Cellular communication system is the most widely used communication system as commercial purpose. Mobile phones have become much more than mere communication devices. The encouragement for Telecommunication operators towards the energy consumption problem is to optimize the utilization of network equipment. Energy consumption of BSs is considerable even when traffic load is low. In our study, we consider UMTS scenario with a simplified traffic model describing. This paper offers a mechanism of energy efficient with dynamically operation depends on traffic load, bit rate and cellular capacity. In this paper, concept of cell zooming by using centralized algorithm is investigated, and simulation result shows that the proposed algorithm can greatly reduces the energy consumption up to 70%, which leads to green cellular network.