• 한국ITS학회:학술대회논문집
• /
• v.2006 no.10
• /
• pp.108-112
• /
• 2006

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.12
• /
• pp.2195-2200
• /
• 2008

The use of WLAN technology specially 802.11 b and g has seen huge subscriber growth in a relatively short time period due to low cost and ease of installation of WLAN hardware. These technologies provide multiple data rates ranging from 1 to 54 Mbps depending on modulation used in physical layer. This paper presents the performance of 802.11b and g under different data rates in mobile IPv4 environment. OPNET is used in the study as the network simulator. The performance metrics used in this wort is data traffic received by a WLAN station roaming amongst Access Point(AP) of different ESSs. It is found that much data packets are lost during handover between mobile agents. The traffic received by the roaming station varies based on the data rates provided by two different WLAN technologies.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.22 no.6
• /
• pp.116-126
• /
• 2008

This paper describes the Dual-band WLAN transmitter with 2.4[GHz], 5[GHz]. Dual-band WLAN transmitter was designed at 2.4[GHz] and 5[GHz]. The Dual-band WLAN transmitter has a amplifier which operate at 2.4[GHz] and 5[GHz] frequency and two VCO(Voltage Controlled Oscillator) or VCO has a wide scope of frequency. these problem cause a size and a power consumption, The Dual-band WLAN transmitter module was proposed to solve these. the transmitter was designed to get output signals of IEEE 802.11a's 5.8[GHz] band signal using frequency multiplication way or to act a amplifier about the 2.4[GHz] band signal of IEEE 802.11b/g, according to inputed frequency and bias voltage that a eve using single transmission block. The output spectrum get the improved specification of ACPR of 4[dB], 6[dB], 16[dB] at +11[MHz], +20[MHz], +30[MHz] offset of center frequency compared to no linearization, was satisfied to transmit spectrum mask of IEEE 802.11a wireless Lan.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.1A
• /
• pp.115-124
• /
• 2007

In this paper, the I/Q mismatch problem between the transmission line and antenna switch is solved by a new CPW matching circuit for a VoWLAN terminal with 54 Mbps communication speed through the IEEE 802.11 b/g CCK/OFDM. I/Q performances with the new matching circuit are analyzed and improved by the output spectrum mask, the characteristics of the EVM(Error Vector Magnitude) due to the nonlinear CCK/OFDM demodulation data, and receiver's sensitivity.

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

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2014.05a
• /
• pp.104-107
• /
• 2014

Nowadays, smart devices such as smart phones, tablets PC, etc... are exchanging messages using WLAN(Wi-Fi) technologies for sending and receiving messages. With the growth of the smart devices users, the WLAN (Wi-Fi) medium communication could be loaded and then the Quality of Service is undesirable. Currently, there are five types of Wireless LAN such as802.11 a / b / g / n / ac supporting the communication between smart devices and the most used it WLAN 802.11n. Unfortunately, if the WLAN 802.11n is being used by a lot of users, there is poor Quality of Service due to the interference. In this paper, we analyze the Quality of Service provided by the 802.11n and compare with the next generation of wireless 802.11ac.

• Proceedings of the IEEK Conference
• /
• 2003.11c
• /
• pp.187-190
• /
• 2003

최근 IEEE에서 WLAN을 표준으로 하는 802.11g가 확정되면서 이를 지원하는 AP가 출시되었다. AP에서 사용되는 OS는 POSIX를 기반으로 된 Linux 같은 OS를 통하여 구현되고 있 다. 이 논문에서는 가장 범용으로 사용되고 있는 Rad Hat을 기반으로 한 embeded linux를 만들어본다. 이와 함께 embeded linux를 가지고서 Network 기능을 추가하고, AP 하드웨어 드라이버 및 AP 모듈을 올려서 구연한다. 여기에 추가적으로 DHCP나 Web UI기능 등의 부가 기능을 추가하여 AP를 구현하는데 목적이 있다.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
• /
• v.8 no.1
• /
• pp.18-23
• /
• 2009

The conventional channel selection method for a ZigBee communication network basically detects the energy values in all channels. In the ISM band, no license is required to use channels in this band, so there may exist various interference factors in this band. It is well known that WLAN is the major interference factor degrading the performance of ZigBee in the ISM band. In this paper, we propose an efficient channel selection algorithm which uses the pattern of two types of WLAN channel uses as the a priori information of IEEE 802.11 band IEEE 802.11g. By using the proposed algorithm, we may save the time required to select channels for the ZigBee communications.

• Proceedings of the Korean Information Science Society Conference
• /
• 2003.10c
• /
• pp.490-492
• /
• 2003

본 논문에서는 3G 이동 통신 시스템과 IEEE 802.11 WLAN 시스템 간의 통합을 위한 프로토콜 계층을 설계한다. 통합 알고리즘을 휘한 핵심은 서로 다른 다양한 시스템의 MAC 계층을 IP 계승을 통해 통합하는 AII IP 구조에서, 이종간 핸드오프 지원을 위한 새로운 적응 계층(Adaptation Layer)을 추가하는 것이다. 적응 계승에서 요구되는 기능들은 끊김 없는 계층적 핸드오프, 시스템의 발견과 최적의 인터페이스 선택. QoS 지원. AAA 등이다. 다양한 이슈들 중에 계층적 핸드오프를 위한 시스템 발견과 최적의 인터페이스 선택을 위한 알고리즘에 대해 살펴보도록 하겠다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.12A
• /
• pp.1320-1328
• /
• 2007

In recent year, the popularity of WLAN has generated much interests on improvement and performance analysis of the IEEE 802.11 protocol. In this paper, we analyze two medium access methods of the IEEE 802.11 MAC protocol by investigating the MAC layer packet service times when arrival packet sizes have a general probability distribution. We use the M/G/1/K queueing model to analyze the throughput and the delay performance of IEEE 802.11 MAC protocol in a wireless LAN. We compare the performances of Basic access method and RTS/CTS access method. We take some numerical examples for the system throughput and the queue dynamics including the mean packet delay and packet blocking probability.