Design And Implementation Of MIMO-OFDM Baseband Data Transmission System

MIMO-OFDM (Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing) is one of the hot points of modern wireless communication technology. With the advantages of improving the transmission rate and anti multipath interference, it has been widely applied in the WLAN (Wireless Local Area Networks) and 4G networks.Firstly, this paper studies the synchronization problem in MIMO-OFDM system, summarizes the previous research and puts forward a kind of improved preamble structure based on CAZAC (Constant Amplitude Zero Auto Correlation) sequence and gives the corresponding algorithm of time synchronization. The new algorithm can directly get the timing point in time synchronization, and complete the integer frequency offset estimation, thereby greatly reducing the complexity of synchronization. The simulation results show that, the improved time synchronization algorithm has good performance.Secondly, this paper designs and implements a MIMO-OFDM baseband transmission system on FPGA Platform based on IEEE 802.11n protocol. The transmitter of the system includes modules of channel coding, modulation and mapping, space-time coding, OFDM modulation. And the receiver includes synchronization, channel estimation, MIMO decoding, OFDM decoding, etc. This paper has introduced the principle and structure of each module, and the simulation results proved the correctness of the design.At the same time, this paper adopts the method of quantization of the received signal to optimize of the symbol synchronization algorithm complexity and reduce the cost of hardware resources by transforming the complex complex multiplication into a simple mapping. The simulation results show that, "quantification" can improve the synchronization efficiency, reduce resource consumption and the same time guarantee the performance of symbol synchronization.Finally, this paper has run the baseband system on the Xilinx Virtex-6 ML605 evaluation board, and analysed the signals with ChipScope Pro. The test results show that, every module can run stably and prove the effectiveness of the system.