High-order Binary Offset Carrier Signals Research Articles

Positioning Performance Limits of GNSS Meta-Signals and HO-BOC Signals.

Global Navigation Satellite Systems (GNSS) are the main source of position, navigation, and timing (PNT) information and will be a key player in the next-generation intelligent transportation systems and safety-critical applications, but several limitations need to be overcome to meet the stringent performance requirements. One of the open issues is how to provide precise PNT solutions in harsh propagation environments. Under nominal conditions, the former is typically achieved by exploiting carrier phase information through precise positioning techniques, but these methods are very sensitive to the quality of phase observables. Another option that is gaining interest in the scientific community is the use of large bandwidth signals, which allow obtaining a better baseband resolution, and therefore more precise code-based observables. Two options may be considered: (i) high-order binary offset carrier (HO-BOC) modulations or (ii) the concept of GNSS meta-signals. In this contribution, we assess the time-delay and phase maximum likelihood (ML) estimation performance limits of such signals, together with the performance translation into the position domain, considering single point positioning (SPP) and RTK solutions, being an important missing point in the literature. A comprehensive discussion is provided on the estimators’ behavior, the corresponding ML threshold regions, the impact of good and bad satellite constellation geometries, and final conclusions on the best candidates, which may lead to precise solutions under harsh conditions. It is found that if the receiver is constrained by the receiver bandwidth, the best choices are the L1-M or E6-Public Regulated Service (PRS) signals. If the receiver is able to operate at 60 MHz, it is recommended to exploit the full-bandwidth Galileo E5 signal. In terms of robustness and performance, if the receiver can operate at 135 MHz, the best choice is to use the GNSS meta-signals E5 + E6 or B2 + B3, which provide the best overall performances regardless of the positioning method used, the satellite constellation geometry, or the propagation conditions.

Delayed sampling technique for high‐order BOC signals acquisition

Binary offset carrier (BOC) signals are applied in modernised global navigation satellite system. High-order BOC signals provide good performance in spectrum separation and signal tracking. However, for high-order BOC signals, the sampling frequency is much higher than that of binary phase-shift keying signals, which increases computational complexity. Meanwhile, the zero crossings in the correlation function degrade the detection performance. In this Letter, band-pass sampling is introduced for BOC signals to reduce the computational complexity and remove the zero crossings. A delayed replica of the received signal is used to construct a complex signal which is sampled with a much lower sampling frequency than the Nyquist frequency. The correlation function of the sampled signal has no secondary peaks. Thus, the detection probability is higher and the computational complexity is lower.

Collective Unambiguous Positioning With High-Order BOC Signals

The unambiguous estimation of high-order binary offset carrier signals in harsh propagation conditions is still an open problem in the literature. This paper proposes to overcome the limitations observed in state-of-the-art unambiguous estimation techniques based on the application of existing direct positioning techniques and the exploitation of the spatial diversity introduced by arrays of antennas. In particular, the ambiguity problem is solved as a multiple-input multiple-output estimation problem in the position domain.

A Main Peak Extraction Method for High-Order BOC Signals

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.

A Design Method of Code Correlation Reference Waveform in GNSS Based on Least-Squares Fitting.

The multipath effect is one of the main error sources in the Global Satellite Navigation Systems (GNSSs). The code correlation reference waveform (CCRW) technique is an effective multipath mitigation algorithm for the binary phase shift keying (BPSK) signal. However, it encounters the false lock problem in code tracking, when applied to the binary offset carrier (BOC) signals. A least-squares approximation method of the CCRW design scheme is proposed, utilizing the truncated singular value decomposition method. This algorithm was performed for the BPSK signal, BOC(1,1) signal, BOC(2,1) signal, BOC(6,1) and BOC(7,1) signal. The approximation results of CCRWs were presented. Furthermore, the performances of the approximation results are analyzed in terms of the multipath error envelope and the tracking jitter. The results show that the proposed method can realize coherent and non-coherent CCRW discriminators without false lock points. Generally, there is performance degradation in the tracking jitter, if compared to the CCRW discriminator. However, the performance promotions in the multipath error envelope for the BOC(1,1) and BPSK signals makes the discriminator attractive, and it can be applied to high-order BOC signals.

Decimation Double-Phase Estimator: An Efficient and Unambiguous High-Order Binary Offset Carrier Tracking Algorithm

Traditional binary offset carrier (BOC) tracking algorithms process the upper and lower sideband signals together, and thus, the sampling frequency and computational requirements are much higher than that required for binary phase-shift keying tracking algorithms, especially for high-order BOC signals. Addressing existing limitations, this letter proposes a decimation double-phase estimator (DDPE) tracking algorithm for BOC signals. The algorithm uses a normal carrier and a subcarrier with a constant frequency to shift the upper and lower sideband signals of BOC to the zero frequency and decimates the signal before processing by the correlator. The residual carrier and the subcarrier are then tracked by the double-phase estimator algorithm. Decimating the signals significantly reduces the computational complexity, and for a BOC(6 n , n ) signal, the DDPE is found to reduce 86% of correlator operations with a signal-to-noise ratio loss of 0.5 dB.

A Triple-Loop Tracking Method for High-Order BOC-Modulated Signals

This paper proposes a triple-loop trackingmethod for high-order binary-offset-carrier (BOC)modulated signals. We introduced the characteristics of high-order BOC signals, and then describedthe principle of the triple-loop tracking method, and outlined its framework. The proposed scheme isapplicable to both generic high-order sine- and cosine-phased BOC-modulated signals. The methodremoves the threats brought by the side-peaks ambiguities, while keeping the same sharp correlationof the main peak, thus, allowing for better tracking precision. Simulation results show the validity ofour method in improving the system tracking performances.