Anomaly-aware IP Scheduler with Admission Control for 802.11n Base Station

IEEE 802.11n standard has fulfilled the promise of improved performance when compared to the previous generation of Wireless Local Area Networks (WLANs) with the possibility of physical transmission rate up to 600 Mbps. But the well known performance anomaly of 802.11 still remains an open issue. A mobile station tends to change its modulation and coding scheme and transmit at lower bit rate due to the signal fading and interference. Besides, the 802.11 commercial devices adopt a simple First-In-First-Out (FIFO) scheduler without isolating the traffic flows addressed to different destinations. These have lead to a problem: whenever one or more stations transmit at lower bit rate, the performance of all the stations is heavily degraded. Our experimental results have pinpointed this problem. To counteract this problem, we propose an easy to deploy and portable solution to be implemented in the 802.11n base station, known as anomaly-aware IP scheduler with admission control. This cross-layer approach requires no modification to the current 802.11 standard and runs on top of the Linux kernel. The experimental results have shown the feasibility of our solution in minimizing the performance anomaly problem.