Research On The Wireless Resource Management In Cognitive Radio Networks

Wireless resource management is one of the key techniques in cognitive radio networks, which attracts great research attention. This dissertation is supported by the National Natural Science Foundation of China, international cooperation project and other fundings. The dissertation contains valuable work on both theories and applications.Based on the deeply researching on the principles of cognitive radio and orthogonal frequency division multiplexing (OFDM) technologies, the following contributions and innovative ideas are achieved:A novel method using bipartite graph matching is proposed to realize the dynamic spectrum access. An idealized method and an operative method are presented respectively based on the famous Kuhn-Munkre algorithm. Experimental results show that proposed algorithms dramatically maximize the spectrum utilization and reduce allocation conflictions among users.Specifying the case where both secondary users (SUs) and primary users (PUs) are OFDM modulated, the power allocation for subcarriers of SUs is modeled into a constrained optimization problem, where the mutual interference between the SU and the PUs is comprehensively formulated as the restrictions on the SUs' transmission power. For single SU case, an algorithm based on water-filling theory and an algorithm based on numerical analyses are respectively proposed to realize the power loading, on this basis, a suboptimal integral-bit loading algorithm is further presented; for multiple SUs case, an algorithm based on water-filling theory is proposed. Simulation results are exhibited to confirm the efficiency of the proposed power and bit loading algorithms.Considering the capacity loss of the primary system caused by the newly accessing SUs in dense cognitive networks including plentiful secondary nodes, a distributed binary power allocation (admittance criterion) is proposed. The restriction on the distance between secondary and primary transmitters is achieved; and the restriction on the distance between secondary transmitter and primary receiver is achieved when the primary receiver is undetectable. These two restrictions reflect that the capacities of both primary system and secondary system can be ensured to the predefined extents if these two restrictions on the distances are respectively satisfied in two cases.To achieve the maximized aggregate throughput of the secondary network without interferring the primary network, the jointly optimal allocation of sensing time and power for a two-user cooperatively cognitive network is developed by sequential optimization. The analyses and the simulation results demonstrate that the sequential optimization is able to seize the globe optimal value perfectly.Finally, the content of the whole dissertation is summarized, and several valuable research directions of cognitive radio are discussed.