the computational time of the LR problem, especially in the heterogeneous platform. The second part of this thesis addresses the problem of feedback in FDD systems. In these systems, a quantized version of the channel is usually provided by the receivers through the feedback link. In order to keep a high efficiency, the channel must be quantized using as few bits as possible. First, the use of the frequency correlation to reduce the feedback information is explored. Two different schemes based on vector quantization (VQ) and the Karhunen-Loève (KL) transform, respectively, are presented and compared with existing schemes in terms of performance and complexity. Results show that both techniques are able to significantly reduce the feedback overhead by taking advantage of the frequency correlation. Finally, the spatial correlation is leveraged to reduce the feedback information. A spatial statistical characterization of the spatial channel model (SCM) from the 3rd Generation Partnership Project (3GPP) for a highly correlated environment is presented. Based on this characterization, a channel quantization scheme for highly correlated environments is proposed. In order to obtain a statistical characterization for both high and low correlations, a simpler model such as the Kronecker correlation model is considered. Based on this characterization, two quantization schemes have been presented and evaluated using a realistic channel model such as the SCM. Results show that both schemes are able to reduce the feedback overhead in highly and moderately correlated scenarios. / Domene Oltra, F. (2015). Evaluation of precoding and feedback quantization schemes for multiuser communications systems [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/46971 / Alfresco

Yes / This is the eighth workshop to be organised under the postgraduate programmes in electrical and electronic engineering (EEE). The workshop concludes the Research Seminar Series, which has provided a platform for disseminating the latest research activities in related technologies through its weekly seminars. The EEE courses cover a broad range of technologies and this is reflected in the variety of topics presented during the workshop. In total, thirty-three papers have been selected for the proceedings, which have been divided into seven sections. The workshop aims to be as close to a `real¿ event as possible. Hence, authors have responded to a Call for Papers with an abstract, prior to the submission of the final paper. This has been a novel experience for many, if not all of the contributors. Clearly, authors have taken up the challenge with enthusiasm, resulting in what promises to be an interesting and informative workshop.

Este trabalho visa estudar e implementar a integração entre o domínio de comutação de circuitos e o IP Multimedia Subsystem (IMS) para suportar handovers verticais, ou seja, entre redes de acesso distintas, por exemplo, Global System for Mobile communications (GSM) e WiFi, em especial no Serviço Voice Call Continuity (VCC). Entretanto muito pouco é especificado sobre a integração entre os domínios nas normas das diversas entidades de padronização que tratam sobre o assunto. Assim, apresenta-se uma proposta para essa integração, criando-se uma nova entidade funcional para realizá-la, o Call Data Storage Function (CDSF), que interage com os demais módulos do Serviço VCC e garante que algumas informações que devem ser trocadas entre os módulos não sejam perdidas, devido à conversão de protocolos de sinalização na interface entre tais domínios. O CDSF auxilia também no controle da alocação de endereços de referência utilizados no encaminhamento de chamadas de um domínio para o outro. São definidos os protocolos de acesso ao CDSF, bem como os métodos disponíveis. Em sua concepção, recorre-se a uma modelagem modular, que permite futuras melhorias, apenas por troca de módulos. Como estudos de caso para validar a proposta são apresentados cenários de chamadas que utilizam o Serviço VCC, passando pelo CDSF. Por fim, conclui-se que a integração entre os domínios é viável se a proposta deste trabalho for utilizada. Também se demonstra que a separação dos planos de controle dos planos de dados (de usuário) é uma das contribuições fundamentais da arquitetura NGN para o sucesso de suas implementações, como por exemplo o IMS.Além disso, destacam-se as vantagens que o Serviço VCC pode agregar ao IMS, contribuindo para sua adesão em menor prazo pelas operadoras de telecomunicações, dado que esse serviço contribui para a integração de redes, cada vez mais convergentes, agregando mobilidade e continuidade à sua utilização. / This work intends to study and implement the integration between the circuit switching domain and the IP Multimedia Subsystem (IMS) to support vertical handovers that are between different access networks, such as Global System for Mobile communications (GSM) and WiFi. Therefore the specifications are incomplete about this topic in standards from the entities who works with this subject. Then, is presented a new proposal for this integration: a new functional entity to realize this integration: the Call Data Storage Function (CDSF), which interacts with other modules of VCC Service and guarantees that some information shared between modules are not lost, due to conversion of signalling protocols in the interface between domains. Besides that, CDSF helps in the control of allocation of reference address that are used to route calls from one domain to another. Access protocols to CDSF are defined and CDSF methods are exposed. The CDSF design uses a modular approach, which allows future improvements, just changing modules. As case studies to validate this work proposal, call scenarios are presented that uses the VCC Service, using CDSF. Finally, it is concluded that the integration between domains is viable if this work proposal is used. It is presented, as well, that the separation between control plans and data plans is one of the main contributions of NGN architecture to the success of its implementations, like IMS. Furthermore, it is exposed the advantages that VCC Service can aggregate to IMS, contributing for more rapidly adoption by telecommunications operators, considering that this service helps the networks integration, adding convergence, mobility and continuity.

