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A scheme of applying unequal spreading to LDPC-Coded IDMA system was proposed. The issue of LDPC-Coded IDMA system with equal spreading and unequal spreading was studied. Gaussian approximation was applied to the messages probability density distribution function between nodes on factor graph of LDPC-Coded spreading system. We compare two cases, the first is optimization of LDPC with fixed spreading...
Based on factor graph representation of IDMA (interleave division multiple-access) systems, an interleaver design criterion is proposed. The progressive edge growth (PEG) algorithm proposed for LDPC codes is adapted to multi-user interleavers pattern design. Simulation results show that the designed interleavers perform over random interleavers especially when the number of users is relative large.
Based on factor graph and sum-product algorithm, an iterative acquisition algorithm for multiple PN codes is proposed. This algorithm combines the BP decoding algorithm and the chip level MUD as an iterative loop to fulfil the task of parallel acquisition for multiple PN codes. Simulation and analysis results show that the performance of this algorithm is slightly poorer than the full parallel search...
Based on factor graph and sum-product algorithm, an iterative acquisition algorithm for multiple PN codes is proposed. This algorithm combines the BP decoding algorithm and the chip level MUD as an iterative loop to fulfill the task of parallel acquisition for multiple PN codes. Simulation and analysis results show that the performance of this algorithm is slightly poorer than the full parallel search...
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