Simulation-based Methodology Research Articles

Expert design systems for telecommunications

Abstract The area of telecommunications network design and management is complex and solutions can become algorithmically intractable for moderately large networks. It is, therefore, a promising applications area for expert systems; however, a survey of the published literature reveals a paucity of integrated systems combining design and optimization of network-based problems. We present a distributed expert telecommunications provisioning system which uses a simulation-based optimization methodology for queueing networks. Our architecture admits parallel simulation of multiple configurations. A knowledge-based search drives our performance optimization of the network. The search process is a randomized combination of Steepest Descent and Branch and Bound algorithms, where the generating function of new states uses qualitative reasoning, and the gradient of the objective function is estimated using a heuristic Score Function method. We found a random search based on the relative order of the performance gradient components to be a powerful qualitative reasoning technique. The system (P3) is implemented as a loosely coupled expert system with components written in PROLOG, SIMSCRIPT, and C. We demonstrate the efficacy of our method through an example from the domain of Jackson queueing networks.

A bootstrap method of distribution mixture proportion determination

A simulation-based methodology for distribution mixture proportion determination is presented. A Monte Carlo study using Gaussian population data and cosmic-ray-experiments data proved the reliability of the methods proposed.

Locking performance in a shared nothing parallel database machine

A quantitative performance study of two-phase locking in a parallel database machine using a simulation-based methodology is described. The DBSIM simulation methodology uses models at two levels: a Petri net model at the higher level and a queuing network model at the lower level. The Petri net model captures the characteristics of parallelism and synchronization at the workload level, while the queuing network model captures queuing aspects of the system at the physical resource level. Transactions in a workload are specified using a performance-oriented specification language based on the transaction component graph, a data flow graph with database operators. The transaction specifications are translated into Petri net representations to derive the simulation experiments. The workload is a transaction taken from an order-entry application. A shared-nothing parallel machine architecture is assumed. Results of analysis of a two-phase locking strategy with machine sizes ranging from 4 to 256 processors are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Simulation-Based Load Synthesis Methodology for Evaluating Load-Management Programs

Simulation-Based Load Synthesis Methodology for Evaluating Load-Management Programs

A simulation-based methodology for optimization of ambulance service policies

A simulation-based methodology for the evaluation of the emergency ambulance system in the Vancouver, Canada, metropolitan area has been created. Outputs from the simulation of the system are utilized in the creation of the objective function of a branch and bound optimization procedure. The solutions are thus obtained at a significantly lower cost than if only simulation were used. The final solutions were verified by simulation runs.