• The Transactions of the Korea Information Processing Society
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• v.7 no.12
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• pp.3923-3932
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• 2000

In mobile network, wireless links may be overloaded due to a high concentratioJl of mobile hosts in a given cell. As a result, the required QOS(Quality of Service) cannot be provided to all flows in that cell. So, there exists adaptive applications which can operate with various bandwidth levels. When a wireless link is overloaded, it can adapt by reducing the bandwidths of flows, is referred to as rate adaptation. In this paper, we analyze the performance of existing rate adaptation methods by simulations. The result of simulation experiments shows that average-fair adaptation scheme has very low network overhead but high bandwidth variance of flows, which causes the worse quality of service. We propose a rate adaptation method refined by combining fair adaptation and average-fair adaptation, and shows the refined method can provide lower bandwidth variance of flows by simulations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.63-66
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• 2015

As smart-phones become popular, mobile data traffic has been dramatically increasing and intensive researches on the next-generation mobile communication network is in progress to meet the increasing demand for mobile data traffic. In particular, heterogeneous network (HetNet) is attracting much interest because it can significantly enhance the network capacity by increasing the spatial resue with macro and small cells. In the HetNet, we have several problems such as load imbalance and interference because of the difference in transmit power between macro and small cells and cell range expansion (CRE) can mitigate the problems. In this paper, we propose a new cell selection scheme with adaptive cell range expansion bias (CREB) for ultra dense HetNet and we analyze the performance of the proposed scheme in terms of average cell transmission rate through system-level simulations and compare it with those of other schemes.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.1
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• pp.39-43
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• 2007

In high speed communication networks, the determination of a transmission rate is critical for the stability of a closed-loop network system with the congestion control scheme. In ATM networks, the available bit rate (ABR) service is based on a feedback mechanism, i.e., the network status is transferred to the ABR source by a resource management (RM) cell. RM cells contain the traffic information of the downstream nodes for the traffic rate control. However, the traffic status of the downstream nodes can not be directly transferred to the source node in the IP based networks. In this paper, a new rate-based congestion control scheme using an exponential weighted moving average algorithm is proposed to build an efficient feedback control law for congestion avoidance in high speed communication networks. The proposed congestion control scheme assures the stability of switch buffers and higher link utilization of the network. Moreover, we note that the proposed congestion scheme can flexibly work along with the increasing number of input sources in the network, which results in an improved scalability.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.102-104
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• 2011

최근 비디오 스트리밍과 대화형 비디오 서비스 등과 같은 광대역 멀티미디어 서비스를 지원하기 위하여 Wimax와 같은 4G 무선네트워크 시스템 기술이 발전해 왔다. 4G 무선네트워크의 OFDM(Orthogonal Frequency Division Multiplexing)과 MIMO(multi Input Multi Output)은 사용자들에게 매우 유연한 QoS(Quality of Service) 서비스를 제공해 줄 수 있다.[1] 이 논문에서는 다양한 네트워크 상황에서 멀티캐스트 그룹에게 효율적인 방법으로 통신 자원을 할당하기 위해 OFDM 방법을 사용 하였다. 이에 본 논문에서는 한 셀(cell) 내의 서로 다른 멀티캐스트의 그룹의 다른 SNR(Signal to noise Ratio)의 사용자 분포에 따른 적응적인 scalable 비디오 멀티캐스트 방식을 제안한다. 더 나은 수신율을 가진 사용자는 최적의 MCS(Modulation and Coding Scheme) 할당을 통해 서로 다른 화질의 scalable 비디오 계층 중 높은 해상도의 비디오를 받을 수 있다. 논문에서는 전체 전송률을 최적화 하는 대신 전송받은 전체 비디오의 평균 화질을 최적화하는 방법을 제안한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.10
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• pp.1873-1880
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• 2016

Most of the energy used to operate a cellular network is consumed by a base station (BS), and reducing the transmission power of a BS is required for energy-efficient cellular networks. In this paper, a distributed transmit power control (TPC) algorithm is proposed based on the flocking model to improve the energy efficiency of a cellular network. Just as each bird in a flock attempts to match its velocity with the average velocity of adjacent birds, in the proposed algorithm each mobile station (MS) in a cell matches its rate with the average rate of the co-channel MSs in adjacent cells by controlling the transmit power of its serving BS. Simulation results show that the proposed TPC algorithm follows the same convergence properties as the flocking model and also effectively reduces the power consumption at the BSs while maintaining a low outage probability as the inter-cell interference increases. Consequently, it significantly improves the energy efficiency of a cellular network.

