Kyaw Soe Lwin

Throughput measurements for access-point installation optimization in IEEE802.11n wireless networks

Currently, high-speed IEEE802.11n interfaces using MIMO have become common in access points (APs) and personal computers (PCs) for wireless local-area networks (WLANs). This trend leads to further expand the application areas for WLANs. In this paper, we present throughput measurement results of IEEE802.11n devices with various placement orientations in indoor environments. They show that measured throughputs are strongly affected by the roll and yaw angles at the installation of AP due to the multiple antennas in MIMO, which should be considered in optimizing the installation of APs in indoor fields.

A Minimax Approach for Access-Point Setup Optimization Using Throughput Measurements in IEEE802.11n Wireless Networks

Recently, an IEEE802.11n access point (AP) has become common in the wireless local-area network (WLAN) due to the high-speed data transmission using the multiple input multiple output (MIMO) technology. However, the signal propagation from the 802.11n AP may not be uniform in the circumferential direction because of multiple antennas in MIMO, in addition to the height direction. As a result, the data transmission speed between the AP and a host can 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 height and the angles 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. Then, we optimize the AP setup by changing the height and directions while measuring throughputs. For evaluations, we confirm the accuracy of the model using measurement results and the throughput improvements at most hosts including the bottleneck one in the field by our approach.

A parameter optimization tool and its application to throughput estimation model for wireless LAN

Most of algorithms or logics to solve mathematical problems adopt multiple parameters such as coefficients and thresholds whose values should be carefully selected to enhance the performance. Conventionally, their developers or users tune them by trial and error, where they repeat to apply algorithms or logics with proper parameter values to available input data sets and modify them based on the results. As a result, this tuning process may consume a great deal of energy and not always provide the optimal ones. In this paper, we present a versatile parameter optimization tool to explore optimal values of parameters for various algorithms/logics. We show the effectiveness through applications for the throughput estimation model for wireless local-area networks, with the extension of the model.

A User-PC Computing System as Ultralow-cost Computation Platform for Small Groups

Recently, a personal computer (PC) has rapidly evolved the computing ability due to the highest CPU clock, more CPU cores, and the larger memory. Then, the collection of idling CPU cycles in conventional PCs of the members in a group such as a university laboratory significantly enhances the level of parallel computing platform with very small costs. This low-cost computation environment is of great interest in schools, especially in developing countries. To realize this concept, in this paper, we propose a User-PC Computing (UPC) system based on the master-worker model. First, we present the design and implementation of the UPC master using Linux and for the UPC worker with both Linux and Windows. Then, because the job scheduling takes a key role in determining the overall computing performance, we present an efficient job scheduling method using performance measurement results of worker PCs by benchmark programs, in addition to a conventional round-robin one. We verify the effectiveness of our proposed UPC system through experiments using several benchmark and application programs.

A Channel Assignment Extension of Active Access-Point Configuration Algorithm for Elastic WLAN System under Limited Channels

Previously, we proposed the active access-point (AP) configuration algorithm for elastic Wireless Local-Area Network (WLAN) systems using heterogeneous APs. This algorithm activates or deactivates APs depending on traffic demands, assuming that any active AP can use a different channel to avoid interferences among APs. However, the number of non-interfered channels in IEEE 802.11 protocols is limited. In this paper, we propose an extension of this algorithm to consider the channel assignment to the active APs under this limitation. After the channel assignment to the active APs, AP associations of hosts are improved to further minimize interferences by averaging loads among different channels. The effectiveness of our proposal is evaluated using the WIMNET simulator.