GPSL2C信号仿真和分析研究
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摘要
美国政府启动的GPS现代化的一个主要措施是在L2频段上增加第二个民用码-L2C(L2 Civil)码以满足民用用户对复杂环境下高精度导航定位的需求。至2010年2月,能发送L2C码信号的现代化GPS Block IIR-M卫星已经达到8颗,国际GPS服务机构(IGS)也组织成立了L2C码信号跟踪站网络。L2C信号采用前向纠错编和时分复用技术,具有更低的载波跟踪门限和数据解调门限使得L2C能够实现在室内、树阴遮蔽等微弱信号条件下的捕获。同时,日益增长的双频GPS用户可以利用L1C/A信号和L2C信号校正电离层传输延时来消除电离层误差和快速解决相位模糊度。另外由于采用更为紧凑的导航电文帧格式以及分离的有数据通道和无数据通道使得L2C信号比传统的L1 C/A码信号具有更多的优势,必将会得到广泛深入的应用,对L2C信号的深入研究越来越引起学术界的重视。
本文以GPS现代化新增民用信号的仿真处理作为研究目标,以GPS L2C信号处理作为研究对象。由于信号模拟器是新信号研究的重要方法和工具,故本文主要内容集中于GPS L2C信号软件仿真技术的探索和研究,以及L2C信号的捕获算法的实现,包括基于快速傅里叶变换的圆周卷积算法和基于双块零扩展的算法。本文的主要工作可以概况为以下几点:
1.在对导航电文结构探索和研究的基础上,对传统的GPS导航电文结构和民用导航电文结构进行了对比分析。从电文结构、电文内容和电文播发三个方面进行了比较,说明了L2C民用导航电文的先进性。
2.详细分析了GPS L2C信号的组成结构和特点,重点强调了与C/A码不同的时分多址机制和前向纠错技术,并通过Simulink的仿真模块实现了CM码,CL码的产生以及最终的L2C信号的生成。并通过对仿真生成的信号进行自相关特性和频谱特性的验证,证明了仿真信号的正确性,为下一步仿真信号的捕获研究提供理论依据和技术支撑。
3.介绍了针对GPS L2C信号的捕获方法,包括理论推导和必要的模型设制,然后通过跟踪仿真实验进行了实现。主要对两种方法进行实现,一种是基于快速傅里叶变换和反变换的循环卷积捕获法和基于双块零扩展的捕获法。跟踪实验结果表明,两种方法都具有稳定和优越的捕获性能。
本文在阐述了L2C信号的构成和产生的基础上,使用Simulink对L2C信号进行仿真,并分析了GPS L2C信号的时域和频域的特性,阐述了明确的设计思路,并通过仿真实验初步验证了其可行性,为现代化的GPS软件接收机的研究提供可靠的信号数据源。并在此基础上研究L2C信号的基于FFT的循环卷积算法和改进的双块零捕获算法,利用Matlab平台实现了对L2C信号的捕获处理。最后对L2C码的民用导航电文和C/A码的导航电文从结构、内容和播发三个角度分别进行了比较,为深入研究GPS L2C信号提供了有益的探索,具有较强的借鉴意义。
One of the major measure in new GPS modernization initiative announced by the U.S. government is the addition of two civil signals, one of which is denoted as L2C in order to meet the growing requirement of civilian users for high-precision positioning in complex environment. Currently, L2C is transmitted by eight modernized GPS IIR-M satellites. It’s expected that it will be fully available in future years. The International GPS Service agency has built up the L2C tracking station network. Because of FEC (forward error correction) and TDM (time division multiplex), L2C lowers the data demodulation and carrier tracking threshold, and makes it possible to track the weak signals in wooded areas and inside buildings. Besides, L2C will provide civilian users the ability to correct for ionosphere delays by making dual-frequency measurements, thereby significantly increasing accuracy. Also with the tight data structure and the separated data and data-less channel, L2C is likely to become the signal of choice for extensive use.
This paper addresses the new civilian GPS signal simulation and processing problem and aims at the GPS L2C signal. The signal simulator is one of the most important research methods and tools is, so this paper focuses on the research of GPS L2C signal’s software simulation and the acquisition method of the L2C signal, including the circular convolution algorithm based on FFT/ IFFT and the Modified Double Block Zero Padding method. The primary work of this paper can be generalized as the following:
1. This paper analyses the GPS L2C signal structure and characteristics, with emphasis on the time-division-multiple-access mechanism and the forward error correction technology, which are different from the C/A Code. Then we do the simulation of CM code, CL code and ultimately the L2C signal through the module design in the Simulink platform. The autocorrelation and spectral characteristics have proved the correctness of the simulation signals, which serves as a theoretical and technical basis for further studying of GPS L2C signal.
