Unambiguous method for DLL BOC signals tracking

The global navigation satellite system (GNSS) signal modulation type plays a crucial role in determining the performances of positioning, navigation and timing (PNT) services. Currently, the binary offset carrier (BOC) modulation signal and binary coded symbol (BCS) modulation signal are both bipolar signals, which greatly restrict the room of improving the GNSS signal performance. Therefore, multi-level coded symbol (MCS) modulation has received great attention in the field of GNSS signal design. The MCS modulation is the most extensive step-coded symbol modulation mode, where BOC modulation and BCS modulation are its special cases. Since the waveform symbol of the MCS modulation signal can be arbitrarily valued, the optimal GNSS signal can be designed. However, like the BOC modulation signal, the MCS modulation signal also has the problem of ambiguous tracking, and then results in a large pseudo range measurement error, which is unacceptable for the new generation GNSS with high accuracy. In recent years, the unambiguous tracking of GNSS signals has become a hot research subject in the navigation signal processing domain and many methods are presented, and those methods can be divided into three categories:BPSK-like method, bump jump (BJ) method, and side-peak cancellation (SC) method. However, these methods are designed for BOC signal, and they are not suitable for MCS signal. Therefore, in this paper we propose a general unambiguous tracking algorithm based on the pseudo correlation function (PCF), which is suitable for MCS modulated signals. Firstly, the unitary expression of MCS modulated signal based on waveform value vector is given, then the unitary formula of cross-correlation function for MCS signal is derived and the definition of PCF is given. Then the constraint condition which should be satisfied to realize unambiguous tracking is analyzed in depth, and the universal constructing method of two reference signals and the relationship between each other are derived according to this constraint condition, which brings great convenience for solving the specific MCS signal. The code tracking loop model of GNSS receiver based on the proposed method is illustrated. It is observed that the proposed method can receive different MCS signals under the same receiver loop framework, and can simplify the design of the receiver while eliminating the tracking ambiguous problem. Finally, as a special case of MCS signal, the applications of the proposed method in four kinds of BOC signals are discussed respectively, and then the waveform value vector of the reference signal and the unitary expression of code discriminator are derived. Simulation results show that the proposed method can effectively solve the ambiguous tracking problem of MCS signal, which has good performance and broad application prospect.

Binary offset carrier (BOC) modulation signals have been widely adopted in global navigation satellite systems (GNSSs) such as Galileo and modernized global positioning system [1] [2]. Although this kind of modulation offers excellent performances, a main drawback of BOC modulation is that ambiguous acquisition and biased tracking for its multi-peak autocorrelation function (ACF). This article presents herein a novel acquisition technique allows removal of side peaks thoroughly and acquire better acquisition performance. This scheme is applicable to BOC (n, n) modulation signals. Theoretical analysis and system simulation demonstrate the algorithm proposed has better performance in acquisition aspect compared with other typical algorithms under the influence of additive white Gaussian noise.

With the rapid development of Global Navigation Satellite Systems (GNSS). The binary offset carrier (BOC) signal was proposed to separate new navigation signal from traditional BPSK in frequency and it has better accuracy and anti-multipath performance compared with the BPSK of the same code rate. But the ambiguity caused by the multi-peaks of auto-correlation function makes traditional acquisition technique not applicable to BOC.A novel unambiguous acquisition algorithm for sine BOC signals is proposed in this paper. There are two types of local reference signals: the BOC signal and a designed binary auxiliary signal. They are both correlated with the received signals. Then, a correlation function unambiguous for acquisition of BOC signal is obtained by multiplying the two correlation results. In the acquisition stage of BOC(10,5), the detection probability of the proposed method is approximately 1.5 dB better than that of GRASS and 2 dB better than that of SPAR. For BOC(14,2), the detection probability advantages of the proposed method increase to 6 dB and 7.5 dB . In conclusion, the proposed method can eliminate ambiguity and has significant performance advantages compared with the above methods.

Navigation receivers of global positioning systems that are operated in complex electromagnetic environment must have an increased noise immunity characteristic. One way of such noise immunity rising is to use incoherent operating mode of navigation receiver. There are known processing algorithms for navigation signals with Binary Phase Shift Keying (BPSK) modulation. But in the near-term outlook Global Navigation Satellite Systems (GLONASS), Global Positioning Systems (GPS) and Galileo known navigation signals with Binary Offset Carrier (BOC) modulation will be radiated. Processing algorithms for such signals are not described in scientific literature. So it is interesting to work out processing algorithms for BOC modulated signals in incoherent operating mode of navigation receiver. The article is devoted to synthesis and analysis of incoherent subcarrier tracking system under receiving BOC (1,1) navigation signals. To synthesize an optimal tracking system, optimal estimation theory and dual estimation method are used that allow taking into account multi-peak a posteriori distribution of delay that caused by the periodic process (digital sinusoid) in the radio signal modulation function. When analyzing the synthesized estimation algorithm, the procedure for describing delay discriminators and dual variable discriminators were used in the form of a statistical equivalent, including discrimination and fluctuation characteristics. New equations have been obtained that describe optimal tracking system for incoherent mode of a navigation receiver. New expressions for delay and dual variable discriminators are derived. The article gives a scheme for these discriminators and formulas for their statistical characteristics. Simulated results are provided that illustrate accuracy characteristics enhancement. The obtained tracking algorithms may be used in the navigation consumer equipment of GLONASS, GPS, Galileo and other radio-navigation satellite systems operating with BOC(1.1) modulated signals.