This research is the array processing help wireless communication techniques to increase the signal accuracy. This technique has an important part of prevalent applications. The wireless communication system, radar, and sonar. Beamforming is one of methods in array processing that filters signals based on their capture time at each element in an array of antennas spatially. Numerous studies in adaptive array processing have been proposed in the last several decades, which are divided in two parts. The first one related to non-adaptive beamforming techniques and the next one related to digitally adaptive Beamforming methods. The trade-off between computational complexity and performance make them different. In this thesis, we concentrate on the expansion of array processing algorithms in both non-adaptive and adaptive ones with application of beamforming in 4G mobile antenna and radar systems. The conventional and generalized side-lobe canceller (GSC) structures beamforming algorithms were employed with a phase array antenna that changed the phase of arrivals in array antenna with common phased array structure antennas. An eight-element uniform linear array (ULA), consisting of di-pole antennas, represented as the antenna array. An anechoic chamber measures the operation of beamforming algorithms performance. An extended modified Kaiser weighting function is proposed to make a semi-adaptive structure in phased array beamforming. This technique is extended to low complexity functions like hyperbolic cosine and exponential functions. Furthermore, these algorithms are used in GSC beamforming. The side-lobe levels were so lower than other algorithms in conventional beamforming around -10 dB. On the other hand, a uniform linear arrays for smart antenna purposes designed to utilize in implementing and testing the proposed algorithms. In this thesis, performance of smart antenna with rectangular aperture coupled microstrip linear array which experimental investigations carried out for obtaining X-band operation of rectangular microstrip antenna by using aperture coupled feeding technique. Frequency range set at approximately 8.6 to 10.9 GHz, by incorporating frequency range of the antenna resonates for single wideband with an impedance bandwidth of 23%. The enhancement of impedance bandwidth and gain does not affect the nature of broadside radiation characteristics. This thesis describes the design, operation, and realization of the beamforming such as Sidelobe level (SLL) control and null forming array antenna are examined with the prototype. An antenna radiation pattern beam maximum can be simultaneously placed towards the intended user or Signal of interest (SOl), and, ideally nulls can be positioned towards directions of interfering signals or signals not of interest (SNOIs). Finally, we focused on the adaptive digitally algorithms in compact antenna that faces with mutual coupling. The variable step-size normalized lease mean square (VS-NLMS) algorithm is implemented in beamforming. This algorithm utilizes continuous adaptation. The weights are attuned that the final weight vector to the most satisfied result. The gradient vector can be achieved by iterative beamforming algorithm from the available data. This algorithm is compared with LMS, NLMS, VSS-NLMS algorithms, it is determined that the VSS-NLMS algorithm is better performance to other algorithms. Finally, we introduced novel adaptive IP-NNLMS beamformer. This beamformer reaches to faster convergence and lower error floor than the previous adaptive beamformers even at low SNRs in presence of mutual coupling. The experimental results verified the simulation results that the proposed technique has better performance than other algorithms in various situations. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Este trabalho visa estudar e implementar a integração entre o domínio de comutação de circuitos e o IP Multimedia Subsystem (IMS) para suportar handovers verticais, ou seja, entre redes de acesso distintas, por exemplo, Global System for Mobile communications (GSM) e WiFi, em especial no Serviço Voice Call Continuity (VCC). Entretanto muito pouco é especificado sobre a integração entre os domínios nas normas das diversas entidades de padronização que tratam sobre o assunto. Assim, apresenta-se uma proposta para essa integração, criando-se uma nova entidade funcional para realizá-la, o Call Data Storage Function (CDSF), que interage com os demais módulos do Serviço VCC e garante que algumas informações que devem ser trocadas entre os módulos não sejam perdidas, devido à conversão de protocolos de sinalização na interface entre tais domínios. O CDSF auxilia também no controle da alocação de endereços de referência utilizados no encaminhamento de chamadas de um domínio para o outro. São definidos os protocolos de acesso ao CDSF, bem como os métodos disponíveis. Em