• The KIPS Transactions:PartC
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• v.12C no.2 s.98
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• pp.217-222
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• 2005

The IEEE 802.11 based wireless local area networks are candidates to lead the broadband connectivity in the home and office scenarios. Recently IEEE proposed the 802.11e as a new standard to provide appropriate Quality of Services to a plethora of emerging real-time multimedia and high demanding applications such as high definition movie and audio distribution, video-conference and voice over IP. This paper studies the IEEE 802.11e/IEEE 802.11b interactions focusing on potential unfairness problems that might appear in networks with heterogeneous wireless LAN technologies as well as in the IEEE 802.11e deployment phase.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10A
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• pp.1003-1013
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• 2006

There is a serious problem in an 802.11g VoWLAN (Voice over Wireless LAN) terminal that talk time is less than 30% compared with an 802.11b terminal. It is almost impossible to achieve talk time level of the 802.11b MAC transmission method because IEEE 802.11g uses OFDM modulation, which is a kind of multi-carrier method and OFDM transmission speed is 54 Mbps faster than normal modulation. In this paper, a new concept of a Holdover time as a power saving method during a call with 802.11g terminal is suggested for the first time. Increase in the number of engaged terminals as a result of holdover time causes to QoS problem because of the increase in the number of back-off and then contention window. In this paper, to solve the QoS problem, a new approach is suggested such that when in down lint the sequence number of 802.11 G.711 is analyzed in the MAC of the terminal and then the Hold over time depending on loss rate is changed. Also, consumption of an electric current of 802.11b/g and MAC parameter's performance due to busy traffic caused by increase in the number of terminal are analyzed and then real data using VQT and Airopeek are analyzed.

• The KIPS Transactions:PartC
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• v.11C no.4
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• pp.497-508
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• 2004

The existing wireless LAN standard IEEE802.11b has many vulnerabilities from security point of view. The authentication mechanisms in IEEE802.11b have many vulnerabilities. As a result to complement the weak of IEEE802.11b authentication, the IEEE802.1x had been developed in the sense of providing strong user authentication with appropriate mechanism. But this mechanism does not perform AP authentication and there are also some weak points. And in confidentiality and message Integrity case, WEP is weak from key stream reuse attack, IV reuse attack and so on. For that reason, in this paper we propose secure wireless LAN system. Our system provides strong user authentication, confidentiality, and message integrity based on existing IEEE802.1x framework and TLS.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2317-2322
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• 2009

In this paper, look into the applicable communication for unmanned vehicle system development, and make an alternative idea to IEEE 802.11a. "IEEE 802.11a" is differently from "IEEE 802.11b/g"-which used to 2.4GHz ISM band-as it use OFDM modulation system of 5GHz band, as contrasted with "IEEE 802.11b/g" of ISM band, it has advantage against falling-off the capability caused by interfered, and provide maximum 54Mbps communication speed. Made a priority tested Soft Roaming and Hard Roaming to ensure the sound boom of unmanned vehicle in the flat parking. According to the each effect value, Present a most suitable method of applicable to "IEEE 802.11a" to unmanned vehicle system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1A
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• pp.65-71
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• 2006

In IEEE 802.11b wireless network, the access point(AP) sends beacons periodically to manage stations when they are running in low power mode. Stations contend for the transmission medium after they receive a beacon and continuously check its state until it becomes available. Thus the energy consumption of each station increases as the load of wireless network. In this paper, we propose a method to reduce energy consumption controlling virtual bitmap in wireless network with multiple stations. The problems of low power mode in IEEE 802.11b wireless interface are described and a new method to reduce energy consumption is proposed. The proposed method is simulated with the network simulator, ns2, and compared with the low power mode of the IEEE 802.11b. The result measured in terms of station's wakeup time shows some enhancement in energy consumption when multiple stations are communicating through the AP in wireless network.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.5
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• pp.21-29
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• 2008

This paper proposes a carrier frequency of set estimation algorithm for IEEE802.11n system. As IEEE802.11n is a multiple input multiple output(MIMO) system, so there are several combining techniques which are used in multiple receive antenna system. In this paper, we propose hybrid carrier frequency offset estimation algorithms using combining techniques in multiple receive antenna systems, and show that the proposed selection combining carrier frequency offset (CFO) estimation algorithm can estimate carrier frequency offset within 1/10 MSE error at SNR 10 dB in channel B and within 1/2 MSE error at SNR 10 dB in channel D rather than the conventional MIMO CFO one.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7B
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• pp.780-788
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• 2011

The lack of QoS (Quality of Service) support functionalities in IEEE 802.11 DCF mode makes it difficult to provide real-time multimedia services in WLANs. In this paper, we propose an effective available bandwidth measurement method in IEEE 802.11b DCF environments. The proposed method measures the total channel idle time and the collision probability during each measurement period. Then, the available bandwidth is calculated by considering those measured information and the transmission overheads at MAC and PRY layers. The performances of the proposed method are evaluated using OPNET simulator. The simulation results show that the proposed method provides more exact results than existing comparable schemes.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.118-122
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• 2013

In this study, We show that multiple UAVs (Unmaned Air Vehicle) have datalink system which includes the IEEE 802.11b technology. we are predicting and calculating to the number of the UAV and data rate between UAV and ground control system, using the IEEE 802.11 standards which include the transmit/receive the delay time and theoretical maximum throughput (TMT).

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.4 no.2
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• pp.9-17
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• 2005

Coexistence of different wireless systems that share the 2.4 GHz ISM frequency band is becoming one of the most important issue. This paper presents a model of the interference that IEEE 802.11b affected by IEEE 802.15.4. The packet error rate (PER) of IEEE 802.11b under the interference of IEEE 802.15.4 is analyzed. The PER is obtained by using the bit error rate (BER) and the collision time. Further, this paper suggests a packet length to reduce the effect of the IEEE 802.15.4 interference and obtain a maximum throughput of the IEEE 802.11b. The analytical results are validated using simulation.

• Journal of Communications and Networks
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• v.10 no.3
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• pp.301-307
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• 2008

In this paper, the impact of channel sensing methods to IEEE 802.15.4 under the interference of IEEE 802.11b are analyzed. Two different channel sensing methods, energy detection and carrier sense, are considered. An average transmission delay, a throughput, and a power drain rate are used as performance measures. Those performance measures of IEEE 802.15.4 under the interference of IEEE 802.11b are analyzed mathematically. The simulation results are shown to validate the analytic results.