The shipborne automatic identification system (AIS) signals received by satellite based receiver have the advantages of low complex structure low signal to noise ratio (SNR). Moreover, the Gaussian pulse shaping filter in Gaussian filtered minimum shift keying (GMSK) modulation can cause inter-symbol interference (ISI)，and the non-coherent GMSK detector is sensitive to noise. To deal with these issues, a modified decision feedback algorithm is presented. It is to narrow the bandwidth of postdetection filter to sufficiently suppress the noise in the output of frequency discriminator. Meanwhile, we adjust the feedback level according to the bandwidth of the postdetection filter in order to compensate for the resulting distortion as well as ISI caused by Gaussian filter. We also design a method to calculate the actual feedback level for the proposed modification in practical system by utilizing the synchronization preamble and starting flag in AIS frame. Simulation results show that a bit error ratio (BER) of 10-5 can be obtained as the SNR is 4.5dB by using the proposed method. Its simple structure and effectiveness enable its promising application in other GMSK mobile systems.
TANG Ran,ZHAO Yingxin,WU Hong
. Automatic Identification System Signal Detection Algorithm Based on
Improved Feedback Decision[J]. Journal of Shanghai Jiaotong University, 2019
, 53(5)
: 610
-615
.
DOI: 10.16183/j.cnki.jsjtu.2019.05.014
［1］潘宝凤, 梁先明. 星载AIS接收系统设计及关键技术［J］. 电讯技术, 2011, 51(5): 1-5.
PAN Baofeng, LIANG Xianmin. Satellite-based AIS receiver system design and related key techniques［J］. Telecommunication Engineering, 2011, 51(5): 1-5.
［2］GALLARDO M J, SORGER U. Coherent receiver for AIS satellite detection ［C］//International Symposium on Communications, Control, and Signal Processing. Limassol, Cyprus: IEEE, 2010: 1-4.
［3］NELSON D J, HOPKINS J R, BARTOS A L. Coherent demodulation of AIS-GMSK signals in co-channel interference ［C］//Conference Record of the 45th Asilomar Conference on Signals, Systems and Computers. Pacific Grove, CA, United States: IEEE, 2011: 295-299.
［4］张乃通, 李晖, 张钦宇. 深空探测通信技术发展趋势及思考［J］. 宇航学报, 2007, 28(4): 786-793.
ZHANG Naitong, LI Hui, ZHANG Qinyu. Thought and developing trend in deep space exploration and communication［J］. Journal of Astronautics, 2007, 28(4): 786-793.
［5］GAO L, LIU J. Design of dual-channel AIS digital receiver ［C］//Proceedings of the 2012 2nd International Conference on Instrumentation and Measurement, Computer, Communication and Control. Harbin, Heilongjiang, China: IEEE, 2012: 238-242.
［6］ACHMAD M, NAZMI F, ANTRISHA S. Signal analysis of GMSK modulation-based CubeSat automatic identification system receiver ［C］//International Conference on Information Technology, Computer, and Electrical Engineering. Semarang, Indonesia: IEEE, 2016: 439-442.
［7］ZHANG T, GUO M, DING L. Soft output viterbi decoding for space-based AIS receiver ［C］//Asia-Pacific Conference on Communications, APCC. Yogyakarta, Indonesia: IEEE, 2016: 383-387.
［8］吴伟仁, 节德刚, 丁兴文, 等. 深空测控通信中GMSK体制非相干解调算法研究［J］. 宇航学报, 2014, 35(12): 1437-1443.
WU Weiren, JIE Degang, DING Xingwen, et al. A noncoherent demodulation algorithm of GMSK for deep-space missions［J］. Journal of Astronautics, 2014, 35(12): 1437-1443.
［9］丁兴文, 朱智勇, 李海涛. 基于维特比算法的GMSK信号非相干解调技术研究［J］. 遥测遥控, 2011, 32(1): 18-21.
DING Xingwen, ZHU Zhiyong, LI Haitao. Noncoherent demodulation with Viterbi decoding for GMSK signals［J］. Journal of Telemetry Tracking and Command, 2011, 32(1): 18-21.
［10］OHNO K, ADACHI F. GMSK frequency detection using decision feedback equalization［J］. Electronics Letters, 1987, 23 (25): 1350-1351.
［11］ADACHI F, OHNO K. Performance analysis of GMSK frequency detection with DFE in digital land mobile radio［J］. Radar and Signal Processing, IEE Proceedings F, 1988, 135(3): 199-207.
［12］谭宜涛, 杨海钢, 黄娟, 等. 基于关键路径的三模冗余表决器插入算法［J］. 电子与信息学报, 2012, 34(2): 487-492.
TAN Yitao, YANG Haigang, HUANG Juan, et al. Voter insertion algorithm based on critical path for triple module redundancy［J］. Journal of Electronics & Information Technology, 2012, 34(2): 487-492.
［13］KALET I, SHITZ S, HADDAD Z. Examples of continuous phase modulation using discriminator detection［J］. IEEE Transactions on Communications, 1986, 34(11): 1148-1150.
［14］ANTON B. Hardware-software complex testing receivers of the automatic identification system ［C］//Proceedings of the 2015 IEEE North West Russia Section Young Researchers in Electrical and Electronic Engineering Conference. Saint-Petersburg, Russia: IEEE, 2015: 120-124.
