Global Navigation Satellite Systems not only require a significant number of satellites in orbit but also a rather complex and worldwide distributed ground infrastructures including satellite orbit and integrity monitoring stations, uplink stations, control centers, etc. These systems aim at providing evenly distributed performance globally and they do not necessarily provide relatively improved performance over specified area such as dense populated areas. All these issues clearly illustrate the complexity associated with the deployment and operation of a GNSS. The cost and complexity of constructing and maintain a GNSS limit the capability of some countries or regions to develop their own GNSS thus those countries are looking for agreements or analyzing the possibility of deploying their own augmentation systems. This situation may change if the development of low cost regional navigation systems became a reality A possible alternative solution could be the development of regional navigation systems aiming at providing a completely independent system, over the region of interest. These systems shall be able to operate autonomously, being possible to navigate only with these systems without assuming the existence of other systems like GPS, GLONASS or Galileo. These systems shall be interoperable with other systems allowing improved performances over the regions of interests and shall take into account the strategic interest of the regions. Thus, this study implements a GNSS software simulator to investigate several possible constellation designs for Taiwan's future regional satellite navigation system. The preliminary results in terms of the satellite visibility, DOP values, and the robustness to urban canyon effect do illustrate the performance of proposed constellation is not far from GPS in Eastern Asia region. The indices mentioned above can be considered as the criteria to select the best option for the future development. Thirty two cases are conducted to investigate more possible constellations. Ultimately, the constellation with fewer satellites but provides the most stable performance over this region is considered as the suitable candidate.