The Impact of Primary User Velocity on Spectrum Sensing in Cognitive Radio Networks.

Abstract

The demand for Radio spectrum needed for applications such as Mobile Telephony, Digital Video broadcasting, Wireless Local Area Networks, Wireless Sensor Networks is enormous and continues to grow. This has created a problem of spectrum scarcity. In addition spectrum is assigned in a fixed manner to licensed users, yet much of the licensed spectrum is idle during certain times and or locations.Cognitive Radio Networks (CRNs) are emerging as a solution to increase spectrum utilization by using unused or less used spectrum in radio environments. In these networks, unlicensed users (secondary users) are allowed to access licensed spectrum without causing interference to licensed users (primary users). To enable access to idle or underutilized spectrum, CRNs use spectrum sensing to detect spectrum holes accurately. However, these networks are prone to errors like miss detection and false alarm due to factors such as shadowing, multi path, mobility of users. These errors increase the risk of interference on the primary user's transmissions and under utilization of the spectrum. This project studied the effect of mobility of the primary users, particularly their velocity, on the performance of CRNs This was done by considering two performance metrics: detection capability and transmission capacity of the secondary users. The movement of primary users was modeled using random walk and random way point mobility models. Closed form expressions for the performance metrics were derived and simulated. The simulation results showed that the mobility of primary users decreased the chances of the secondary user detecting primary users' transmissions. The results also showed that this mobility increased the secondary users' transmission opportunities.