• Journal of the Korea Society of Computer and Information
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• v.6 no.1
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• pp.67-73
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• 2001

This paper proposes a new scheduling algorithm for broadband ATM access network. The existed scheduling algorithms (Train, Chao. Dynamic scheduling algorithm) have high cell loss rate and waste channel. These proposed mechanism utilize to control of multimedia services based on the quality of service level of the input traffic This paper suggests a functional architecture of scheduling and the scheduling algorithm to satisfy various QoS requirements. The performance measures of interest, namely steady-state cell loss probability and average delay, average delay, are discussed by simulation results.

• Journal of Platform Technology
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• v.8 no.2
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• pp.22-31
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• 2020

The construction and operation of industrial automation has been actively taking place from manufacturing plan to production for improving operational efficiency of production line and flexibility of equipment. ISO/TC184 is standardizing on operating methods that can share information of programmable device controllers such as PLC and IoT that are geographically distributed in the production line. In this study, the design of the cell controller consists of PLC group and IoT group that perform signals such as temperature sensors, gas sensors, and pressure sensors for thermal processes and corresponding motors or valves. The operation and analysis of the cell controller were performed using SDN(Software Defined Network) and the three types of process services performed in thermal processes are real-time transmission service, loss-sensitive large-capacity transmission service, and normal transmission service. The simulation result showed that the average loss rate improved by about 17% when the traffic increased before and after the application of the SDN route technique, and the delay in the real-time service was as low as 1 ms.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.380-382
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• 1998

ABR 은 ATM의 서비스 중에서 가장 최근에 추가된 것으로서 트래픽 소스의 전송률을 제어하기 위해서 피드백 메커니즘을 사용한다. ABR 서비스의 성능은 스위치를 통해서 피드백되는 RM 셀에 의해서 결정적인 영향을 받는다. ATM 표준에는 EPRCA, CAPC, ERICA 등의 알고리즘을 다루고 있다. 하지만 이러한 스위치 알고리즘에 대한 성능평가 및 분석 은 자세히 이루어지지 않고 있다. 본 논문에서는 현재 사용중인 ABR 스위치 알고리즘 중 단순히 큐의 길이에 위해 폭주를 판단하는 EPRCA 방법에 대해서 자세히 분석하고 EPRCA 의 단점을 극복하기 위해서 큐의 길이뿐만 아니라 새로운 변수 즉 평균 분산 및 표준편차을 이용해서 각 송신원의 공정성을 높이고 시스템의 효율성을 증대시키는 방안을 제시한다.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.11
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• pp.44-52
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• 1998

In this paper, we proposed a node architecture and cell routing strategies for ATM applications in WDM multihop networks. The proposed node architecture employs the optical delay loop for storing the cell which is failed in out-link contention. This optical delay loop allows the delay of one cell without the electro-optic conversion. Therefore, we can get the advantages of S&F(Store-and-Forward) routing in Deflection-based all-optical networks. To support the ATM applications efficiently. we considered the transmission priority of ATM cell so that high priority cell can be transmitted with lower loss and shorter delay than low priority one. Two kinds of routing strategies are designed for this architecture: Scheme-Ⅰand Scheme-Ⅱ. Scheme-Ⅰapplies S&F routing to high cell and Deflection routing to low cell, i.e., high cells are routed along the shortest path based on S&F routing, but low cells are deflected or lost. Schem-Ⅱ is similar to Scheme-Ⅰexcept that low cells can occupy the optical loop if it is available. This Scheme-Ⅱ increases the utilization of network resources without decreasing the throughput of high cell by reducing the low cell loss rate when traffic load is low. Simulation results show that our routing strategies have better performance than conventional ones under non-uniform traffic as well as uniform traffic.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7A
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• pp.786-793
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• 2004

Autonomous data rate control scheme of current IxEV-DO uplink networks can not supper the various QoS requirements of heterogeneous traffics nor hold rise-over-thermal OtoT) constraints. In this paper, an uplink resource management scheme called the modified weighted g-fair (MWGF) scheduler with RoT filling is proposed and evaluated for heterogeneous traffics in cdma2000 type uplink networks. The proposed scheme belongs to a family of centralized resource management schemes and offers QoS guarantee by using priority metrics as well as lower system loading by holding RoT constraints using RoT filling method. With some case-study simulations, the proposed algorithms shows lower average delays of real time users compared to that of autonomous rate control by 29 - 40 ％. It also shows the 1.0 - 1.3 dB lower received RoT level than autonomous rate control schemes, leading to lower network loading.