A novel smart-DCF scheme for high-speed WLANs

In this paper, a novel Smart-DCF scheme is proposed for high-speed WLANs. The proposed Smart-DCF scheme may be viewed as a merger of the IEEE 802.11 DCF and PCF schemes. It can achieve a virtually collision-free WLAN environment and efficiently support a desirable quality-of-service requirement as in PCF while maintaining simplicity of medium access with the CSMA mechanism as in DCF. The Smart-DCF scheme can almost completely eliminate the signal collision problem, which is the major factor limiting performance of the standard IEEE 802.11 DCF scheme. In Smart-DCF, each client station relies on smart backoff timer information from a master station for use during the backoff procedure of each signal transmission. The master station schedules the backoff timer for each client station such that no collision would occur, and can effectively support a quality-of-service requirement by smartly scheduling the backoff timers for each station based on the traffic or station´s privilege such that a higher-priority station can get a chance to transmit sooner or more frequently. Each client station acquires the smart backoff timer information through an acknowledgement frame from the master station for its previous frame transmission. If the client station has not yet acquired the smart backoff timer information from the master station for any reason, it employs a random backoff value to initiate the current backoff procedure. The backoff slot structure is smartly designed so that the random backoff stations can easily determine their allowable backoff slots. Since the signal collision problem is almost completely eliminated, the proposed Smart-DCF scheme is expected to considerably outperform the standard IEEE 802.11 DCF scheme. The numerical results show that the throughput improvement can be more than 40 percents in many cases.