2. Two acquisition methods are introduced, including the theory reasoning and necessary module design. We realize the two methods by signal simulation experiments, one is the circular convolution method based on FFT/IFFT, the other is the Modified Double Block Zero Padding method. Acquisition results show that the two methods have a stable and superior performance capture..
3. Based on the exploration of the navigation, this thesis compares the traditional navigation message and the navigation message structure of civil signals from the perspectives of message structure, message content and message broadcast way, which shows the advancement of the civil navigation message.
Based on the analysis of the L2C signals constitute and its generation mechanism, this paper uses the MATLAB to simulate the signal and analyzes the time and frequency domain feature of the simulated signals. The design thought is clear and the feasibility has been proved by simulations, which can be used as the signal resource of the modern GPS receiver. This thesis deeply investigates L2C acquisition methods, one is the FFT-Based Circular Correlation and the other is the Modified Double Block Zero Padding. Finally, this thesis compares the CNAV and NAV. This paper provides a useful exploration and a good reference for the deeper studying of GPS L2C Signal.
本文以GPS现代化新增民用信号的仿真处理作为研究目标,以GPS L2C信号处理作为研究对象。由于信号模拟器是新信号研究的重要方法和工具,故本文主要内容集中于GPS L2C信号软件仿真技术的探索和研究,以及L2C信号的捕获算法的实现,包括基于快速傅里叶变换的圆周卷积算法和基于双块零扩展的算法。本文的主要工作可以概况为以下几点:
1.在对导航电文结构探索和研究的基础上,对传统的GPS导航电文结构和民用导航电文结构进行了对比分析。从电文结构、电文内容和电文播发三个方面进行了比较,说明了L2C民用导航电文的先进性。
2.详细分析了GPS L2C信号的组成结构和特点,重点强调了与C/A码不同的时分多址机制和前向纠错技术,并通过Simulink的仿真模块实现了CM码,CL码的产生以及最终的L2C信号的生成。并通过对仿真生成的信号进行自相关特性和频谱特性的验证,证明了仿真信号的正确性,为下一步仿真信号的捕获研究提供理论依据和技术支撑。
3.介绍了针对GPS L2C信号的捕获方法,包括理论推导和必要的模型设制,然后通过跟踪仿真实验进行了实现。主要对两种方法进行实现,一种是基于快速傅里叶变换和反变换的循环卷积捕获法和基于双块零扩展的捕获法。跟踪实验结果表明,两种方法都具有稳定和优越的捕获性能。
本文在阐述了L2C信号的构成和产生的基础上,使用Simulink对L2C信号进行仿真,并分析了GPS L2C信号的时域和频域的特性,阐述了明确的设计思路,并通过仿真实验初步验证了其可行性,为现代化的GPS软件接收机的研究提供可靠的信号数据源。并在此基础上研究L2C信号的基于FFT的循环卷积算法和改进的双块零捕获算法,利用Matlab平台实现了对L2C信号的捕获处理。最后对L2C码的民用导航电文和C/A码的导航电文从结构、内容和播发三个角度分别进行了比较,为深入研究GPS L2C信号提供了有益的探索,具有较强的借鉴意义。
One of the major measure in new GPS modernization initiative announced by the U.S. government is the addition of two civil signals, one of which is denoted as L2C in order to meet the growing requirement of civilian users for high-precision positioning in complex environment. Currently, L2C is transmitted by eight modernized GPS IIR-M satellites. It’s expected that it will be fully available in future years. The International GPS Service agency has built up the L2C tracking station network. Because of FEC (forward error correction) and TDM (time division multiplex), L2C lowers the data demodulation and carrier tracking threshold, and makes it possible to track the weak signals in wooded areas and inside buildings. Besides, L2C will provide civilian users the ability to correct for ionosphere delays by making dual-frequency measurements, thereby significantly increasing accuracy. Also with the tight data structure and the separated data and data-less channel, L2C is likely to become the signal of choice for extensive use.
