Joint Spectrum And Power Allocation Scheme In Cognitive Radio Networks

Cognitive radio technology breakthroughs the limitations of fixed access to the spectrum in traditional wireless networks, thus realize dynamic spectrum access and greatly enhancing the spectrum utilization. Based on cognitive radio concept, the emergence of a spectrum perception, spectrum sharing, spectrum switching and so on related technologies provide support for the dynamic spectrum access. In the spectrum sharing field, spectrum allocation and power allocation are two important concrete technologies. In this paper, those two kinds of technology are studied separately, and then a joint solution for resource allocation is proposed.Firstly, this paper studies two different interference models protocol model and physical model, focus on the interference range criterion in protocol model. Meanwhile, two important defects of interference range are pointed out. To eliminate those two defects, this paper puts forward a novel interference criterion based on Signal-to-noise ratio constraint (SC), and gives a MUI threshold. According to this criterion, a physical interference model is established.In addition, this paper also studied power allocation algorithm based on game theory. Using the noncooperative game to model power allocation problems, a pricing function method was used to improve the system sum-rate. Different utility function and pricing coefficient for improving the system performance were compared and analyzed by simulation.Secondly, a weight based heuristic spectrum allocation algorithm is studied. Different weights setting are ananlysed for improving system performance. In addition, this paper puts forward a weight Settings based on the principle of max-min fairness. Using different weights Settings, heuristic algorithm are simulated and compared. The results show that the proposed weights setting method can improve the Jain's fair coefficient about 20% compared with other weight setting method. In addition, this paper gives a adjustment method based on fairness coefficient of proposed weight. By adjusting the fairness coefficient, the system can make a tradeoff between improving fairness and system throughput.Finally, this paper puts forward a joint spectrum and power allocation scheme based on Spatial Division Multiple Access (STDMA), in which the spectrum allocation and power allocation are integrated into a unified framework. Using the proposed SC interference criterion, both spectrum allocation and power allocation can meet user target signal-to-noise ratio, as well as improve the system throughput and fairness together. The proposed scheme is especially fit for the system in which the number of channels is far less than the number of links. Experiments show that compared to the joint scheme based on interference proposed in, the proposed scheme can improve the system throughput as 40% when the number of channel is one fifth of the number of link. Simulation results also shows that, the proposed STDMA scheme can be balanced between efficiency and fairness through proper adjustment of scheme parameters.