In the past decade, there has been great motivation to improve the efficiency of power amplifiers (PAs) in handset transmitter systems in order to address critical issues such as poor battery life and excessive heat. Currently, the focus lies on high data rate applications such as wideband code division multiple access (WCDMA) and long term evolution (LTE) standards due to the stringent efficiency and linearity requirements on the PA. This thesis describes a simulation-based study of techniques for enhancing the efficiency of a CMOS power amplifier for WCDMA and LTE applications. The primary goal is to study the concepts of envelope and average power tracking in simulation and to demonstrate the effectiveness of these supply modulation techniques on a CMOS PA design. The P1dB and IMD performance of a Class A/AB CMOS PA has been optimized to operate with high peak-to-average modulation with WCDMA and LTE signals. Behavioral models of envelope and average power tracking are implemented using proposed algorithms, and a system-level analysis is performed. Envelope tracking is seen to offer a peak PAE improvement of 15% for WCDMA, versus a fixed voltage supply, while average power tracking renders a maximum efficiency gain of 9.8%. Better than -33dBc adjacent channel leakage-power ratio (ACLR) at 5MHz offset and EVM below 4% are observed for both supply tracking techniques. For LTE, envelope and average power tracking contribute to a peak PAE enhancement of 15.3% and 7%, respectively. LTE ACLR begins failing the -30dBc specification above 22.5dBm output power during envelope tracking operation in the PA implementation described here. / text

After the performance improvement rate in single-core processors decreased in 2000s, most CPU manufacturers have steered towards parallel computing. Parallel computing has been in the spotlight for a while now. Several hardware and software innovations are being examined and developed, in order to improve the efficiency of parallel computing. Signal processing is an important application area of parallel computing, and this makes parallel computing interesting for Ericsson AB, a company that among other business areas, is mainly focusing on communication technologies. The Ericsson baseband research team at Lindholmen, has been developing a small, experimental basic operating system (BOS) for research purposes within the area of parallel computing. One major overhead in parallel applications, which increases the latency in applications, is the communication overhead between the cores. It had been observed that in some signal processing applications, it is common for some tasks of the parallel application to have a large data size but a small code size. The question was risen then, could it be beneficial to move code instead of data in such cases, to reduce the communication overhead. In this thesis work the gain and practical difficulties of moving code are investigated through implementation. A method has been successfully developed and integrated into BOS to move the code between the cores on a multi-core architecture. While it can be a very specific class of applications in which it is useful to move code, it is shown that it is possible to move the code between the cores with zero extra overhead.

Telecommunication systems are under constant development. Currently 3GPP is working on an evolution of the 3G-standard, under the name 3G Long Term Evolution (LTE). Some of the goals are higher throughput and higher peak bit rates. A crucial part to achieve the higher performance is channel dependent scheduling (CDS). CDS is to assign users when they have favorable channel conditions. Channel dependent scheduling demands accurate and timely channel quality reports. These channel quality indication (CQI) reports can possibly take up a large part of the allocated uplink. This thesis report focuses on the potential gains from channel dependent scheduling in contrast to the loss in uplink to reporting overhead. System simulations show that the gain from channel dependent scheduling is substantial but highly cell layout dependent. The gain with frequency and time CDS, compered to CDS in time domain only, is also large, around 20\%. With a full uplink it can still be a considerable gain in downlink performance if a large overhead is used for channel quality reports. This gives a loss in uplink performance, and if the uplink gets to limited it will severely affect both uplink and downlink performance negatively. How to schedule and transmit CQI-reports is also under consideration. A suggested technique is to transmit the CQI reports together with uplink data. With a web traffic model simulations show that a high uplink load is required to get the reports often enough. The overhead also gets unnecessary large, if the report-size only depends on the allocated capacity.

