Noname manuscript No. (will be inserted by the editor) A Joint Optimization of Data Ferry Trajectories and Communication Powers of Ground Sensors for Long-term Environmental Monitoring

the date of receipt and acceptance should be inserted later Abstract Recently, various hybrid wireless sensor networks which consist of several robotic vehicles and a number of static ground sensors have been in-vestigated. In this kind of system, the main role of the mobile nodes is to deliver the messages produced by the sensor nodes, and naturally their tra-jectory control becomes a significant issue closely related to the performance of the entire system. Previously, several communication power control strate-gies such as topology control are investigated to improve energy-efficiency of wireless sensor networks. However, to the best of our knowledge, no commu-nication power control strategy has been investigated in the context of the hybrid wireless sensor networks. This paper introduces a new strategy to uti-lize the communication power control in multiple data ferry assisted wireless sensor network for long-term environmental monitoring such that the lifetime of the sensor network is maximized. We formally define the problem of our interest and show it is NP-hard. We further prove there exists no approxi