Aufbau einer LBS Infrastruktur im WLAN

[pt] Recentemente, tem sido observado um crescimento explosivo na utilização de redes de acesso local sem fio (Wireless Local Area Networks - WLANs), utilizando equipamentos de nível de radiação restrito operando em bandas independentes de outorga de uso de rádio freqüência, tanto para uso corporativo como doméstico e para prover acesso pago em ambientes públicos como aeroportos, hotéis, centros de convenções, campi universitários e mesmo restaurantes e cafés. Se estas redes serão complementares ou competidoras das redes celulares de terceira e quarta gerações é ainda uma questão polêmica e aberta. Os objetivos deste trabalho são o desenvolvimento um modelo de propagação de sinais na faixa de freqüência de 2,4 GHz em ambientes fechados (indoor), para a previsão de cobertura de WLANs, e prover ao projetista de redes wireless uma metodologia um bom dimensionamento da rede. São apresentados os principais modelos semi-empíricos já existentes na literatura técnica e, a partir de medidas realizadas em diferentes ambientes, é proposto um ajuste de parâmetros de um modelo de propagação indoor bastante completo. As medidas realizadas incluem as perdas de penetração em paredes de diferentes materiais, o efeito de difração em quinas de paredes, efeito de movimentação de pessoas no ambiente, além do coeficiente de perda de propagação com a distância. Os modelos desenvolvidos foram implementados numa ferramenta de software para o planejamento de cobertura de redes wireless indoor que permite realizar o projeto a partir da planta baixa do ambiente disponibilizada em arquivos de imagem. / [en] Recently, an explosive growth in the use of Wireless Local Area Networks - WLANs, using restricted radiation levels and operating in license exempted frequency bands, has been observed, not only for corporative domestic use but also to provide paid internet access in public environments such as airports, hotels, convention centers, university campus and even restaurants and coffee shops. The question if these networks will be complementary or will compete with third and forth generation of cellular networks, is still a controversial and opened. The objectives of this work are the development a model for propagation in closed environments (indoor) at the 2,4 GHz frequency band for the coverage planning of WLANs and to provide the wireless network designer with a complete project methodology . The most important semi-empirical models available in the technical literature are presented and, based on measurements carried out in different environments, a fairly complete model with fitted parameters is proposed. The measurements include losses of penetration in walls of different materials, the effect of diffraction at wall edges, the effect of movement of people in the environment and the rate of loss with distance coefficient. The developed models have been implemented in a software tool for coverage planning of wireless indoor networks that allows the development of the project starting from blue prints of the environment available as digital image files.

Indoor positioning is a rapidly growing research area, enabling new innovative location-aware applications and user-oriented services. Location Fingerprinting (LF) is the positioning technique of coupling a physical location with observed radio signal measurements. In the terms of indoor LF using Wireless Local Area Network (WLAN) it refers to the use of network measurements from the WLAN Access Points (APs) to tag known locations. A data set is created containing reference fingerprints for the area of interest and is known as a radio map. A radio map can later be used to find a user's location in the area of interest. WLAN infrastructures are vulnerable to many kinds of faults and malicious attacks, including, an attacker jamming the signal from an AP, or an AP becoming unavailable during positioning due to power outage. These faults can be collectively characterized as an AP-failure. In LF positioning systems, AP-failure faults can significantly degrade the performance of a LF system due to the difference between the current fingerprints and radio map created with all APs being available. It is desirable to detect such faulty APs, in order to take actions towards fault-mitigation and restoration, in case of a malicious attack. In this work, we have developed a fault detection algorithm that uses inertial sensors (i.e., accelerometer, magnetometer) available in smartphones to detect AP-failure faults in LF systems. Inertial Measurement Unit (IMU) has become an integral part of all high-end smartphones. IMU can be used to infer location information on the smartphone. The main idea is to have two parallel position streams, the LF positioning and the IMU positioning, and to compare the mean positioning error between the two. Since IMU positioning is fairly accurate once provided with starting coordinates, we use it to detect abnormal behaviour in LF positioning system, such as highly erroneous estimates signifying an AP-failure fault present in the system. The performance of the proposed detection algorithm is evaluated with several real-life AP-related faults. The proposed algorithm exhibits low probability of false alarms in the detection of faulty APs. The conclusion is that using IMU based positioning is an effective and robust solution in terms of fault detection in LF systems.

