The principle of cognitive radio technology is to enhance the proficiency of the wireless systems by using the frequency band among unlicensed users also. A cognitive radio system has been designed with single incumbent and three secondary transmitters. The secondary user transmits subjectively with the end goal that it doesn't hinder the execution of the primary node. There are a few variables which are utilized to enhance the Cognitive radio system quality. Modulation Techniques are one of them. In this paper we show the relationship between the modulation technique and network congestion and Modulation techniques such as 64-QAM,16-QAM and QPSK are compared. Network congestion and throughput of all these three techniques is shown. For Network design and simulation, the NetSim Software tool has been used.
