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Collaborative spectrum sensing exploits multiuser diversity by combining spectrum sensing information from multiple secondary users to make joint decisions about spectrum occupancy. In hard fusion schemes, each secondary user makes a hard decision on spectrum occupancy and a fusion center makes a final decision by combining the individual hard decisions according to a fusion rule. In soft fusion schemes, each secondary user provides a signal power measurement to the fusion center, which performs further processing on the collection of all observations to make a final decision. In this paper, we propose hard and soft fusion collaborative spectrum sensing schemes based on online hidden bivariate Markov chain modeling of the signals received by secondary users. Compared to prior collaborative sensing schemes, the proposed model-based schemes do not rely on precomputed thresholds or weights, and achieve superior performance. Online estimation of hidden bivariate Markov models provides predictive information that can be used to improve the performance of dynamic spectrum access. Numerical results are presented to demonstrate the performance and communication overhead tradeoffs of the proposed collaborative spectrum sensing schemes.

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Abstract-This paper analyzes the aggregate interference in a cognitive radio network. We consider a model in which the secondary transmitters are geographically distributed according to a Poisson point process in a wireless environment subject to shadowing noise and path loss. The secondary transmitters may transmit simultaneously and consequently incur an aggregate interference level on the primary system. We derive the moment generating function and the expectation of the aggregate interference for this model using properties of the Poisson point process. Based on the interference analysis, a scheme is proposed to estimate the maximum transmission power for each of the active secondary transmitters so as to satisfy a constraint on the aggregate interference. Our numerical results show a significant gain in the achievable capacity for the secondary system relative to an earlier scheme in which only a single secondary transmitter was permitted to transmit at any given time.