Journal of Applied Science and Engineering

Published by Tamkang University Press


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I-Shyan Hwang This email address is being protected from spambots. You need JavaScript enabled to view it.1, San-Nan Lee1 and Yen-Pin Kuo1

1Department of Computer Engineering and Science, Yuan-Ze University, Chung-Li, Taiwan 320, R.O.C.


Received: April 18, 2005
Accepted: November 2, 2005
Publication Date: June 1, 2006

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This paper proposes a novel real-time packet rescheduling algorithm using a token-passing protocol to achieve QoS on WDM (Wavelength Division Multiplexing) Ring Access Networks. The proposed rescheduling algorithm is called PEM (PDS-EATS-MTD) algorithm. The PDS (PriorityDifferentiated Scheduling) algorithm deals with real-time packets and allows them to be transmitted first, such that the front line of the prescheduled nonreal-time packets can be inserted into the queue. The EATS (Earliest Available Time Scheduling) algorithm selects the earliest available data channel, independently of the availability of the destination. The MTD (Minimum Time Difference) algorithm selects the minimum-time-to-wait channel to transmit the nonreal-time packet and is quick to establish the path of the real-time packets. The updated information including the Scheduled Data Table and the Channel Available Time Table, is then broadcasting to other access nodes using token-passing protocol to maintain the status of packet scheduling/rescheduling consistency. Overall, the PEM algorithm outperforms NPEM, PEE, and EATS in terms of average delay time for different traffic loads and number of channels.

Keywords: Packet Rescheduling, Token-passing Protocol, Quality of Service, WDM Ring Access Network, PEM Algorithm


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