Research On WiMAX Channel Codec Technology Based On Virtual Radio

The use of software radio for wireless communication systems is an important direction for future development. Virtual radio is the latest trend in software radio development, which is based on general computer instead of application-specific devices to realize digital signal processing. The virtual radio WiMAX system studied in this thesis is an important foundation to explore the green broadband wireless communications. The bottleneck of communication system based on general computer is the real-time performance of CPU signal processing. Therefore, complex algorithm and time-consuming module need to be optimized. The WiMAX system channel coding uses Convolution Turbo Codes, which has high coding efficiency, good performance and low decoding delay compared with Turbo Codes. But the Max_Log_MAP algorithm is relatively complex in the decoding process, which limits the improvement of decoding rate.This thesis mainly studies the WiMAX system channel codec technology based on virtual radio. First, the codec principles and component decoder algorithm of Convolutional Turbo Codes are analyzed, and the performance on different sequence length, different modulation modes, different coding rate and different iteration number is simulated. Then the decoding iteration number is optimized on the uplink of WiMAX system in fading channel. This thesis presents a combined adaptive optimization scheme under the conditions that system performance is acceptable, making the average iteration number far below the fixed maximum iteration number, thereby improving the decoding rate. Finally, parallel optimization is carried out for the Max_Log_MAP algorithm based on virtual radio. After the fixed-point quantization, CPU core instruction SIMD(Single Instruction Multiple Data) is used to do parallel processing, that eventually makes decoding rate increase by about 3.05 times, achieving the purpose of optimization.