Research Of High-effective Utilization Of Cognitive Radio Spectrum With USRP

With the rapid development of wireless communication, the radio spectrum resource becomes even more valuable. The utilization of spectrum resource is low due to the current static frequency allocation principles, which can not meet the requirements of the increasing of radio communication services. Under the circumstances, Cognitive Radio comes into being. Cognitive Radio technology can make secondary user find the free frequency that is temporarily not used by primary users, which is defined as reutilization. Cognitive Radio is to be a solution to the problem of the deficient spectrum resources. Its research fields incl ude spectrum sensing, allocation and sharing. Spectrum sensing as the most important and core technology among this, which is the base and precondition of realizing other technology. This thesis researches the problem of spectrum sensing, It combines theory with practice that can realize highly utilization of spectrum resources.Based on traditional energy detecting algorithm, the thesis proposes a new adaptive double-threshold distributed cooperative energy detecting algorithm. The main innovation points of this algorithm are that secondary users can set up threshold based on SNR(signal noise ratio) of primary users and a distributed cooperative energy detecting manner is proposed in order to avoid the centralized cooperative energy detecting manner depend on the central node heavily. We also studied the performance of this algorithm by simulating finally.In the thesis, a software radio system consisting of MATLAB and USRP(Universal Software Radio Peripheral) is applied as a new modeling, simulation and experiment testbed for wireless communication system design. With the testbed, we first completed the wireless transmission that adopted QPSK modulation in the real channel, and then we realized the adaptive double-threshold distributed cooperative energy detecting algorithm for spectrum sensing and estimated available spectrum bandwidth. Finally we designed a GUI interface as a demonstration system of available spectrum bandwidth.Analysis and experiment results show that the new testbed can easily used to design wireless system communication, implement the function of transmitting, receiving and spectrum sensing.