Research And Implementation Of Modulation Recognition Based On Monitoring Receiver

As radio technology rapidly develops, it become so important to make more efficient use of radio spectrum resources that a large number of radio spectrum monitoring systems are applied to the monitoring task. Electromagnetic environment become increasingly complex, monitoring systems need a great deal of functional requirements in order to copy with the change. Among those functions of monitoring system, automatic modulation recognition of signal type becomes the indispensable function in the progressive development of monitoring systerm. This dissertation makes a deep study on modulation recognition based on the monitoring receiver and have finished the following parts research work about modulation recognition system implemented on DSP module of monitoring receiver.Firstly, the communication mechanism of monitoring receiver system has been designed, which communicate between DSP and other modules including PC and FPGA. At the same time, DSP internal thread scheduling and modulation recognition workmode is presented. Internal thread of DSP system is scheduled by DSP/BIOS operating system. The explicit scheduling scheme is introduced that how the thread work in each workmode of modulation recognition. In the DSP module of receiver system, GPIO and McBSP interface are used to communicate with FPGA, and TCP/IP protocol is used to communicate with PC software.Secondly, the modulation recognition algorithm is analysised. Instantaneous information of signal is extracted by digital quadratual mixing algorithm, which is more suitable for the monitoring receiver than other algorithm, and the decision tree is used to classify the type of signal. In matlab, the data which collect from receiver is used for the simulation experiments. A decision tree method is introduced by analysising the trends of 7 kinds of signal characteristic parameters. The algorithm is adjusted for the various applications situation, when the algorithm is applied to the receiver system.Thirdly, the stability of the entire system is analyzed, which include the device and program in unusual circumstances. It is studied to deal with abnormal situations by available system resources. The realization of the system self-test programs and exception handling is given.Finally, based on the entire monitoring receiver system, an intergration test has been conducted, including the work mode of testing, as well as modulation recognition rate for 12 kinds of signals. The test shows that the overall success recognition rate is over 91% when the signal-to-noise ratio(SNR) is more than 10 dB.