Timeslot-sharing algorithm with a dynamic grouping for WDM broadcast-and-select star networks Jyh-Horng Wen a,b , Kuo-Ting Huang a,c , Cheng-Ying Yang d, * , Tzu-Chen Tsai a a Department of Electrical Engineering, National Chung Cheng University, 160, San-Hsing, Ming-Hsiung, Chiayi 621, Taiwan b Department of Communication Engineering, National Chi Nan University 1, University Road, Puli, Nantou 545, Taiwan c Department of Electrical Engineering, Wu Feng Institute of Technology, 117, Chian-Kuo Road, Ming-Hsiung, Chiayi 621, Taiwan d Department of Computer Science and Information Engineering, National Formosa University, 64, Wen-Hwa Road, Hu-Wei, Yun-Lin, Taiwan Received 3 November 2004; received in revised form 21 November 2005; accepted 21 November 2005 Available online 4 January 2006 Abstract The all-to-all transmission schedule is suitable for Wavelength division multiplexing (WDM) broadcast-and-select star networks under uniform traffic patterns. The performance suffers degradation under non-uniform traffic conditions. The timeslot-sharing algo- rithm with a dynamic grouping is proposed to decrease the degradation under the non-uniform traffic matrices. According to a given traffic matrix, the algorithm decomposes the given traffic matrix into a transmission matrix and a residual matrix. The algorithm aims to obtain a transmission matrix with most entries and to approach a uniform traffic matrix. Also, its complexity is evaluated. In the simulations, the system with the proposed algorithm provides a superior performance based on throughput, packet delay and node’s buffer size. The results show that the algorithm is an efficient solution to improve the performance under uniform and non-uniform traffic distributions. Ó 2005 Elsevier Inc. All rights reserved. Keywords: System performance; WDM broadcast-and-select network; All-to-all transmission schedule; Timeslot-sharing algorithm; Traffic matrix 1. Introduction With the popularization of the Internet which allows people to easily access world-wild information, data and network communications attract significant interest in research (Zhuge et al., 2001; Chan et al., 2001; Chung et al., 2002). New communication networks are required to support highly bursty Internet and multimedia traffic. Both the increased demand for multimedia services and end-user expectation for higher bandwidth are forcing the network operators to search for mechanisms that can cost-efficiently and ubiquitously provide high-speed access in their regions of operation. Fiber optical communications bring the networks to a new era. The advantages of optical communications include increased bandwidth, less sensitiv- ity to electrical and magnetic interference, and increased security (Miller, 2000). Wavelength division multiplexing (WDM) technology is recognized as a promising scheme for a new generation of multi-user high-speed optical com- munication networks (Scheutzow et al., 2003; Zhu et al., 2003; Saradhi et al., 2004). In this scheme, the wide low- loss spectrum of the optical fiber is divided into non-over- lapping channels for node-to-node communications, where the optical media is capable of speeds far exceeding the maximum speeds of the electronic interface components at each node. The star topology is one common way to connect nodes in a WDM optical network, where all the nodes send mes- sages through a broadcast medium which can be achieved by a passive star coupler (Bianco et al., 2003; Dasylva and Srikant, 1999; Chlamtac and Fumagalli, 1994). This 0164-1212/$ - see front matter Ó 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.jss.2005.11.569 * Corresponding author. Tel.: +886 5 6315053; fax: +886 5 6315198. E-mail addresses: wen@ee.ccu.edu.tw (J.-H. Wen), kthuang@wireless. ee.ccu.edu.tw (K.-T. Huang), cyang@nfu.edu.tw (C.-Y. Yang). www.elsevier.com/locate/jss The Journal of Systems and Software 79 (2006) 1110–1119