HEURISTIC ALGORITHMS FOR CONSTRUCTING OPTIMIZED STRUCTURES OF LINEAR MULTIHOP LIGHTWAVE NETWORKS

We propose to exploit the capabilities of emerging lightwave technology in order to construct photonic implementations of ''adaptive'' and ''optimized'' distributed queue dual bus (DQDB) structures. These (virtual) structures are linear and multihop in nature, and they can be constructed on any physical topology by exploiting the broadcast-and-select property of WDM lightwave networks [1]-[3]. This study is important since it will allow DQDB (IEEE 802.6) networks to scale up by taking advantage of the various attractive properties of lightwave technology when they become available. The specific problem is on topological design, and it can be stated as follows: Given that the network nodes must be connected linearly and that the node positions in the network can be adjusted by properly tuning their (optical) transmitters and receivers, what is the best pattern for interconnecting them? Two sets of heuristic optimization algorithms are formulated. The first set is concerned with minimizing the maximum flow in any link. The second set of heuristics requires the knowledge of not only the traffic matrix but also the distance matrix, and these heuristics are aimed at minimizing the network-wide mean packet delay. A dynamic node migration heuristic is also formulated under which neighboring nodes swap their positions based on local information in order to preserve the optimality criterion in effect when the offered traffic changes. The performance of these heuristics are compared, some of their properties are analyzed, while their other attractive properties are highlighted via numerical examples.