• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.848-850
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• 2014

Mobile Ad hoc Networks(MANET) is consist of node that has mobility, MANET build cluster formation for using energy efficient. In existing LEACH algorithm elect cluster head node in coverage area by distribution function. However, when the cluster head node, that elected by distribution function, is divided coverage area unevenly, the network can't consumption energy efficiency. To solve this problem, we proposed CSWC(Coverage Scheduling Weight-value Control) algorithm. When the coverage area is divided nonchalance, proposed algorithm increased number of hops, that determines coverage area, for balance coverage area. As the result proposed algorithm is set balance coverage area, the network consumption energy efficiency.

• The KIPS Transactions:PartC
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• v.8C no.3
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• pp.287-298
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• 2001

본 논문에서는 ATM 기반 MPLS 망에서 효율적으로 IP 서비스를 전송하기 위한 동적 버퍼관리 방식의 Dynamic GSMP V3(General Switching Management Protocol Version 3)의 VLSI 구현을 위한 하드웨어 구조를 제안하고 설계하였다. 또한 현재 표준화중인 GSMP와 동적 버퍼관리 방식을 수용한 GSMP를 셀 손실률 측면에서 비교 분석하였다. ATM 스위치 상에 연결 제어의 성능 향상을 위해 스위치 상에 연결 제어의 성능 향상을 위해 스위치에서 연결설정 및 제어를 수행하는 Dynamic GSMP V3의 Slave 블록을 삼성 SoG 0.5$\mu\textrm{m}$ 공정으로 설계하였다. 기존의 방식과 제안한 방식의 성능 평가를 위해 확률 랜덤 변수에 의해 발생된 셀과 최소 버퍼 알고리즘을 이용하여 모의 실험을 하였으며, 이때 셀 손실률이 향상되었음을 알 수 있었다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.9 s.351
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• pp.165-174
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• 2006

In this paper, we propose a new contention window control algorithm to increase TCP performance in wireless multi-hop networks. The new contention window control algorithm is suggested to reduce the hidden and exposed terminal problems of wireless multi-hop networks. Most of packet drops in wireless multi-hop networks results from hidden and exposed terminal problems, not from collisions. However, in normal DCF algorithm a failed user increases its contention window exponentially, thus it reduces the success probability of fined nodes. This phenomenon causes burst data transmissions in a particular node that already was successful in packet transmission, because the success probability increases due to short contention window. However, other nodes that fail to transmit packet data until maximum retransmission attempts try to set up new routing path configuration in network layer, which cause TCP performance degradation and restrain seamless data transmission. To solve these problems, the proposed algorithm increases the number of back-of retransmissions to increase the success probability of MAC transmission, and fixes the contention window at a predetermined value. By using ns-2 simulation for the chain and grid topology, we show that the proposed algorithm enhances the TCP performance.

• The Journal of the Korea Contents Association
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• v.11 no.11
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• pp.34-41
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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 uses BEB backoff algorithm based on CSMA/CA. The BEB backoff algorithm shows excellent performance relatively in situation that competition between stations is less, but its performance is decreases as the competition increases. This paper proposes and analyses mathematically an enhanced backoff algorithm. To reduce the collision probability, the proposed algorithm increases the contention window to maximum after collision and decreases the contention window smoothly after successful transmission. To prove efficiency of proposed algorithm, simulations are conducted and analyzed.

• Journal of Internet Computing and Services
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• v.7 no.1
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• pp.151-164
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• 2006

The DCF of IEEE 802.11 standard coordinates transmissions onto the shared communication channel based on CSMA/CA protocol. Currently, 802,11 is the most widely deployed wireless LAN standard. In this paper, for 802.11-based wireless LAN we propose a service differentiation scheme adopting different contention window sizes and retransmission schemes for two different types of data packets and we present a Markov model for the state of a given station under a finite load traffic condition. We then derive an algorithm to find the transmission probability and the throughput. The proposed model is validated through simulation under various system settings.

• 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.

• Journal of the Korea Society of Computer and Information
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• v.10 no.4 s.36
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• pp.249-257
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• 2005

A Markov model for the IEEE 802.11 standard which is the most widely deployed wireless LAN protocol, is designed and the channel throughput is evaluated. The DCF of 802.11, which is based on CSMA/CA protocol, coordinates transmissions onto the shared communication channel. In this paper, under a finite load traffic condition and the assumption of packet loss after the final backoff stage. We present an algorithm to find the transmission probability and derive the formula for the channel throughput. The proposed model is validated through simulation and is compared with the case without packet losses.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12B
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• pp.1106-1114
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• 2003

Several analytic models describe transmission control protocol (TCP) performance such as steady-state throughput as an averaged ratio of number of transmissions to latency. For more detailed analysis of TCP latency, the latency during packet losses are recovered should be considered. In this paper, we derive the expected duration of loss recovery latency considering the number of packet losses recovered by retransmissions. Based on the numerical results verified by simulations, TCP using selective acknowledgement (SACK) option is more effective than TCP NewReno from the aspect of loss recovery latency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.9
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• pp.2298-2306
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• 2014

In this paper, we propose an open loop power control algorithm to control transmission power of the On-The-Move(OTM) Satcom terminal in GEO satellite communication environment. The proposed algorithm identifies the current channel state restricted by an obstacle or an antenna depointing loss based on the received beacon signal strength. On the basis of the determined signal attenuation causes, the OTM Satcom terminal turns off the RF output when an antenna tracking is failed. If the OTM Satcom terminal experiences a channel blockage by an obstacle, the terminal spreads the transmit data to increase data reception probability. To evaluate the performance of the proposed algorithm, we compare an adjacent satellite interference level and an outage probability. The results show the performance of the proposed algorithm is better than that of the conventional algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9A
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• pp.1425-1433
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• 1999

In this Paper, we analyzed the HIPERLAN(Hlgh PErformance Radio LAN) MAC(Medium Access Control) protocol, which was a standard for Wireless LANs defined by ETSI. We analyzed mathematically the elimination phase and the yield phase of the channel contention phase of CAC(Channel Access Control) layer in the infinite population model of the HIPERLAN using EY-NPMA(Elimination Yield-Nonpreemptive Priority Multiple Access)protocol. Also we analyzed the probability of successful transmission in the transmission phase. And, we proved results of a mathematical analysis by the simulation of HIPERLAN MAC protocol.