Automatic Modulation Recognition Of Communication Signals For Software Radio

Software radio is regarded as a revolutionary radio technology, which emerges as microelectronics and computer technologies have developed rapidly in the recent years. Its basic idea is to constitute an opening, standardization and modularization general hardware platform, and based on which accomplishing as many as possible communication functions, such as working frequency band, modulation-demodulation type, encrpytion model and communication protocol, through software. Its final purpose is making the communication system break away from the constraint of the systematic structure of the hardware. Implementing various of functions by software under relatively general and steady structure, and also makes evolution more convenient and easily . Software radio has drawn great attention recently.The traditional communication is in accordance with an appointed modulation pattern, with fixed parameters and hardware structure. So the range of its application is very limited. The traditional communication system has many shortcomings which bringing much inconvenience for system expanding. Software radio possesses the universal, multi-modulation and the specific property of multiple frequency bands. Owing to multi-modulation, automatic modulation recognition technology is needed. How to combine the method of automatic modulation recognition with demodulation technique in software radio , and implementation of receiving and demodulating the communication signals automatically, is one of the key technologies in realizing software radio. So automatic modulation recognition technology has important application prospects .Facing the above mentioned problems, and does the following work:Chapter one explains the origin concept of software radio at first, thenrecommends the necessity of automatic modulation recognition technology in software radio. Summarizes the history and current research situation about automatic modulation recognition at last.Chapter two discusses the structure and key techniques for software radio, emphatically analyzing and comparing the three kinds of basic structure of software radio, in order to do the relevant background introduction for the follow-up automatic modulation recognition.Chapter three illustrates kinds of daily digital modulation technology. Giving the mathematics model of modulated signal, and observing the instantaneous amplitude and frequency through emulation in order to establish a foundation of accomplishing digital modulation recognition.Chapter four is the main part of the thesis. Utilizing instantaneous amplitude, phase and frequency information of the modulated signal, some high quality features,proved in theory,are extracted. And then through designing the neural network classifiers, simulates under MATLAB platform about {OOK,4PAM,2FSK,4FSK,2PSK,4PSK,8PSK} and {OOK,4PAM,2FSK,4FSK, 2PSK,4PSK,8PSK, 16QAM,32QAM}.Chapter five discusses the algorithm of classifier combination. The combination of multiple classifiers is one of the effective ways to improve the recognition performance. The same characteristic features are offered, combines several classifiers' outputs, the recognition capability is improved. And directly to the MLP classifiers that mentioned in chapter four, experimental analysis is carried on.The general work of this paper is summarized and the further research direction is pointed out in the last chapter.