• Journal of applied mathematics & informatics
• /
• v.12 no.1_2
• /
• pp.395-408
• /
• 2003

Common Channel Signaling(CCS) networks need special controls to avoid overload of signaling networks and degradation of call process-ing rate, since they play an important role of controlling communication transfer networks. Congestion control and flow control mechanisms are well described in ITU-T recommendation on Signaling System No.7(SS7). For the practical provisions, however, we need an analysis on the relation among service objects, system requirements and implementation of congestion control algorithms. SS7 provides several options for controlling link congestion in CCS networks. In this paper we give a general queueing model of congestion control algorithm which covers both the international and national options. From the queuing model, we obtain the performance parameters such as throughput, message loss rate and mean delay for the international option. To show the performance of the algorithm, some numerical results are also given.

• Proceedings of the KSR Conference
• /
• 2008.06a
• /
• pp.1946-1954
• /
• 2008

In urban railways operated by 10 cars or 8 cars per trainset, passengers split up and board a train. On-board passengers for each car are not aware of congestion level of other cars of the train. Passengers waiting at stations can not predict congestion rate of the car which they get on. Therefore, the number of passengers is not equally distributed. The cars with a relatively low congestion level and the ones with a high level coexist in the train. The objective of this paper is to enhance passenger convenience and improve train operational efficiency through operational headway adjustments according to congestion level of each car. It also aims to spread passengers out evenly and assess the degree of congestion on each car by measuring the weight of each car including passengers during peak and off-peak hours.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.11 no.4
• /
• pp.344-350
• /
• 2011

Higher integrated density in 3D ICs also brings the difficulties of routing, which can cause the routing failure or re-design from beginning. Hence, precise congestion estimation at the early physical design stage such as floorplan is beneficial to reduce the total design time cost. In this paper, an effective estimation method of routing congestion is proposed for 3D ICs at floorplan stage. This method uses synthesized virtual signal nets, power/ground network and clock network to achieve the estimation. During the synthesis, the TSV location is also under consideration. The experiments indicate that our proposed method had small difference with the estimation result got at the post-placement stage. Furthermore, the comparison of congestion maps obtained with our method and global router demonstrates that our estimation method is able to predict the congestion hot spots accurately.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.12
• /
• pp.1965-1970
• /
• 2016

This paper studies generator rescheduling technique for congestion management in power system with wind farms. The proposed technique is formulated to minimize the rescheduling cost of conventional and wind generators to alleviate congestion subject to operational line overloading. The generator rescheduling method has been used with incorporation of wind farms in the power system. The locations of wind farms are selected based upon power transfer distribution factor (PTDF). Because all generators in the system do not need to participate in congestion management, the rescheduling has been done by generator selection based on the proposed generator sensitivity factor (GSF). The selected generators have been rescheduled using linear programming(LP) optimization techniques to alleviate transmission congestion. The effectiveness of the proposed methodology has been analyzed on IEEE 14-bus systems.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.54 no.6
• /
• pp.359-365
• /
• 2005

This paper presents an reduced-order near-optimal controller for the congestion control of Available Bit Rate (ABR) service in Asynchronous Transfer Mode (ATM) networks. We introduce the model, of a class of ABR traffic, that can be controlled using a Explicit Rate feedback for congestion control in ATM networks. Since there are great computational complexities in the class of optimal control problem for the ABR model, the near-optimal controller via reduced-order technique is applied to this model. It is implemented by the help of weakly coupling and singular perturbation theory, and we use bilinear transformation because of its computational convenience. Since the bilinear transformation can convert discrete Riccati equation into continuous Riccati equation, the design problems of optimal congestion control can be reduced. Using weakly coupling and singular perturbation theory, the computation time of Riccati equations can be saved, moreover the real-time congestion control for ATM networks can be possible.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.2 no.2
• /
• pp.75-82
• /
• 2007

Wireless Sensor Network(WSN) is composed of a large number of sensor nodes and accomplish a common task such as environment monitoring or asset tracking. This paper proposed a congestion control mechanism applying the ECN mechanism and the cross layer design to cope with temporal congestion in WSN. We experimented with the proposed congestion control mechanism using ns-2 simulator and measured the throughput of sink node. Simulation results show that the suggested mechanism can improve the performance of packet throughput by dealing with the congestion of network efficiently.

