| In wireless communications, when the symbol period is smaller than the signal multipath delay spread, in the other words, when a frequency selective fading channel is existed, the received signal will suffer a serious inter-symbol interference (ISI). To solve this problem, the iterative detection and decoding technology is adopted. This technology based on the idea of turbo iteration can improve the system performance by passing soft messages between the detector and decoder. The algorithm based on maximum a posteriori (MAP) can achieve the optimal detection performance at the cost of high complexity, and its implementation has a serial structure, it’s quite difficult to realize in practice.The sum-product algorithms based on the factor graph which has unique parallel scheduling rules are widely used in the the iterative detection at the receiver. In this paper,we propose a joint iterative detection and decoding of information scheduling rule which is accomplish in a overall structure based on existed research.And then,we use this algorithm respectively in single input single output (SISO) system and multiple input multiple output (MIMO) system. The main content of this paper is as follows:1. We proposed a joint iterative detection and LDPC decoding message-passing scheduling rules in SISO frequency selective fading channels based on factor graph.The system performance suffered from the short loops slightly because of the random channel coefficients.2. We used the factor graph model to describe the MIMO channel detecor,and analysed the message-passing schedule under the sum-product algorithm.3. We expanded the joint iterative detection and decoding message-passing scheduling rules to the MIMO frequency selective fading channels, called FG_LDPC algorithm. Through the analysis of simulation results,the proposed algorithm can obtain good performance compare to the optical MAP algorithm,and the parallel processing way was more convenient to hardware implementation. |
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