The Multiple Prioritized Access Mechanism Of Cognitive Network

The developments of wireless communications technology and diversi-fied methods of transmission require higher standards of reliability of network and full utilization of resources. IEEE802.11e standard offers QoS which is needed by service of voice, multimedia and so on. The proposition of Cognitive Network improves the utili-zation of frequency spectrum effectively. The main tasks of this paper are to study the EDCA and DCF access mechanisms of WLAN and work over the correlative theory and structure, so that we can introduce EDCA mechanism into the Cognitive Networks ex-pecting that will guarantee the multi-source multi-rate access service access classified effectively. The Primary Users are allowed to access immediately whenever they have packets to transmit in the licensed bands, while the Secondary Users (which is also called the Cognitive User) perceive the current network conditions and use the idle li-censed spectrum without interrupting the Primary Users. IEEE802.22 Wireless Standard is a typical application.The innovations of this paper are as follows. First of all, we develop an access control for the Cognitive Networks, which adapts the EDCA mechanism of WLAN and sets different priorities for Cognitive users. Secondary, we propose a new prioritized access control algorithm for Cognitive Network, which adapts Gating Mechanism, Linear Backoff Algorithm, Stall Avoidance Scheme etc. to enhance the performance. Finally, we use and extend NS2 to satisfy the Multi-priority access with multi-interface and multi-channel. The Primary User and the Cognitive Users connect to the same node, which satisfies multi-interface and multi-channel. We can reach the conclusion that the performance of Cognitive Network used mechanism of EDCA is better than that of used mechanism of DCF. The spectrum utilization of Cognitive Network is higher than that of Non-cognitive Network. Primary Users would not be interfered by Cognitive User.