1 Mobile sensor nodes should be well deployed so that they maximize the area coverage with the constraint that each node has at least K neighbours, where K is a userspecified parameter. The MSNS (Mobile Sensor Node Simulator) designed in this paper visualizes the real map objects created by a GML, and the movement of each sensor node which autonomously extends the constrained coverage introduced by [1]. We explain how each sensor node avoids obstacles in our simulator, while extending the rate of the constrained coverage. And then, we describe the design of MSNS and simulation results. From a user, MSNS takes two parameters: the number of mobile sensor nodes deployed and the constraint parameter K. It calculates and shows the coverage rate and the average number of neighbour nodes in a realtime manner.