Modulation Recognization Based On Decision Tree And Realization Of Gnu Radio Module

Basic idea of SDR is fulfill all the radio features by loading corresponding software program based on a general, standardized and modularized hardware platform. It's possible to break all the dependence on hardware-based design method and design method which is faced to usage. The characteristics of modulated signal are multi-band, multi-institutional and multi-functional. So it's necessary to recognize the parameters of modulated signal before its demodulating. This recognition procedure is more important in non-cooperative communication mode or complicated electronic war. The automatic modulation recognition has become an important research topic.In this thesis the modulation recognition has two steps. The first one is processing, in which input sample signal are transformed to special patterns. These special patterns contain and represent the signal modulation features. The second is classification, in which the transformed signal patterns are classified and recognized by certain algorithm. Modulation methods are usually divided into two major categories pulse modulation and sine wave modulation. Pulse modulation uses a pulse sequence or a group of digital signal as the carrier wave, and sine wave modulation use high-frequency sin wave. This thesis focuses on the sin wave modulation, and the Decision Tree classification algorithm. Decision Tree has high efficiency and low computational complexity, and can be applied in embedded system, PDA for example. This thesis will introduce a method, which can recognize the 95% probability of AM,FM and QPSK signal at S/N 8dB.GNU Radio is a free software development toolkit that provides the signal processing runtime and processing blocks to implement software radios using readily-available, low-cost external RF hardware and commodity processors. It's a widely used software radio hardware platform, which improve the flexibility and expansibility of the whole system. This thesis use GRC platform and its graphical interface to illustrate the modulation identifying process and get the recognition result. This is the foundation of the future research on GNU Radio.