ABSTRACT
There are today about 15 billion devices on the Internet of Things (IoT) and there would be 50 billion connected devices by 2020 according to a report by Cisco and DHL [1]. As a subdomain, wireless sensor networks (WSNs) are more and more widely used in various fields, for example, to monitor physical and environmental conditions in areas where human access is seemingly obstructed. Smart cities are also another application domain based on the collaboration of a number of WSNs
