Analysis, Modelling and Design of an Indoor Positioning System for biomedical applications

The indoor positioning systems (IPS) became very attractive in a recent past, because they can be used in more applications and in different scenarios. In fact, the use of an indoor positioning system allows to provide location-based services (LBS), e.g., safety information, indoor navigation, location-based advertisements and so on. Moreover, the IPS can be exploited in medical surgery applications where it is required a very precise and accurate position estimation. For example, in radiotherapy systems, the treatment zone must be localized with a sub-mm precision to focus the radiation beam in the precise body area and so limit the damages to the healthy. In this thesis a novel solution is proposed to evaluate the position of an active target placed in harsh indoor environments. The proposed solution exploits a GPS-like scheme composed by a single transmitter and four synchronized receivers. One of them is selected as system origin and the position are evaluated computing the Time Difference of Arrival of the received signals. The hardware of each nodes is based on the Software-Defined Radio architecture to obtain a scalable and feasible positioning system able to adapt its characteristics as function of the design specifications. Moreover, it requires simple software instructions to change the properties of the transmit signal, whereas the analog blocks can be designed to cover a wide frequencies range. Hence, the target positions are evaluated in digital domain by means of a signal processing algorithm that can be implemented by a FPGA or a DSP. The transmit signal combines the properties of well-known Zadoff-Chu sequences with the characteristics of the OFDM modulation scheme to obtain a signal very robust against the multipath. The sense signal is composed by only pilot subcarriers that represent a specific coefficient of the Zadoff-Chu sequence.