Long Term Evolution (LTE) constitutes a significant milestone in the evolution of 3G systems towards fourth generation (4G) technologies. The performance targets promised by LTE makes it an ideal solution to accommodate the ever increasing demand for wireless broadband. LTE's promised performance targets were made possible due to improvements such as a simplified system access architecture and a fully IP-based platform. LTE has also great enhancements in its enabling radio technologies by introducing Orthogonal Frequency Division Multiplexing (OFDM) and advanced antenna technologies. In addition, LTE capabilities are further improved with enhanced Quality of Service (QoS) support for multiple data services, such as voice and other multimedia applications. LTE packet scheduling plays an essential role as part of LTE's Radio Resource Management (RRM) to enhance the system's data rate and to support the diverse QoS requirements of mobile services. LTE packet scheduler should intelligently allocate radio resources to mobile User Equipments (UEs) such that the LTE network adheres to its performance requirements. In our work, we perform a performance evaluation of multiple LTE scheduling algorithms proposed for LTE uplink transmission. The evaluation takes place in single and mixed traffic scenarios to exploit the strengths and weaknesses of proposed algorithms. Simulation results illustrated the importance of a scheduler's awareness of uplink channel conditions and QoS requirements in the presence of single and multiple traffic scenarios. Accordingly, we provide recommendations for future scheduling algorithm proposals, and ways to enhance the existing schedulers. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2011-05-07 12:43:54.983

Nowadays, with a worldwide market penetration of over 50% in the mobile telecommunications sector, there is also an unrelenting demand from the subscribers for ever increasing transmission rates and availability of broadband-like experience on the handset. Due to this, research in next-generation networks is rife. Such systems are expected to achieve peak data rates of up to 1 Gbps through the use of innovative technologies such as multiple-input and multipleoutput (MIMO) and orthogonal frequency division multiple access (OFDMA). Two more ways of boosting capacity have also been identified: shrinking cell sizes and greater reuse of resources in the same area. This forms the foundation of the research presented in this thesis. For operators, the costs involved with planning and deploying additional network infrastructure to provide a dense coverage of small, high capacity cells cannot be justified. Femto-cells, however, promise to fulfil this function. These are user-deployed mini base stations (BSs), known as home evolved NodeBs (HeNBs), which are envisaged to be commonplace in homes and offices in the coming years. Since they drastically reduce communication distances to user equipments (UEs) and reuse the resources already utilised in the macro-cell, they help boost the system capacity significantly. However, there are issues to be addressed with the deployment of femto-cells, such as increased interference to the system and methods of access. These and other problems are discussed and analysed in this thesis. One of the first steps towards femtocell research has been the study of the time division duplex (TDD) underlay concept, whereby an indoor UE acts as a relay between the evolved NodeB (eNB) and other indoor UEs. In order to gain a deeper understanding of how and under what conditions such a self-organising network can be deployed, a mathematical analysis of the distribution of path losses in a network of uniformly distributed nodes has been performed. In connection with this, research has also been done in the identification of well connected nodes in such networks. Next, extensive simulations on traditional cellular networks with embedded femto-cells have been carried out in order to demonstrate the benefits of femto-cell deployment. This research has shown that femto-cells can cause severe downlink (DL) interference to badly placed macro UEs. Finally, a novel interference avoiding technique that addresses this problem is investigated.

To allow access to the network at all times a base station has to continuously stay active. While being active, a base station does not usually transmit data constantly. Typically, the base stations either send out lots of data or barely anything at all, yet, the network is actively drawing power the whole time. Succeeding in lowering the power consumed when the data rate is often so low would therefore lead to great benefits, both economically and environmentally, as well as new prospects of innovation in engineering. The process of how to dynamically change from a capacity optimized mode to an energy optimized mode as well as when to do this change is studied in this thesis for LTE. By using methods such as antenna muting and psi-omni coverage, the power consumption can decrease. These solutions however also decreases performance, and has to be activated with great care in mind not to cause any major impact on user performance. The dynamic configuration is dependent on the load of the system, changing to an energy efficient mode when traffic is low and to a capacity optimized mode when the network needs to supply high data rates. Simulations show that most energy savings can be found in rural and urban environments. Dynamic antenna muting achieved, summarizing macro environments, 24.9% energy savings with 95.27% downlink data rates compared to the reference case of using sector mode continuously i.e MIMO. In the same environments, dynamic psi-omni coverage together with antenna muting achieved energy savings of 43.8% with 89.3% downlink data rates compared to typical sector mode. Traffic rates are based on future demands in Europe by 2015, assuming that 20% of the subscribers are downloading 900 MB/h and the other 80% subscribers, at 112.5 MB/h.

