• The KIPS Transactions:PartC
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• v.18C no.4
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• pp.251-254
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• 2011

In a WLAN, the data reception rate of a user station depends not only on the received signal strength (RSS) from an AP (Access Point) but also on the contention level of the AP. However, since only the RSSs measured at the physical layer have been used for a station to select an AP to associate with, the station may not satisfy the minimum quality requirements necessary for a seamless IPTV service. Thus, in this paper, we propose an AP selection method to support quality requirements of the IPTV service in a wireless LAN without modifying the IEEE 802.11 standard. A user station keeps monitoring a contention level of APs around it and a quality of an ongoing IPTV service. If the quality deteriorates below a threshold, the station reassociates with another AP having the least load so that the ongoing IPTV program is played without disruption.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3A
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• pp.209-216
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• 2005

This paper generally relates to the field of wireless local area networks(WLANs), and more particularly, to AP selection and association methods for the performance of a station. In these days, IEEE 802.11 Wireless LAN network is widely deployed and used as an emerging service to connect high-speed Internet in the public wireless environment. But, if there are many users in hot spot area, they suffer a severe decrease of performance. Thus it needs an association and access control mechanism especially when it is used in the public environment. In this paper, we suggest a selection and association method using Beacon or Probe Response frames based IEEE 802.11. Station selects AP using the information of the capacity area in a Beacon or a Probe Response frame. According to the present paper, an association method for a public WLAN service, which includes a WLAN user terminal and an AP for relaying WLAN communications to and from the user terminal, includes the steps of the user terminal asking the AP's states for access to a radio channel; and the station selects and associates with the AP According to the above-described selection in a high speed wireless Internet service based on public WLAN technologies that are currently in operations. Further, it is possible to improve the efficiency of network management.

• Journal of Advanced Navigation Technology
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• v.7 no.2
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• pp.149-155
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• 2003

This paper generally relates to the field of wireless local area networks(WLANs), and more particularly, to AP selection and association methods for the performance of a station. In these days, IEEE 802.11 Wireless LAN network is widely deployed and used as an emerging service to connect high-speed Internet in the public wireless environment. But, if there are many users in hot spot area, they suffer a severe decrease of performance. Thus it needs an association and access control mechanism especially when it is used in the public environment. In this paper, we suggest a selection and association method using Beacon or Probe Response frames based IEEE 802.11. Station selects AP using the information of the capacity area in a Beacon or a Probe Response frame. According to the present paper, an association method for a public WLAN service, which includes a WLAN user terminal and an AP for relaying WLAN communications to and from the user terminal, includes the steps of the user terminal asking the AP's states for access to a radio channel; and the station selects and associates with the AP. According to the above-described selection in a high speed wireless Internet service based on public WLAN technologies that are currently in operations. Further, it is possible to improve the efficiency of network management.

• Journal of KIISE:Information Networking
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• v.37 no.6
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• pp.489-493
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• 2010

In an indoor localization method taking the lateration-based approach, the distance between a target and an AP (Anchor Point) is estimated using RSS (Received Signal Strength) measurements. Since the characteristics of a radio signal randomly vary in time and space, errors are unavoidable in distance estimation with measured RSS. Since the accuracy of distance estimation affects the localization accuracy of a lateration-based method, additional APs hearing a target have been used for localization in the literature. However, lots of experimental results show that the accuracy of a lateration-based method is improved by using carefully selected APs measuring the high quality RSSs which the distances estimated is close to the actual distances between nodes as reference APs, not using merely more APs. In this paper, we focus on selection method of reference AP and distance estimation method reflecting on environmental dynamics. We validate our method by implementing an indoor localization system and evaluating the accuracy of our method in the various experimental environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6B
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• pp.338-348
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• 2005

Currently, IEEE 802.11 Wireless LAN (WLAN) is rising as the most popular means for the broadband wireless access network. In this thesis, we propose a QoS(Quality of Service)-Oriented mechanism using handshaking method of scanning phase in IEEE 802.11 handoff. In conventional process for handoff, the major criterion to select the best AP(Access Point) among candidates is normally based on the RSS(Received Signal Strength), which does not always make the selected network guarantee the maximum achievable performance. Even though the link quality with a neighboring AP is excellent, the AP may not be a good candidate to handoff to simply because MAC(Medium Access Control) protocol of IEEE 802.11 standard is contention-based such as CSMA/CA. Therefore, if we apply network level information to AP selection criteria, we can achieve better handoff efficiency rather than before. The analysis and simulation results applied to our new mechanism show clearly better performance than AP selection based on traditional handoff method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.632-634
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• 2012

