Different spectrum decision methods in a Cognitive radio network were analyzed in this paper. The technology of Cognitive Radio networks needs to make a decision which spectrum band is the best among the available free bands. Spectrum decision is closely related to all operational parameters, channel characteristics and any activity of primary users. Also, spectrum decision depends on all cognitive users inside network activities. The process of spectrum decision is not based only on cognitive users’ local observations but also on primary network channels statistical information, such as interference, path loss, wireless link errors, link layer delay. After the definition of available spectrum bands had been held, the most corresponding band of spectrum with considering channel characteristics and QoS requirements should be chosen. Spectrum decision methods can be classiﬁed as: non-load- balancing, probability-based and sensing-based spectrum decision.
An analytical system model is proposed to compare channel selection algorithms by main operational parameters to minimize total system selection time. The considered methods, which are based on balancing trafﬁc load, can distribute secondary users load to multiple channels, in contradistinction to non-load-balancing methods that choose the first channel with the lowest busy probability. When the secondary users trafﬁc load is low, the probability- based method shows a reduce of total system time, otherwise, when trafﬁc load is high the sensing-based method can improve system performance.
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