Multicarrier Modulation as a Navigation Signal of Opportunity

The global positioning system (GPS) generally provides worldwide high-accuracy positioning. However, GPS requires lines of sight to multiple satellites and may be blocked or jammed, hence backup navigation techniques are of interest. Navigation via signals of opportunity uses existing radio infrastructure as ad hoc navigational beacons. A mobile receiver determines its position by computing a time difference of arrival (TDOA) between signal reception time at the mobile and at a reference receiver. The drawback is that this requires communication between the reference and mobile receivers. In this paper, we show that multicarrier modulation is an ideal candidate for a navigation signal of opportunity. We show that communication between the reference and mobile can be very minimal for multicarrier modulation compared to other modulation types, since the block structure inherently aids synchronization of the two received signals. Simulations are used to quantify the performance of the TDOA estimate as a function of the SNR and the bandwidth between the reference and the mobile.