Upgraded OPEN-ZB 802.15.4 simulation model

IEEE 802.15.4/ZigBee represents set of comercial standards targeted for implementation in low power wireless applications, such as wireless sensor networks. OPENZB model was used for simulation of IEEE 802.15.4 networks using OPNET Modeler. We upgraded this model by adding functionalites which enabled testing this kind of networks under real-world scenarios such as presence of hidden nodes and cluster-tree topology.