start-ver=1.4 cd-journal=joma no-vol=7 cd-vols= no-issue=2 article-no= start-page=248 end-page=270 dt-received= dt-revised= dt-accepted= dt-pub-year=2017 dt-pub=20171004 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=A Channel Assignment Extension of Active Access-Point Configuration Algorithm for Elastic WLAN System and Its Implementation Using Raspberry Pi en-subtitle= kn-subtitle= en-abstract= kn-abstract= 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. en-copyright= kn-copyright= en-aut-name=Md. Selim Al Mamun en-aut-sei=Md. Selim Al Mamun en-aut-mei= kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=FunabikiNobuo en-aut-sei=Funabiki en-aut-mei=Nobuo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=Kyaw Soe Lwin en-aut-sei=Kyaw Soe Lwin en-aut-mei= kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=Md. Ezharul Islam en-aut-sei=Md. Ezharul Islam en-aut-mei= kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=KaoWen-Chung en-aut-sei=Kao en-aut-mei=Wen-Chung kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil=Okayama University kn-affil= affil-num=2 en-affil=Okayama University kn-affil= affil-num=3 en-affil=Okayama University kn-affil= affil-num=4 en-affil=Okayama University kn-affil= affil-num=5 en-affil=National Taiwan Normal University kn-affil= en-keyword=Elastic WLAN system kn-keyword=Elastic WLAN system en-keyword=interference minimization kn-keyword=interference minimization en-keyword=channel assignment kn-keyword=channel assignment en-keyword=active access-point configuration algorithm kn-keyword=active access-point configuration algorithm en-keyword=testbed kn-keyword=testbed en-keyword=Raspberry Pi kn-keyword=Raspberry Pi END start-ver=1.4 cd-journal=joma no-vol=7 cd-vols= no-issue=2 article-no= start-page=187 end-page=207 dt-received= dt-revised= dt-accepted= dt-pub-year=2017 dt-pub=20171004 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=A Minimax Approach for Access Point Setup Optimization in IEEE 802.11n Wireless Networks en-subtitle= kn-subtitle= en-abstract= kn-abstract= 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. en-copyright= kn-copyright= en-aut-name=Kyaw Soe Lwin en-aut-sei=Kyaw Soe Lwin en-aut-mei= kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=FunabikiNobuo en-aut-sei=Funabiki en-aut-mei=Nobuo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TaniguchiChihiro en-aut-sei=Taniguchi en-aut-mei=Chihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=Khin Khin Zaw en-aut-sei=Khin Khin Zaw en-aut-mei= kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=Md. Selim Al Mamun en-aut-sei=Md. Selim Al Mamun en-aut-mei= kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=KuribayashiMinoru en-aut-sei=Kuribayashi en-aut-mei=Minoru kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=KaoWen-Chung en-aut-sei=Kao en-aut-mei=Wen-Chung kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= affil-num=1 en-affil=Okayama University kn-affil= affil-num=2 en-affil=Okayama University kn-affil= affil-num=3 en-affil=Okayama University kn-affil= affil-num=4 en-affil=Okayama University kn-affil= affil-num=5 en-affil=Okayama University kn-affil= affil-num=6 en-affil=Okayama University kn-affil= affil-num=7 en-affil=National Taiwan Normal University kn-affil= en-keyword=Wireless local area network kn-keyword=Wireless local area network en-keyword=access point setup kn-keyword=access point setup en-keyword=MIMO kn-keyword=MIMO en-keyword=throughput estimation model kn-keyword=throughput estimation model en-keyword=parameter optimization kn-keyword=parameter optimization END