Maps of chosen areas in Chicago, San José, London and Shibuya, areimported from Open Street Map into matlab in order to run LTE networksimulations for various scenarios. Firstly, two path loss models arecompared, the empirically based WINNER model and a set of sitespecificmodel. Secondly, low load network simulations are runseparately at two different carrier frequencies, 700MHz and 2GHz, forcity specific base station deployments. Simulation results show thatuser performance is quite unique for each city and that deploymentstrategies and city environments are strongly influencing path gain,SINR and throughput. In general, user performance in UL issignificantly worse at 2GHz than at 700MHz, whereas DL performance isnot as affected by the change in carrier frequency.

Ingeniera Civil Eléctrica / En Chile y el mundo, la demanda de servicios móviles de alta velocidad está creciendo a una tasa exponencial desde el lanzamiento de las redes móviles de segunda generación (2G). Actualmente, los operadores de redes móviles se ven enfrentados a un aumento en el volumen de tráfico de datos demandado, así como al alza de las exigencias de sus abonados, los que esperan siempre una mejora sustancial entre una tecnología y otra, en cuanto a calidad y velocidad de transmisión de datos. Con la finalidad de mejorar la calidad y velocidad de transmisión de datos de la red Long Term Evolution (LTE) de Entel, se construye un modelo que evalúa su capacidad de acceso. Para ello, se seleccionan tres clusters de celdas dentro de la Región Metropolitana que tienen distintas características de funcionamiento, composición y categorización. Utilizando la proyección de la demanda desarrollada por la empresa, se estima la demanda proyectada para cada uno de los clusters y para cada uno de sus perfiles de usuario que los componen. Gracias al aporte de datos históricos y estadísticas por parte de Entel, se logra caracterizar cada celda, llegando a una expresión que define el comportamiento de todos los tipos de celdas dentro de cada cluster, en este trabajo se consideran tres tipos de celda por cluster cada uno asociado a una banda de frecuencias. Con la definición de estas curvas características se puede obtener la capacidad de cada celda indicando los requerimientos de calidad que determine el usuario del modelo, así se llega a hacer una evaluación de capacidad comparando la demanda y la oferta proyectadas en el tiempo. Como resultado de la evaluación de capacidad, el modelo permite predecir el momento en que la red no dé abasto a la capacidad demandada. Además, dentro de la herramienta se desarrolló un simulador de expansión, que con diferentes modalidades, logra indicar cuántas celdas y sitios deben ser instalados de acuerdo a los requerimientos del operador. Se realizaron distintos análisis de sensibilidad de los que se puede concluir que la herramienta construida funciona de una manera adecuada con respecto a los resultados esperados por la empresa. Los casos de estudio fueron interrogantes reales que suceden en Entel actualmente, por lo que además se puede afirmar que el modelo desarrollado en este trabajo de título es aplicable y utilizable por operadores de una red real con la necesidad de una evaluación de capacidad. El modelo de capacidad de acceso de la red LTE fue desarrollado en MS Excel, elegido por su simplicidad y facilidad en la ejecución. Programa que permite vincular los datos obtenidos de los servidores de Entel, lo que admite que esta herramienta se actualice constantemente y que el resto de los clusters de la red nacional sean ingresados de forma amigable , así expandir la evaluación a todo el país, contribuyendo a la mejora en la calidad de los servicios de la red completa. / Este trabajo ha sido parcialmente financiado por Entel S. A.

