Contingency Plans for Air Traffic Management

Abstract We present two heuristics based on constraint technology that solve the problem of generating air traffic management contingency plans, which are used in the case of a catastrophic infrastructure failure within EUROCONTROL, the European Organisation for the Safety of Air Navigation. Of the heuristics presented, one is based on constraintbased local search and tabu search, and the other one is a constraint programming and large neighbourhood search hybrid algorithm. The heuristics show that it is feasible to automate the development of contingency plans, which is currently done by human experts; this is desirable for several reasons, for example it would allow the contingency plans to be generated with an increased frequency. The generated plans were evaluated, by EUROCONTROL, to be as good as the human-made ones. 1 Air Traffic Management and Contingency Planning Air traffic management (ATM) at EUROCONTROL, the European Organisation for the Safety of Air Navigation, is about managing and ensuring a safe, efficient, and fair flow of air traffic, assuming a negligible amount of side-effects, such as adverse weather conditions. During normal operation, the Central Flow Management Unit (CFMU) of EUROCONTROL uses several stages, each in increasing detail, to satisfy its operational goals: 1. A strategic stage, taking place several months before the day of operation. 2. A pre-tactical stage that starts six days before the day of operation. 3. An online tactical stage during the day of operation. This stage is called the air traffic flow and capacity management (ATFCM) stage [2], and has two main functions: (a) Calculate the demand of each airspace volume using live flight plan information. (b) Adjust the number of allocated departure slots of the involved aerodromes, such that they optimise the objectives defined in the pre-tactical stage. These objectives typically include, but are not limited to, minimising the total flight delay and air volume overload

Models and Solution Techniques for Frequency Assignment Problems

Wireless communication is used in many different situations such as mobile telephony, radio and TV broadcasting, satellite communication, and military operations. In each of these situations a frequency assignment problem arises with application specific characteristics. Researchers have developed different modeling ideas for each of the features of the problem, such as the handling of interference among radio signals, the availability of frequencies, and the optimization criterion. This survey gives an overview of the models and methods that the literature provides on the topic. We present a broad description of the practical settings in which frequency assignment is applied. We also present a classification of the different models and formulations described in the literature, such that the common features of the models are emphasized. The solution methods are divided in two parts. Optimization and lower bounding techniques on the one hand, and heuristic search techniques on the other hand. The literature is classified according to the used methods. Again, we emphasize the common features, used in the different papers. The quality of the solution methods is compared, whenever possible, on publicly available benchmark instances

Constraint models for multiple interference in the channel assignment problem

For the channel assignment problem, the adequacy of binary channel separation constraints based on the single interferer assumption and/or a constant re-use distance has been questioned by several authors. The single interferer assumption is convenient for channel assignment purposes as it leads to a generalised graph-colouring model which is simple to formulate and very popular. However, it is desirable to approximate the operational criteria more closely than a single interferer assumption model allows, by modelling the effects of multiple simultaneous interferers. This thesis addresses the problem of modelling multiple interferers in channel assignment using constraints, with a view to finding an efficient and convenient approach which offers resilience against multiple interference whilst minimising additional spectral requirements. Motivated by a discussion of the literature concerning single and multiple interference, the thesis analyses the coverage failure as progressively higher numbers of multiple simultaneous interferers occur, characterising those interferers which lead to coverage reduction. A hybrid sequential and simulated annealing heuristic is applied which obtains optimised channel assignments for analysis, created under the single interferer assumption, for two-hundred-and-forty problem cases. The library of test cases is created using a purpose-built problem generator which is applied to create problems with differing randomised distributions of transmission sites. The analysis informs the consideration of methods for the reduction/elimination of multiple interferer effects. A multiple interference model based on higher order constraints called co-channel set constraints is assessed. Results concerning the theoretical properties of these constraints, and their satisfaction, are presented. An alternative way forward is then considered, which involves challenging the commonly applied assumption that the multiple interferer assumption implies constraints are necessarily non-binary. New methods are introduced that incorporate multiple interference into the generalised graph-colouring formulation i.e. binary constraints. The methods are tested using the test problem library optimised assignments are made and their resilience against multiple interference and the spectral requirements are used to evaluate the approaches. Evidence is provided that one of the methods provides an improved model for channel assignment with multiple interference and can be recommended for use to provide constraints which perform well under the multiple objectives concerned.EThOS - Electronic Theses Online ServiceGBUnited Kingdo