Dynamic Spectrum Perception And Data Transmission Based On The GNU Radio

Now, we are in the era of information explosion era, people get information anytime and anywhere, growing demand for communication services, more and more communication terminal needs to be access to the wireless network, this makes the frequency spectrum resource becomes more and more precious. The traditional method of dividing and licensing spectrum lead to many spectrums are frequently under-utilized, there is the phenomenon of spectrum holes exist. How to improve the utilization efficiency of spectrum resources and relieve the shortage of spectrum resources become very important in the current research content. The cognitive radio theory describes a kind of technology that can intelligent perception, learning and adapting to the surrounding channel, it can use idle authorized spectrum. In this paper, we use universal software radio peripheral(USRP) as the RF end, use open source sofrware-defined radio project(GNU Radio) to processing the communication data in the receiver and sender. Finally, we test the feasibility of cognitive radio platform.Firstly, the transmission principle of the system established by the GNU Radio and USRP were analyzed. We study the principle of each communication module and connections between the different modules, clearly understand the data stream processing in the physical layer and MAC layer. We establish the actual emission scenarios in the laboratory, according to the experimental needs to improve the default frame structure in the GNU Radio, referring to the structure of the802.11frame to improve frame encapsulation in GNU Radio, enable it to complete point-to-point transmission.Based on the actual system scenarios, we analyze the existing spectrum sensing strategies and selection energy detection algorithm based on frequency domain in this experiment. We use signal module in GNU Radio to complete the FFT based on blackman-harris window function. The FFT samples are processed to obtain the frequency energy value, we can use multiple steps narrowband energy detection broadband spectrum sensing.We complete OFDM transmission implemented on the software platform according to the principles of OFDM and basic transmission process of GNU Radio, determine the transmission parameters relative to the actually transmitted bandwidth We select the appropriate transmission parameters as the frame body in MAC layer frame. Cognitive master users sent the signaling frame to the slave users, completed the end to end transmission reconfiguration according the parameters. We observe and analyze the Sender OFDM spectrum after reconfiguration, complete realization of adaptive OFDM transmission. Finally, we use BPSK and QPSK modulation methods to test the performance of implemented platform, and the experiment results are presented in this paper.