Research And Implementation Of Key Technologies Of SDR Based Air-ground Cooperative Broadband Wireless Communication

With the continuous progress of science and technology,the communication between some specific environments and special scenarios is put on the research agenda.Especially in the environment of serious multi-path interference such as roadway operation and tunnel rescue,it is very important to ensure the communication quality and reduce the complexity of the communication scheme.In this thesis,based on a typical protocol of OFDM technology-IEEE 802.11 a,combined with LDPC,DAPSK modulation technology with the advantages of anti-multipath effect and no need for channel estimation at the receiver is used;a communication scheme based on time-domain difference key technology of OFDM +16DAPSK + LDPC is proposed.XILINXZEDBOARD,which integrates FPGA and ARM,is used as the hardware implementation platform in combination with AD9361,so that the system has the characteristics of software-defined Radio(SDR).The main study contents and contributions are as follows:(1)The basic theory of symbol synchronization algorithm,16 DAPSK modulation algorithm and LDPC coding algorithm is analyzed in depth.According to the proposed system scheme,the symbol synchronization algorithm,LDPC code structure selection and LDPC decoding algorithm selection are compared and analyzed from the aspects of hardware implementation,performance gain and time consumption.Abstract 16 DAPSK phase soft demodulation,amplitude soft demodulation algorithm implementation scheme,better fit Min-Sum decoding algorithm.(2)In AWGN channel,the bit error rate is compared with 16 QAM modulation without channel estimation scheme and 16 DAPSK hard demodulation scheme.The results show that the proposed scheme has 1.9 d B and 10 d B performance gains at a bit error rate of 10-3,respectively;in multipath channel,the bit error rate is compared with 16 QAM modulation without channel estimation and 16 DAPSK combined convolution channel coding Viterbi decoding scheme,and the results show that the proposed scheme has 8 d B performance gains at a bit error rate of 10-2,respectively.(3)Hardware realization and design test system,use XILINXZEDBOARD to design and realize the data interaction module of baseband and RF end,carry out RF configuration for AD-FMCOMMS2-EBZ evaluation board with SDR characteristics through its PS end,and give the system test steps;through the hardware resource occupation table provided by VIVADO software platform,compare with the channel coding as convolution coding scheme,compared with the 16 QAM combined with LDPC coding scheme,LUT,LUTRAM,FF and BRAM resources are saved by 8%,5%,7% and 25%,respectively,in the hardware implementation.The bit error rate for random testing in an indoor environment was 9.18 ×10-5.