It has been shown that using appropriate channel coding schemes in wireless environments, transmission energy can be significantly reduced by controlling the packet transmission time. This paper seeks optimal solutions for transmission control problems, motivated by this observation and by the need to minimize energy consumption in wireless networks. A downlink scheduling problem is formulated, and it is shown that its solution can be efficiently obtained through an approach decomposing an optimal sample path through certain "critical tasks" which in turn can be efficiently identified. Our approach deals with a more general setting than the one in [1] where the "MoveRight" algorithm is proposed. We include simulation results showing that our algorithm is significantly faster than the MoveRight algorithm. Finally, we analyze the transmission scheduling problem in a multiple node path and show that this problem can be transformed to a much simpler downlink transmission control problem.
This paper deals with the location assignment and storage/retrieval scheduling problem simultaneously in multi-shuttle automated storage/retrieval systems. Both the situations of performing a single operation cycle and multiple operation cycles are considered. Two related models, including an integer programming model and a dynamic programming model, are developed to formulate the problem. A two-phase tabu search algorithm is proposed to solve the integer programming model for the situation of performing a single operation cycle. Based on the search results, a construction heuristic is developed to improve the solution for the situation of performing multiple operation cycles. The computational results show that the two-phase tabu search algorithm can find better solutions than GA + MNN methods especially for the large-sized problems. In addition, it reveals that the construction heuristic can also significantly improve the quality of the solution for the situation of performing multiple operation cycles.
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