具有不等错误保护特性的LDPC 编码调制方案

针对LDPC（low-density parity-check）编码调制系统，提出了一种新的具有不等错误保护特性的调制方案，在一个码字内，利用不同的调制方式对于重要的比特给予较强的保护，对于次要的比特给予较弱的保护，该方案既适用于非规则LDPC码，也适用于规则LDPC码。计算机仿真结果表明，新方案的性能是传统16QAM及4QAM的折衷，当采用1／2码率时，其频带利用率与8PSK相同，但是误码率性能优于8PSK。新方案的性能优于现有文献中基于比特可靠性的调制映射方案，并采用EXIT（extrinsic information transfer）图对新方案的优异性能给出了解释。

New UEP mapping strategy in LDPC-coded modulation systems

A new modulation strategy for low-density parity-check (LDPC) coded modulation system was proposed, which was suitable for unequal error protection (UEP). In one codeword, the more important bits were given stronger protection than less important bits through different mapping strategies, which could be applied to both regular LDPC codes and irregular LDPC codes. The new modulation strategy can make a good trade-off between conventional 4QAM and 16QAM. Compared with 8PSK, when coding rate is 0.5, the new strategy can provide a better BER performance meanwhile the same spectral efficiency. And the new modulation strategy also performs better than the bit-reliability based mapping strategy in reference existed. Extrinsic information transfer (EXIT) charts were used to explain this im-provement for regular and irregular LDPC codes respectively.