基于CCSDS标准的卫星遥控LDPC编码方案探讨
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摘要
随着天地一体化及遥控可靠性需求的不断提高,传统卫星遥控标准中广泛采用的BCH码很难满足未来卫星遥控链路复杂多样的需求。为此,文章将卫星遥控指令分为短指令模式和内存上注指令模式两大类,设计低密度奇偶校验(LDPC)编码方案。对于帧长较短的遥控指令,采用3种码长较短的LDPC码,与目前空间数据系统咨询委员会(CCSDS)遥控标准推荐的BCH(63,56)码相比,在误码字率为10~(-5)量级时,可以额外获得4～6dB的增益。对于大数据量的内存上注指令,应用现有CCSDS遥测标准推荐的LDPC(8160,7136)编码方案,当误码字率为10~(-5)量级时,所需信噪比(Eb/N0)约为3.8dB,编码增益约为7dB。为了实现LDPC编码方案,文章设计了与BCH码相似的协议格式,改动量较小且具有良好的兼容性,不会对已有遥控系统产生影响。译码方案采用并行的FPGA译码器架构及最小和译码算法,其译码复杂度较低,硬件实现资源占用较少,具有可行性。
With the continuous improvement of space-ground integration and telecommand(TC)reliability,the BCH code which is widely used in the satellite TC standards is impossible to meet the complex and variable needs of the TC channel for the future satellites.In this paper,two broad classes of commands are identified for LDPC coding scheme design.For the simple commands with short block length,three LDPC codes with short block length are applied.Compared with the BCH(63,56)code recommended by the current CCSDS TC standard,4 dB to 6 dB coding gain can be obtained for LDPC codes when the word error rate is 10~(-5).For the large volume commands,this paper refers to the LDPC(8160,7136)coding scheme recommended by the CCSDS telemetry(TM)standard.When the word error rate is 10~(-5),the required Eb/N0 of LDPC(8160,7136)code is around 3.8 dB and the coding gain is around 7 dB.For the LDPC coding scheme,the protocol of the LDPC codes remains similar to that for the current BCH code,with small changes and good compatibility.The decoding scheme adopts the parallel FPGA decoder structure and min-sum decoding algorithms,with low decoding complexity and less hardware resources.
With the continuous improvement of space-ground integration and telecommand(TC)reliability,the BCH code which is widely used in the satellite TC standards is impossible to meet the complex and variable needs of the TC channel for the future satellites.In this paper,two broad classes of commands are identified for LDPC coding scheme design.For the simple commands with short block length,three LDPC codes with short block length are applied.Compared with the BCH(63,56)code recommended by the current CCSDS TC standard,4 dB to 6 dB coding gain can be obtained for LDPC codes when the word error rate is 10~(-5).For the large volume commands,this paper refers to the LDPC(8160,7136)coding scheme recommended by the CCSDS telemetry(TM)standard.When the word error rate is 10~(-5),the required Eb/N0 of LDPC(8160,7136)code is around 3.8 dB and the coding gain is around 7 dB.For the LDPC coding scheme,the protocol of the LDPC codes remains similar to that for the current BCH code,with small changes and good compatibility.The decoding scheme adopts the parallel FPGA decoder structure and min-sum decoding algorithms,with low decoding complexity and less hardware resources.
引文
[1]CCSDS.CCSDS 130.0-G-3Overview of space communications protocols[S].Washington D.C.:CCSDS,2014
[2]CCSDS.CCSDS 231.0-B-2 TC synchronization and channel coding[S].Washington D.C.:CCSDS,2010
[3]万鹏,彭利文,华中杰.基于CCSDS标准的航天器上行遥控链路协议体系与可靠性技术[J].飞行器测控学报,2016,35(4):309-315Wan Peng,Peng Liwen,Hua Zhongjie.Communication protocols and reliability methods of uplink telecommand in space missions based on CCSDS recommendations[J].Journal of Spacecraft TT&C Technology,2016,35(4):309-315(in Chinese)
[4]CCSDS.CCSDS 230.2-G-1 Next generation uplink[S].Washington D.C.:CCSDS,2014
[5]CCSDS.CCSDS 231.1-O-1Short block length LDPCcodes for TC synchronization and channel coding[S].Washington D.C.:CCSDS,2015
[6]Mackay D J C,Neal R M.Near Shannon limit performance of low density parity check codes[J].Electronics Letters,1997,33(6):457-458
[7]CCSDS.CCSDS 131.0-B-2 TM synchronization and channel coding blue book issue 2[S].Washington D.C.:CCSDS,2011
[8]CCSDS.Uplink coding for new TC standard,draft orange book[S].Washington D.C.:CCSDS,2008
[9]D Divsalar,S Dolinar,C Jones.Short protographbased LDPC codes[C]//Proceedings of MILCOM 2007-IEEE Military Communications Conference.New York:IEEE,2007:1-6
[10]J Thorpe.Low-density parity-check codes constructed from protographs[R].Los Angeles,CA:IPN Progress,2004:2292-2296
[11]CCSDS.CCSDS 230.1-G-2 TC synchronization and channel coding-summary of concept and rationale[S].Washington D.C.:CCSDS,2006
[12]CCSDS.CCSDS 211.2-B-2Proximity-1space link protocol-coding and synchronization sublayer[S].Washington D.C.:CCSDS,2013
[2]CCSDS.CCSDS 231.0-B-2 TC synchronization and channel coding[S].Washington D.C.:CCSDS,2010
[3]万鹏,彭利文,华中杰.基于CCSDS标准的航天器上行遥控链路协议体系与可靠性技术[J].飞行器测控学报,2016,35(4):309-315Wan Peng,Peng Liwen,Hua Zhongjie.Communication protocols and reliability methods of uplink telecommand in space missions based on CCSDS recommendations[J].Journal of Spacecraft TT&C Technology,2016,35(4):309-315(in Chinese)
[4]CCSDS.CCSDS 230.2-G-1 Next generation uplink[S].Washington D.C.:CCSDS,2014
[5]CCSDS.CCSDS 231.1-O-1Short block length LDPCcodes for TC synchronization and channel coding[S].Washington D.C.:CCSDS,2015
[6]Mackay D J C,Neal R M.Near Shannon limit performance of low density parity check codes[J].Electronics Letters,1997,33(6):457-458
[7]CCSDS.CCSDS 131.0-B-2 TM synchronization and channel coding blue book issue 2[S].Washington D.C.:CCSDS,2011
[8]CCSDS.Uplink coding for new TC standard,draft orange book[S].Washington D.C.:CCSDS,2008
[9]D Divsalar,S Dolinar,C Jones.Short protographbased LDPC codes[C]//Proceedings of MILCOM 2007-IEEE Military Communications Conference.New York:IEEE,2007:1-6
[10]J Thorpe.Low-density parity-check codes constructed from protographs[R].Los Angeles,CA:IPN Progress,2004:2292-2296
[11]CCSDS.CCSDS 230.1-G-2 TC synchronization and channel coding-summary of concept and rationale[S].Washington D.C.:CCSDS,2006
[12]CCSDS.CCSDS 211.2-B-2Proximity-1space link protocol-coding and synchronization sublayer[S].Washington D.C.:CCSDS,2013