OFDM Receiver Research And Design Based On Array Signal Processing

In wireless communications, the introduction of array signal processing technology based on multi-antenna enable the system to adjust its beam patterns based on the arrival direction of signal, decreasing the interferences, improving the signal to interference ratio. Array signal processing make the existing mobile communication system expand the coverage area of base station, lower power consumption of mobile phones, increase system capacity, reduce system interference and improve receiving sensitivity.Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation technique, which has much advantages, such as high utilization rate of frequency band, simple structure, strong anti-fading. In wireless communications systems, wireless cellular using frequency reuse technology will result in a Co-Channel Interference (CCI). OFDM system is sensitive to the impact of interference. When the system is exist of CCI, it will lead to decline in BER performance and narrow coverage of the system. Therefore, we consider the usage of the array antenna in OFDM receiver. With adaptive beamforming, we can isolate the interfering signals from expectating users, eliminate or reduce the impact of co-frequency interference, thereby enhancing the reception performance and expanding system capacity.This dissertation focusing on the array signal processing technology and OFDM receiving technology has made a comprehensive and systematic research on OFDM receiver based on the signal processing technology, including system algoruthm simulation and implementation of the whole receive system based on FPGA. First it introduces the mathematical models and space-time channel models of array antennas, analyses the DOA estimation and adaptive beam forming technology, and then focuses on the two methods that combine of array signal processing technology and OFDM system, namely, PRE-FFT and POST-FFT. It makes analysis and simulation on various algorithms of the two modes and make some improvements. And it has finished contrast simulations in different time delay expansion, expansion of perspective, SNR, SIR for PRE-FFT and POST-FFT approach, pointing out their own characteristics and application environment. At the same time, the dissertation has discussed the algorithm of transmit beamforming, and analyse the programme of OFDM signal transmit beamforming in time division and frequency division duplex.Based on the contrast simulation and analysis of various algorithms, this dissertation selects one that has good performance and low demand for hardware resources for FPGA-based hardware design. It summarizes the complete process design, main parameters and frame structure. And then it describes hardware implementation of the array signal processing in detail, presents circuit schematic of the DOA estimates and beamforming based on DCD iteration and data processing steps of the OFDM demodulation. And the floating-point simulation of each module and the whole system are also finished.