Development and Evaluation of UTDoAas a Positioning Method in LTE

Sammanfattning: 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.