Optimization Algorithm Research Of Distributed Beamforming Over Cognitive Relay Networks

Nowadays, the rapid development of wireless multimedia services, the quick changes of wireless communication environment, the extreme differenti-ation of the user requirements and the investment protection limits, a large of coexisting heterogeneous wireless network subsystems have been created by these factors; Another hand, the static and rigid access methods for wireless spectrum resources in traditional wireless networks have brought some serious phenomenon such as the coexistence of resource shortage and waste and the low resource utilization rate. Therefore, the system must have the highly cog-nitive ability in the aspect of wireless networks environment and user environ-ment, such as cognitive users can share the licensed spectrum of primary users under the proper interference temperature. And based on above ability, the fea-sible cooperative communication (CC) method should be adopted to overcome the channel fading. In a word, the research on distributed beamforming (DB) technology of cognitive relay network possesses great practical significance.On the strength of distributed beamforming in cognitive relay network, the project studies cognitive one-way relay network and cognitive two-way relay network.In chapter two, the project compares the performance of three algorithms that one-bit feedback synchronization algorithm phase-angle-based, one-bit feedback synchronization algorithm matrix-based and semi-definite program-ming (SDP) over cognitive one-way relay network. Our objective is to maxi-mize the received Signal to Interference and Noise Ratio (SINR) of the cogni-tive network guaranteeing the requirements of both total transmit power con-straint for cognitive relay nodes and interference temperature. Our simula-tion results demonstrate that proper one-bit feedback numbers can make the performance of both one-bit feedback synchronization algorithm phase-angle- based and one-bit feedback synchronization algorithm matrix-based similar to the performance of the SDP algorithm.In chapter three, the project investigates the SINR balancing approach considering joint power control and distributed beamforming for cognitive two-way relay networks where the network relay nodes are subject to both individ-ual transmit power and interference temperature constraints. Using an itera-tive idea with bisection method and semi-definite relaxation we can efficiently solve the optimization problem. Our numerical results reveal that proper power control and distributed beamformer can significantly improve the SINR perfor-mance, especially when the both transceivers transmit power constraints are unbalanced.