Browsing by Keyword "Cognitive radio"
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Item Centralized and distributed spectrum channel assignment in cognitive wireless networks: A Harmony Search approach(2012-02) Del Ser, Javier; Matinmikko, Marja; Gil-López, Sergio; Mustonen, Miia; IAThis paper gravitates on the spectrum channel allocation problem where each compounding node of a cognitive radio network is assigned a frequency channel for transmission over a given outgoing link, based on optimizing an overall network performance metric dependant on the level of interference among nearby nodes. In this context, genetically inspired algorithms have been extensively used so far for solving this optimization problem in a computationally efficient manner. This work extends previous preliminary research carried out by the authors on the application of the heuristic Harmony Search (HS) algorithm to this scenario by presenting further results and derivations on both HS-based centralized and distributed spectrum allocation techniques. Among such advances, a novel adaptive island-like distributed allocation procedure is presented, which dramatically decreases the transmission rate required for exchanging control traffic among nodes at a quantifiable yet negligible performance penalty. Extensive simulation results executed over networks of increasing size verify, on one hand, that our proposed technique achieves near-optimum spectral channel assignments at a low computational complexity. On the other hand, the obtained results assess that HS vastly outperforms genetically inspired allocation algorithms for the set of simulated scenarios. Finally, the proposed adaptive distributed allocation approach is shown to attain a control traffic bandwidth saving of more than 90 with respect to the naive implementation of a HS-based island allocation procedure.Item Iterative power and subcarrier allocation in rate-constrained orthogonal multi-carrier downlink systems based on hybrid harmony search heuristics(2011-08) Del Ser, Javier; Bilbao, Miren Nekane; Gil-López, Sergio; Matinmikko, Marja; Salcedo-Sanz, Sancho; IAThis paper presents a novel iterative hybrid algorithm for subcarrier and power allocation in a cognitive orthogonal frequency division multiple access (OFDMA) downlink. In the considered setup a primary base station forwards information to K distant receivers by using a single OFDM waveform, whereas a secondary base station subject to stringent per-user rate constraints interferes with the former by sending information from users to the same set of destinations. Power and user allocation at both base stations is jointly performed by the proposed algorithm to maximize the overall throughput of the setup while satisfying, at the same time, the imposed rate constraints. Our proposal, which stems from an hybridization of the harmony search (HS) and differential evolution (DE) algorithms along with a greedy local repair method, is shown through computer simulations over the extended vehicular A ITU channel model to be an effective and practical resource allocation procedure for cognitive OFDMA downlinks.