Chun-Xiang Chen

An adaptive scheduler to provide QoS guarantees in an input-buffered switch

This paper proposes an adaptive scheduler for an input-buffered switch to provide the quality of service (QoS) guarantees for various traffic classes. The algorithm introduced in the scheduler is based on the bandwidth reservation of each connection. The novelty of our scheduler is that it uniformly deals with various traffic classes without strict priority, and it is flexible to effectively use the remaining resources of the switch for any traffic pattern without starvation. By comparing with some well-known schedulers, the effectiveness of our scheduler in terms of throughput, packet delay and delay deviation, is clarified by computer simulation.

Throughput Efficiency of Go-Back-N ARQ Protocol on Parallel Multi-Channel with Burst Errors

In this paper, we investigate the throughput efficiency of tne Go-BacK-N ARQ protocol on parallel multiple cnanneis witn Burst errors. We assume that packet errors occur according to a two-state Markov chain on each channel. The effect of the decay factor of the Markov chain on throughput efficiency is evaluated based on the results of numerical analysis.

Performance analysis of Go-Back-N ARQ scheme on parallel channel system

In a parallel channel system, some idle channels appear if the packets waiting for transmission are less than the number of parallel channels in a slot. This paper considers a two-parallel-channel system under the Go-Back-N ARQ scheme. To effectively use the idle channels, we propose a modified packet assignment method based on the basic method. The basic assignment method assigns the packet of smaller sequence number to the higher-quality channel, and the modified one effectively uses the idle channels in the basic assignment method by transmitting packet copies in the idle channels. The queue lengths in the transmission buffer for both the basic and modified assignment methods are analyzed. Also the delay times are investigated by computer simulation. The numerical results show that although the throughput for the basic method is identical to that for the modified one, the average queue length and the delay time are remarkably reduced by the modified method.

Performance analysis of multiclass traffic in ATM networks

In B-ISDN (broadband integrated services digital network) the ATM (asynchronous transfer mode), which is fixed-length packet transport scheme, is a promising proposal. Since the packet length is fixed, it has the potential to perform various service requests of users. Thus, the authors present a queueing model which has two kinds of user sources, priority source and nonpriority source. Priority cells get superior service to nonpriority cells, because of their delay-critical natures; it is assumed that the arrival of nonpriority cells, including the blocked and retransmitted cells, is a Poisson process. Based on this model, the discard probability of the priority cells and the mean delay time of the nonpriority cells are evaluated, and they are validated by computer simulations. The numerical results show that the performance of nonpriority cells is also highly dependent upon the arrival pattern of priority cells.<<ETX>>

Performance Evaluation of Dynamic ARQ Error Control Scheme for Multichannel Communication System

In this paper, we propose two dynamic error control schemes and apply them to the multichannel data communication system. The proposed schemes are based on the basic Stop-and-Wait ARQ and Selective Repeat ARQ protocols, The former and latter are used for the error controls in a round-trip time and among the multiple channels in a slot, respectively. The state of each channel is assumed as Markov chain with two states. The operations of the proposed schemes are described and their performances are evaluated through computer simulation. The numerical results show that the performances of the proposed schemes are improved remarkably comparing with the traditional one.