The Virtual Radio Implementation Of Channel Decoder In Wideband Wireless Communications

With the rapid development of wireless technology, new wireless commutations systems anddevices appear continuously. Virtual radio system based on General Purpose Processor (GPP) is ageneral purpose, extendable platform, which can achieve different functions by launching differentsoftwares. However, the realization of real time processing signal in physical layer is a hot spot inresearch.The LDPC decoding algorithms in CMMB standard and Turbo decoding algorithms in LTEstandard were realized. By analyzing the simulation results, Normalized BP_based algorithm andMax-Log-MAP algorithm were chosen for LDPC and Turbo code, respectively. To optimize thesetwo decoding algorithms, a fixed-point modification was performed. This modification includestwo parts, namely the selection of precision and the selection of saturated position, and it wasapplied to both input data and intermediate variables. The performance loss between float-point andfixed-point is less than0.2dB, which is satisfying.Then the two decoders were optimized using SIMD instructions. The optimizations for LDPCdecoder include:(1) Parallelism optimization of the update process of Variable Node and CheckNode;(2) Optimization of memory access operations. The optimizations for Turbo decoder aremainly focused on the calculation of parameters α, β and γ in SISO. An Intel Core i7-3960Xplatform was adopted to verify the performance. The simulation results show a92Mbps-722Mbpsthroughput. As to the Turbo decoder, which was test on Pentium(R) Dual-Core T4400platform, thethroughput of single SISO decoder using SIMD is2.71times faster than before.