Date of Award
Bikdash, Marwan U.
The main focus of this thesis is to understand how congestion that is due to link failure propagates to successive upstream links, and how well the network maintains system ï¬‚ow under abnormal conditions. Alleviating network failures depends on how congestion propagates through the network. In general, units of trafï¬c can move from their origin to their destination quite rapidly, but the change in ï¬‚ow rates tends to propagate slowly. We develop novel capacity collapse propagation models that extends signiï¬cantly the concept of cell-transmission used to partition links into sections. The sampling is done in such a way that density wave propagates through a section of the link in one time interval. A general framework to model interaction between merging and diverging ï¬‚ow patterns is developed. The models considered for the nodes take into consideration the different types of intersections that may exist in the network. The capacity collapse propagation models can better represent networks with substantial propagation delay. The speed of the capacity collapse waves will be shown to depend on the magnitude of the failure. We integrate our models within the multicommodity ï¬‚ow framework, in which each commodity (origin-destination pair) uses k 2N link-disjoint paths to satisfy ï¬‚ow-rate demands. The congestion in the links is used to update the prices of the links, thus affecting the cost of travelling. We solve several minimum-cost linear-programming problems to control path ï¬‚ow-rate routing decisions triggered by the changes in the cost coefï¬cients. We conclude that proposed path ï¬‚ow-rate rerouting in response to the congestion in the links could contribute signiï¬cantly to network survivability. Numerical simulations of the proposed models are used to illustrate the concepts.
Gebremariam, Wogayehu Y., "Lp-Based Flow-Rate Control And Modeling Of Capacity Collapse Propagation" (2013). Theses. 326.