In this paper we investigate the reduction in sensing time that can be gained by using a coarse-fine sensing scheme. Since the speed gains that can be obtained are dependent upon the SNR distribution across the bands, we generate an example SNR distribution based on the Irish DTV network for use in this paper. The coarse-fine sensing scheme in this system uses an energy detector first to order the channels based on the expectation of occupancy. We derive an expression for the probability of occupancy of each of these ordered channels. Using this expression we generate design curves for the coarse-fine sensing scheme. Simulation results are then provided that will confirm these design curves. Using these curves, designers can then select the optimum value for the number of coarse detector samples.
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