Posicionamento cooperativo para redes sem fios heterogéneas

Doutoramento em Engenharia ElectrotécnicaFuture emerging market trends head towards positioning based services placing a new perspective on the way we obtain and exploit positioning information. On one hand, innovations in information technology and wireless communication systems enabled the development of numerous location based applications such as vehicle navigation and tracking, sensor networks applications, home automation, asset management, security and context aware location services. On the other hand, wireless networks themselves may bene t from localization information to improve the performances of di erent network layers. Location based routing, synchronization, interference cancellation are prime examples of applications where location information can be useful. Typical positioning solutions rely on measurements and exploitation of distance dependent signal metrics, such as the received signal strength, time of arrival or angle of arrival. They are cheaper and easier to implement than the dedicated positioning systems based on ngerprinting, but at the cost of accuracy. Therefore intelligent localization algorithms and signal processing techniques have to be applied to mitigate the lack of accuracy in distance estimates. Cooperation between nodes is used in cases where conventional positioning techniques do not perform well due to lack of existing infrastructure, or obstructed indoor environment. The objective is to concentrate on hybrid architecture where some nodes have points of attachment to an infrastructure, and simultaneously are interconnected via short-range ad hoc links. The availability of more capable handsets enables more innovative scenarios that take advantage of multiple radio access networks as well as peer-to-peer links for positioning. Link selection is used to optimize the tradeo between the power consumption of participating nodes and the quality of target localization. The Geometric Dilution of Precision and the Cramer-Rao Lower Bound can be used as criteria for choosing the appropriate set of anchor nodes and corresponding measurements before attempting location estimation itself. This work analyzes the existing solutions for node selection in order to improve localization performance, and proposes a novel method based on utility functions. The proposed method is then extended to mobile and heterogeneous environments. Simulations have been carried out, as well as evaluation with real measurement data. In addition, some speci c cases have been considered, such as localization in ill-conditioned scenarios and the use of negative information. The proposed approaches have shown to enhance estimation accuracy, whilst signi cantly reducing complexity, power consumption and signalling overhead.As tendências nos mercados emergentes caminham na direção dos serviços baseados em posicionamento, criando uma nova perspectiva na forma como podemos obter e utilizar informação de posicionamento. Por um lado, as inovações em tecnologias da informação e sistemas de comunicação sem fios permitiram o desenvolvimento de inúmeras aplicações baseadas em localização, tais como a navegação e monitorização de veículo, aplicações de redes de sensores, domótica, gestão de ativos, segurança e serviços de localização sensíveis ao contexto. Por outro lado, as próprias redes sem fios podem beneficiar da informação de localização dos utilizadores de forma a melhorarem as performances de diferentes camadas de rede. Routing baseado em localização, sincronização e cancelamento de interferência são os exemplos mais representativos de áreas onde a informação de localização pode ser útil. Soluções de localização típicas dependem de medições e de aproveitamento de métricas de sinal dependentes da distância, tais como a potência do sinal recebido, o tempo ou ângulo de chegada. São mais baratos e fáceis de implementar do que sistemas de localização dedicados com base em fingerprinting, com a desvantagem da perda de precisão. Consequentemente, algoritmos inteligentes de localização e técnicas de processamento de sinal têm de ser aplicados para compensar a falta de precisão das estimativas de distância. A cooperação entre nodos é usada nos casos em que as técnicas convencionais de posicionamento não têm um bom desempenho devido à inexistência de infraestrutura adequada, ou a um ambiente interior com obstruções. O objetivo é ter uma arquitetura híbrida, onde alguns nós têm pontos de ligação a uma infraestrutura e simultaneamente estão interligados através ligações ad-hoc de curto alcance. A disponibilidade de equipamentos mais capazes permite cenários mais inovadores que tiram proveito de múltiplas redes de acesso de rádio, bem como ligações peer-to-peer, para o posicionamento. A seleção de ligações é usada para otimizar o equilíbrio entre o consumo de energia dos nós participantes e da qualidade da localização do alvo. A diluição geométrica de precisão e a Cramér Rao Lower Bound podem ser utilizadas como critrio para a escolha do conjunto adequado de nodos de ancoragem e as medições correspondentes antes de realizar a tarefa de estimativa de localizaçãoo. Este trabalho analisa as soluções existentes para a seleção de nós, a fim de melhorar o desempenho de localização e propõe um novo método baseado em funções de utilidade. O método proposto é então estendido para ambientes móveis e heterogéneos. Foram realizadas simulações bem como avaliação de dados de medições reais. Além disso, alguns casos específicos foram considerados, tais como a localização em cenários mal-acondicionados e uso de informação negativa. As abordagens propostas revelaram uma melhoria na precisão da estimação, ao mesmo tempo que reduziram significativamente a complexidade do cálculo, o consumo de energia e o overhead do sinal

