Research On Adaptive And Mix Modem Technology Based On Cognitive Radio

Cognitive radio is spectrum share technology. Different from a static way to distribute and regulate the wireless spectrum, cognitive radios can dynamic access the spectrum, and can use the free spectrum without affecting the licensed users. So it is a good way to solve the problem of frequencies scarcity, and becomes the pop technologies. Nowadays plenty of the researches of cognitive radio technogies concentrate on the spectrum sensing and cross-layer design. However, cognitive radio systems don't only need cognitive ability, but also need reconfigurating ability including frequency, modulation, power, bandwidth and so on. And it puts forward new request to modem designer. However, there is little research results about this.According the "863" project of adaptive and mix wave modem technology based on cognitive radio, we study the technologies of spectrum sensing, estimation of communication channel quality, adaptive and mix modem techonology. We study the performance, improvement and feasibility of above technologies, put forward the implementary scheme, simulate and implement the whole system.The dissertation is organized as follows.Chapter one introduces the development of wireless communication technology, the concept, research results and key technologies of cognitive radio, and points out the meaning of research. Finally, we explain the main job of this paper.Chapter two researches the spectrum sensing technology. Firstly, we set up the model of spectrum sensing problem. Secondly, we put forward the criterion and the function of spectrum sensing. Then we analyze the arithmetics of spectrum sensing, and point out the advantages and disadvantages of the arithmetics.Chapter three researches the technology of channel quality estimation. Firstly, we introduce the technology of channel quality and describe the model of SNR estimation. Secondly, we explain the arithmetics of SNR estimation, and improve them. Thirdly, we discuss the CRLB of the SNR estimation. Finally, we simulate and compare all the arithmetics, and point out which is the best.Chapter four researches the technology of adaptive and mix modem. Firstly, we explain the purpose of design, and put forward the system scheme of multi-mode adaptive and mix medem including OFDM MQAM and MCPM. Secondly, we study the arithmetic of uniform preamble, and synchronous arithmetic of MPSK-MQAM modem. At last, we study the adaptive strategy of the system.Chapter five discusses the design and implement of the whole system. Firstly, we explain the criterion of design. Secondly, explain the hardware sheme, the spectrum sensing sheme and the adaptive and mix modem sheme. Thirdly, we simulate and implement the system, and point out the performance of the system.We hope that we can provide abundant and agile PHY layer transceiver to the cognitive radio system by the study of this thesis.