This paper investigates the research issues in Wireless Sensor Networks (WSNs), which is a new computing paradigm that emerged from the fusion of the SCADA (Supervisory Control and Data Acquisition) systems and Ad hoc networks technologies. WSNs provide network connectivity without the aid of any preexisting networking infrastructure. Very small sensor nodes, capable of sensing, data processing, and wireless communication, brought the idea of WSNs based on joint effort of a large number of

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... . WSNs are becoming an increasingly vital technology that will be used in a variety of applications such as inventory tracking, home automation, physiological monitoring, habitat monitoring, home automation, precision agriculture, and forest fire detection. Dynamic network topology, limited battery power, and constrained wireless bandwidth are the special characteristics of WSNs which make management of it significantly more challenging than conventional wired networks. This paper presents an overview of research trends and challenges in the design and implementation of WSNs. It summarizes the potential challenges that influence the WSNs design. Prospective applications of WSNs are described to show the importance of WSN. It also investigates the research issues of communications protocol at different layers.