Cooperative Game Theory and Its Application in Localization Algorithms

Complementary medicin

Chapter Cooperative Game Theory and Its Application in Localization Algorithms

Complementary medicin

Use of negative information in positioning and tracking algorithms

To avoid additional hardware deployment, indoor localization systems have to be designed in such a way that they rely on existing infrastructure only. Besides the processing of measurements between nodes, localization procedure can include the information of all available environment information. In order to enhance the performance of Wi-Fi based localization systems, the innovative solution presented in this paper considers also the negative information. An indoor tracking method inspired by Kalman filtering is also proposed

TownshipNet: A Localized Hybrid TVWS-WiFi and Cloud Services Network

This paper describes a network architecture to provide low cost last mile access and cloud services for local content sharing in a poorly resourced township environment. We describe how ICT solutions are developed in close partnership with the local community who will benefit from the interventions. We analyze the data usage patterns of mobile users in the township to provide us with a real understanding of the needs of the community. This data usage analysis is used to inform the design of the network and of the localized cloudlet services. The network consists of hybrid TV White Space and WiFi backhaul and WiFi public access points

A Correlation between RSSI and Height in UHF Band and Comparison of Geolocation Spectrum Database View of TVWS with Ground Truth.

An investigation into the Received Signal Strength Indica- tor (RSSI) dependency on receiver antenna height in UHF band is con- ducted. The results show a high correlation between RSSI and height on channels with high signal strength. There is approximately 2.5 dBm RSSI gain per 1 m increase in height above ground up to 8.5 m. From 8.5 m to 12 m, there is no consistent observable increase in RSSI. Further- more, the geolocation spectrum databases (GLSD) view of white space in the television band is compared with the ground truth. Results show signal presence on some of the channels indicated free by the spectrum database. These findings imply that an increase in transmission range of UHF links can be achieved by increasing receiver height. White space devices using A GLSD should additionally require spectrum scanning to determine clear channels

Performance analysis of a collaborative DSA-based network with malicious nodes

This work analyses the performance of a Dynamic Spectrum Access (DSA) network with secondary nodes to provide Internet services, and studies the impact of malicious nodes and cooperative secondary nodes on the performance of the network and spectrum utilization. The work mathematically models the throughput, latency, and spectrum utilization with varying numbers of malicious nodes, secondary nodes, miss probabilities, and false alarm probabilities, and studies their effect on the performance of the network. The results point to rapid spectrum starvation as the number of malicious nodes increase, as well as the negative impact of too many secondary nodes crowding out available spectrum with resultant degradation of throughput and latenc

INethi Community Network: A First Look at Local and Internet Traffic Usage

This poster presents iNethi, a community wireless network deployed in a peri-urban township of Cape Town, South Africa. Initial usage clearly indicates a demand for Internet-based external services and, to a lesser extent, local services. We focus on the initial months of our deployment, and interaction with locally installed INethi services, as well as the impact of access to the Internet. We present data from our traffic logs, captured during a period of six months. We observed that a large proportion of data is being consumed by software or antivirus updates. The data collected and trends observed will allow iNethi operators to make necessary adjustment to the networks

Head to Head Battle of TV White Space and WiFi for Connecting Developing Regions

TV White Space networks are gaining momentum worldwide as an important addition to the suite of wireless protocols available for connecting developing regions. However, there has been no thorough investigation of scenarios where TV White Space performs better or worse than alternative low-cost wire- less technology such as WiFi. This paper analyzes the performance of 5 GHz WiFi links and TV White space links using down-converted WiFi, typically used as wireless backhaul for poorly connected regions, in different scenarios including line-of-sight links and links obstructed by trees and structures. The experiments make use of 802.11a/b/g WiFi and TV White Space equipment that down- converts standard 802.11 a/b/g WiFi from the 2.4 GHz band into the UHF band. The paper finds that 5 GHz links outperformed TVWS where clear line-of-sight is available and point-to-point links are required. TVWS however is a clear choice where there are obstructions and where wider coverage is needed. Some interesting observations on the negative effect of TV transmissions in adjacent channels a few channel-hops away from the channel being used for TVWS are also provided

Localize-It: Co-designing a Community-Owned Platform

One of the most difficult, yet undocumented, aspects of information and communications technologies and development (ICTD) projects is that of establishing partnerships around which researchers’ interventions will develop, be tested and grow. Constraints on timing and funding usually lead to short-term projects, in which benefits are biased towards researchers rather than the partner community. In order to avoid empty and unethical promises and to increase the potential benefit for the community, we consider the process of developing participatory partnerships in ICTD projects. The objective is to make the project community owned, allowing the participants to develop what they value as important. Using the case of a township-based wireless community content sharing network, we describe the potential and some of the challenges with this approach. The paper highlights building blocks, such as ethical behaviour and trust, to avoid recreating the dichotomy between research and practice, and building a constructive collaboration