Design Of STBC MC-CDMA Base-band System With LDPC Code And High-order Modulation On FPGA

At present,the third generation(3G) mobile communication technology has already started commercial application.To meet the requirement of multimedia correspondence in the future,a lot of research is made on B3G technology.New technologies such as channel coding,Multiple Input and Multiple Output(MIMO), Orthogonal Frequency Division Multiplexing(OFDM) as well as Multi-carrier CDMA, which is the combination of OFDM and code division multiple access(CDMA),are applied unceasingly,to improve the correspondence system to obtain a greater capacity, higher transmission speed and better error code performance.The theory research indicated that Multi-carrier CDMA combining with MIMO may improve the system's performance in a great degree,which will satisfy the requirement of mobile communication in the future.For this reason,this article mainly selected MC-CDMA to combine with the space-time block coding(STBC),associated with the low density parity check(LDPC) code and different modulation technology (QPSK and 16QAM),proposed the up link physics level structure on STBC-MC-CDMA baseband system,and realized it on the Virtext4SX35 chip provided by Xilinx Corporation using the Field Programmable Gate Array(FPGA).In this article we mainly designed some types of modules,such as QPSK,16QAM modulation and demodulation modules,STBC coding and detection modules, MC-CDMA modulation and demodulation modules,LDPC coding and decoding modules,which are easy to realize on FPGA.We compiled programs to run each module using the Verilog hardware description language,and accomplished simulation debugging and the electric circuit's synthesis on FPGA using Modelsim6.3g and ISE10.1.Moreover,we selected different modules to build the STBC-MC-CDMA baseband real time system which modulated by the methods of QPSK and 16QAM,and combined LDPC code with them.Finally,we carried on the fixed-point simulation on these 4 systems with Modelsim6.3g,obtained the error bit rates of every system,and selected QPSK-STBC-MC-CDMA system to download to the FPGA chip to realize hardware circuit.Our work made beneficial exploration on the practical application of B3G baseband communications system and obtained excellent experiment results.