| 摘要 |
The capacity-achieving signaling strategy for a particular channel should consider the joint design of channel code and modulation. Nevertheless, coding theorists and practitioners have recognized that a well-designed LDPC code can achieve capacity-approaching performance universally across a range of data transmission and storage channels. A good example is the forward error correction scheme adopted recently by the second generation standards for digital video broadcasting (DVB), wherein the same LDPC code are expected to be reused over satellite, terrestrial and cable channels. However, to accommodate the spectral efficiency of each channel type, the coded bits should be mapped to the modulator judiciously. A large random bit interleaver is employed in BICM system, which typically yields good performance for an arbitrary choice of constellation mapper. However, it is problematic for high-speed implementation of coding and modulation due to the complexity. This motivates us to impose structural simplicity on the bit interleaver configuration so that the coded bits are de-multiplexed systematically into parallel groups to feed the constellation mapper. In this description, we focus on the design of bit demultiplexers for multilevel modulation by applying the framework of multi-edge type (MET) LDPC. Considering the channel-dependence of a given code ensemble is dominated by the mutual information between the channel input and output, we propose to simplify the analysis of the decoding behavior by using a set of surrogate binary erasure channels (BEC). Simulation results indicate that the proposed bit demultiplexer surpasses the performance of the interleaving strategy standardized in DVB-T2. |
