Energy efficiency is an important issue in the study of wireless sensor networks. Given a set of targets and a set of sensors with bounded lifetime, the maximum lifetime    $k$   -coverage problem is to schedule active/sleeping status of sensors to maximize the time period during which every target is covered by at least    $k$    active sensors. Previously, it was known that when the sensing ranges are uniform, this problem has a polynomial-time    $(4+\varepsilon )$   -approximation for    $k=1$    and    $(6+\varepsilon )$   -approximation for    $k=2$   . In this paper, we make significant progress by showing that for any positive integer    $k$   , there exists a polynomial-time    $(3+\varepsilon )$   -approximation.
['Zhao Zhang', 'James Willson', 'Zaixin Lu', 'Weili Wu', 'Xuding Zhu', 'Ding Zhu Du']
Approximating Maximum Lifetime $k$ -Coverage Through Minimizing Weighted $k$ -Cover in Homogeneous Wireless Sensor Networks