LDPC码在卫星导航系统中的应用(英文)  

Application of LDPC Codes in Satellite Navigation Systems

作　　者：何善宝[1] 刘崇华[1] 林益明[1] 

机构地区：[1]北京空间飞行器总体设计部,北京100094

出　　处：《航天器工程》2009年第3期72-76,共5页Spacecraft Engineering

基　　金：国家重大科技专项工程

摘　　要：作为一种接近香农极限的信道编码,近年来LDPC码被广泛采用,例如欧洲第二代数字视频广播卫星标准DVB-S2和空间数据咨询委员会(CCSDS)遥测信道编码标准就分别采用了LDPC码。文章将讨论LDPC码在卫星导航系统中的应用,内容涵盖星上编码与接收机解码。GPS联合项目办公室在接口规范(Draft IS-GPS-800,Navstar GPS Space Segment/User Segment L1C Interfaces,19 April 2006)中展现了L1电文结构中的LDPC码。子帧2和子帧3将分别用一个独立的24bit循环冗余检验(CRC)算法。加入CRC比特之后每一子帧将进一步被长度为1200/548码率为1/2的LDPC码编码。文章将给出同等长度同等码率的不同类型的LDPC码。它们表现出了优异的译码性能、简单的编码结构和较低的译码复杂度。另外一个优点是其校验矩阵无需用一系列的冗余表格来表示。这种LDPC码的构造方法可以被扩展到其它卫星导航系统,比如欧洲的伽俐略(Galileo)系统和中国的北斗(Compass)系统。Low Density Parity Check （LDPC） codes are being accepted in many applications as a type of advanced channel codes approaching Shannon limit. For example, LDPC codes have been used in DVB-S2 and will be adopted in telemetry channel coding standard of CCSDS. This paper discusses an application of LDPC codes in satellite navigation systems, including encoding on spacecraft and decoding in user receivers. GPS Joint Program Office has presented LDPC codes of L1 message structure in Interface specification （Draft IS-GPS-800, Navstar GPS Space Segment/User Segment L1C Interfaces, 19 April 2006）. Subframe2 and 3 shall utilize 24-bit Cyclic Redundancy Check （CRC） algorithm with a separate CRC for each subframe. Each of the two subframes shall be further encoded using LDPC codes with length 1 200/548 and rate 1/2. This paper gives a different kind of LDPC codes from above FEC codes with the same length and rate. They exhibit excellent decoding performance, simple encoding structure and low decoding complexity. Another advantage is that the parity check matrix can be denoted without a series of redundant tables. Finally, this construction method of LDPC codes can be extended to other satellite navigation systems, such as Galileo system of Europe and Compass system of China.

关 键 词：卫星导航 GPS LDPC码 准循环码 

分 类 号：TN967.1[电子电信—信号与信息处理]