Resource Allocation In Cognitive Radio Networks Based On Uncerten Environment

The radio frequency spectrum is a kind of non-renewable scarce natural resource, but the spectrum utilization is very low. Cognitive radio is an emerging technology that shows great promise to dramatically improve the efficiency of spectrum utilization. Since there exists uncertainty in cognitive radio networks, such as the uncertainty of the topology structure, the uncertainty of the spectrum state, the uncertainty of the environment as well as the uncertainty of the channel state information. These uncertainties will affect the power control strategy of the cognitive user. Taking the uncertainties into consideration and keeping the primary user from harmful interference is major problems at present.In this paper, we consider the uncertainty of the channel state information. For it may cause interference to the primary user, we propose two power control strategies to provide effective protection to the primary users’transmission quality.Firstly, this paper investigates the background and significance of researching on cognitive radio, reviews current research and the development of cognitive radio network power control technology. The challenges faced by cognitive radio power control technology are also discussed, and several power control algorithm are introduced. Analysis and consider the impact bring by the uncertainty of the channel state information to the power control strategy.Secondly, for the uncertainty of the channel state, a joint rate and power control strategy between several cognitive users in a orthogonal frequency division multiplexing system is proposed. The adjustment factor and interference constraints violation probabilities are added in the algorithm. Simulation results show that the total rate of the cognitive users have been optimized while the harmful interference to the primary user is controlled effectively.Finally, in order not to affect the communication quality of the primary user, the power allocation scheme is proposed. By adding constraints to the probability of new primary user’s interrupt events, we achieve the goal of protecting the primary user and complete the allocation of power between users. Simulation results prove that this strategy greatly reduces the probability of events that the primary user’s transmission be interrupted and protect the communication quality of the primary user effectively.