ARAGÃO, David Bôto Paz. Propostas para controle de congestionamento em rede LTE ocasionado pela comunicação máquina-a-máquina. 2015. 83 f. Dissertação (Mestrado em Ciências da Computação)-Universidade Federal do Ceará, Fortaleza, 2015. / Submitted by Jairo Viana (jairo@ufc.br) on 2016-12-21T18:38:15Z No. of bitstreams: 1 2015_dis_dbparagao.pdf: 3605749 bytes, checksum: 9cc000dd2773ba3d5f2835984902f89a (MD5) / Approved for entry into archive by Jairo Viana (jairo@ufc.br) on 2016-12-21T18:39:32Z (GMT) No. of bitstreams: 1 2015_dis_dbparagao.pdf: 3605749 bytes, checksum: 9cc000dd2773ba3d5f2835984902f89a (MD5) / Made available in DSpace on 2016-12-21T18:39:32Z (GMT). No. of bitstreams: 1 2015_dis_dbparagao.pdf: 3605749 bytes, checksum: 9cc000dd2773ba3d5f2835984902f89a (MD5) Previous issue date: 2015 / Machine-to-machine (M2M) is a communication model that will play an important role in vision of the Internet of Things (IoT). The Long-term Evolution (LTE) is expected to become a potential access networks for the M2M communication. A problem that arises from this scenario is the congestion caused by the huge number of M2M devices trying to access the network. Many solutions can be found in the literature that addresses this problem. However, only few mechanisms define priority among the different type of devices or present a dynamic approach to dynamically allocate resources of the random access channel. In this paper, we propose five mechanisms that aim to reduce the congestion caused by LTE network in the context of M2M devices. The first mechanism is centered in the devices and aim to control the access device to the network based in the congestion level presented by the network. The other four mechanisms model the scarcity of the time and preamble resources as a bankruptcy problem. For each resource, two approaches are proposed. The solutions presented to the bankruptcy problem follow from two an axiomatic approach and a cooperative game strategy. The impact over the H2H devices, the energy efficiency, and the prioritization among the different types of M2M devices are some of the main aspects analyzed by the proposed mechanisms. The result obtained through simulation show that the proposed mechanisms present advantages in one or more of the aspects analyzed. All approaches were simulated in the network simulator NS-3. / O modelo de comunicação máquina-a-máquina (M2M) desempenhará um papel importante na visão da Internet das Coisas (IoT - Internet of Things). As redes Long-term Evolution (LTE) apresentam-se como potenciais redes de acesso para o M2M. Um dos problemas que emergem dessa integração é o congestionamento gerado pelo excesso de dispositivos M2M solicitando acesso a essas redes. Muitas são as soluções já apresentadas para este problema. Contudo, aspectos como priorização inter e intraclasses entre os dispositivos e estratégias para alocação dinâmica de recursos ainda são pouco explorados. Neste trabalho são propostos cinco mecanismos para controlar o congestionamento ocasionado pelos dispositivos M2M no contexto das redes LTE. O primeiro mecanismo proposto utiliza uma abordagem centrada nos dispositivos para controlar o uso dos recursos do canal de acesso aleatório. Os outros quatro mecanismos modelam a escassez dos recursos de tempo e preâmbulos para atender a demanda dos dispositivos como um problema de falência. Para cada tipo de recurso, tempo e preâmbulo, duas propostas são apresentadas. O problema da falência é abordado a partir de uma solução axiomática e usando uma estratégia utilizando jogos cooperativos. O impacto sobre os dispositivos H2H, a eficiência energética e a priorização entre as classes de dispositivos M2M são alguns dos principais aspectos analisados pelos mecanismos propostos. Com base nos resultados obtidos através de simulação, os mecanismos propostos apresentam vantagens em relação a um ou mais dos aspectos analisados. Todos os mecanismos foram simulados no simulador de rede NS-3.

