Improving coverage and connectivity is a very important issue in wireless sensor networks. The unattended or uncovered region in a sensing field is called a coverage hole. A coverage hole impacts the performance of the wireless sensor network, disconnects the network topology and causes delay in data transmission. These coverage holes can be healed randomly or each hole can be assigned a priori...

OBJECTIVE To evaluate the impact of Medicare Part D coverage gap (donut hole) on adherence to diabetes medications. STUDY DESIGN Retrospective cohort analysis based on pharmacy claims data. METHODS The sample included 12,881 Medicare Part D beneficiaries with diabetes who entered the coverage gap in 2008. Sample patients had 3 different levels of coverage in the donut hole: no coverage, gen...

Coverage is one of the most important issues in Wireless Sensor Networks (WSNs). However, full coverage only can be achieved when surplus mobile sensors contribute a coverage area larger than the hole size. When there is no surplus mobile sensor to cover a big hole, previous studies have utilized mobile sensors by moving the hole from one location to another, therefore achieving temporal full-c...

Wireless Sensor Networks (WSN) consists of distributed low-cost sensing nodes with autonomous network. Several anomalies can occur in wireless sensor networks that may form various coverage holes. These holes may disturb the existing coverage or connectivity, and impair desired functionalities of networks. Hence, it is essential to detect and recovery coverage holes in order to ensure the full ...

In wireless sensor networks, coverage is a fundamental issue affecting the quality of service. A coverage hole may appear anywhere in the area being monitored at any time because of many reasons. Thus, hole detection and healing have become major challenges towards achieving perfect coverage. This study provides a novel algorithm using trees and graph theory to detect and describe the existing ...

This paper considers a mobile WSN that contains a big hole. To achieve the full coverage purpose or enhance the tracking quality, three distributed algorithms are proposed for moving the existing big coverage hole to a predefined location. Firstly, the sink chooses a promising direction for hole movement. Then the Basic, Forwardonly and Any-Direction movement mechanisms are proposed to move the...

Failures are inevitable in wireless sensor networks, and it is important to detect and patch the “coverage hole”. In this paper, we propose an efficient recovery algorithm based on minimum distance redundant nodes. By numerical algorithm, the sink node gets the centre of the “coverage hole”, and then wakes up a redundant node, which has the minimum distance to the centre, to recover the hole. S...

This paper develop a practical and energy-efficient distributed algorithm for the detection of coverage holes in a wireless sensor network. It assumes that the location of sensor nodes is available. We do this in two phases. First we want to identify a set of nodes of which encircle a coverage hole. This is done by introducing a concept of mono-covered arc, which represents the circumference of...

Now a day’s, it has been a great idea of research on using Wireless Sensor Networks (WSNs) to assist in the initial deployment of sensor nodes. Hole problem in WSNs is the most fundamental Problem in WSNs. Hole means a communication gap in WSNs. Finding an optimal sensor deployment strategy that would minimize the cost, reduce the node failure and also reduce the communication overhead. Then it...