Research On Dynamic Spectrum Access In Cognitive Radio Network

Cognitive Radio (CR) will provide higher spectrum efficiency by using vacant spectrum for communication with the guaranty of Primary Users (PU). Dynamic Spectrum Access (DSA) request Secondary User (SU) access the network in time and make some adjustments in the changeable wireless environment. This dissertation focus on the DSA technology in the IEEE 802.22 CR network, it is a kind of centralized network, and research on the DSA scheme based on both non-hopping and Dynamic Frequency Hopping (DFH).This dissertation propose two scenarios for researching on CR network, one is multi-cells with no users (including PUs and SUs), and the other is single cell with multi-users (also including PUs and SUs).These two scenarios focus on different metrics.The first scenario focus on the amount of used channel, while the second scenario focus on the amount of collision, ratio of valid delivery and effective throughput. What's more, this dissertation also proposes the PU and SU's behavior model.This dissertation describes the traditional DSA technology in IEEE 802.22 systems, it uses the in-band channel sensing mechanism, but as the Quiet Time (QT), periodic suspension of data transmission will significantly impair the data transmission efficiency of SUs.Therefore, A new DSA scheme based on DFH has been proposed for IEEE 802.22 system. In DFH, data transmission is performed in parallel with spectrum sensing without interruptions, so improve the data transmission efficiency of SUs.In this dissertation, we compare this hopping mode with non-hopping one by computer simulation.The results show that, on the one hand, CR technology can provide higher spectrum efficiency to some extent, alleviate the pressure bring by the limited spectrum resources, on the other hand, on the other hand, although the DSA scheme based on DFH requires a little more channels than the non-hopping mode, it can reduce the collision with PUs,achieve higher ratio of valid delivery and higher throughput, thus it can improve system performance effectively, in particular, enhanced QoS of SUs.