Research Of Adaptive Modulation And Coding Based On FPGA

With the development of communication technologies, mobile broadband technology has become a direction in the field of communication. The IEEE802Working Group has formulated technical specifications such as802.11,802.16, etc. Wi-Fi technology in the automotive industry, consumer electronics and other fields has been very popular; For the application of Wimax, operators in countries like the United States, Japan, etc have made it clear to commercial use, although without large-scale applications, but we can predict that Wimax with faster information transmission will be widely used. Field programmable gate array (Field Programmble Gate Array, FPGA) having characteristic of strong real-time and parallel processing capability can process signal in time, and has features like short development cycle, flexible design, etc. So it has a large number of applications in wireless communications.802.16d supports a variety of modulation and coding modules, according to the part of WirelessMAN-OFDM in802.16d Air Interface Specification Physical Layer Protocol, this thises design an FPGA-based baseband adaptive modulation coding system, based on the feedback information of channel quality, the system controls its way of working:using convolutional Turbo Code (convolutional Turbo Codes, CTC) as channel coding, when in good channel conditions, the system uses16QAM modulation combined with a higher coding efficiency to improve the efficiency of information transmission; when the channel quality is poor the system uses QPSK modulation combined with a lower coding efficiency to ensure the transmission quality. By using Xilinx Inc. the ISE10.1integrated development environment, this thises ues the Verilog hardware description language to complete the design of Convolutional Turbo Code module under the16QAM modulation and QPSK modulation, puncturing reuse module, bit interleaving module, and modulation module, and it also designs a pipelined architecture so that the system can handle a continuous stream of data. This thises discusses several adaptive algorithms, taking into account the hardware conditions and the complexity of the implementation, algorithm based on the SNR threshold is selected. This thises uses Modelsim6.0simulation tool to simulate the unit module and the whole adaptive modulation and coding system, downloads the system to Xilinx’s Vertex-II Pro system development board for the test, and collects experimental data by using on-chip logic analysis instrument Chipscope chip, then analyze the results by combining with the simulation results.Simulation and test results show that, the system can switch modulation modes according to the feedback signal to noise ratio of user, each module works correctly and achieve the desired adaptive modulation and coding functions.