MiFi: Managed WiFi for QoS assurance, Fairness and High Throughput of Current IEEE 802.11 Networks with Multiple Access Points

In this paper we present a system for supporting fairness in IEEE 802.11 MAC layer while maximizing the overall throughput. The issue of fairness becomes critical as IEEE 802.11 wireless LAN are widely deployed in nationwide networks linking tens of thousands of "hot-spots" for the purpose of providing both real-time (voice) and non real-time (data) services to a large population of mobile users. Our scheme for providing fairness is motivated by the observed "best-effort" behavior of the 802.11 MAC layer, which is characterized by starvation of individual users and unfair allocation of resources, hampering its ability to support any kind of QoS guarantees. Our system, for providing fairness, relies on centralized coordination of the Access Points (APs). During any given time of the "contention-free" period only a set of non-interfering APs is activated while the others are silenced. Moreover the amount of service granted to an AP is proportional to its load and the system's performance is optimized by employing efficient scheduling algorithms. We show that such a system can be implemented without requiring any modification of the underlying MAC protocol standard or the behavior of the mobile stations. Our scheme is complimentary to the emerging 802.11e standard for QoS and guarantees to overcome the hidden node and the overlapping cell problems. Our simulations establish that not only the system supports fairness and hence can provide QoS guarantees for real-time traffic but is also able to provide high throughput.