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1.
CCRW技术在MBOC调制信号下多径抑制性能 总被引:1,自引:0,他引:1
由于频谱与二相移键控(BPSK)信号有较好的分离度且具有良好的跟踪性能,多元二进制偏置载波(MBOC)调制为GPS现代化和Galileo系统所采用,其多径抑制技术也成为研究热点。选取了四种典型的码相关参考波形(CCRW)技术,研究了其应用于MBOC信号时的多径抑制性能,并与BPSK和BOC(1,1)调制下的多径抑制性能进行了比较。通过仿真可知,在同等条件下,W2、W3、w4CCRW技术在时系多元二进制偏置载波(TMBOC)调制下多径抑制性能最差,在二进制偏置载波(CBOC)调制下性能最优,但三种方法均优于W1CCRW. 相似文献
2.
在Galileo系统建设和GPS现代化的进程中,为实现与BPSK(Bi-phase Shift Keying)的频谱分离,采用了BOC(Binary Offset Carrier)调制。BOC调制在码跟踪精度、多径抑制等方面比BPSK调制具有更好的性能,但其自相关函数的多相关峰特性使得在测距中可能产生偏差,因此,消除相关峰的模糊度是BOC信号接收中非常关键的问题。介绍了一种基于QBOC码的BOC信号码跟踪环路(“BOC十QBOC-BOC”),并推导出该环路码跟踪性能的解析表达式,最后的仿真结果验证了理论推导的正确性,可为BOC信号接收机的设计提供参考。 相似文献
3.
MBOC(multiplexed binary offset carrier)是GPS—GALILEO互用和兼容性工作组推荐的信号调制体制,其实现方式分为TMBOC和CBOC两种,其中TMBOC(6,1,4/33)已被GPSL1C信号所采用。多径是众多卫星导航系统应用的主要误差源之一,由于不具备时间和空间的相关性,无法通过差分技术消除。本文基于窄相关技术和Double—Delta技术对TMBOC(6,1,4/33)的抗多径性能进行了分析,并与BPSK(1)及BOC(1,1)进行了对比。在同等条件下,TMBOC(6,1,4/33)的抗多径性能优于或等同于BPSK(1)及BOC(1,1)。 相似文献
4.
介绍了GPS与Galileo共用信号的演变过程,通过BOC(1,1)在兼容性、互操作性方面的表现,以及将MBOC(6,1,1/11)与之相比较,描述了MBOC(6,1,1/11)在这两个方面的表现。可供我国卫星导航信号体制设计借鉴学习,为GPS/Galileo接收机设计提供参考。 相似文献
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伽利略系统(Galileo)是全球四大卫星导航系统之一,目前已初步具备全球定位能力。研究Galileo的信号质量和双/三频定位性能不仅对Galileo系统应用具有重要价值,对多全球卫星导航系统(GNSS)融合定位也有重要促进作用。在使用基准站网(MGEX)地面跟踪站的基础上,分析了伽利略信号的载噪比、多路径、以及双/三频精密单点定位(PPP)的定位精度。结果表明,Galileo与GPS相比,载噪比E5> E5a≈E5b≈L5>E1≈L1>L2,多路径误差E5 相似文献
8.
Youssef Tawk Cyril Botteron Aleksandar Jovanovic Pierre-André Farine 《GPS Solutions》2012,16(2):243-258
The world of global navigation satellite systems has been enhanced with several new or improved signals in space aiming to
optimize accuracy, reliability, navigation solution, and interoperability between different constellations. However, such
developments bring various challenges to the receivers’ designers. For example, acquisition and tracking stages turn into
more complex processes while handling the increasing bandwidth requires additional processing power. In this context, we study
the code tracking of Galileo E5ab in a full band or of only one of its components, i.e., either E5a or E5b. More specifically,
an architecture for tracking the E5 pilot channel as an AltBOC(15,10) or BPSK(10) modulation is introduced, and the performance
of well-known discriminator types is analyzed using analytical derivations and simulations of linearity and stability regions,
thermal noise tracking errors, multipath error envelopes and tracking thresholds. Different parameters, such as the front-end
filter bandwidth, the early/late chip spacing, un-normalized and normalized discriminators, are taken into consideration.
The results obtained are used to illustrate the main advantages and drawbacks of tracking the E5 signal as well as to help
defining the main tracking loop parameters for an enhanced performance. 相似文献
9.
