• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.126-134
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• 2006

Traditional TCP implementations have the under-utilization problem in large bandwidth delay product networks especially during the startup phase. In this paper, we propose a delay-based congestion control(DCC) mechanism to solve the problem. DCC is subdivided into linear and exponential growth phases. When there is no queueing delay, the congestion window grows exponentially during the congestion avoidance period. Otherwise, it maintains linear increase of congestion window similar to the legacy TCP congestion avoidance algorithm. The exponential increase phase such as the slow-start period in the legacy TCP can cause serious performance degradation by packet losses in case the buffer size is insufficient for the bandwidth-delay product, even though there is sufficient bandwidth. Thus, the DCC uses the RTT(Round Trip Time) status and the estimated queue size to prevent packet losses due to excessive transmission during the exponential growth phase. The simulation results show that the DCC algorithm significantly improves the TCP startup time and the throughput performance of TCP in large bandwidth delay product networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4B
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• pp.692-699
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• 2000

We build and analyze some types of queueing model to discuss capacity dimensioning of access links of a LAN interworking unit connected to the Internet backbone network. We assume that the IWU has a FIFO buffer to transmit IP packets to the Internet through the backbone. In order to analyze the system, we use a Poisson process and an MMPP process as input traffic models of IP packets and we use a general service time distribution as a service time model. But we use both an exponential service time and a deterministic service time in numerical examples for simple and efficient performance comparisons. As performance measures, we obtain the packet loss probability and the mean packet delay. We present some numerical results to show the effect of arrival rate, buffer size and link capacity on packet loss and mean delay.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1758-1763
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• 2004

This paper focuses on congestion control for ATM network with uncertain time-variant delays. The time-variant delays can be distinguished into two distinct components. The first one is represented by time-variant queueing delays in the intermediate switches that are occurred in the return paths of RM cells. The next one is a forward path delay. It is solved by the VBR model which quantifies the data propagation from the sources to the switch. Robust $H_8$ control is studied for solving congestion problem with norm-bounded time-varying uncertain parameters. The suitable robust $H_8$ controller is obtained from the solution of a convex optimization problem through LMI technique.

• Journal of the Korean Operations Research and Management Science Society
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• v.34 no.3
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• pp.137-153
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• 2009

In this paper, we present an analytic model that evaluates the performance of B-MAC protocol under contention transmission conditions of two senders in a single-hop wireless sensor network. Our model considers the impact of several important factors such as sleep cycle, the backoff mechanism and incoming traffic loads. After obtaining the service delay distribution of a sending node and expected delay of a receiving node, an iterative algorithm is presented for calculating the performance measures such as expected energy consumption usage per packet and latency. Simulation results show that the proposed analytic model can accurately estimate the performance measures under different traffic conditions.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1174-1177
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• 1987

The design of flow control protocols for integrared networks with complete voice traffic on the data link level is investigated. The class of admissible flow control policies analyzed maximized the average data link throughput subject to an average system time delay constraints a finite intervals (O,s). In particular, it is shown that the optimum control law is bang-bang (window flow mechanism). The window size L can be analytically derived from maximum tolerated time delay T, the input arrival C of the queueing system, the duration of the time interval S, the initial number of packets in the queue.

• Journal of the Korean Operations Research and Management Science Society
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• v.19 no.1
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• pp.85-98
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• 1994

The distribution of random sum of i. i. d. exponential random variables is called GHP (Generalized Phase-Type) distribution. The class of GPH distributions is large enough to include PH (Phase-Type) distributions and has several properties which can be applied conveniently for computational purposes. In this paper, we show that any distribution difined on R$^{+}$ can be app-roximated by the GPH distribution and demonstrate the accuracy of the approximation through various numerical examples. Also, we introduce an efficient way to compute the delay and waiting various numerical examples. Also, we introduce an efficient way to compute the delay and waiting time distributions of the GPH/GPH/1 queueing system which can be used as an approximation model for the GI/G/1 system, and validate its accuracy through numerical examples. The theoretical and experimental results of this paper help us accept the usefulness of the approximations based on GPH distribution.n.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.6
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• pp.1503-1513
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• 1998

This paper is related to a performance analysis of B-NT system, which is essential compositional equipment of B-ISDN access network. A simulator enabling performance analysis according to the change of network configuration topology and the change of user traffic is developed in this study. The developed B-NT, system simulator consists of graphic user interface module, simulation program automatic generator module, and B-NT system model library module. As examples of the results of performance analysis using the simulator, end-to-end user cell transmission delay time, queueing delay time in each system, and cell loss rate in the head node switch are presented. The simulator developed in this paper can be utilized in determining the network topology of B-NT system.

• Journal of Communications and Networks
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• v.14 no.5
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• pp.510-517
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• 2012

This paper analyzes the performance of voice-over-Internet protocol (VoIP) services in terms of the system throughput, the packet delay, and the signaling overhead in a mobile WiMAX system with a hybrid automatic repeat request (HARQ) mechanism. Furthermore, a queueing analytical model is developed with due consideration of adaptive modulation and coding, the signaling overhead, and the retransmissions of erroneous packets. The arrival process is modeled as the sum of the arrival rate at the initial transmission queue and the retransmission queue, respectively. The service rate is calculated by taking the HARQ retransmissions into consideration. This paper also evaluates the performance of VoIP services in a mobile WiMAX system with and without persistent allocation; persistent allocation is a technique used to reduce the signaling overhead for connections with a periodic traffic pattern and a relatively fixed payload. As shown in the simulation results, the HARQ mechanism increases the system throughput as well as the signaling overhead and the packet delay.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1482-1484
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• 2010

A new TCP protocol can succeed for large bandwidth delay product when it meets network bandwidth utilization efficiency and fair sharing. We introduce a novel congestion control algorithm which employs queueing delay information in order to calculate the amount of congestion window increment in increase phase, and reduces congestion window to optimal estimated bound as packet loss occurs. Combination of such methods guarantees that the proposal utilizes fully network bandwidth, recovers quickly from packet loss in wireless link, and preserves fairness for competing flows mixed short RTT and long RTT. Our simulations show that features of the proposed TCP meet the desired requirements.

• The KIPS Transactions:PartC
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• v.9C no.6
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• pp.847-856
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• 2002

Cellular network applications are growing drastically and this requires a fast and efficient transport method between the base station and the mobile switching center. One possible solution is to use ATM links. The low data rate and small-sized packets in the typical cellular applications imply that significant amount of link bandwidth would be wasted, if this small sized packet is carried by one ATM cell. For efficient operation for such cellular and low bit rate applications, a new type of ATM Adaptation Layer, AAL Type 2, has been proposed. In this paper, the principles of AAL Type 2 are briefly described along with the introduction of other alternatives which have formed the basis for this new AAL. The result from the simulation to study the performance of the AAL Type 2 is discussed from the view point of packet delay and ATM cell use efficiency. Due to the variable size of packets in this application, the fairness issue in serving variable sized packets is also discussed along with the effect of fair queueing algorithm implemented at AAL Type 2.