The recent researches on the tracking of binary offset carrier (BOC) modulated signals have been studied focusing onresolving the ambiguity problem caused by the multiple side-peaks in BOC autocorrelation. In this paper, we proposea novel unambiguous BOC tracking scheme with an improved tracking performance by using partial-pulses of BOCsignals. Firstly, we observe that a sub-carrier consists of two partial rectangular pulses referred to as partial-pulses,and then, generate multiple partial-correlations composing the BOC autocorrelation. Finally, a correlation function withno side-peak is constructed by combining the partial-correlations, and then, a delay lock loop employing the proposedunambiguous correlation function adjusts the phase of the local BOC signals. From numerical results, it is confirmedthat the proposed scheme provides a better tracking performance than the conventional schemes in terms of thetracking error standard deviation.

Binary Offset Carrier (BOC) modulation technology is gradually replacing the traditional BPSK modulation signal as the main modulation method of the new generation satellite navigation signal due to its superiority in multipath suppression performance and code tracking accuracy. However, the tracking and mis-locking problem of BOC signals has become a key point limiting the widespread application of BOC signals. In this paper, we use code reference waveform (CCRW) technology and optimized Bump-jump (BJ) algorithm to analyze the multipath performance of low-order BOC signals under five code reference waveforms. Aiming at the high peak BOC signal with many peaks and high peak-to-peak ratio, we propose a new code reference waveform ensures the high-order BOC signal has good anti-multipath performance and solves the problem of extremely easy mis-locking of its receiver.

The optimized design of the spreading modulation technique is considered to be the major way to achieve both spectrum compatibility and performance improvement. To allow a variety of signals to share the limited frequency band of GNSS and further improve the signals’ ranging accuracy and anti-interference performance, several new spreading modulation techniques have been proposed in recent years. In this chapter, we will introduce a variety of typical spreading modulation techniques such as BPSK with rectangular chips (BPSK-R), binary offset carrier (BOC), binary coded symbol (BCS), composite BCS (CBCS), time-multiplexed BOC (TMBOC), composite BOC (CBOC), quadrature multiplexed BOC (QMBOC), as well as alternative BOC (AltBOC). The processing ambiguity threat of BOC and MBOC signals and possible solutions are also discussed. Considering that in the next-generation GNSS implementations, new requirements and new constraints will constantly emerge and new modulation methods will be needed, this chapter is not meant to be regarded as a review of the development of navigation signal modulation technology, or an interpretation of the signal formats being used by several major satellite navigation systems. Instead, we regard the spreading modulations used in satellite navigation signals as general techniques and focus our discussion on the principles of these modulation techniques and the design ideas behind their generation processes.

Binary Offset Carrier (BOC) modulation signals have been applied in Global Navigation Satellite Systems (GNSS) because they offer a higher positioning accuracy and higher multipath rejection. However, there is a drawback in that the autocorrelation functions have multiple side peaks, meaning that this technique also leads to the large main peak estimation error problem and a low correlation decision efficiency problem. In this paper, we propose a new Main Peak Extraction (MPE) method for high-order BOC signals to solve these problems. In the new method, the synthesis cross-correlation function is established, and the geometry graph is formatted to calculate the estimation main peak. We eliminate all side peaks and improve the main peak phase estimation precision under the condition that the sub-carrier phase is offset. The results of the simulation demonstrate that the new method can achieve better main peak decision efficiency, side peak cancellation ability and phase estimation performance than traditional methods.

