Abstract
Wireless sensor networks (WSNs) have attracted much attention in recent years. In the many-to-one WSNs, the nodes located around the sink relay the data from other sensor nodes, which depletes their energy more quickly, resulting in energy holes and hot spot areas. When an energy hole appears, data cannot be sent from other sensors to the sink even though most of the sensors still have energy. In this paper, we generally classified the schemes proposed for solving the energy hole problem. In addition, we investigated the basic mathematical modeling of network connectivity and coverage, energy consideration, and optimum width of coronas in the corona-based WSNs.