This paper addresses the new civilian GPS signal simulation and processing problem and aims at the GPS L2C signal. The signal simulator is one of the most important research methods and tools is, so this paper focuses on the research of GPS L2C signal’s software simulation and the acquisition method of the L2C signal, including the circular convolution algorithm based on FFT/ IFFT and the Modified Double Block Zero Padding method. The primary work of this paper can be generalized as the following:
1. This paper analyses the GPS L2C signal structure and characteristics, with emphasis on the time-division-multiple-access mechanism and the forward error correction technology, which are different from the C/A Code. Then we do the simulation of CM code, CL code and ultimately the L2C signal through the module design in the Simulink platform. The autocorrelation and spectral characteristics have proved the correctness of the simulation signals, which serves as a theoretical and technical basis for further studying of GPS L2C signal.
2. Two acquisition methods are introduced, including the theory reasoning and necessary module design. We realize the two methods by signal simulation experiments, one is the circular convolution method based on FFT/IFFT, the other is the Modified Double Block Zero Padding method. Acquisition results show that the two methods have a stable and superior performance capture..
3. Based on the exploration of the navigation, this thesis compares the traditional navigation message and the navigation message structure of civil signals from the perspectives of message structure, message content and message broadcast way, which shows the advancement of the civil navigation message.
Based on the analysis of the L2C signals constitute and its generation mechanism, this paper uses the MATLAB to simulate the signal and analyzes the time and frequency domain feature of the simulated signals. The design thought is clear and the feasibility has been proved by simulations, which can be used as the signal resource of the modern GPS receiver. This thesis deeply investigates L2C acquisition methods, one is the FFT-Based Circular Correlation and the other is the Modified Double Block Zero Padding. Finally, this thesis compares the CNAV and NAV. This paper provides a useful exploration and a good reference for the deeper studying of GPS L2C Signal.
引文
[1]魏二虎,史冠军,胡雪霁.(2005) GPS现代化及其影响[J].测绘通报.页数:24-35.
[2]LCDR Richard D.,Wai Cheung, Paul M. Novak, Thomas A. Stansell.(2001) The New L2 Civil Signal.[J] GPS World: 28-34.
[3]金际航,边少锋.(2005)美国全球定位系统GPS现代化进展[J].传播电子工程.总第146期.海军工程大学电气工程系.武汉.
[4] Kaplan, Elliott D. & Hegarty, Christopher J., editors (2006). Understanding GPS Principles and Applications, Second Edition[M]. Beijing. Publishing House of Electronics Industry.
[5]李军杰,张红珍,张东明.(2005) GPS现代化一起影响[J].昆明冶金高等专科学校学报.第21卷,第3期.云南昆明.
[6]刘基余.(2011). GPS现代化及其影响[J].数字通信世界.页数:24-30
[7]庄自强.(2010).基于MATLAB的GPS信号的仿真研究[D].山东理工大学硕士学位论文山东.
[8] ICD-GPS-200D (2004). Interface control document. ICD-GPS-200, Revision D, Navstar GPS Space Segment/Navigation User Interface, NAVSTAR GLOBAL POSITIONING SYSTEM, Suite 1866, EI Segundo, CA 90245-4659. U.S.A.
[9]郑鸿飞(2009).引入FEC&ARQ技术保障IPTV视频传输质量[J].电信快报:第9期.页数:38-46.
[10] N. I. Ziedan and J. L. Garrison.(2004).“Unaided Acquisition of Weak GPS Signals Using Circular Correlation or Double-Block Zero Padding”. In Proc IEEE-PLANS 2004, pages461-170, Monterey, CA.
[11]James Bao-yen Tsui,(2004) Fundamentals of Global Positioning System Receivers: A Software Approach, 2nd Edition, Wiley-Interscience
[12] Akos, Dennis (1997). A Software Radio Approach to Global Navigation Satellite System Receiver Design. Ohio University, Athens, OH.
[13]李作虎,郝金明,李建文,秦士琨,宋雪源(2009). GPS软件接收机仿真实验及算法验证[J].测绘科学技术学报:第26卷第1期.页数:56-59.
[14]Dr. Chun Yang(2003). Tracking of GPS Code Phase and Carrier Frequency in the Frequency Domain[J]. ION GPS/GNSS 2003, 9-12. Portland, OR.