Emilie Rebeyrol Olivier Julien Christophe Macabiau Lionel Ries Antoine Delatour Laurent Lestarquit 《GPS Solutions》2007,11(3):159-171
Spectrum limitations for navigation systems require that the various navigation signals broadcast by the Galileo system must
be combined and must utilize bandwidth-efficient modulations. At the L1 band, one of the most important questions is how to
combine all the Open Service signals and the Public Regulated Service signal at the payload level, while maintaining good
performance at reception. The Interplex modulation, a particular phase-shifted-keyed/phase modulation (PSK/PM), was chosen
to transmit these signals because it is a constant-envelope modulation, thereby allowing the use of saturated power amplifiers
with limited signal distortion. The Interplex modulation was also taken as baseline at the E6 band to transmit the three channels
and the services associated on the same carrier frequency. At the E5 band, the modulation must combine two different services
on a same constant envelope composite signal, while keeping the simplicity of a BOC implementation. The constant envelope
Alternate Binary Offset Carrier (ALTBOC) modulation was chosen as the solution to transmit the Galileo E5 band signal. The
main objective of this paper is to study these Galileo modulations. After the introduction, the E5 band signals are described,
followed by the Alternate BOC modulation which has been chosen to transmit them. The second part describes the general formulation
of the Interplex modulation and its key parameters for an optimal multiplexing of the Galileo L1 band signals. Since the Galileo
Open Service signals at the L1 band are still not yet completely specified, different test cases are considered and their
impact on the resulting choice for the Interplex modulation parameters is exposed. 相似文献
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Ambiguity resolution for triple-frequency geometry-free and ionosphere-free combination tested with real data 总被引:5,自引:3,他引:2
The recent GPS Block IIF satellites SVN62 and SVN63 and the Galileo satellites GIOVE-A, GIOVE-B, PFM and FM2 already send signals on more than two frequencies, and more GNSS satellites will provide tracking data on at least three frequencies in the near future. In this paper, a simplified general method for ambiguity resolution minimizing the noise level for the triple-frequency geometry-free (GF) and ionosphere-free (IF) linear combinations is presented, where differently scaled code noise on the three frequencies was introduced. For the third of three required linear combinations, the most demanding one in triple-frequency ambiguity resolution, we developed a general method using the ambiguity-corrected phase observations without any constraints to search for the optimal GF and IF linear combination. We analytically demonstrate that the noise level of this third linear combination only depends on the three frequencies. The investigation concerning this frequency-dependent noise factor was performed for GPS, Galileo and Compass frequency triplets. We verified the theoretical derivations with real triple-frequency GPS and Galileo data from the Multi-GNSS Experiment (M–GEX) of the International GNSS Service (IGS). The data of about 30 M–GEX stations around the world over 11 days from 29 April 2012 to 9 May 2012 were used for the test. For the third linear combinaton using Galileo E1, E5b and E5a, which is expected to have the worst performance among all the GNSS frequency triplets in our investigation, the formal errors of the estimated ambiguities are in most cases below 0.2 cycles after 400 observation epochs. If more GPS satellites sending signals on three frequencies or more stations tracking Galileo E6 signal are available in the future, an improvement by a factor of two to three can be expected. 相似文献
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Geometry-free undifferenced, single and double differenced analysis of single frequency GPS, EGNOS and GIOVE-A/B measurements 总被引:3,自引:1,他引:2
This paper demonstrates a geometry-free GNSS measurement analysis approach and presents results of single frequency GPS, EGNOS
and GIOVE short and zero baseline measurements. The purpose is to separate the different contributions to the measurement
noise of pseudo range code and carrier phase observations at the receiver. The influence of multipath on the different combinations
of observations is also determined. Quantitative results are presented for the thermal code and phase measurement noise and
for the correlation between the observations. Comparison of the results with theoretical approximations confirms the validity
of the used approach. Results from field measurements clearly show less thermal noise on the Galileo E1BC observations than
on the GPS L1C/A observations due to the new signal modulation. The feasibility of ambiguity resolution with a geometry-free
model is also discussed including the significant impact of multipath thereon. 相似文献
14.
采用窄相关技术和双△相关技术,对BPSK(1)信号和BOC(1,1)信号在不同预相关带宽和不同相关器间隔时的平均加权多径误差包络进行了仿真,提取了多径误差典型值。结果表明,随着相关器间隔的减小,多径误差逐渐减小,但当相关器间隔为0.1个码片时,多径误差的减小已不明显;多径误差并不是随着预相关带宽的增大一直减小,而是有一... 相似文献
15.
Modernized GPS and Galileo will provide triple-frequency signals for civil use, generating a high interest to examine the improvement of positioning performance using the triple-frequency signals from both constellations over baselines up to hundreds or thousands of kilometers. This study adopts a generalized GPS/Galileo long-range approach to process the mutually compatible GPS and Galileo triple-frequency measurements for high-precision long baseline determination. The generalized approach has the flexibility to deal with GPS and Galileo constellations separately or jointly, and also the capability to handle dual or triple-frequency measurements. We compared the generalized long-range approach with the Bernese v5.0 software on two test baselines located in East Asia and obtained highly compatible computational results. Further, in order to assess possible improvement of GPS/Galileo long baseline determination compared with the current dual-frequency (L1/L2) GPS, we simulated GPS and Galileo measurements of the test baselines. It is shown that the current level of accuracy of daily baseline solutions can be improved by using the additional Galileo constellation. Both the additional constellation and the triple-frequency measurements can improve ambiguity resolution performance, but single-constellation triple-frequency ambiguity resolution is more resistant to the influences of code noise and multipath than dual-constellation dual-frequency ambiguity resolution. Therefore, in environments where large code noise or multipath is present, the use of triple-frequency measurements is the main factor for improving ambiguity resolution performance. 相似文献
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Nobuaki Kubo 《GPS Solutions》2009,13(4):271-280
Instantaneous real-time kinematic (RTK) techniques are one approach to achieving real-time high-accuracy positioning. The
object of this paper is to show the advantage of adding velocity information to instantaneous RTK positioning. In this paper,
velocity from Doppler frequency measurements is used to help resolve integer ambiguities in the LAMBDA method. In urban areas,
pseudorange measurements can suffer from significant errors due to strong multipath, despite the use of advanced multipath-mitigation
techniques. However, Doppler frequency measurements do not deteriorate as much as pseudoranges, because the multipath error
on Doppler frequency measurements is only in the range of several centimeters. Our proposed method has been tested by both
static and moving users in sub-urban environments. Single-epoch ambiguity fixing performance was improved compared to conventional
ambiguity resolution without velocity information. 相似文献
18.
