Double-threshold Cooperative Spectrum Sensing Algorithm And Its FPGA Simulation Implementation Under Multi-fusion Criterion

The rapid development of wireless communications has led to limited spectrum resources exhausted, and increasingly scarce spectrum resources has begun to restrict future development trend of wireless communications nowadays. Cognitive radio(CR) is mainly using smart spectrum sensing technology, evaluate the white spaces in the wireless communication environment and the opportunity to access authorization spectrum, greatly increasing the efficiency of spectrum use and provide a new way for the development of wireless communications. However, the timeliness, dynamic nature and complexity of spectrum sensing bring challenges to cognitive radio system.Firstly, the paper introduces the research background and current status of cognitive radio, describes the concept of spectrum sensing, which is divided into single-node sensing, cooperative sensing and blind sensing three categories, and elaborates single-node sensing and cooperative sensing of several perceptual models.Secondly, considering energy detection algorithm's shortages and the difference of channel, to improve the reliability of spectrum sensing and reduce the burden of the cognitive radio network and the fusion center, a cooperative sensing algorithm based on dynamic double threshold and D-S theory is proposed. This algorithm combines double threshold energy detection with D-S theory. By using the double threshold energy detection, some CR users obtain the local decision directly. At the same time, the two thresholds can be adjusted adaptively according to the status of channels. D-S theory is used in two thresholds that CR users need to send the local decision data to the fusion center and thus reduce the data transmission.Finally, in order to achieve the timeliness of spectrum sensing, improve the operation rate of the data, this paper introduced the concept of multi-rate processing, and probes into the basic theory of multi-rate processing. Then, based on the principle of multi-rate signal processing, use the FPGA emulation platform to achieve the numerical control oscillator, extractor, interpolation and high speed digital filter, which laid a foundation for subsequent high-speed processing of the data.