Interference Coordination Mechanisms For WLANs With AP Dense Deployment

With the rapid development of mobile Internet, the data service of wireless mobile networks is also explosively growing. In the meantime, fast growing number of users of wireless local area networks(WLANs) results in a sharp increase in the network density. The architecture of WLANs gradually evolves from sparse traditional autonomous network architecture to large-scale centralized architecture. Since the small-coverage property of WLANs exhibits small-cell characteristics of LTE networks, the integration of LTE and WLAN heterogeneous networks is greatly promoted, which can achieve the data traffic offloading and balance in the networks. The novel multiple radio access technologies(RATs) in LTE/WLAN have been deemed as a basic access technology for the fifth-generation communication(5G) systems.However, with increasingly wide deployment of WLAN which makes the network more intensive, the wireless access points and the number of users increase sharply. Due to the features of AP random deployment, the interferences of dense AP deployment in WLAN will be more obvious and severely degrade network performance. Thus, effective interference coordination mechanisms are imperative and important for radio resource management optimization in dense WLAN.In this thesis, we theoretically analyze the impact of interference of dense deployment of APs on system performance in WLANs and propose effective interference coordination schemes to optimize system performance. In these schemes, we develop efficient algorithms including channel assignment and power control under the centralized architecture of WLAN with CAPWAP protocol. Specifically, we have conducted investigations in the following two aspects.(1) We address interference coordination in WLANs with dense AP deployment, by formulating the design as a weighted graph coloring problem for dynamic network topology. Our model aims at minimizing overall system interferences. Then we prove that the problem of our defined channel assignment with the limited channels in WLAN is an NP-hard and thus propose a heuristic channel assignment algorithm to mitigate interferences for APs. Simulation results show that our proposed algorithm can effectively mitigate system interferences and significantly improve network throughput.(2) According to SINR of users, we identify two types of network scenarios: high and low-medium SINR scenario. According to different scenarios, we model the dynamic power control as a geometric programing problem which maximizes system throughput. Then, we solve the problem by using interior point method. Numerical results reveal that dynamic power control algorithm can effectively mitigate system interferences and ensure QoS of users in dense AP deployment WLANs.