We obtain an association policy for STAs in an IEEE 802.11 WLAN by taking into account explicitly two aspects of practical importance: (a) TCP-controlled short file downloads interspersed with read times (motivated by web browsing), and (b) different STAs associated with an AP at possibly different rates (depending on distance from the AP). Our approach is based on two steps. First, we consider an analytical model to obtain the aggregate AP throughput for long TCP-controlled file downloads when STAs are associated at k different rates r1, r2, : : :, rk; this extends earlier work in the literature. Second, we present a 2-node closed queueing network model to approximate the expected average-sized file download time for a user who shares the AP with other users associated at a multiplicity of rates. These analytical results motivate the proposed association policy, called the Estimated Delay based Association (EDA) policy: Associate with the AP at which the expected file download time is the least. Simulations indicate that for a web-browsing type traffic scenario, EDA outperforms other policies that have been proposed earlier; the extent of improvement ranges from 12.8 to 46.4 for a 9-AP network. To the best of our knowledge, this is the first work that proposes an association policy tailored specifically for web browsing. Apart from this, our analytical results could be of independent interest
@cite_18: Wireless LANs have been widely deployed, and multiple access points (APs) are likely to become much more available for wireless stations (STAs) which can roam from one AP to another by some rule. We focus on an efficient and fair way to use the wireless access resources provided by multiple APs. In particular, our major concern is to develop a decentralized way to enable each STA to select an appropriate available AP independently. A straightforward way is to select the AP with the strongest signal; however, this is shown to need further improvement. Hence, we propose decentralized AP selection strategies to achieve an efficient and fair share of wireless access resources, and evaluate them by simulations. The results show that the proposed strategies can attain an excellent throughput performance by use of the number of active STAs sharing each AP, even if STAs employ the strategies only when entering the wireless LAN. In addition, if STAs roam from one AP to another, the total throughput and fairness can be further improved very much.
@cite_3: An algorithm to reduce congestion and balance users' load in IEEE 802.11b g Wireless Local Area Networks (WLANs) is presented, which takes into account overlapping channel interference between Access Points (APs) and the signal-to-interference ratio (SIR) experienced by the users. After finding the best channel assignment at the APs, the algorithm then finds the Most Congested Access Point (MCAP). It reexamines the users' association with APs by minimizing the congestion at the MCAP. Simulation results show that the proposed algorithm is capable of significantly reducing the overall congestion in the WLAN while mitigating channel interference. Our algorithm has also been shown to be scalable and it performs well for networks of different topologies.
@cite_12: 
From the extensive literature on association in WLANs, several themes can be discerned. In the first group, a newcomer STA assesses each AP (that it can hear) by finding out the per-STA throughput received by STAs associated with it currently @cite_12 , @cite_18 and @cite_3 . In these papers, the authors derive expressions for aggregate AP throughput (with UDP traffic), taking into account the number of STAs associated, as well as the probability of packet loss due to collisions. From this, the per-STA throughput can be calculated, and the newcomer associates with the AP for which the per-STA throughput is the highest.