Interference Management in WLAN Mesh Networks Using Free-Space Optical Links

• Published in: Journal of lightwave technology Vol. 26; no. 13; pp. 1735 - 1743
• Main Authors: Rajakumar, V., Smadi, M.N., Ghosh, S.C., Todd, T.D., Hranilovic, S.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.07.2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Activation; Applied sciences; Business and industry local networks; Channels; Costs; Detection, estimation, filtering, equalization, prediction; Electromagnetic interference; Exact sciences and technology; Free-space optical link; Frequency assignment; genetic algorithm; Genetic algorithms; Heuristic; hybrid RF/FSO network; Information, signal and communications theory; Interchannel interference; Interference; Interference constraints; interference mitigation; Links; Local area networks; Mesh networks; Networks; Networks and services in france and abroad; Operations research; Optical fiber communication; Optical fiber LAN; Optical telecommunications; Radio frequency; Signal and communications theory; Signal, noise; Studies; Telecommunications; Telecommunications and information theory; Teleprocessing networks. Isdn; Wireless communication; Wireless LAN; wireless LAN mesh network; Wireless networks; Wireless optical communications; Performance evaluation; Cost minimization; Positioning; Wireless LAN; Free-space optical link; wireless LAN mesh network; Noise reduction; Optical telecommunication; Evolutionary algorithm; Cochannel interference; Wireless telecommunication; Free space optics; interference mitigation; Optical links; Radio wave; Meshed network; hybrid RF/FSO network; Frequency allocation; Radio link; Radiofrequency; Interference suppression; Free space propagation; Genetic algorithm; Heuristic method; Channel allocation; Signal processing; NP complete problem; Wireless network
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2007.909197

Frequency channels are assigned in wireless local-area network (WLAN) mesh networks subject to strict cochannel interference constraints. Since Wi-Fi may be freely used by other networks, added interference may eventually invalidate the original frequency assignment, making full link activation impossible. In this paper, we address this problem by selectively installing supplementary free-space optical (FSO) links when radio-frequency (RF) link performance has deteriorated. To minimize cost, the number of FSO links that are needed should be as small as possible. We first formulate the channel assignment problem with the objective of maximizing the number of simultaneous link activations while satisfying cumulative RF interference constraints. A proof is given for the NP-completeness of the joint frequency assignment and FSO link placement problem. We then propose an efficient heuristic to solve the channel assignment problem using a genetic algorithm. Results are then presented for various mesh networks which show that the proposed algorithm has good results compared with the computed bounds. The presented results show that the use of FSO links permits WLAN mesh network deployment in interference-prone situations.