• Journal of KIISE:Information Networking
• /
• v.27 no.2
• /
• pp.206-218
• /
• 2000

Retransmissions on the DLC layer are essential to ABR service providing the low CLR (cell loss ratio) over the unreliable wireless channel with high bit error rate. In the wireless ATM, the DLC layer below ATM layer performs the retransmission and reordering of the cells to recover the cell loss over the wireless channel and by doing so, the effect of the wireless channel characteristics with high bit error rate can be minimized on the ATM layer which is designed under the assumption of the low bit error rate. We propose, in this paper, the schemes to reflect the changes of the transmission rate over the wireless channel on the ABR rate control. Proposed scheme can control the source rate to the changes of the transmission rate over the wireless channel and reduce the required buffer size in the AP (access point). In the simulation, we assume that the DLC layer can inform the ATM layer of the wireless channel quality as good or bad. Our simulation results show that the proposed schemes require the smaller buffer size compared with the existing scheme, enhanced dynamic max rate control algorithm (EDMRCA). It is also shown that the scheme with the intelligent DLC which adjusts the rate to the wireless channel quality not only provides the low CLR with smaller buffer requirement but also improves the throughput by utilizing the wireless bandwidth more efficiently.

• Proceedings of the KIEE Conference
• /
• 2003.07d
• /
• pp.2134-2136
• /
• 2003

ATM 네트워크 중에서 ABR 서비스만이 피드백(feedback) 메커니즘이 가능하며, 이를 이용한 체증제어(congestion control)연구가 다양한 방법으로 진행되고 있다. 본 연구에서는 현대 제어기법을 이용한 ABR 서비스의 체증제어 문제에 관심을 가지고, ABR 서비스 트래픽의 체증을 억제하고 체증 발생시 제어함으로써 최대의 QoS(Quality of Service)를 보장하도록 한다. 문제해결을 위해 제어 이론을 기반으로 한 ABR Explicit Rate 알고리즘을 이용하며, 불확실한 외란에 대해서도 강인하고 안정된 성능을 보이는 시스템 모델을 연구한다. 그리고 이 시스템에 대한 $H_{\infty}$ 제어기를 설계하고 시뮬레이션을 통하여 설계한 제어기의 타당성을 보인다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.8A
• /
• pp.1160-1168
• /
• 2000

This paper presents a real-time integrated traffic management (RITM) scheme that can effectively manage variable bit rate (VBR) and available bit rate (ABR) traffics having unpredictable characteristics in asynchronous transfer mode (ATM) networks. An unique feature of this scheme is that it has a special ATM cell control block which makes it possible to monitor bursty traffics in real-time so that the delay incurred to measure cell arrival rate is minimized. Additionally, the proposed scheme intends to dynamically reassign the leftover network resources to VBR/ABR connections without any deterioration in quality of service (QoS) of the existing connections. The RITM scheme has been verified to reliably monitor incoming traffics and to efficiently manage network resources by computer simulations. The capability of managing the incoming ATM traffics in real-time helps determine an optimal acceptable number of user connections for a given network condition. We can use this value as a threshold to protect the network from being congested and to find out a cost-effective buffer design method.

• Journal of the Korea Society of Computer and Information
• /
• v.7 no.3
• /
• pp.80-91
• /
• 2002

A general goal of the AT%(Asynchronous Transfer Mode) network is to support connect across various network. On ATM networks, ABR services are provided using the remained ban after allocation CBR and VBR traffic. Realtime services such as transmitting audio or video data may be provided using CBR ado VBR which have a constrained transmission delay, but in these cases, the communications bandwidth may be wasted. In this paper a simulation has been performed to compare and evaluate the performance between the ERICA(Explicit Rate Indicate Avoidance) and EPRCA(Enhanced Proportional Rate Control Algorithm) switches which use Explicit Rate switch algorithm for ABR switch. The variation of the ACR at the source end system, the queue length, the utilization rate of the link bandwidth and the share fairness at the transient and steady states are used as the evaluation criteria for the simulation. As a result of simulation, ERICA algorithm switch was ten times long compared to ERPCA switch to achieve assigned fair share. so EPRCA switch is superior to ERICA about load response. For Fair share and stability, ERICA switch is excellent to EPRCA switch.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.3B
• /
• pp.487-492
• /
• 2000

The ABR(available bit rate) service has been developed to support data application over ATM(asynchronous Transfer mode) networks, and TCP is the most widely used transport layer protocol in existing data networks. Thus, the performance improvement of TCP over ABR is an issue of cardinal importance. In this paper, we propose algorithm of the adjustment of congestion window size utilizing RM(resource Management) cell information. The motivation is to use more reliable information in ER(explicit rate) field within RM cell to determine TCP window size. Simulations are performance using the suggested algorithm is improved, as compared to TCP-reno.

