The Problem of Joint Scheduling and Power Assignment in Wireless Sensor Networks

In this work we address the problem of joint link scheduling and power assignment in WSNs. It focuses on finding a feasible schedule and a power assignment scheme such that the schedule length is minimized and the concurrent transmissions have a fair quality in terms of SINR (Signal-to-Interference-and-Noise Ratio). As the problem is shown to be NP-hard we propose a greedy heuristic for the scheduling problem which seeks to minimize the number of time slots for link scheduling. Our goal is to design an algorithm that performs transmission power control in order to guarantee fair SINR link transmissions. This insures that every node that is actively transmitting in the network chooses a transmission power which will minimally affect the other concurrent transmissions. Hence, we opt for a cooperative strategy which intends to maximize the minimum value of SINR. This problem is modeled and solved using an iterative algorithm based on linear programming which provides an optimal solution. The solution of this problem may be crucial for the performance of WSNs as it impacts different network requirements such as lifetime (energy savings), delay (schedule length) and throughput (number of concurrent links in a time slot).