Cognitive radios are designed in order to provide highly reliable communication for all users of the network, wherever and whenever needed and to facilitate effective utilization of the radio spectrum. The issue of spectrum underutilization in wireless communication can be solved in a better way using Cognitive radio (CR) technology. Because of fading or shading of the channel there will be uncertainties in the received signal strength which will lead to wrong interpretation. To avoid this, we propose spectrum sensing scheme for efficient data transmission for both primary and secondary users. For spectrum sensing we use Centralized Coordinated Techniques. Here in this technique we have Cognitive Radio controller. Propose spectrum sensing scheme for efficient data transmission for both primary and secondary users. For spectrum sensing we use Centralized Coordinated Techniques. Here in this technique we have Cognitive Radio controller. When one Cognitive Radio detects the presence of primary user then it allocates the channel for that user. When primary user free, it allocates the available spectrum to secondary users.