• The KIPS Transactions:PartC
• /
• v.10C no.3
• /
• pp.305-310
• /
• 2003

The performance of various GFR implementations has been recently studied due to the interest to provide bandwidth guarantees with a simpler implementation than ABR in ATM networks. One of the important factors is buffer management for guaranteeing QoS in GFR service. An efficient buffer management algorithm is necessary to guarantee MCR for untagged cell in ATM switch. In this paper, we propose and evaluate a buffer management scheme to provide the GFR service guarantees. The proposed scheme can control the cell discarding for fairness in each VC, and compared with Double-EPD and DFBA. Our results show that the proposed buffer management with per-VC queuing achieves significant enhancement on goodputs and fairness index than those of existing methods.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.39 no.8
• /
• pp.7-13
• /
• 2002

In this paper, we propose an traffic control algorithm for efficient link utilization of ATM-ABR service based on fuzzy logic. The proposed algorithm, controls transmission rates of source according to switch buffer size and input cell tate by using the fuzzy rate . For this method we developed a model and algorithm of fuzzy traffic control method and fuzzy traffic controller which based on ER of VS/VD. For the fuzzy traffic controller, we also designed a membership function, fuzzy control rules, and a max-min inferencing method.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.23 no.5
• /
• pp.1384-1396
• /
• 1998

This paper ivestigates the performance of a relative rate (RR) switch algorithm for the rate-based available bit rate (ABR) flow control in asynchronous transfer mode (ATM) networks. A RR switch may notify the network congestion status to the source by suing the congestion indication (CI) bit or no increase (NI)bit in the backward RM (BRM) cells. A RR switch can be differently implemented according to the congestion detectio and notification methods. In this paper, we propose three implementation schemes for the RR switch with different congestion detection and notification methods, and analyze the allowed cell rate (ACR) of a source and the queue length of a switch in steady state. In addition, we derive the upper and lower bounds for the maximum and minimum queue lengths for each scheme respectively, and evaluate the effects of the ABR parameter values on the queue length. Furthermore, we suggest the range of the rage increase factor (RIF) and rate decrease factor (RDF) parameter values which can prevent buffer overflow and underflow at a switch.

• The KIPS Transactions:PartC
• /
• v.10C no.1
• /
• pp.51-60
• /
• 2003

One of the most important matters in designing network and realizing service, is to grip on the traffic characteristics. Conventional traffic prediction and analysis used the models which based on the Poisson or Markovian. Recently, experimental research on the LAN, WAN and VBR traffic properties have been pointed rut that they weren't able to display actual real traffic specificities because the models based on the Poisson assumption had been underestimated the long range dependency of network traffic and self-similar peculiarities, it has been lately presented that the new approach method using self-similarity characteristics as similar as the real traffic models. Therefore, in this paper, we generated self-similar data traffic like real traffic as background load. On the existing ABR congestion control algorithm, we analyzed by classify into ACR, buffer utilization. cell drop rate, transmission throughput with the representative EFCI, ERICA, EPRCA and NIST twitch algorithm to show the efficient reaction about the burst traffic.

• Journal of the Korea Computer Industry Society
• /
• v.3 no.1
• /
• pp.95-104
• /
• 2002

This paper presents some studies on the Internet TCP/IP(Transmission Control Protocol-Internet Protocol) traffic over ATM(Asynchronous Transfer Mode) UBR(Unspecified Bit Rate) and ABR(Available Bit Rate) classes of service. Fuzzy logic prediction has been used to improve the efficiency and fairness of traffic throughput. For TCP/IP over UBR, a novel fuzzy logic based cell dropping scheme is presented. This is referred to as fuzzy logic selective cell drop (FSCD). A key feature of the scheme is its ability to accept or drop a new incoming packet dynamically based on the predicted future buffer condition in the switch. This is achieved by using fuzzy logic prediction for the production of a drop factor. Packet dropping decision is then based on this drop factor and a predefined threshold value. Simulation results show that the proposed scheme significantly improves TCP/IP efficiency and fairness. To study TCP/IP over ABR, we applied the fuzzy logic ABR service buffer management scheme from our previous work to both approximate and exact fair rate computation ER(Explicit cell Rate) switch algorithms. We then compared the performance of the fuzzy logic control with conventional schemes. Simulation results show that on zero TCP packet loss, the fuzzy logic control scheme achieves maximum efficiency and perfect fairness with a smaller buffer size. When mixed with VBR traffic, the fuzzy logic control scheme achieves higher efficiency with lower cell loss.