Design And Implementation Of MPSK Communication System Based On GNU Radio

In traditional radio engineering, the crucial underlying processings such as physical layer processing and media access control are implemented by Application-Special Integrated Circuit(ASIC). With the increasing complexity of wireless systems, its disadvantages such as high cost and difficulty in modification and upgrade are arising gradually. Software Defined Radio can load different software in a general hardware platform, thus realizing the functions of different physical layers and data link layers. Wireless systems based on Software Defined Radio have the advantages of high flexibility and low cost, and are easy to realize the later upgrade and modification. Therefore, Software Defined Radio is used in many radio engineering situations, and has broad application prospects.This thesis reviews the study background and related research status of Software Defined Radio, and outlines its theoretical basis and several structures, with emphasis on the analysis and comparison of advantages and disadvantages of these structures. Then the internal structure and programming style of GNU Radio are summarized, and the hardware structure and signal processing of Universal Software Radio Peripheral(USRP) are given, followed by the method to configure its running parameters through the USRP Hardware Driver(UHD). The main contributions of this thesis are as follows:(1) The block diagram of the overall design of the wireless communication system based on Software Defined Radio is given with the detailed description of each signal processing module and its necessity. The transmitter mainly includes the modules of data source, packet encoder, baseband digital modulation, digital signal interpolation, digital up-conversion, digital-to-analog conversion and analog up-conversion, while the receiver mainly includes the modules of analog down-conversion, analog-to-digital conversion, digital down-conversion, digital signal decimation, symbol synchronization, carrier synchronization, baseband digital demodulation, packet decoder and data sink.(2) On the basis of GNU Radio and USRP platform, the transmitter and receiver are realized by Python language respectively, and the implementation process of each module is described in detail. Phase Shift Keying(PSK) is used to modulate the signal for its good anti-noise performance and good scalability of its code. An intensive study of the carrier synchronization and symbol synchronization are made. An overview of the causes and solutions of the two problems are given. A symbol synchronization module based on poly-phase filter-banks and a carrier synchronization module based on the Costas loop are adopted in the receiver. Meanwhile, the GUI design is introduced in order to provide convenience for the following test.(3) A brief introduction to the setup and test of the software and hardware platform is given, and the function of sending and receiving data of the designed system is tested. The operation results of the system under certain parameters are shown, verifying the overall function of the whole system. Then the transmission and receiving gain of USRP are adjusted to test its performances under different Signal-to-Noise Ratio(SNR) conditions. Moreover, the functions of the frame synchronization, symbol synchronization and carrier synchronization modules are verified by the comparison and analysis of their input and output waveforms through GUI design.Finally, we summarize the whole thesis and present future research topics.