The ability to find the location of a mobile user has become of utmost importance. The demands of first responders necessitates the ability to accurately identify the location of an individual who is calling for help. Their response times are directly influenced by the ability to locate the caller. Thus, applications such as Enhanced 911 and other location-based services warrant the ability to quickly and accurately calculate location. The FCC has also put in place a timeline for indoor location accuracy requirements that must be met by the mobile communications service providers. In order to meet these requirements, there are many means of performing indoor geolocation that require research; in this thesis two specific methods of identifying the location of a user will be investigated. In the first part, the indoor localization of a target, whose exact location is unknown, in a LTE network is studied. In this problem the time difference of arrival of the LTE uplink signals sent from the target to an observer are used as the means to estimate the target position. The two-dimensional location of a user is then estimated through the use of a nonlinear least-squares algorithm. To improve this approach, a cooperative localization technique in uplink LTE is proposed in which the User Equipment (UE) communicates with base stations as well as other handsets. Through simulated results it is shown that utilizing collaboration can improve location estimation and outperform non-collaborative localization. In the second part, the indoor localization of a target, focusing on its third dimension or elevation, is studied through the use of barometric pressure sensors in mobile handsets. Finding the third dimension of location, or the correct height above the ground level which equates to the floor in a building that a UE is on, cannot be performed with two-dimensional measurement models. For this problem, the pressure sensors are used to accurately find an immediate pressure measurement and allow for the altitude of a handset to be calculated. This altitude can be translated into an estimation for a specific floor of a building given the use of a ground floor pressure reference. Through simulation results it is then shown that the accuracy of third dimension or indoor-floor localization can be improved with the use of collaborative pressure sensors of other mobile handsets. / Master of Science

Although positioning has been one of the main target study areas in mobile communication in the last decade, it still receives strong attention in recent years focusing more on the indoor users. Nowadays, a wide range of different methods are available to estimate the position of the target user under certain circumstances. One of these methods is Uplink Time Difference of Arrival (UTDoA), which has been defined in 3GPP Release 11 for Long Term Evolution (LTE) networks, and is the focus of this master thesis. In Uplink based positioning, to estimate the position of a User Equipment (UE), the UE only needs to generate and transmit the reference signal and the main computational effort of time estimation, is moved from the UE towards the network side. This might be one advantage compared to Observed Time Difference of Arrival (OTDoA), while further performance properties of UTDoA in LTE are investigated in the course of this master thesis. In parallel with the 3GPP Study Item on Indoor Positioning which mainly was based on downlink OTDoA, this thesis studies on the potential use of UTDoA in LTE under the same type of agreed deployment scenarios and simulation parameters. For time estimation based on the Sounding Reference Signals (SRSs), the uplink channel has been modeled and simulated. Finally, the position estimation of the UE is derived by multilateration techniques using the time/distance estimations of the received SRS at each eNodeB. The metrics of positioning results are based on Cumulative Distribution Functions (CDF) of horizontal and vertical positioning error. The study shows that reasonable horizontal position accuracy can be achieved, while a number of pico cells are added to the network to enhance the macro-only scenario. However, this positive effect could not be observed in vertical position estimation. A further investigated aspect is the influence by other active UEs considered as interference. The outcome shows, that the accuracy is strongly and negatively affected by introducing interference. A final observation focuses on the SRS bandwidth and that for bandwidths below 10 MHz additional degradations in performance are seen. / Trots att positionering har varit ett av huvudmålen för forskning inom mobil kommunikation under det senaste decenniet, får det fortfarande mycket uppmärksamhet och under de senaste åren har forskningen fokuserats mer på inomhusanvändare. Idag finns en mängd olika metoder för att estimera positionen för en specifik användare under vissa omständigheter. En av dessa metoder är Uplink Time Difference of Arrival (UTDoA) som har definierats i 3GPP Release 11 för Long Term Evolution (LTE)-nätverk och är fokus för detta examensarbete. I positionering baserad på upplänken, vilken används för att skatta positionen för en User Equipment (UE), behöver UE:n bara generera och sända en referenssignal och den huvudsakliga beräkningskraften för tidsestimeringen flyttas från UE:n till nätsidan. Detta kan vara en fördel jämfört med Observed Time Difference of Arrival (OTDoA), detta examensarbete undersöker ytterligare prestandaegenskaper hos UTDoA i LTE. Parallellt med 3GPP:s studie för inomhuspositionering, som huvudsakligen baseras på nerlänk OTDoA, studerar denna avhandling den potentiella användningen av UTDoA i LTE med samma typ av överenskomna scenarier och simuleringsparametrar. För tidsuppskattning baserad på Sounding Reference Signals (SRSs) har kanalen upplänkmodellerats och simulerats. Slutligen är positionsestimeringen av UE:n härledd genom multilaterationstekniker med hjälp av tids- och distansestimeringar av de mottagna SRS vid varje eNodeB. De mått som används för positioneringsresultat baseras på kumulativ fördelningsfunktion av det horisontella och vertikala positioneringsfelet. Studien visar att en rimlig noggrannhet kann uppnås i den horisontella dimensionen då ett antal pico-celler adderas till nätverket för att förbättra makroscenariot. Denna positiva effekt kunde emellertid inte observeras i den vertikala positionsestimeringen. En ytterligare undersökt aspekt är påverkan av andra aktiva UEs, som betraktas som interferens. Resultaten visar att noggrannheten är starkt negativt påverkad då störningar i form av interferens införs. En slutlig observation fokuserar på bandbredden av SRS och det visar på försämringar i prestanda för bandbredder under 10 MHz.