sua concepção, recorre-se a uma modelagem modular, que permite futuras melhorias, apenas por troca de módulos. Como estudos de caso para validar a proposta são apresentados cenários de chamadas que utilizam o Serviço VCC, passando pelo CDSF. Por fim, conclui-se que a integração entre os domínios é viável se a proposta deste trabalho for utilizada. Também se demonstra que a separação dos planos de controle dos planos de dados (de usuário) é uma das contribuições fundamentais da arquitetura NGN para o sucesso de suas implementações, como por exemplo o IMS.Além disso, destacam-se as vantagens que o Serviço VCC pode agregar ao IMS, contribuindo para sua adesão em menor prazo pelas operadoras de telecomunicações, dado que esse serviço contribui para a integração de redes, cada vez mais convergentes, agregando mobilidade e continuidade à sua utilização. / This work intends to study and implement the integration between the circuit switching domain and the IP Multimedia Subsystem (IMS) to support vertical handovers that are between different access networks, such as Global System for Mobile communications (GSM) and WiFi. Therefore the specifications are incomplete about this topic in standards from the entities who works with this subject. Then, is presented a new proposal for this integration: a new functional entity to realize this integration: the Call Data Storage Function (CDSF), which interacts with other modules of VCC Service and guarantees that some information shared between modules are not lost, due to conversion of signalling protocols in the interface between domains. Besides that, CDSF helps in the control of allocation of reference address that are used to route calls from one domain to another. Access protocols to CDSF are defined and CDSF methods are exposed. The CDSF design uses a modular approach, which allows future improvements, just changing modules. As case studies to validate this work proposal, call scenarios are presented that uses the VCC Service, using CDSF. Finally, it is concluded that the integration between domains is viable if this work proposal is used. It is presented, as well, that the separation between control plans and data plans is one of the main contributions of NGN architecture to the success of its implementations, like IMS. Furthermore, it is exposed the advantages that VCC Service can aggregate to IMS, contributing for more rapidly adoption by telecommunications operators, considering that this service helps the networks integration, adding convergence, mobility and continuity.

There is evidence that athermal radiofrequency radiation can alter Heat Shock Protein (HSP) expression or protein phosphorylation, or alter MAP kinase signalling. Effects of long-term exposure in brain tissue due to repeated HSP perturbation (eg an inhibition of apoptosis) have been hypothesised (French et al, 2001). This study aimed to investigate the RNA expression profile (12,000 genes) and HSP family protein expression levels after either acute 1-hour or chronic 4-day intermittent exposures to simulated GSM radiation in a human primary fibroblast model. The results found minimal or no effects of GSM. Flasks were exposed to 900 MHz (217 Hz modulation) at 0.18 W/kg SAR within a Transverse Electromagnetic Mode chamber (TEM cell). Cultures rested for 2 hours before exposures. Affymetrix U95A microarray analysis of a single pilot set of experiments showed that about 40 genes were reported as upregulated &gt=2.5 fold in each condition. There was no evidence of altered expression of any MAPK-associated genes. Target genes reported in both conditions (CBFA2T1, ZNF148, ITGA1), and genes altered in one condition (CCS, PLEC1, BIRC5), and marginally altered HSP72 were selected for PCR analysis. No other members of the HSP family were altered. In three replicate experiments assayed by real-time PCR, six genes were either unchanged or showed randomly variable expression. However HSP72 RNA showed possible consistent slight upregulation of 1.37 +/- 0.21 in the chronic condition. Western immunoblots of HSP-60, -70, -72 and -V90 proteins showed no significant changes 5 hours after exposure. In preliminary studies using a serum starvation protocol, ERK-1 phosphorylation was unaltered after 5 or 30 minutes GSM (single experiments). When flasks were transiently cooled, ERK-1 phosphorylation was increased 20 minutes later, indicating a source of artefact in some protocols. An inflammatory challenge experiment with a low-dose of the cytokine IL-1???? found that acute GSM exposure post-challenge inhibited NF????B-mediated GRO???? induction by 1.5 fold (2 experiments). Preconditioning with mild heat induces transient inhibition of both NF????B signalling and apoptosis. Other studies indicate that EMF exposures similarly evoke cytoprotection. It is suggested that GSM evoked cytoprotective signalling in this inflammatory model.

