A significant impact on the spectrum efficiency and quality of service (QoS) of a secondary user (SU) is the ability to capture a frequency slot for transmission in an idle channel. Hence, the SU needs to sense the related spectrum in order to classify a licensed frequency band as occupied or vacant. Spectrum sensing can be a demanding task for a single user due to the random nature of the wireless channel and networks. Cooperative sensing by eight SU nodes have been proposed in this paper to mitigate the effects of channel fading and try to detect the presence/absence of two primary users (PUs). A sensing policy for coordinating the cooperative process is proposed based on two levels hierarchical-fuzzy logic system (H-FLS) by adding a Hopping Sequence (HS) module to the detectors. Two hopping methods are proposed, Random Hopping (RA-H) and Sequential Hopping (SE-H). The simulation results shows enhancement in probability of detection over conventional cooperative sensing.
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