In order for the connection to the wireless network from the list of priorities of the wireless AP to AP profile automatic connection by selecting the preferred method to register a profile, which is determined at the time of the change, the user does not respond to the demands of the part. In this study, the frequency of the user's access in accordance with the wireless AP, and by creating a profile, the user needs to meet with regard to network access adaptive research.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.11a
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• pp.1371-1374
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• 2005

지금까지 IEEE 802.11 WLAN 에서 많이 연구되어진 주제는 노드들 간의 공평성(fairness)과 처리량(throughput)을 높이는데 중점이 맞추어진 것들이 대부분이었다. 성능을 높이기 위한 AP의 CW값에 관한 연구는 노드들 간에 관한 연구에 비하여 비교적 적은 편이다. 지금은 노드들과 AP가 충돌하게 되면 BEB(Binary Exponential backoff)방식으로 셋팅되어 사용하게 있기 때문에 1:N의 불공평한(unfairness) 상황이 발생한다. AP에서 노드들로 가는 하향링크(downlink) 전송이 많은 상황에서 AP가 다른 노드들과 똑같은 채널 접근확률을 가지는 것은 바람직하지 않기 때문에 AP에게 우선권(priority)을 주어 전체 성능을 높이는 것이 필요하다. 따라서 본 논문에서는 AP의 CW(Contention Window)값이 변화함에 따라 전체 성능에 끼치는 영향과 노드 수의 변화에 따른 AP의 적절한 백오프 CW값을 분석해 보고자 한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4269-4292
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• 2014

Currently, increasing numbers of access points (AP) are being deployed in enterprise offices, campuses and municipal downtowns for flexible Internet connectivity, but most of these access points are idle or redundant most of the time, which causes significant energy waste. Therefore, with respect to power conservation, applying energy efficient strategies in WIFI networks is strongly advocated. One feasible method is dynamically managing network resources, particularly APs, by powering devices on or off. However, when an AP is powered on, the device is initialized through a long boot time, during which period clients cannot be associated with it; therefore, the network performance would be greatly impacted. In this paper, based on a global view of an entire WLAN, we propose an AP selection technology, known as Temporary Access Selection (TAS). The criterion of TAS is a fusion metric consisting of two evaluation indexes which are based on throughput and battery life, respectively. TAS is both service and clients' preference specific through balancing the data rate, battery life and packet size. TAS also works well independently in traditional WLANs in which no energy efficient strategy is deployed. Moreover, this paper demonstrates the feasibility and performance of TAS through experiments and simulations with Network Simulator version 3 (NS3).

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.4
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• pp.1611-1629
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• 2016

Recently, deploying WiFi access points (APs) for facilitating indoor localization has attracted increasing attention. However, most existing mechanisms in this aspect are typically simulation based and further they did not consider how to jointly utilize pre-existing APs in target environment and newly deployed APs for achieving high localization performance. In this paper, we propose a measurement-based AP deployment mechanism (MAPD) for placing APs in target indoor environment for assisting fingerprint based indoor localization. In the mechanism design, MAPD takes full consideration of pre-existing APs to assist the selection of good candidate positions for deploying new APs. For this purpose, we first choose a number of candidate positions with low location accuracy on a radio map calibrated using the pre-existing APs and then use over-deployment and on-site measurement to determine the actual positions for AP deployment. MAPD uses minimal mean location error and progressive greedy search for actual AP position selection. Experimental results demonstrate that MAPD can largely reduce the localization error as compared with existing work.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.983-984
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• 2008

This paper proposes a variable break that can offset prediction error as well as a pre-selection methods, based on the variable break, for enhanced unit selection. In Japanese, a sentence consists of several APs (Accentual phrases) and MPs (Major phrases), and the breaks between these phrases must predicted to realize text-to-speech systems. An MP also consists of several APs and plays a decisive role in making synthetic speech natural and understandable because short pauses appear at its boundary. The variable break is defined as a break that is able to change easily from an AP to an MP boundary, or from an MP to an AP boundary. Using CART (Classification and Regression Trees), the variable break is modeled stochastically, and then we pre-select candidate units in the unit-selection process. As the experimental results show, it was possible to complement a break prediction error and improve the naturalness of synthetic speech.