基于G.9960协议的高阶QAM调制与解调  

Modulation and Demodulation of High Order QAM Based on G.9960

作　　者：李正明[1] 姚如贵[1] 王伶[1] 黄登山[1] 

机构地区：[1]西北工业大学电子信息学院,陕西西安710072

出　　处：《微电子学与计算机》2011年第3期89-93,共5页Microelectronics & Computer

基　　金：自然科学基金项目(60802083);西北工业大学基础研究基金项目(JC200817);西北工业大学科技创新基金项目(2008KJ02023);西北工业大学电子信息学院E之星基金

摘　　要：G.9960是国际电信联盟(ITU-T)制定的下一代家用网络标准,采用正交频分复用(OFDM)和高阶QAM调制相结合的技术,实现高速可靠的数据传输.将讨论高阶QAM调制和软解调的算法.偶数阶调制使用方形星座图,将格雷码形式排列的二进制序列,映射成复数点;奇数阶调制使用十字型星座,将格雷码形式的二进制序列映射为复数点后,再依据一定的规则加以旋转.基于Bahl等人提出的逐符号最大后验概率译码算法,推导了对数似然比计算公式;由于对数似然比计算涉及对数运算,因此利用取最大值代替指数对数运算来进行简化.仿真结果表明,在AWGN信道下,信噪比为8 dB时,使用简化的软解调算法,2048QAM-LDPC系统的误码率可达到3×10-5,4096QAM-LDPC系统的误码率可达到5×10-4.简化的软解调算法,计算量较小,误码率低,具有良好的性能.G.9960 is a standard for next-generation home networking being developed by the International Telecommunication Union′s Standardization Sector（ITU-T）.The standard adopts Orthogonal Frequency Division Multiplexing（OFDM） and Quadrature Amplitude Modulation（QAM）,to achieve high throughout and reliable data transmission.In this paper,we specify the algorithm of high order QAM and soft-decision decoder.Even-order modulation uses square-shape constellation map;the binary sequence is recognized as Gray code,and is mapped to complex number.Odd-order modulation uses cross-shape constellation map;the binary sequence is recognized as Gray code,firstly mapped into complex number,and then rotated according to some formulation.Based on Bahl′s maximum posterior probability decoding algorithm for incoming each symbol,logarithm likelihood ratio（LLR） algorithm is deduced.As LLR algorithm refers to logarithmic operation,maximum value is used to substitute logarithmic and exponential operation to simplify the computation.Simulation results show that,when signal noise ratio（SNR） is 8dB,the bit error ratio（BER） of 2048QAM-LDPC system can reach to 3×10-5,and the BER of 2048QAM-LDPC system can reach to 5×10-4,in AWGN channels.Simplified soft-decision demodulation algorithm has low calculation amount and BER.In hence,it is a well-behaved algorithm.

关 键 词：QAM调制 软解调 家用网络 QC-LDPC 

分 类 号：TN943.6[电子电信—信号与信息处理]