Research On Cognitive Coexistence Algorithms In Non-Slot System

Wireless communications have experienced a tremendous growth in recent years and are becoming ubiquitous. The rapid proliferation of wireless devices has resulted in an overly crowded spectrum and made interference an important performance impediment. Interference is especially serious in unlicensed bands, for heterogeneous technologies have equal spectrum access rights while lacking of coordination among them. In order to alleviate interference, cognitive radio is present as a novel framework for access and share spectrum among interfering systems.Based on the statistic prediction model of WLAN, the cognitive coexistence methods in spectrum sensing error scenario are studied in this dissertation. Firstly, the concepts of dynamic spectrum accessing and the statistic prediction model of WLAN are introduced. Simultaneously, an optimal spectrum access algorithm based on known sensing error is proposed for the case of one shared channel between WLAN and Bluetooth systems. The influence of the performance of the proposed method caused by different sensing error is also studied. Secondly, on the basis of studies on the spectrum accessing process in multiple shared channels, both a suboptimal channel selection strategy and a historic information-based channel selection strategy are proposed for the cases of fully observation and partial observation respectively. Finally, the coexistence of infrastructure and ad-hoc networks is addressed and an optimal power and time allocation algorithm is introduced and simulated. Through analyzing of the result of performance, the characteristics of the algorithm are concluded.