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In opportunistic spectrum access (OSA), secondary radios (SRs) are allowed to access the channel whenever primary radios (PRs) are not transmitting. The PR's spectrum activities are normally assumed to be a 2-state continuous Markov on-off process which can be modeled as two independent exponential random variables. On the other hand, some simulations prefer using a 2-state discrete Markov chain....
In order to opportunistically utilize the licensed frequency band, secondary radios need to sense the spectrum for the presence of the primary radio. Non-cooperative and cooperative sensing schemes have been reported in the literature. In this paper, an improved spectrum sensing scheme, where cooperative sensing is performed only selectively according to a predefined criterion, is proposed. Our studies...
We propose an estimator that will jointly estimate the channel and the carrier frequency offset (CFO) for orthogonal frequency-division multiplexing (OFDM) systems based on the maximum-likelihood criterion. The proposed estimator uses only one received OFDM symbol to perform estimation and does not require the knowledge of power delay profile, except that the number of delay paths should be known...
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