Partial integer decorrelation: optimum trade-off between variance reduction and bias amplification 总被引:2,自引:2,他引:0
Different techniques have been developed for determining carrier phase ambiguities, ranging from float approximations to the
efficient solution of the integer least square problem by the LAMBDA method. The focus so far was on double-differenced measurements.
Practical implementations of the LAMBDA method lead to a residual probability of wrong fixing of the order one percent. For
safety critical applications, this probability had to be reduced by eight orders of magnitude, which could be achieved by
linear multi-frequency code–carrier combinations. Scenarios with single or no differences include biases due to orbit errors,
satellite clock offsets, as well as residual code and phase biases. For this case, a linear combination of Galileo E1 and
E5 code and carrier phase measurements with a wavelength of 3.285 m and a noise level of a few centimeters is derived. This
ionosphere-free combination preserves the orbit and clock errors, and suppresses the E1 code multipath by 12.6 dB. Since integer
decorrelation transformations, as used in the LAMBDA method, inflate biases, the number of such transformations must be limited,
and applied in a judicious order. With a Galileo type constellation, this leads to a vertical standard deviation of ca. 20 cm,
while keeping the probability of wrong fixing extremely low for code biases of 10 cm, and phase biases of 0.1 cycle, combined
in a worst case. 相似文献
19.
Modeling and quality control for reliable precise point positioning integer ambiguity resolution with GNSS modernization 总被引:3,自引:2,他引:1
Recent research has demonstrated that the undifferenced integer ambiguities can be recovered using products from a network solution. The standard dual-frequency PPP integer ambiguity resolution consists of two aspects: Hatch-Melbourne-Wübbena wide-lane (WL) and ionosphere-free narrow-lane (NL) integer ambiguity resolution. A major issue affecting the performance of dual-frequency PPP applications is the time it takes to fix these two types of integer ambiguities, especially if the WL integer ambiguity resolution suffers from the noisy pseudorange measurements and strong multipath effects. With modernized Global Navigation Satellite Systems, triple-frequency measurements will be available to global users and an extra WL (EWL) model with very long wavelength can be formulated. Then, the easily resolved EWL integer ambiguities can be used to construct linear combinations to accelerate the PPP WL integer ambiguity resolution. Therefore, we propose a new reliable procedure for the modeling and quality control of triple-frequency PPP WL and NL integer ambiguity resolution. First, we analyze a WL integer ambiguity resolution model based on triple-frequency measurements. Then, an optimal pseudorange linear combination which is ionosphere-free and has minimum measurement noise is developed and used as constraint in the WL and the NL integer ambiguity resolution. Based on simulations, we have investigated the inefficiency of dual-frequency WL integer ambiguity resolution and the performance of EWL integer ambiguity resolution. Using almanacs of GPS, Galileo and BeiDou, the performances of the proposed triple-frequency WL and NL models have been evaluated in terms of success rate. Comparing with dual-frequency PPP, numerical results indicate that the proposed triple-frequency models can outperform the dual-frequency PPP WL and NL integer ambiguity resolution. With 1 s sampling rate, generally, only several minutes of data are required for reliable triple-frequency PPP WL and NL integer ambiguity resolution. Under benign observation situations and good geometries, the integer ambiguity can be reliably resolved even within 10 s. 相似文献
20.
In satellite navigation, the key to high precision is to make use of the carrier-phase measurements. The periodicity of the carrier-phase, however, leads to integer ambiguities. Often, resolving the full set of ambiguities cannot be accomplished for a given reliability constraint. In that case, it can be useful to resolve a subset of ambiguities. The selection of the subset should be based not only on the stochastic system model but also on the actual measurements from the tracking loops. This paper presents a solution to the problem of joint subset selection and ambiguity resolution. The proposed method can be interpreted as a generalized version of the class of integer aperture estimators. Two specific realizations of this new class of estimators are presented, based on different acceptance tests. Their computation requires only a single tree search, and can be efficiently implemented, e.g., in the framework of the well-known LAMBDA method. Numerical simulations with double difference measurements based on Galileo E1 signals are used to evaluate the performance of the introduced estimation schemes under a given reliability constraint. The results show a clear gain of partial fixing in terms of the probability of correct ambiguity resolution, leading to improved baseline estimates. 相似文献