The development of a method to ensure interference free transmission with various system constraints to achieve maximum secondary network capacity in an underlay cognitive radio (CR) network is still a challenging issue. Due to the lack of explicit support from the primary system, CR sensing algorithms often face difficulties in reliably estimating the primary signals. This problem becomes even worse when the primary user is a pure receiver. In this paper, we propose a distributed neighbor coordinated adaptive power control estimation mechanism to guarantee a reliable protection for primary users. With reliable transmission power control for the secondary transmitter, the power allocation problem of the CR system is modeled into a constrained Lagrange multipliers optimization problem to guarantee reliable sum rate maximization. Based on a comprehensive analysis from the topology and spectrum access scenario, we simplify the complex interference relationship between primary users and CR transmission pairs and propose an iterative power allocation algorithm with a suboptimal bit loading algorithm, along with fully distributed and neighbor coordinated channel selection strategies. Simulation results show that our proposed power spectrum mask estimation algorithm with capacity maximization model can greatly reduce interference to primary nodes and can successfully enhance the overall throughput.
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