Recently, Wireless Local-Area Network (WLAN) has become prevailing as it provides flexible Internet access to users with low cost through installation of several types of access points (APs) in the network. Previously, we proposed the active AP configuration algorithm for the elastic WLAN system using heterogeneous APs, which dynamically optimizes the configuration by activating or deactivating APs based on traffic demands. However, this algorithm assumes that any active AP may use a different channel from the other ones to avoid interferences, although the number of non-interfered channels in IEEE 802.11 protocols is limited. In this paper, we propose the extension of the AP configuration algorithm to consider the channel assignment to the active APs under this limitation. Besides, AP associations of the hosts are modified to improve the network performance by averaging loads among channels. The effectiveness of our proposal is evaluated using the WIMNET simulator in two topologies. Finally, the elastic WLAN system including this proposal is implemented using Raspberry Pi for the AP. The feasibility and performance of the implementation are verified through experiments using the testbed.

Recently, an IEEE 802.11n access point (AP) prevailed over the wireless local area network (WLAN) due to the high-speed data transmission using the multiple input multiple output (MIMO) technology. Unfortunately, the signal propagation from the 802.11n AP is not uniform in the circumferential and height directions because of the multiple antennas for MIMO. As a result, the data transmission speed between the AP and a host could be significantly affected by their relative setup conditions. In this paper, we propose a minimax approach for optimizing the 802.11n AP setup condition in terms of the angles and the height in an indoor environment using throughput measurements. First, we detect a bottleneck host that receives the weakest signal from the AP in the field using the throughput estimation model. To explore optimal values of parameters for this model, we adopt the versatile parameter optimization tool. Then, we optimize the AP setup by changing the angles and the height while measuring throughput. For evaluations, we verify the accuracy of the model using measurement results and confirm the throughput improvements for hosts in the field by our approach.

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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.

Reversible logic has come to the forefront of theoretical and applied research today. Although many researchers are investigating techniques to synthesize reversible combinational logic, there is little work in the area of sequential reversible logic. Latches and flip-flops are the most significant memory elements for the forthcoming sequential memory elements. In this paper, we proposed two new reversible logic gates MG-1 and MG-2. We then proposed new design techniques for latches and flip-flops with the help of the new proposed gates. The proposed designs are better than the existing ones in terms of number of gates, garbage outputs and delay.Comment: IOSR Journal of Computer Engineering (IOSR-JCE) 5.6(2012