[15]Mark L. Psiaki(2001). Bloack Acquisition of Weak GPS Signals in a Software Receiver[J]. ION GPS2001, 11-14. Salt Lake City, UT
[16]Dr. Chun Yang.(2001). FFT Acquisition of Aperiodic, Puncture, and Overlaid Code Sequences in GPS. In ION GPS, Sigtem Technology, Inc. Salt Lake City, UT.
[17] Mark L. Psiaki.(2004). FFT-Based Acquisition of GPS L2 Civilian CM and CL Signals. In ION GNSS 17th International Technical Meeting of the Satellite Division, pages 21-24, Long Beach, CA.
[18]N. I. Ziedan.(2004). Globla Navigation Satellite System Receiver For Weak Signals under All Dynamic Conditions. Ph.D. Dissertation, Purdue University, West Lafayette, IN, USA.
[19]Nesreen I. Ziedan(2005), Acquisition and Fine Acquisition of Weak GPS L2C and L5 Signals under High Dynamic Conditions for Limited-Resource Applications[J]. ION GNSS 18th International Technical Meeting of the Satellite Division,13-16. Long Beach, CA.
[20]Nesreen I. Ziedan and J. L. Garrison.(2003). Bit Synchronization and Doppler Frequency Removal at Very Low Carrier to Noise Ratio Using a Combination of the Viterbi Algorithm with an Extended Kalman Filter [J]. In Proc. ION/GNSS 2003, Portland, OR.
[21]Arinc Engineering Services, LLC. Navstar Global Positioning System Interface Specification, Navistar GPS Space Segment/Navigation User interface, IS-GPS-200[R]. Rev.D ed. EI Segudo U.S.A: GPS Program Office. 2006
[22]Arinc Engineering Services, LLC. Navstar Global Positioning System Interface Specification, Navistar GPS Space Segment/Navigation User interface, IS-GPS-200[R]. Rev. 2 ed. Draft. EI Segudo U.S.A: GPS Program Office. 2005
[23]Arinc Engineering Services, LLC. Navstar Global Positioning System Interface Specification, Navistar GPS Space Segment/Navigation User interface, IS-GPS-200[R]. Rev. Aed. Draft. EI Segudo U.S.A: GPS Program Office. 2008
[24]Shu Lin, Daniel J. Costello J(2007).差错控制编码[M].第2版.北京:机械工业出版社.
[25] Parkinson, Bradford W. & Spilker Jr., James J., editors (1996). Global Positioning System: Theory and Applications, volume 163 of Progress in Astronautics and Aeronautics. American Institute of Aeronautics and Astronautics, Inc.,Washington,DC.
[26] SPS (1995). Global positioning system standard positioning service signal specification. U. S. Department of Defense.
[27] Gromov, K., Akos, D., Pullen, S., Enge, P. & Parkinson, B. (2000). GIDL: Generalized interference detection and localization system. In 13th International Technical Meeting of the Satellite Division of the iInstitute of Navigation, pages447–457, Salt Lake City, UT.
[28] Haykin, S. (2000). Communication Systems. John Wiley & Sons, 4th edition, New York, NY.
[29]陈南(2008).卫星导航系统导航电文结构的性能评估[J].武汉大学学报,信息科学版, 33(5):512-515.
[2]LCDR Richard D.,Wai Cheung, Paul M. Novak, Thomas A. Stansell.(2001) The New L2 Civil Signal.[J] GPS World: 28-34.
[3]金际航,边少锋.(2005)美国全球定位系统GPS现代化进展[J].传播电子工程.总第146期.海军工程大学电气工程系.武汉.
[4] Kaplan, Elliott D. & Hegarty, Christopher J., editors (2006). Understanding GPS Principles and Applications, Second Edition[M]. Beijing. Publishing House of Electronics Industry.
[5]李军杰,张红珍,张东明.(2005) GPS现代化一起影响[J].昆明冶金高等专科学校学报.第21卷,第3期.云南昆明.
[6]刘基余.(2011). GPS现代化及其影响[J].数字通信世界.页数:24-30
[7]庄自强.(2010).基于MATLAB的GPS信号的仿真研究[D].山东理工大学硕士学位论文山东.
[8] ICD-GPS-200D (2004). Interface control document. ICD-GPS-200, Revision D, Navstar GPS Space Segment/Navigation User Interface, NAVSTAR GLOBAL POSITIONING SYSTEM, Suite 1866, EI Segundo, CA 90245-4659. U.S.A.
