With the advent of advanced wireless standards has come the ability to address more sophisticated problems. One such issue is to provide robust navigation in challenging environments. Our approach to develop a signals of opportunity (SoOP) based cooperative navigation network that has the potential to provide improved performance and extend coverage under a variety of difficult conditions from jamming to multipath fading. Under the premise that GPS is not always available, we employ SoOP as the core of this radionavigation system. A critical advantage of signals of opportunity is that they are more abundant and of significantly higher received signal power than other GNSS signals. There are many signals that are available but not all meet the requirements of robust navigation. Of particular importance are digital television (DTV), AM radio, and 3G cellular signals. Our basic premise is to implement these signals to provide geolocation capability using time difference of arrival (TDOA) which requires cooperation among users. We extend these concepts further to the development of a cooperative network that can be used to provide coverage to users outside the range of the navigation signals. We also demonstrate that cooperation can be used to mitigate the effects of multipath fading and provide simulation results.