Development and validation of an OFDM/DVB-T sensor for positioning

The use of Global Navigation Satellite System (GNSS) for positioning has grown significantly in recent years thanks in particular to the development of several mass-market applications, such as car navigation or mobile positioning. Unfortunately, in difficult environments such as dense urban or indoor areas, GNSS exhibits degraded performances in terms of precision and availability. The use of signals of opportunity is one of the solutions to replace or assist GNSS in those environments. These signals are communication signals that are usually designed to provide a service in dense environment and can thus be used in location where GNSS is unavailable. Several commercial positioning services based on signals of opportunity already exist such as ROSUM with ATSC digital TV signals, or Skyhook with Wi-Fi signals. This paper investigates the potential of the digital TV European (but used worldwide) standard DVB-T, based on an OFDM air interface, to supply a navigation service. To support a previously proposed DVB-T receiver architecture, a DVB-T receiver simulator is presented that includes the principal blocks required for communication with enhanced navigation-oriented functionalities. In particular, this simulator includes a Delay Lock Loop (DLL) for accurate synchronization purpose. The theoretical expressions of pseudo-range sigma error and tracking threshold in case of Line-Of-Sight (LOS) signal are proposed and compared to simulation results, in order to validate the DLL module of the simulator. Then, performances in a more realistic Rayleigh multipath channel are presented. This paper also proposes description and explanations of impairments due to absence of LOS signal in urban environment and points out the limits of existing urban channel propagation models for a positioning solution.