Satellite navigation and positioning have become an indispensable component of smart devices and applications. In order to avoid signal interference in L1 frequency and provide novel services, Global Positioning System III (GPS III) updated a modern signal named L1C and tested in three Quasi-Zenith Satellite System (QZSS) satellites launched in 2017. In December 2018, the first GPS III satellite was launched, which implies the joint positioning using QZSS and GPS L1C signal is improved. L1C signal offers a series of advanced designs in signal modulation, message structure and coding, etc. In this regard, this paper presents complete methodologies for L1C signal joint receiving processing. For the on-air signals, this paper presents a methodology and results from collecting and assessing binary offset carrier (BOC) modulation and time-multiplexed BOC (TMBOC) modulation used in L1C signal. Using the same omnidirectional antenna and the test-equipment, the L1C signal was collected in Xi’an and Sanya, China, respectively. Experiments in Xi’an verified the joint positioning method to complement the GPS III and QZSS satellite constellations. The methodology in this paper evaluates the positioning error of BOC(1,1) and TMBOC(6,1,4/33) under the same environment and satellite constellation in Sanya. It is also verified that the joint positioning error is less than the QZSS-only positioning due to the optimization of the satellite constellation.

Binary offset carrier (BOC) modulated signals have been introduced in global navigation satellite systems such as Galileo and modernized Global Positioning System. This type of modulation creates multiple side peaks in autocorrelation function. Thus, it causes challenges in the stages of signal acquisition and tracking. In this paper, we present a new method of side-peak cancellation for BOC-modulated signals in order to remove or diminish the side peaks while keeping the sharp and narrow main peak. This proposed method could be applied to cosine-BOC(n, n) modulated signals, which are adopted to Galileo signals. Moreover, this method has better performance in reducing the error caused by multipath propagation than traditional method.

This paper proposes an unambiguous tracking method based on the optimized combined autocorrelation function (ACF) for the cosine-phased binary offset carrier (cosine-BOC) modulated signals, which are applied in global navigation satellite system (GNSS). The main idea is to generate a specially constructed local reference waveform for cosine-BOC modulated signals, which is equivalent to get a group of samples of the ACF, then the unambiguous combined correlation function is obtained by weighting and adding these samples. Simulations show that the proposed method not only eliminate the ambiguity completely, but also maintains a narrow main-peak to obtain outstanding tracking accuracy performance of the cosine-BOC modulation. Additionally, the proposed method is proven to be with good performance in moderate and long multipath interferences mitigation.

The long PN code in a Binary Offset Carrier (BOC) modulated signal has a higher rate than the GPS C/A code, which makes the acquisition process in the new global navigation satellite system (GNSS) much more complex.To achieve a fast acquisition of the GNSS signal with a reduced number of correlators and low computational complexity, a two-stage deterministic compressed (DS) GNSS acquisition technique has been proposed.Nevertheless, the ambiguous threat of BOC signal isn't taken into account in the DS technique.To eliminate the ambiguity threat in the acquisition process of BOC (m, n) signal, an unambiguous deterministic compressed acquisition is proposed in this paper.The main idea of the proposed technique is to introduce a simplified GRASS algorithm in the second stage measurement.Theoretical analysis and simulation results show that, at the expense of some performance degradation the proposed technique can completely remove the undesired positive side peaks of BOC (m, n) signal, and reduce the chance of false peak acquisition compared with the DS technique.

It is well known that code and carrier-phase multipath, which has been under study for over two decades, is the limiting error sources in high-precision differential GPS applications. In virtually every study, however, the effects of autocorrelation function are considered little. This article focuses on the bounds of code and carrier-phase multipath error in terms of GNSS (Global Navigation Satellite Systems) signals autocorrelation functions, which result from a fundamental theoretical description and mathematical modeling of GNSS receiver. Firstly, an overview of the characteristics of the BOC (Binary Offset Carrier) signal ACF (autocorrelation function) is given in the paper. The impact on the DLL (delay-lock loop) and PLL (phase lock loop) discriminator functions are derived in the followed section and consequently a general description of multipath errors are obtained for the BOC signals. This quantifies the influence of limited bandwidth on receiver tracking error due to multipath. Finally, the simulation results show a distinct change in the error envelope for BOC signals from which has been got using current GPS C/A code signal.

Improving tracking accuracy with subcarrier assistance and code monitoring for BOC modulated signal

One typical use of sensor networks is monitoring targets. The sensor networks classify, detect, locate, and track targets. The ML (Maximum likelihood) algorithm is one of the estimation algorithms of target location and has high accuracy to estimate target location. However, the calculation amount of the ML estimation algorithm is large. Energy-Ratios Source Localization Nonlinear Least Square (ER-NLS) is proposed to realize the ML algorithm. ER-NLS is the algorithm of estimating source location by using the ratio of sensors' receiving energies. However, ER-NLS has to search all the areas, so that the calculation amount of ER-NLS is large. In this paper we propose a method of reducing search area for localization. The proposed method uses the ratio of sensors' receiving energies. It can be used with the ML algorithm. We show that the proposed method with the ML algorithm can reduce the search areas to estimate the target location and thus reduce the complexity, while achieving the RMSE (root mean square error) close to that of the ML algorithm.