• International Journal of Internet, Broadcasting and Communication
• /
• v.11 no.1
• /
• pp.17-26
• /
• 2019

The Constrained Application Protocol (CoAP) is a specialized web transfer protocol proposed by the IETF for use in IoT environments. CoAP was designed as a lightweight machine-to-machine protocol for resource constrained environments. Due to the strength of low overhead, the number of CoAP devices is expected to rise rapidly. When CoAP runs over UDP for wireless sensor networks, CoAP needs to support congestion control mechanisms. Since the default CoAP defines a minimal mechanism for congestion control, several schemes to improve the mechanism have been proposed. To keep CoAP lightweight, the majority of the schemes have been focused mainly on how to measure RTT accurately and how to set RTO adaptively according to network conditions, but other approaches such as rate-based congestion control were proposed more recently. In this paper, we survey the literature on congestion control for CoAP and discuss the future research directions.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.6
• /
• pp.1127-1136
• /
• 2017

In wireless networks, the packet loss due to the bit error is misinterpreted as loss due to the congestion state, so TCP congestion control occurs frequently and performance degradation occurs. This degradation also occurs in MPTCP(Multipath TCP), which is an extension protocol of original TCP. In MPTCP, the overall performance of the multipath is degraded. In this paper, we propose a congestion control scheme which measures the bandwidth on each path of MPTCP and reduces the congestion window size by the measured bandwidth when packet loss occurs, in order to solve the MPTCP performance degradation in the wireless environment. We also implemented the proposed congestion control in the Linux kernel and compared it with the original MPTCP in the testbed and real wireless networks. Experimental results show that the proposed congestion control has better throughput performance than original MPTCP congestion control in the wireless environment.

• KIPS Transactions on Software and Data Engineering
• /
• v.3 no.11
• /
• pp.487-494
• /
• 2014

This paper focuses on an advanced congestion control scheme for M2M(Machine-to-Machine) communications in 3GPP LTE-A standard. A large number of MTC(Machine-type-Communication) devices try to access to LTE-A networks and send data to the networks all at once. In this characteristics, M2M communications will bring the serious network congestion problems into LTE-A cellular networks. To solve this critical problem, a congestion control mechanism will be required and it has been studied since Rel-10 LTE-A systems based on backoff mechanism for mobility management and session management. In this paper, we briefly introduce the main concept and operation about the congestion control scheme in 3GPP LTE-A standard. Also, simulation results for the basic congestion control and advanced congestion control scheme in MTC communication environment are provided and the improvement direction is considered in future 3GPP LTE-A standard.

• Journal of KIISE
• /
• v.41 no.11
• /
• pp.974-981
• /
• 2014

These days, use of multimedia streaming service and demand of QoS (Quality of Service) improvement have been increased because of development of network. QoS of streaming service is influenced by a jitter, delay, throughput, and loss rate. For guaranteeing these factors which are influencing QoS, the role of transport layer is very important. But existing TCP which is a typical transport layer protocol increases the size of congestion window slowly and decreases the size of a congestion window drastically. These TCP characteristic have a problem which cannot guarantee the QoS of UHD multimedia streaming service. In this paper, we propose a router buffer based congestion control method for improving the QoS of UHD streaming services. Our proposed scheme applies congestion window growth rate differentially according to a degree of congestion for preventing an excess of available bandwidth and maintaining a high bandwidth occupied. Also, our proposed scheme can control the size of congestion window according to a change of delay. After comparing with other congestion control protocols in the jitter, throughput, and loss rate, we found that our proposed scheme can offer a service which is suitable for the UDH streaming service.