Research On Cognitive Radio Network MAC Protocol Which Is Based On IEEE802.11 Medium Access Control

The wireless communication technology has been widely used in daily life, but the limited spectrum resources and low utilization of the spectrum resources make the lack of spectrum more and more serious. Cognitive Radio (CR) was proposed by Joseph Mitola in 1999, which was based on the conception of Software Radio and enhanced it. The CR Network has a cognitive process that can perceive current network conditions, and then plan, decide and act on those conditions and the network can learn from these adaptations and use them to make future decisions, all while taking into account end-to-end goals, which can increase the utilization of the spectrum resources and the prime user in the CR Network cannot be disturbed.The IEEE802.22 standard promises to be the first practical implementation of Cognitive Radio technology. It is based on dynamic spectrum sensing and opportunistic access of the bands that are not currently in use by TV transmitters. The distinctive and most critical requirement for the IEEE802.22 air interface is the flexibility and adaptability. This stems from the fact that IEEE802.22 operates in a spectrum where incumbents (such as wireless microphones) may appear and disappear arbitrarily and where the collocated operation of multiple networks will be commonplace, as IEEE802.22 operates under license exempt regulatory model. This requirement has a direct impact on the various dynamic spectrum access (DSA) and dynamic spectrum sharing (DSS) mechanisms present at the PHY and the Medium Access Control (MAC) layers, which will be discussed in detail in this paper.The MAC protocol in the wireless communication coordinates and controls the access process to the medium. The Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA), as a MAC protocol, has been widely used in Wireless Local Area Network (WLAN). Different from the MAC of IEEE802.11, the application of CR technology suffers the uncertain spectrum and frequency width, which can not ensure the access of mobile users to be valid. To solve the problem, in this paper, we first analysis the CSMA/CA mechanism in IEEE802.11 in detail, and then we modify the CSMA/CA mechanism in order to make it suit the CR environments, in which the spectrum can be effectively used. In addition, we make some proposals for the spectrum sharing and the spectrum management based on the conception of spectrum pooling and interfere temperature.