一种光通信系统中基于16-QAM的LDPC编码调制方案  

An LDPC coded modulation scheme based on 16-QAM in optical communication systems

作　　者：何丽[1] 梁天宇[1] 

机构地区：[1]重庆邮电大学光纤通信技术重点实验室,重庆400065

出　　处：《光电子．激光》2013年第11期2128-2134,共7页Journal of Optoelectronics·Laser

基　　金：国家自然科学基金(61071117;61171158;61275077);重庆市科委(2009BB2285;2010BB2413;2010BB2409);重庆市教委(KJ110519;KJ110527)资助项目

摘　　要：设计了一种适用于16-QAM(quadrature amplitude modulation)系统的LDPC(low density parity check)级联编码调制方案。方案采用了本文所设计的一种低复杂度的软解调与二进制LDPC结合的算法,降低译码复杂度并增加方案的实用性;同时方案兼容当前OUT-4帧的级联码结构,这样可以利用级联码巧妙有效地解决LDPC码的错误平层问题。仿真结果表明,本文提出的LDPC级联编码调制方案,在误码率(BER)为10-8时,较G.709标准中的RS(255,239)的NCG(net code gain)提高了2.8dB;同时,较ITU-T G.975.1标准中两种码率相近的RS(255,239)+CSOC(n/k=7/6,J=8)级联码和正交级联BCH码,在BER为10-8时,本文方案的NCG分别提高了1.3dB和0.2dB,且冗余度较两种方案都低。此外,本文方案实现了3.28bits/symbol的SE(spectral efficiency)。在BER为10-8时,本文方案较频谱效率低于它的4-QAM、8-QAM以及8-QAM-RS(255,239)分别有着3.5、6.4和2dB的增益。比较标准中建议的FEC(forward error correction)方案,本文提出的方案在NCG和SE两方面性能上都有所提升。In this paper,an LDPC concatenated coded modulation scheme based on 16-QAM optical system,including the encoding and decoding algorithms,is proposed.The low complexity soft de-mapp ing algorithm is adopted and the ITU-T requirement of 100Gbit/s optical transmission systems is considered in this sch eme.The simulation results show that when bit error rate （BER） is 10-8,the net code gain （NCG） of proposed scheme is 2.8dB more than that of RS（255,9）.And its NCG is 1.3dB and 0.2dB more than that of RS（255,9） ＋CSOC（n/k=7/6,J=8） and orthogonally concaten ated BCH code,respectively,which are two of FEC schemes with similar code-rate in ITU-T G.975.1.At the same time,the redundancy of the prop osed scheme is lower than that of the two schemes. On the other hand,the spectral efficiency （SE） of the proposed scheme is 3.28bi t/symbol.Compared with the NCG of other schemes with lower SE,such as 4-QAM,8-QAM and 8-QAM-RS（255,9）,the propos ed scheme also has 3.5dB,6.4dB and 2dB additional gains,respectively.Therefore,the proposed scheme has advantages in bo th NCG and SE.

关 键 词：编码调制 LDPC码 级联码 光通信 

分 类 号：TN929.11[电子电信—通信与信息系统]