Resource Allocation For Cr Mimo Systems

With the continuous development of wireless communication, more and more advanced technologies have a higher demand of the spectrum resources which causes the contradiction between low utilization rate of authorized frequency spectrum and shortage of unauthorized spectrum resources. Therefore, it has hindered the speed of development greatly. As the key to solve this problem, CR MIMO which intends to reuse spectrum resources have got a great attention and widely studied. It not only improves the spectrum utilization but also increases the capacity. Meanwhile, it can remove the interference to the authorized users. In this thesis we consider SS (spectrum sharing) mode and find the suitable IT (interference temperature) constraints in CR MIMO systems.The main contributions of this thesis can be summarized as two points:First, we study the resource allocation strategy in CR MIMO systems under the interference power constraints. Considering the statistical properties of Rayleigh fading channels, this thesis first proposes a new method to gain the average interference power (AIP) constraints for PR in CR MIMO systems. Then we design the optimal transmit strategy for a CR link to maximize the ergodic capacity subject to the AIP constraints and CR transmit power constraints. Simulation results show that the proposed scheme is not only more feasible but also improving the ergodic capacity of both PR and CR.Second, in consideration of some special cases, this thesis introduces some other constraints to protect PR’s communications. Especially, we work hard to acquire the PR capacity loss constraints based on the channel learning in CR MIMO systems to provide protection to PR. Then, we get the optimal transmit strategy for a CR link to maximize the ergodic capacity subject to the PR capacity loss constraints and the CR transmit power constraints. In other words, we can achieve the tradeoff between environment learning and data transmission by this way. Simulation results show that the proposed method which protects the QoS of PR can improve the ergodic capacity of CR when the PR link experienced a deep fading channel or PR transmit power is extremely low.