The Key Technologies Research Of Point-To-Point Communication Based On Cellular Cognitive

Proposed in1999, Cognitive Radio (CR) has been greatly developed by worldwide communication standard group. With the development of theoretical research, CR has been applied in practical system gradually. As one of the key techniques in CR, spectrum sensing has also become a hot topic, and its relative technique has been more and more mature. The paper mainly studies the realization of short distance D2D in GSM cellular system and builds a point-to-point communication system with Gnuradio and USPR open source software-defined radio platform. In this paper, we mainly put our focus on the implementation of such point-to-point system. The main contributions are as follows,(1) The sensing of the static information of cellular channel. The static information is defined as the fixed frequency information assigned to this cell and its neighboring cell by cellular system. It’s mainly broadcasted in BCCH channel. In this paper, we studied the wireless interface protocol of GSM network, achieved the demodulation of BCCH channel by transplanting Airprobe software to the communication platform. Alos, we added the function of frequency-hopping searching for BCCH channel and extracting the system information. The tests have shown the ability of sensing static information accurately.(2) The sensing of the dynamic information of cellular channel. The dynamic information is defined as the real-time occupation state of the channel. It’s mainly sensed by energy detection technique. Here, we proposed appropriate energy detection algorithm, jumping-point of energy ratio based sensing algorithm and iteration based adaptive spectrum sensing algorithm,for large-range spectrum sensing and small-range spectrum sensing, respectively. We also gave both the theoretical analysis and experimental results of these two algorithms. The results show that these two algorithms both have good performance and can satisfy the need of the platform. Also, they own a low computational complexity, and are easy to implement.(3) Interference suppression and its strategy. Here, we studied the DFT based interference suppression technique and its strategy for CDMA used in the system. We proposed two strategies, thresholding and parting. Compared with traditional all-suppressed and neither-suppressed strategies, our methods perform better and have a wider range of usage. Also, we analysed the possible communication environment which our platform may encounter in GSM network from the experimental results and proposed corresponding interference suppression strategy.