ZigBee is a low cost, low-power consumption and long battery life network that is based on the IEEE 802.15.4 standard; which is most usually used to transfer low data rates information in the Wireless Personal Area Network (WPAN). In the Wireless Personal Area Network (WPAN) network, capability of sensor network and mobile network are combined that have energy limit and sensing range limits. Here a network is composed of a number of Sub-Network or groups with the selection of group leader. Group formation is defined under sensing range limit, density limit and type of nodes. The selection of group leader is defined under velocity analysis, energy and average distance after that inter group and intra group communication is performed and then Handoff mechanism is performed when nodes switch the group or group switch the base station.