Based On Software Defined Radio, 3g Modem Technology

Digital modulation and demodulation techniques are important parts of air interface standards in 3G mobile communication systems. In the real environment,the space environment for radio wave propagation is very complex.Depending on the radio channel characteristics, select the appropriate modulation and demodulation method will greatly enhance the mobile communication system's performance.The emergence of the software defined radio technology play a significant role in promoting the development of mobile communications.By constructing a common, standard, modular hardware platform, using software to achieve a variety of radio functions,the wireless communication system be able to have a flexible mechanism for modulation and demodulation to adapt to a variety of communications standards.After reading massive domestic and foreign literature about 3G technology standard,software defined radio and modulation and demodulation techniques,the software defined radio technology applied in the 3G system's modulation and demodulation is studied in this paper.The author's main productions are as follows:(1)According to the definition and characteristics of software defined radio, discussing the architecture for software defined radio and its structure realization.The basic theory and technology of digital in software defined radio,such as signal sampling, multirate signal processing and digital filtering are studied and proved.(2)Analysing the features and performance of ASK,FSK,PSK,QAM, all digital modulation and demodulation methods for MPSK signals are discussed, and conducting the relevant design and simulation.(3)according to 3GPP's TD-SCDMA standard, combined with software defined radio technology, desiging the TD-SCDMA system's modulation and demodulaion model based on QPSK approach, and the entire process simulation carried out by MATLAB, then giving the analysis and summary of the simulation system, the feasibility of 3G modem by software radio technology was verified, and that has a certain reference value for it's 3G apply in the fuyure.