• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10A
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• pp.816-822
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• 2011

This paper provides the performance measurement and analysis of Wireless LAN IEEE 802.11 in a mobile environment. The performance of IEEE802.11b/g and IEEE802.11p that is designed for Vehicle-to-Vehicle(V2V) communication is measured and analyzed. Diameter of communication, link access time and delay are measured as vehicle's speed varies. Also, the performance is checked in a situation that the load to network varies. In conclusion, the futher research topics are discussed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.161-168
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• 2011

This paper provides the performance measurement and analysis of Wireless LAN IEEE 802.11 in a mobile environment. The performances of IEEE802.11b/g and IEEE802.11p designed for Vehicle-to-Vehicle(V2V) communication are measured and analyzed. Diameter of communication and link access time are compared under variation of speed of the vehicle.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.12
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• pp.116-124
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• 2003

According to the convenience and efficiency, IEEE 802.11 WLAN(Wireless LAN) has became rapidly wide-spread on the market. However, QoS support is needed for various multimedia service. In this paper, we consider both MAC method of IEEE 802.11 and IEEE 802.11e and Traffic Category differentiated service by QoS support method. In addition, we study currently existing back-off algorithms in view of comparative analysis. As a result we propose a new back-off algorithm called Collision Rate Based-EDCF. The proposed back-off algorithm confirms the performance by computer simulations in terms of Throughput, and QoS support.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.535-538
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• 2005

Wireless LANs based on the IEEE 802.11 standard are widely spread for use nowadays. Traffic which are conveyed over the WLANs change rapidly from normal data such a Email and Web pages, to multimedia data of high resolution video and voice. To meet QoS (Quality of Service) required by these multimedia traffic, the IEEE 802 committee recently has developed a new standard, IEEE 802.11e. IEEe 802.11.e contains two MAC mechanisms for providing QoS: EDCA(Enhanced Distributed Channel Access) and HCCA (HCF Controlled Channel Access). Using these standardized MAC mechanisms as a building platform, various admission control mechanisms can be combined to offer QoS gurantees for multimedia traffic. This paper surveys these research efforts.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4A
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• pp.412-420
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• 2006

With the appearance of various types of traffic services in communication networks, a study on QoS(Quality of Service) packet scheduling mechanisms which can support differentiated service to each traffic service becomes very important. To meet this requirement, IEEE 802.11 Working Group established the IEEE 802.11e MAC protocol which categorizes every traffic services into 4 access categories(AC) and provides the differentiated service to each AC. In addition, the physical layer of IEEE 802.11a/g standards provide up to 54 Mbps transmission rate per one wireless LAN terminal. However, since the radio resource is hardly limited in wireless channel, it is necessary to find an efficient packet scheduling scheme to maximize the transmission efficiency. Therefore, in this paper, we proposed a new packet scheduling scheme that can enhance the total throughput by setting different contention windows(CW) of CSMA-CA channel access scheme to each wireless LAN terminal according its current channel states. Numerical results derived from using NS-2 network simulator have shown that our proposed packet scheduling scheme can enhance the performance of IEEE 802.11e more and more.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11A
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• pp.870-877
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• 2011

IEEE 802.11 devices are widely used, and terminals can be equipped with multiple IEEE 802.11 interfaces as low-cost IEEE 802.11 devices are deployed. The off-the-shelf IEEE 802.11 devices provide multiple channels and multiple data rates. In practical multi-channel networks, since there is channel heterogeneity which indicates that channels have different signal characteristics for the same node, channels should be efficiently assigned to improve network capacity. In addition, in multi-rate networks, low-rate links severely degrade the performance of high-rate links on the same channel, which is known as performance anomaly. Therefore, in this paper, we propose a heterogeneity aware channel assignment (HACA) algorithm that improves network performance by reflecting channel heterogeneity and performance anomaly. Through NS-2 simulations, we validate that the HACA algorithm shows improved performance compared with existing channel assignment algorithms that do not reflect channel heterogeneity.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.6
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• pp.39-47
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• 2009

This paper presents implementation of two types of the 802.11 MAC engine for the next generation WLAN, 802.11n. The first version of MAC engine consists of hardwired logic and embedded firmware. Hardwired logic includes Tx block, Rx block, Backoff block, and ChannelManage block. Embedded firmware contains Protocol Control block, MLME block, and MSDU processing block. The first version has a time-critical fault during the atomic transmission caused by software overhead, so it can not be applied to 802.11n MAC. For that reason, the second version has additional blocks with hardwired logic modules to reduce software overhead of the first version. This enhanced version has 73Mbps throughput and it is expected to be further improved up to 129 Mbps with frame aggregation which is one of the key additional features of 802.11n. As a result, the second version of MAC engine can be applied to 802.11n MAC.

• Journal of Internet Computing and Services
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• v.13 no.1
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• pp.7-14
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• 2012

In this paper, performance of IEEE 802.11 carrier-sense multiple access with collision-avoidance (CSMA/CA) protocols in saturated traffic conditions is presented taking into account the impact of imperfect channel sensing. The imperfect channel sensing includes both missed-detection and false alarm and their impact on the performance of IEEE 802.11 is analyzed and expressed as a closed form. To include the imperfect channel sensing at the physical layer, we modified the state transition probabilities of well-known two state Markov process model. Simulation results closely match the theoretical expressions confirming the effectiveness of the proposed model. Based on both theoretical and simulated results, the probability of detection is concluded as a dominant factor for the performance of IEEE 802.11.

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.515-527
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• 2009

IEEE 802.11n is an ongoing next-generation WLAN(Wireless Local Area Network) standard that supports a very high-speed connection with more than 100Mb/s data throughput measured at the MAC(Medium Access Control) layer. Study trends of IEEE 802.11n show two aspects, enhanced data throughput using aggregation among packets in MAC layer, and better data rates adapting MIMO(Multiple-Input Multiple-Output) in PHY(Physical) layer. But, the former doesn't consider wireless channel and the latter doesn't consider aggregation among packets for reality. Therefore, this paper analyzes data throughput for IEEE 802.11n considering MAC and PHY connection. A-MPDU(Aggregation-MAC Protocol Data Unit) and A-MSDU(Aggregation-MAC Service Unit) is adapted considering multi-service in MAC layer, WLAN MIMO TGn channel using SVD(Singular Value Decomposition) is adapted considering MIMO and wireless channel in PHY layer. Consequently, Simulation results shows throughput between A-MPDU and A-MSDU. Also, We use Ns-2(Network simulator-2) for reality.

• Journal of Korea Multimedia Society
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• v.13 no.2
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• pp.205-215
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• 2010

It is necessary to provide a fast and secure handover for seamless real-time multimedia services based on IEEE 802.11. In this paper, we propose FMIPv6 handoff protocol integrating L2/L3 layer based on IEEE 802.11 WLAN environment. In that, we propose a hierarchical key management scheme and authentication mechanism for protecting the handover signaling messages. The number of connections with AAA server is minimized for the fast handover. It is also compared and analyzed the handover cost with previous method.