[9]郑鸿飞(2009).引入FEC&ARQ技术保障IPTV视频传输质量[J].电信快报:第9期.页数:38-46.
[10] N. I. Ziedan and J. L. Garrison.(2004).“Unaided Acquisition of Weak GPS Signals Using Circular Correlation or Double-Block Zero Padding”. In Proc IEEE-PLANS 2004, pages461-170, Monterey, CA.
[11]James Bao-yen Tsui,(2004) Fundamentals of Global Positioning System Receivers: A Software Approach, 2nd Edition, Wiley-Interscience
[12] Akos, Dennis (1997). A Software Radio Approach to Global Navigation Satellite System Receiver Design. Ohio University, Athens, OH.
[13]李作虎,郝金明,李建文,秦士琨,宋雪源(2009). GPS软件接收机仿真实验及算法验证[J].测绘科学技术学报:第26卷第1期.页数:56-59.
[14]Dr. Chun Yang(2003). Tracking of GPS Code Phase and Carrier Frequency in the Frequency Domain[J]. ION GPS/GNSS 2003, 9-12. Portland, OR.
[15]Mark L. Psiaki(2001). Bloack Acquisition of Weak GPS Signals in a Software Receiver[J]. ION GPS2001, 11-14. Salt Lake City, UT
[16]Dr. Chun Yang.(2001). FFT Acquisition of Aperiodic, Puncture, and Overlaid Code Sequences in GPS. In ION GPS, Sigtem Technology, Inc. Salt Lake City, UT.
[17] Mark L. Psiaki.(2004). FFT-Based Acquisition of GPS L2 Civilian CM and CL Signals. In ION GNSS 17th International Technical Meeting of the Satellite Division, pages 21-24, Long Beach, CA.
[18]N. I. Ziedan.(2004). Globla Navigation Satellite System Receiver For Weak Signals under All Dynamic Conditions. Ph.D. Dissertation, Purdue University, West Lafayette, IN, USA.
[19]Nesreen I. Ziedan(2005), Acquisition and Fine Acquisition of Weak GPS L2C and L5 Signals under High Dynamic Conditions for Limited-Resource Applications[J]. ION GNSS 18th International Technical Meeting of the Satellite Division,13-16. Long Beach, CA.
[20]Nesreen I. Ziedan and J. L. Garrison.(2003). Bit Synchronization and Doppler Frequency Removal at Very Low Carrier to Noise Ratio Using a Combination of the Viterbi Algorithm with an Extended Kalman Filter [J]. In Proc. ION/GNSS 2003, Portland, OR.
[21]Arinc Engineering Services, LLC. Navstar Global Positioning System Interface Specification, Navistar GPS Space Segment/Navigation User interface, IS-GPS-200[R]. Rev.D ed. EI Segudo U.S.A: GPS Program Office. 2006
[22]Arinc Engineering Services, LLC. Navstar Global Positioning System Interface Specification, Navistar GPS Space Segment/Navigation User interface, IS-GPS-200[R]. Rev. 2 ed. Draft. EI Segudo U.S.A: GPS Program Office. 2005
[23]Arinc Engineering Services, LLC. Navstar Global Positioning System Interface Specification, Navistar GPS Space Segment/Navigation User interface, IS-GPS-200[R]. Rev. Aed. Draft. EI Segudo U.S.A: GPS Program Office. 2008
[24]Shu Lin, Daniel J. Costello J(2007).差错控制编码[M].第2版.北京:机械工业出版社.
[25] Parkinson, Bradford W. & Spilker Jr., James J., editors (1996). Global Positioning System: Theory and Applications, volume 163 of Progress in Astronautics and Aeronautics. American Institute of Aeronautics and Astronautics, Inc.,Washington,DC.
[26] SPS (1995). Global positioning system standard positioning service signal specification. U. S. Department of Defense.
[27] Gromov, K., Akos, D., Pullen, S., Enge, P. & Parkinson, B. (2000). GIDL: Generalized interference detection and localization system. In 13th International Technical Meeting of the Satellite Division of the iInstitute of Navigation, pages447–457, Salt Lake City, UT.
[28] Haykin, S. (2000). Communication Systems. John Wiley & Sons, 4th edition, New York, NY.
[29]陈南(2008).卫星导航系统导航电文结构的性能评估[J].武汉大学学报,信息科学版, 33(5):512-515.