Wireless LAN protected distributed cognitive MAC protocol for secondary system

This paper focuses on a primary and secondary spectrum sharing system with a modified MAC protocol at the secondary network. The assumed primary system is the wireless LAN (WLAN) operated with the protocol of IEEE 802.11 distributed coordination function (DCF). In such spectrum sharing system, it is required that the primary system is protected from the signals of the secondary system. In this paper, in order to keep the communication of the primary systems over the existence of the secondary systems, we propose a modified novel secondary MAC protocol, which can flexibly share the spectrum between WLAN and the secondary system. The proposed secondary MAC protocol of the packet transmission controls the packet transmission by the permission probability according to the primary system channel occupation ratio. The proposed method can keep the communication chance of the primary system without any change of the primary MAC protocol.