A grande popularidade dos dispositivos móveis que provêm acesso ubíquo à Internet de banda larga, através de redes de rádio, e o volume de tráfego gerado por estes dispositivos estão aumentando a cada ano. Além disso, vem ampliando consideravelmente a frequência com que usuários de dispositivos móveis estão usando serviços baseados na Web. Alguns destes usuários podem estar acessando serviços que precisam de transmissão contínua como, por exemplo, vídeos interativos, outros podem estar apenas lendo e-mails, o que não exige um fluxo contínuo de dados. Mais do que isso, usuários com altos níveis de sinal podem atingir melhores taxas de transferência do que os com níveis menores. Portanto, encontrar a melhor relação entre os usuários que estão acessando serviços sensíveis ao atraso e aqueles que maximizam a taxa de transferência, e ainda ser justo na transmissão, é um relevante desafio para o escalonamento dos recursos de uma rede sem fio. Embora as pesquisas de escalonamento de recursos em redes sem fio tenham evoluído neste sentido, o recente aumento do volume de tráfego mencionado pode levar a uma sobrecarga no sistema, comprometendo o escalonamento. A fim de enfrentar estes desafios, o Orthogonal Frequency Division Multiple Access (OFDMA), tecnologia fundamental para o acesso múltiplo em redes de quarta geração, tem sido considerado também para ser utilizado na próxima geração de rádios móveis. Para implementar um serviço efetivo aos usuários, requisitos, tais como, altas taxas de transferência, tolerância baixa ao atraso, minimização da perda de pacotes e maximização da justiça no escalonamento, devem somar-se à característica, de alta densidade de usuários, que surgiu após o advento da popularização dos dispositivos móveis. Portanto, novas estratégias de escalonamento devem ser idealizadas. Nesta dissertação, deu-se um passo além na proposição de um escalonador para as redes móveis de próxima geração, que busca melhorar a relação entre taxa de transferência e atraso, consequentemente, levando a maiores índices de justiça no escalonamento resultante. O escalonador foi especialmente desenvolvido para lidar com altas densidades de usuários, inerentes às redes modernas, e as redes LTE foram utilizadas como caso de estudo. Desta forma, um novo escalonador ótimo que considera provisão dos requisitos acima mencionados, é modelado. Além disso, uma nova heurística parametrizável, baseada na qualidade do canal do usuário, no atraso permitido por cada serviço e na justiça do escalonamento é proposta, a fim de lidar com cenários sobrecarregados. Resultados demonstram que a abordagem de escalonamento proposta leva a uma taxa de transferência apenas 7,5% menor que os valores ótimos, com 25% a menos de perda de pacotes em cenários sobrecarregados. O modelo também garante que o escalonamento resultante seja pelo menos 0,91 na escala do índice de justiça de Jain. Finalmente, os resultados mostram uma melhor relação entre a eficiência espectral e as métricas de QoS. / The huge popularity of mobile devices that provides a ubiquitous Internet broadband access via radio networks and the volume of traffic generated by these devices in the base stations are increasing every year. Furthermore, the frequency which, mobile users are using web-based services, is increasing, requiring high transfer rates such as transmission of interactive videos. These factors have become the main challenges for the scheduling of radio resources. In order to meet these challenges, the Orthogonal Frequency Division Multiple Access (OFDMA), a key technology for multiple access in fourth generation networks, has also been considered for use in next-generation mobile radios. To implement an effective service to users, requirements such as high transfer rates, lower delay tolerance, minimum packet loss and maximum scheduling fairness, should be added to the requirements that emerged after the advent of the popularity of mobile devices. Therefore, new scheduling strategies should be projected. Despite efforts to solve the downlink (DL) scheduling problem on wireless networks, we are not aware of previous attempts that have addressed the above requirements in a single strategy. In this thesis, we took a step further in this direction and still considering the high densities in small cells inherent in modern networks. In additional, we address the radio DL resource scheduling problem for multiple users using LTE networks as a case study. A new optimal scheduler is modeled regarding Quality of Service (QoS) provisioning. In addition, a parameterized heuristic based on user channel quality and service delay is proposed to reach scheduling solutions for overbooked scenarios. Results demonstrate that the proposed scheduling approaches led to a throughput of 7.5% lower than the optimal ones and 25% lower packet losses in overloaded scenarios. Our model also ensures that the resultant scheduling is at least as fair as 0.91 in Jain fairness index. Additionally, the obtained results show a reasonable trade-off between spectral efficiency and QoS metrics.