Software-Defined Radios for Urban and Indoor Navigation

Software-defined radios (SDRs) are being developed to provide positioning and communication (POSCOMM) services inside buildings and tunnels, under tree canopies, and in other environments in which local radio- communication systems are accessible but Global Positioning System (GPS) signals are not present or are degraded. These SDRs could be especially helpful for teams of first responders (e.g., firefighters), and military personnel operating in urban settings. These SDRs are capable of navigating by use of GPS signals and can switch over to time-of-arrival (TOA) pseudolite navigation when GPS signals become unavailable, provided that signals from suitably placed TOA pseudolite transmitter nodes are available.