Beyond 3g Downlink Part Of The Key Modules In The Fixed-point Simulation

These days the technologies concerning the third generation mobile communication (3G) have been researched and developed completely and the manufactures of 3G have been commercialized increasingly. Then the research and the development of the technologies of Beyond 3G have been deployed in all the world. In Beyond 3G communication system, the data rate will reach 100Mbps, so many key techniques are used in it, such as LDPC coding, QAM modulation, OFDM, MIMO and Turbo receiver, and so on. The research of this article is the fixed-point simulation of some of the key techniques of B3G system, based on the downlink of TDD Beyond 3G system which our laboratory designed. In the initial chapter, the development situations of 3G and Beyond 3G are introduced briefly firstly. Then briefly introduce the key technologies used in the downlink of TDD Beyond 3G system which was designed by our university. At the same time, we also briefly introduce the basic notion of the fixed-point error analysis. The second chapter will introduce the TDD Beyond 3G system model, including the system's demand, the system's target and the system's basic parameter. Besides giving the system model graph, this chapter detail the channel coding and decoding model, the modulation and demodulation model and Turbo iterative receiver model. From the beginning of third chapter to the ending of the fifth chapter, the fixed-point simulations about some of the system's key model will be given. At the same time, these chapters will analyze the fixed-point error and give the simulation results. The third chapter will deal with the Fast Fourier Transform (FFT) algorithm, which is the OFDM modulation in system. The principle of FFT algorithm will be given firstly, then analyze the fixed-point error and introduce two methods avoiding overflow, at last the simulation results are given. The fourth chapter mostly deals with the demodulation of Quadrature Amplitude Modulation (QAM). This chapter introduces the soft demodulation algorithm of QAM and a simplified method with high Signal to Noise Ratio (SNR). Concerning the simplified method, this chapter analyzes the fixed-point error and gives the simulation result. The fifth chapter mostly concerns the decoding algorithm of Low-Density Parity Check code (LDPC). Firstly this chapter details the four decoding algorithms which mostly used...