• The KIPS Transactions:PartC
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• v.18C no.3
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• pp.187-194
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• 2011

IEEE 802.11 wireless LAN has become the center of attention for one of the most dominant wireless networking technologies nowadays. In densely deployed wireless LANs, mobile stations are exposed to a number of AP, thus it is needed to select the best AP to associate with. The most common approach is to select the AP with the highest received signal strength. However it does not consider traffic load imposed to each AP so that it may cause the poor network performance. Therefore, in this paper, we propose a throughput estimation scheme for neighboring APs by sniffing the traffic within 802.11 networks. We devise a tool, named "VirtFrame", which is to estimate the station's capable throughput from neighbor APs based on the channel access time by virtually combining the sniffed frames. Simulation results show that our proposed scheme well matches that there exists correlation between the channel access time and the actual throughput of the APs.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.1
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• pp.101-105
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• 2008

This paper proposes an analytical model to calculate VoIP (Voice of IP) capacity over wireless LANs with frequent bit errors. Since the traditional analytical models for VoIP capacity have not included the effect of bit errors, simulations ould only evaluate VoIP capacity over erroneous channels. For analytically accurate estimation of VoIP capacity over noisy channels, we extend the conventional model to include the effect of propagation errors, end-to-end delay, voice quality, the waiting time in AP(Access Point). The experiments show that our model predicts the VoIP capacity of a given network within the range from 3% to 9% difference comparing with the simulation results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.155-159
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• 2004

This paper describes the design and the simulation of a single pole double throw(SPDT) FET switch for wireless LAN(IEEE802.11a ＆ IEEE802.11b) applications using drain impedance transformation network with Microstrip transmission line. At the receiving path insertion losses were from 0.8(㏈) to 1.462(㏈) between 2(㎓) and 4(㎓), from l.26(㏈) to 2.3(㏈) between 4.7(㎓) and 6.7(㎓) and the isolations were under 30(㏈) between 2(㎓) and 6.7(㎓). At the transmitting path insertion loss were from 1.18(㏈) to 2.87(㏈) between 2(㎓) and 4(㎓) from 0.625(㏈) to 1.2(㏈) between 4.7(㎓) and 6.7(㎓) and the isolations were under 30(㏈) between 2(㎓) and 6.7(㎓).

• Journal of Digital Contents Society
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• v.12 no.3
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• pp.299-307
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• 2011

The MAC of IEEE 802.11 WLAN to control data transmission uses two control methods called DCF and PCF. The DCF controls the transmission based on CSMA/CA The BEB backoff algorithm of DCF shows relatively excellent performance in situation that the number of competing station is less, but has a problem that performance of throughput and delay is degraded in situation that the number of competing station is increased. This paper mathematically analyzes an MIMD backoff algorithm considering retry limit that increases the CW to doubled after collision and decreases smoothly the CW to halves after successful transmission in order to reduce the collision probability. To prove efficiency of the MIMD backoff algorithm, lots of simulations are conducted and analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7B
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• pp.892-896
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• 2011

This paper proposes a two-stage synchronization scheme using a serial search non-coherent correlator appropriate for the IEEE 802.15.4a system. The proposed method improved the synchronization performance by using multi-pulse signals unlike the conventional method using single-pulse signals. It also compensated for the degradation of performance at low SNR resulting from the use of fixed threshold by applying the adaptive threshold technique. The proposed method showed a detection probability that is higher by approximately 0.2-0.3 compared with the conventional method in the IEEE 802.15.4a channel model.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.3
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• pp.23-28
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• 2021

In recent years, research on smart factory wireless mobile communication technology that wirelessly remotely controls utilities is being actively conducted. The Wi-SUN(Wireless Smart Utility Network) Alliance proposed Wi-SUN protocol structure suitable for building a platform such as a smart factory as a new wireless communication standardization standard based on EEE802.15.4g/e. It analyzes the performance of the IEEE802.15.4e CSL(Coordinated Sampled Listening) Mode MAC(Media Access Control) in terms of latency and looks at considerations for efficient operation.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.95-95
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• 2004

• Information and Communications Magazine
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• v.26 no.12
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• pp.28-34
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• 2009

본고에서는 최근 3GPP LTE-Advanced와 IEEE 802.16m의 표준화 작업에서 다루어지는 있는 셀간 협력전송기술의 기술적 내용과 향후 표준화 전망에 대해 알아본다.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.439-439
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• 2004

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.3
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• pp.10-19
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• 2009

Wireless LAN systems have been widely implemented for supporting the wireless internet services especially in the hotspot areas such as hospitals, homes, conference rooms, and so on. Compared with wired LAN systems, wireless LAN systems have the advantages of the users' mobility support and low implementation and maintenance costs. IEEE 802.11 wireless LAN systems employ the backoff algorithm to avoid contentions among STAs when two or more STAs attempt to transmit their data frames simultaneously. The MAC efficiency can be improved if the CW values are adaptively changed according to the channel state of IEEE 802.11 wireless LANs. In this paper, a dynamic contention window control algorithm is proposed using the genetic algorithm to improve the MAC throughput of IEEE 802.11 wireless LANs.