The technology of Wireless Local Area Network(WLAN) is getting mature.Even the INTEL,Co developed the WLAN chip (Centrino) that can be embedded in laptops or PDAs. So that , the chip could upgrade the device of the efficiency of WLAN and increase the number of the users. Recently, the WLAN has been a very hot issue, but most of the studies that have been done are concerned with the technique perspective¡Bproperty perspective and strategy; very little research has been conducted to investigate the consumer perspective. Therefore, for saving the resources and enhancing the quality of the WLAN¡¦s research, the purpose of this study is to explore the network users¡¦ acceptance after implement the system based on ¡§the Unified Theory of Acceptance and Use of Technology¡¨(UTAUT). The results of this research indicate that (1) there are 4 key components extracted: ¡uPerformance Expectancy¡v¡B¡uEffort Expectancy¡v¡B¡uSocial Influence¡v and¡uFacilitating Condition¡v;(2) ¡uPerformance Expectancy¡vand¡uEffort Expectancy¡v influence employee¡¦s behavior intention significantly . That is, we can use the model to predict the network users¡¦ behavior onUsing WLAN. On the other hand, this study is also investigate the effect after implement WLAN and made the suggestions to development of Govermant or ISP suppliers in future.

This research considered the efficient transmission of data within a wireless local area network (WLAN) system. A simulation model was developed to study the performance of our protocol, AGG-MAC (aggregated medium access control). AGG-MAC is a simple and elegant medium access control (MAC) protocol designed to improve performance by transmitting a maximal quantity of data with minimal overhead. Our enhancement to IEEE 802.11, AGG-MAC yields dramatic improvements in both local and global throughput. It furthermore reduces jitter in support of real time communications requirements such as voice over IP (VoIP). In support of heterogeneous roaming between Third Generation (3G) Wideband CDMA (WCDMA), specifically Universal Mobile Telecommunications System (UMTS) and WLAN systems, we constructed a simulation environment which allowed the evaluation of AGG-MAC in such a system. We further demonstrated the suitability of AGG-MAC throughout a range of infrastructure and ad hoc based WLAN scenarios. The AGG-MAC protocol enhancement provides significant performance improvements across a range of wireless applications, while interoperating with standard IEEE 802.11 stations. Performance is commensurate to original WLAN MAC performance for applications that do not benefit from packet level aggregation. The key contributions of this research were two-fold. First was the development of an OPNET simulation environment suitable for evaluation of future protocols supporting tightly coupled, heterogeneous WLAN and 3G systems. Secondly was the implementation and testing of the AGG-MAC protocol which aggregates suboptimal size packets together into a single frame, thereby amortizing the overhead. / Ph. D.

Specialists are expecting the knowledge of location will trigger yet another revolution in mobile services. Location-base services (LBS) have attracted many researchers and enterprises and one of the key aspects of LBS is positioning technology. Considering a wider and more complex field - ubiquitous computing, location is the fundamental element. This work focuses on some aspects of the new techniques of terrestrial positioning systems. Wireless LAN is one of the most popular systems used for positioning for indoor environments and public places. We have investigated the trilateration and fingerprinting approaches and the results showed the advantages of fingerprinting. A novel method to generate the fingerprints database based on Universal Kriging (UK) was developed, which can not only significantly decrease the training time, but also increase the accuracy of estimates. In mobile phone positioning systems, most techniques suffer from the non-line-of-sight (NLOS) propagation. We investigated the specifics of NLOS error, and proposed a method to mitigate the errors. Furthermore, a new algorithm named WSMM (wireless signal map matching) was discussed. Simulations and experiments verified the idea, and the accuracy of positioning can be improved greatly. Since fingerprinting technique can utilize rather than suffer from the NLOS propagation, it was also applied in mobile phone positioning system. Experiments showed both the deterministic approach and probabilistic approach can provide better results comparing with other techniques in suburban area. To achieve a robust positioning system and provide more useful information of the user, multisensor combination and data fusion are necessary. As the first step of future research, a mulitsensor synchronization system was developed. This system can promisingly achieve synchronization with error less than 0.4 ms, which is suitable for most land applications. Hence the main findings of this thesis are: (1) a novel method of yielding fingerprint database for both wireless LAN (WLAN) and mobile phone systems when using the fingerprinting technique for positioning; (2) a database method to mitigate NLOS error for mobile phone positioning systems; (3) a low cost synchronization system for integration of multiple sensors.