In this thesis a new approach for characterisation of digital mobile radio channels is investigated. The new approach is based on recognition of the fact that while the fading which is characteristic of the mobile radio channel is very rapid, the processes underlying this fading may vary much more slowly. The comparative stability of these underlying processes has not been exploited in system designs to date. Channel models are proposed which take account of the stability of the channel. Estimators for the parameters of the models are proposed, and their performance is analysed theoretically and by simulation and measurement. Bounds are derived for the extent to which the mobile channel can be predicted, and the critical factors which define these bounds are identified. Two main applications arise for these channel models. The first is the possibility of prediction of the overall system performance. This may be used to avoid channel fading (for instance by change of frequency), or compensate for it (by change of the signal rate or by power control). The second application is in channel equalisation. An equaliser based on a model which has parameters varying only very slowly can offer improved performance especially in the case of channels which appear to be varying so rapidly that the convergence rate of an equaliser based on the conventional model is not adequate. The first of these applications is explored, and a relationship is derived between the channel impulse response and the performance of a broadband system.

<p>In future mobile networks service quality might be poor. A new measure is needed to be able to assess services in terms of their effectiveness and usefulness despite their lacking visual appeal. Cognitive Quality of Service is a way to measure the effectiveness in use of a networked service.</p><p>This thesis introduces Cognitive Quality of Service and puts it in relation to other ways to measure quality in streaming media. Through four studies the concept is used to improve multicast performance in a WLAN, to assess the effectiveness of simple animations compared to video, to build an application that fuses video and animations and to assess the differences between various levels of streaming video quality.</p><p>Guidelines on how to measure Cognitive Quality of Service are introduced based on a review of available literature and later analyzed in light of the studies presented in the thesis. It turns out that the guidelines are sound and should be used as a basis for assessing Cognitive Quality of Service.</p><p>Finally, the usefullness of Cognitive Quality of Service is analyzed. It turns out that it is especially useful when comparing different media, e.g. animations and video. In the video only case even bit-rate might be a useful predictor of subjective quality.</p> / <p>I framtiden kommer användare att titta på videosekvenser i trådlösa apparater, exempelvis mobiltelefoner. På grund av tekniska faktorer som störningar och på grund av kostnaden för det kommer den kvalitet som de erhåller inte att vara jämförbar med till exempel den kvalitet som kan erhållas när man tittar på tv. Trots det kan man anta att sådan video kan vara intressant och upplysande.</p><p>I avhandlingen introduceras och används begreppet Cognitive Quality of Service (CQoS) - kognitiv servicekvalitet. Begreppet definieras av att den överföring som ger den bästa förståelsen och känslomässiga reaktionen också har bäst CQoS. För att mäta CQoS bör man följa vissa riktlinjer, särskilt som det är svårt att mäta förståelse i samband med att man tittar på video.</p><p>Författaren har tillsammans med medarbetare tittat på hur man kan förbättra förhållandena för själva radioöverföringen (studie I). Genom en algoritm som ger multicast-paket bättre skydd mot kollisioner visas att man kan erhålla förbättrad överföringskapacitet för strömmande video i ett trådlöst nätverk.</p><p>Animeringar är ett alternativ till video som kräver låg bandbredd. I ett experiment har man undersökt hur väl animeringar står sig mot video av olika kvalitet när det gäller att upplysa användaren och ge en bra upplevelse (studie II). Det visade sig att animeringar var bättre för förståelsen medan video gav en bättre känslomässig upplevelse. Vanare åskådare föredrog videon medan ovanare åskådare föredrog animeringarna.</p><p>Frågan som ställdes var då hur man kunde kombinera respektive mediums fördelar för att få en så bra blandning som möjligt. Å ena sidan var animeringarna billiga och lätta att förstå medan videon var dyrare och mer intressant. Ett prototypgränssnitt skapades. Där kunde användaren själv välja vilken mix mellan de två alternativen som skulle visas (studie III). Det visade sig att försökspanelen föredrog video och dessutom ville ha mer information om spelare och match.</p><p>Trots animationernas förträfflighet kan man anta att det ändå är video som kommer att dominera i framtiden. En sista studie genomfördes för att se om man kunde finna liknande resultat vid olika kvalitetsgrader i video som man tidigare hade funnit mellan video och animeringar (studie IV). Det visade sig att så länge man höll sig till ett format var sambanden enklare. Mer var helt enkelt bättre upp till en viss gräns där det inte tillförde mer att öka överföringsresurserna för videon.</p><p>Sammanfattningsvis visar studierna att CQoS kan ge värdefull designkunskap. I synnerhet när man jämför olika presentationsformer som i det här fallet animeringar och video. Nästa steg blir att gå vidare med att applicera CQoS i tvåvägskommunikation, särskilt i Conversational Multimedia (CMM)– ungefär bildtelefoni – där det är särskilt goda möjligheter att sammanställa en för omständigheterna anpassad mediamix.</p>