The usage of wireless sensor networks is increasing day by day in different fields from health monitoring to the prediction of volcanic eruption. As a result of this, the complexity of sensor networks are also increasing. In order to rightly predict the behavior of sensor network, simulation tools are a cost effective alternative than setting up real test beds. Though there exists a number of tools for simulating wireless sensor networks, there is a lack of simple tool which can be used to derive the network behavior without setting up much finer details. In this context, we have come up with a simple queuing network model for the performance evaluation of ZigBee-based beacon-enabled wireless sensor networks. We have also validated the results of our model with a widely accepted WSN simulation tool, i.e., ns-2.