Currently, the IEEE 802.11 wireless local-area network (WLAN) has been prevalent around the world due to the advantages of mobility, flexibility, and scalability. WLAN offers the wireless internet-access method through an access-point (AP) at homes, schools, or offices. When multiple APs are deployed in the network field, the proper transmission power of each AP is essential to improve the performance, considering the coverage area, transmission capacity, and interference. In this paper, the authors study the transmission power optimization of concurrently communicating two APs in WLAN. Based on extensive experiment results, the authors propose a method of selecting the best power for each AP from the signal-to-noise ratio (SNR) of receiving signal strength (RSS). For evaluations, the authors implemented the proposed method on the elastic WLAN system testbed using Raspberry Pi for APs and conducted experiments for nine network topologies in two buildings at Okayama University. The results show that the proposal always selects the best power in any topology.
Recently, Wireless Local Area Networks (WLANs) have increased popularity around the world, where users can easily access to the Internet through associations with access points (APs) using mobile devices like smart phones, tablets, and laptops. In a WLAN, it is common that the number of users is always changing by time and users are not evenly distributed in the field. To optimize the number of active APs and the host associations in the network depending on traffic demands from users, previously, we proposed the AP configuration algorithm for the elastic WLAN system. Unfortunately, this algorithm can find the solution for the fixed user state in the network, although users often repeat joining and leaving the network. In this paper, we propose the extension of the AP configuration algorithm to deal with this dynamic nature. Here, as practical situations, this extension considers that at most one host may join or leave at the same time, and any communicating AP cannot be suspended and any communicating host cannot change its associated AP. Through numerical experiments using the WIMNET simulator in two network instances, the effectiveness of the proposal is demonstrated. Furthermore, it is implemented in the elastic WLAN system testbed using Raspberry Pi for the AP. The performance of this implementation is verified through experiments in four scenarios.
Currently, the IEEE 802.11n wireless local-area network (WLAN) has been extensively deployed world-wide. For the efficient channel assignment to access-points (APs) from the limited number of partially overlapping channels (POCs) at 2.4GHz band, we have studied the throughput drop estimation model for concurrently communicating links using the channel bonding (CB). However, non-CB links should be used in dense WLANs, since the CB links often reduce the transmission capacity due to high interferences from other links. In this paper, we examine the throughput drop estimation model for concurrently communicating links without using the CB in 802.11n WLAN, and its application to the POC assignment to the APs. First, we verify the model accuracy through experiments in two network fields. The results show that the average error is 9.946% and 6.285% for the high and low interference case respectively. Then, we verify the effectiveness of the POC assignment to the APs using the model through simulations and experiments. The results show that the model improves the smallest throughput of a host by 22.195% and the total throughput of all the hosts by 22.196% on average in simulations for three large topologies, and the total throughput by 12.89% on average in experiments for two small topologies.
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