• Journal of Advanced Navigation Technology
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• v.13 no.4
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• pp.523-531
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• 2009

In this study, we propose a joint source/channel rate control algorithm for video encoder targeting packet erasure channel. Based on the buffer constraints of video communication systems, encoding rate constraint is presented. After defining source distortion models for coded and skipped video frames and a channel distortion model for packet errors and their propagation, an average distortion model of received video is proposed for a given encoding window. Finally, we define an optimization problem to minimize the average distortion for given channel rates and packet loss rates by controlling spatio-temporal parameters of source video and FEC block sizes. Then, we propose a window-based algorithm to solve the problem in real-time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.12
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• pp.873-875
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• 2014

In this paper we describe an asynchronous MAC protocol with receiver-initiated duty cycling for energy-efficiency in wireless sensor networks(WSN). Legacy asynchronous MAC protocols, X-MAC and PW-MAC, has weaknesses which generates too many control packets and has data collision problem between multiple transmitters, respectively. Therefore, we propose a receiver-initiated asynchronous MAC protocol which generates control packets from transmitter to complement these disadvantages. Compared to the prior asynchronous duty cycling approaches of X-MAC and PW-MAC, the proposed protocol shows a improvement in energy-efficiency, throughput and latency from simulation results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.7
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• pp.1840-1850
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• 1998

In this paper, we propose a priority control algorithm using hop count, called HC-PC(Priority Control Algorithm using Hop-Count) for steaming mode CLS, in wide area ATM networks. In our HC-PC algorithm, hop count of packet is increased by one as traverse CLS hop and is used as loss priority when a CLS buffer is congested. That guards packets with higher priority form congestion. The average packet loss probabilities are evaluated via mathematical analysis for HC-PC algorithm case and no priority control case. The simulationresults indicate that our algorithm may offer better performance in terms of loss fairness for pathe length and yield high utilization of newtork resource.

• The Journal of the Korea Contents Association
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• v.10 no.9
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• pp.45-56
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• 2010

This paper reports a new mechanism for congestion controls. The proposed congestion detection algorithm can be provided with delay and unnecessary energy consumption. Conventional congestion control methods decide congestion by queue occupancy or mean packet arrival rate of MAC layer only, however, our method can perform precise detection by considering queue occupancy and mean packet arrival rate. In addition, the congestion avoiding method according to congestion degree and scheduling method using priority for real time packets are proposed. Finally, simulation results show that proposed congestion detection and control methods outperforms conventional scheduling schemes for wireless sensor network.

• The Journal of the Korea Contents Association
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• v.12 no.4
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• pp.69-75
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• 2012

In this paper, to provide various services of QoS, and moreover applying traffic ratio to CAC(Call Admission Control) algorithm tested how long average data rate and the average packet delay time. When CAC algorithm is not applied, traffic mixture ratio is 1:1:4:4, the FTP Service 0.4, web services 0.6, streaming service 0.7, the packet delay requirements are not satisfied. On the other hand CAC Algorithm is applied, all the service of packet delay are satisfied with arrival rate. Therefore, we can make sure that applying of CAC of traffic control WWW, FTP, Video, VoIP can guarantee the various services of QoS.

• Journal of KIISE:Information Networking
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• v.29 no.2
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• pp.174-180
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• 2002

With the invention of MPLS and the Improvement in traffic engineering, multipath packet forwarding and dynamic load control has become a reality. A dynamic load control, while it can improve network efficiency by controlling loads between paths according to the network state, can lead to unstable and oscillating state because of the staleness of the state information. In this paper, we propose a efficient load control scheme which remains stable. The proposed scheme introduces prediction to reduce the staleness of state message and to prevent oscillation.

• Journal of KIISE:Information Networking
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• v.31 no.1
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• pp.1-10
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• 2004

This study discusses Application-layer FEC using erasure codes. Because of the simple decoding process, erasure codes are used effectively in Application-layer FEC to deal with Packet-level errors. The large number of parity packets makes the loss rate to be small, but causes the network congestion to be worse. Thus, a redundancy control algorithm that can adjust the number of parity packets depending on network conditions is necessary. In addition, it is natural that high-priority frames such as I frames should produce more parity packets than low-priority frames such as P and B frames. In this paper, we propose a redundancy control algorithm that can adjust the amount of redundancy depending on the network conditions and depending on data priority, and test the performance in simple links and congestion links.

• The Journal of the Korea Contents Association
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• v.7 no.1
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• pp.131-138
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• 2007

In wired networks, packet losses mostly occur due to congestion. TCP reacts to the congestion by decreasing its congestion window, thus to reduce network utilization. In wireless networks, however, losses may occur due to the high bit-error rate of the transmission medium or due to fading and mobility. Nevertheless, TCP still reacts to packet losses according to its congestion control scheme, thus to reduce the network utilization unnecessarily. This reduction of network utilization causes the performance of TCP to decrease. In this paper, we predict packet loss by using RSS(Received Signal Strengths) on the wireless and suggest adding RSS flag bit in ACK packet of MH. By using RSS flag bit in ACK, the FH(Fixed Host) decides whether it adopt congestion control scheme or not for the maximum throughput. The result of the simulation by NS-2 shows that the proposed mechanism significantly increases sending amount and receiving amount by 40% at maximum.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2001.11b
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• pp.121-126
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• 2001

본 논문에서는 절단 전력 제어를 사용하는 위성통신 시스템에서 부호율을 채널 상황에 따라 적응시켜 최대의 전송 효율을 얻는 하이브리드 ARQ 타입1 부호율 제어 기법을 제안한다. 제안된 기법의 성능을 분석하기 위하여 먼저 하이브리드 ARQ 타입 1 시스템에서 부호율을 채널 상황에 따라 적응적으로 제어했을 때의 전송 효율과 패킷 오율을 유도한다. 또한, 유도된 패킷 오율식으로부터 절단 전력 제어에서 필요한 목적 수신 SNR값을 사용되는 각 부호율에 대해 구하고, 전송 효율을 최대화하는 최적의 부호율 제어변수를 효율적으로 구할 수 있는 방식을 제안한다. 전송효율 측면에서 분석한 결과 제안된 방법이 기존의 방식에 비하여 우수한 성능을 보여줄 수 있음을 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.12
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• pp.2448-2457
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• 1994

CCITT recommendation X.25 and X.75 have been applied to the PSPDN environment for data communication of packet switching. They have also been used for packet switching in the ISDN exchanges since about the year 1980. This paper presents the throughput of the TDX-10 packet handler as simulating the performance based on memory management and flow control of the resource management algorithm designed originally.