Published online by Cambridge University Press: 04 April 2009
Wireless LAN using IEEE 802.11 networks are now widely deployed athome by residential users or in hot spots by telecommunicationoperators. A hot spot is a place where a set of access points (APs)are located nearby each other and can serve many users. Sinceperturbations can degrade the quality of the signal, a carefulchannel assignment to each AP has to be done. Channel assignment ofAPs at hot spots, and more generally setup configuration andmanagement, is still often done manually. In this paper, we considera modeling that enables optimization of channel assignment withrespect to the dynamic behavior of end-users. We prove our problem'sformulation to correspond to the Minimum Interference FrequencyAssignment Problem, and hence the problem to be NP-hard. We proposeand compare three different tabu search methods to solve theproblem of channel assignment in 802.11 WLAN networks. The firstone, called TabuObj, tackles the problem using directly theobjective function associated with the model. The second one, calledTabuApproxObj, uses a simplified and approximate objectivefunction in order to visit more solutions during the same amount oftime, i.e. to be quicker than TabuObj. The third one, calledTabuLevel, is even more quicker and is based on the followingphilosophy: under time constraints, it could be judicious to explorevery quickly lots of solutions, rather than spending muchcomputation time for the evaluation of each solution, and hence onlyconsidering a few solutions. Those three methods are then comparedbased on time constraints and on the quality of their solutions.