Assignment of tasks to robots in multi-robot system has been under intensive investigation over last years. The method which does not use any explicit communication, but applies a simple model of signal emission and propagation in the environment is presented in this paper. The environment model included obstacles that are to be avoided by the robots. Usability and interesting features of the method are shown on the basis of simulation experiments and their results. The approach enables management of robots movement between locations of tasks and assignment of robots to tasks without explicit communication.