Doctor of Philosophy (Ph.D.) / The buzzword of this decade has been convergence: the convergence of telecommunications, Internet, entertainment, and information technologies for the seamless provisioning of multimedia services across different network types. Thus the future Next Generation Mobile Network (NGMN) can be envisioned as a group of co-existing heterogeneous mobile data networking technologies sharing a common Internet Protocol (IP) based backbone. In such all-IP based heterogeneous networking environments, ongoing sessions from roaming users are subjected to frequent vertical handoffs across network boundaries. Therefore, ensuring uninterrupted service continuity during session handoffs requires successful mobility and session management mechanisms to be implemented in these participating access networks. Therefore, it is essential for a common interworking framework to be in place for ensuring seamless service continuity over dissimilar networks to enable a potential user to freely roam from one network to another. For the best of our knowledge, the need for a suitable unified mobility and session management framework for the NGMN has not been successfully addressed as yet. This can be seen as the primary motivation of this research. Therefore, the key objectives of this thesis can be stated as:  To propose a mobility-aware novel architecture for interworking between heterogeneous mobile data networks  To propose a framework for facilitating unified real-time session management (inclusive of session establishment and seamless session handoff) across these different networks. In order to achieve the above goals, an interworking architecture is designed by incorporating the IP Multimedia Subsystem (IMS) as the coupling mediator between dissipate mobile data networking technologies. Subsequently, two different mobility management frameworks are proposed and implemented over the initial interworking architectural design. The first mobility management framework is fully handled by the IMS at the Application Layer. This framework is primarily dependant on the IMS’s default session management protocol, which is the Session Initiation Protocol (SIP). The second framework is a combined method based on SIP and the Mobile IP (MIP) protocols, which is essentially operated at the Network Layer. An analytical model is derived for evaluating the proposed scheme for analyzing the network Quality of Service (QoS) metrics and measures involved in session mobility management for the proposed mobility management frameworks. More precisely, these analyzed QoS metrics include vertical handoff delay, transient packet loss, jitter, and signaling overhead/cost. The results of the QoS analysis indicates that a MIP-SIP based mobility management framework performs better than its predecessor, the Pure-SIP based mobility management method. Also, the analysis results indicate that the QoS performances for the investigated parameters are within acceptable levels for real-time VoIP conversations. An OPNET based simulation platform is also used for modeling the proposed mobility management frameworks. All simulated scenarios prove to be capable of performing successful VoIP session handoffs between dissimilar networks whilst maintaining acceptable QoS levels. Lastly, based on the findings, the contributions made by this thesis can be summarized as:  The development of a novel framework for interworked heterogeneous mobile data networks in a NGMN environment.  The final design conveniently enables 3G cellular technologies (such as the Universal Mobile Telecommunications Systems (UMTS) or Code Division Multiple Access 2000 (CDMA2000) type systems), Wireless Local Area Networking (WLAN) technologies, and Wireless Metropolitan Area Networking (WMAN) technologies (e.g., Broadband Wireless Access (BWA) systems such as WiMAX) to interwork under a common signaling platform.  The introduction of a novel unified/centralized mobility and session management platform by exploiting the IMS as a universal coupling mediator for real-time session negotiation and management.  This enables a roaming user to seamlessly handoff sessions between different heterogeneous networks.  As secondary outcomes of this thesis, an analytical framework and an OPNET simulation framework are developed for analyzing vertical handoff performance. This OPNET simulation platform is suitable for commercial use.

<p>The fast growth of wireless local area networks today has opened up a whole new market for wireless solutions. Released in 1999, the IEEE 802.11a is a standard for high-speed wireless data transfer that much of modern Wireless Local Area Network technology is based on.</p><p>This project has been about implementing the transmitter part of the 802.11a physical layer in VHDL to run on the Altera Stratix II FPGA. Special consideration was taken to divide the system into parts based on sample rate. This report contains a brief introduction to Orthogonal Frequency Division Multiplexing and to the IEEE 802.11a physical layer as well as a description of the implemented system.</p>

<p>Genom hela arbetet har enkelhet och användbarhet varit ledorden. Detta för att man ska kunna implementera tjänster för en relativt liten målgrupp utan att behöva göra större investeringar. I linje med detta har möjligheter för att kunna erbjuda tjänsten till en större målgrupp och därmed få ned kostnaden per användare eftersökts.</p><p>Rapporten börjar med en studie av 3G, WLAN och Bluetooth för att läsaren ska få en grund i de tekniker på vilka tjänsterna skulle kunna implementeras. Sedan diskuteras dagens tjänster och vilka önskemål om tjänster som framkommit från diskussioner med olika parter. Slutligen exemplifieras ett antal tjänster som skulle kunna tillämpas på dagens tekniker.</p><p>Efter att ha läst rapporten skall läsaren ha fått en uppfattning hur mobila tjänster med hög överföringshastighet bör utformas för att underlätta kommunikation för funktionshindrade.</p>

<p>The past few years have seen great increases in the use of portable devices like laptops, palmtops, etc. This has also led to the dramatic increase demand on wireless local area networks (WLAN) due to the flexibility and ease of use that it offers. Mobile IP and handover are important issues to be considered as these devices move within and between different networks and still have to maintain connectivity. It is, therefore, imperative to ensure seamless mobile IP handover for these devices as they move about.</p><p>In this thesis we undertake a survey to describe the real processes involved in mobile IP handover in WLAN environment for different scenarios. Our work also identifies individual sources of delay during the handoff process, the sum total of which makes up the total latency. Other factors that could militate against the aim of having a seamless handoff in an inter-subnet network roaming were also considered as well as some proposed solutions. These factors are security, packet loss and triangle routing.</p>