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In order to adaptively control network congestion, an ATM switch with input and output buffers using back pressure has been proposed. The characteristic of such an ATM switch has been evaluated by the Monte Carlo (MC) method. However, the conventional MC method can provide cell loss probability on the order of 10–6. Therefore, cell loss probability lower than 10–6 is obtained by extrapolating the values estimated by the MC method. On the other hand, the importance sampling (IS) simulation method was developed to evaluate low-probability events and has been used to estimate the bit error rate of digital communication systems. In order to detect cell loss probability on the order of 10–12 required for QoS in moving image transmission, the IS method is applied to estimate the cell loss probability in the ATM switch using back pressure. In addition, the high-akagawa.peed operation and reliability of this method are evaluated to demonstrate its effectiveness. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 83(9): 111–118, 2000 [ABSTRACT FROM AUTHOR]

In an asynchronous transfer mode (ATM) network, various calls with different transmission quality requirements ranging from tow bit-rate data signals to high bit-tare motion picture signals are applied. Therefore, it is important to determine how to allocate network resources to those calls and to judge whether those calls can be accepted. This paper proposes a can admission control scheme based upon a data table that holds the relationship between average bit-rate and needed bandwidth for aggregated signals in each quality class obtained beforehand by simulation. This proposed scheme assumes broadband services where the aver-age bit rate and burstiness of aggregated signals can be estimated clearly with predictable value ranges. This proposed scheme uses a conventional scheme for service quality class control. The following characterizes this proposed scheme: (1) it is suitable for real time call processing because it has small table search processing and a simple table search algorithm; (2) it realizes more accurate control due to a decreased data volume requirement and more precise data preparation than is the case for some of the conventional schemes; (3) it can be expanded easily to handle increases in the number of quality classes; and (4) it provides control in terms of statistic multiplexing effects between each quality class (also found in some of the conventional schemes). [ABSTRACT FROM AUTHOR]

This paper considers a new transmission method (quasisynchronous transfer mode, Q-STM), as a means to eliminate both the cell loss and the network delay fluctuation in an ATM network. The concept of time-switch in circuit switching is introduced into the ATM switching framework. A switching structure and the call establishment procedure are proposed. In the proposed method, the time-switch is introduced, which eliminates in principle the output port contention in the ATM switching fabric. By preparing a buffer with a certain capacity, cell loss due to buffer overflow in the output port of the ATM switch can be completely eliminated. The concept of subframe is newly introduced, which serves as the unit of time-switching. A three-layered structure is applied to the frame structure, composed of the frame, the subframe, and the slot. This helps to reduce delay due to time-switching, compared to the case in which the concept of subframe is not introduced, while maintaining the flexibility of bandwidth allocation. Additionally, the method is based on ATM switching, and the ordinary ATM cells not bound to the frame can be transmitted and ATM-switched by the idle slot in the frame. This enhances the features of ATM, i.e., effective use of the circuit by the statistical multiplexing effect. The basic characteristics concerning the quality of the ordinary ATM cell are analyzed by simulation. [ABSTRACT FROM AUTHOR]

This paper considers a function to improve the efficiency of the operation administration and maintenance (OAM) of the virtual path (VP) in the AIM network. A VP test method is proposed which can test the connectivity and performance at new VP establishment and locate the fault point at VP failure. The implementation of the method is discussed. The feature of proposed method is that the number of error bits, the number of lost cells, and the number of misdelivered cells can be measured by transmitting and receiving the test OAM cell in any test section of VP. In this piper, the purpose and requirements for the VP test system are described first. Then the mechanisms in the proposed system and the allocation of test functions are considered. A transmission performance measurement algorithm is proposed for the test OAM receiver so that the bit error, the cell loss, and the cell misdelivery can accurately be counted. The structure of the VP test OAM cell to realize the proposed algorithm is presented. Finally, the system parameters of the proposed method are evaluated quantitatively. [ABSTRACT FROM AUTHOR]

In the 2lst century, 10∼30 Mbps video services will be the main traffic services of B-ISDN. Therefore, bandwidth control is effective for dividing a 150-Mbps line into the call bandwidths. A shared buffer-type ATM switch with this function can be achieved by queueing call by call and by reading out cells from the queues according to the bandwidth control table sequence. When the traffic is random with utilization of 0.9, the switch with 128∼512 queues on the 4000-cell shared buffer has sufficiently small cell loss characteristics. Multiqueueing technology is provided by embedded RAMs which point to the first addresses and last addresses of the queues. Queue length control, which limits each queue length, for multiquoueing is provided by the embedded RAMs. A one-board switch with 128 queues on a 4000-cell shared buffer is developed. [ABSTRACT FROM AUTHOR]

This paper considers the application of the modulation level-controlled variable capacity radio channel to asynchronous transfer mode (ATM) networks and analyzes the cell loss characteristic. A system is proposed in which the transmission capacity of the overall system can be enlarged by controlling the number of modulation levels. This helps to enhance the absorption effect for the traffic variation in ATM networks. Therefore, the proposed system can reduce the cell loss probability. As a result of quantitative analysis of the system. it is shown that the cell loss improvement is by the factor of several hundreds to several thousands compared to the virtual path fixed-capacity transmission system and several to several thousands compared to the virtual path capacity control system proposed up to present. [ABSTRACT FROM AUTHOR]

An end-to-end error recovery scheme is a promising way to obtain low end-to-end delays in packet switching networks. However, a too-short timeout interval may cause unnecessary packet retransmissions even when a packet is transmitted successfully to the receiver. On the other hand, a longer timeout interval may introduce large end-to-end delay when a packet is actually lost. Thus, it becomes important to determine an appropriate timeout period in the scheme. This paper analyzes a tandem queueing network system with blocking due to finite capacity in intermediate nodes and investigates the effect of the timeout period on the end-to-end delay performance. It is found that there exists the timeout period minimizing the mean packet transmission delay in the end-to-end error recovery scheme. The delay performance between end-to-end and link-by-link error recovery schemes also is compared and it is found that the delay performances of these schemes are influenced significantly by the node-to-node delay. [ABSTRACT FROM AUTHOR]