GNSS data demodulation over fading environments: Antipodal and<i>M</i>‐ary CSK modulations

Ortega, Lorenzo; Vilà‐Valls, Jordi; Poulliat, Charly; Closas, Pau

doi:10.1049/rsn2.12017

Cited by 6 publications

(3 citation statements)

References 23 publications

(69 reference statements)

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“…However, compared with BPSK, CSK consumes more resources and has higher computational complexity. For CSK signals, scholars have mainly studied the improvement of CSK modulation and demodulation algorithms, as well as the combination of coding techniques to improve the reliability of transmission [23][24][25][26]. The tracking algorithms for BPSK signals are relatively mature, and the research on CSK signal tracking is not sufficient, mainly focusing on reducing the number of correlators and the demodulation complexity.…”

Section: Introductionmentioning

confidence: 99%

Research on Tracking Technique Based on BPSK-CSK Signals

Chen,

Cheng,

et al. 2024

Electronics

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The code-shift keying (CSK) modulation method can achieve higher information transmission rates without changing the spread spectrum signal bandwidth. In order to optimise the spread spectrum modulation and demodulation of GNSS signals, in addition to the signal structure, binary phase-shift keying (BPSK) and CSK signals using time-division multiplexing are proposed. A tracking method based on the BPSK-CSK signals is also proposed, which generates the P-branch local codes by fast Fourier transform to obtain the code-slice spacings for the E-branch and the L-branch local codes. Then, the tracked BPSK signals and tracked CSK signals are compared and analysed. Finally, the bit error rate (BER) and tracking error of each method are compared and analysed by comparing with the tracking of conventional BPSK signals and tracking of CSK signals, in order to verify the convergence process of the I-branch integral value. The BPSK-CSK signal tracking method proposed in this paper combines the high information transmission rate of CSK-modulated signals and the low BER of BPSK signals, and the results provide a solid foundation for high-precision GNSS services.

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Section: Introductionmentioning

confidence: 99%

Research on Tracking Technique Based on BPSK-CSK Signals

Chen,

Cheng,

et al. 2024

Electronics

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“…It uses pseudorange observations, which require the availability and high accuracy of pseudorange observations. However, the pseudorange observations may not always be available and may have large noise due to the impact of multipath effects in the measurement [28]. Therefore, it is imperative to study an alternative method for the dual‐frequency cycle slip detection and repair when pseudorange observations are not available or have insufficient accuracy.…”

Section: Introductionmentioning

confidence: 99%

A new real‐time cycle slip detection and repair approach based on BDS dual‐frequency carrier phase and Doppler observations

Shi

Dong

Qian

et al. 2021

IET Radar Sonar & Navi

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The Global Navigation Satellite System (GNSS) traditional dual-frequency cycle slip detection and repair methods such as the TurboEdit algorithm are restricted by the availability and accuracy of pseudorange observations. Doppler observations represent the instantaneous variation of the carrier phase during the integration time, which are immune to cycle slips. They are less affected by multipath effects compared with the pseudorange observations. Hence, a real-time cycle slip detection and repair approach for the BeiDou Navigation Satellite System (BDS) dual-frequency signals is proposed by combining the carrier phase and Doppler observations. The proposed method adopts the phase-Doppler combination and the geometry-free combination to detect cycle slips, and uses the simple rounding method or the dual-frequency least-square ambiguity decorrelation adjustment (LAMBDA) method to repair cycle slips. The validity of the proposed method is verified by the static and kinematic observation data under 1 s sampling interval and steady ionosphere. The results show that the new method can successfully detect all the small, insensitive, and large cycle slips. Moreover, the fixing rates of the simple rounding method under static and kinematic conditions are above 94% and 83%, respectively, while those of the dual-frequency LAMBDA method are both 100%.

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“…However, a key part of GNSS receivers is the data demodulation stage, which allows recovering essential information. The latter has been long disregarded, with only a few articles [32][33][34][35] in the state-of-the-art, but may be a critical point under interference scenarios, being the principal object of this article.…”

Section: Introductionmentioning

confidence: 99%

Low Complexity Robust Data Demodulation for GNSS

Ortega¹,

Poulliat

Boucheret

et al. 2021

Sensors

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In this article, we provide closed-form approximations of log-likelihood ratio (LLR) values for direct sequence spread spectrum (DS-SS) systems over three particular scenarios, which are commonly found in the Global Navigation Satellite System (GNSS) environment. Those scenarios are the open sky with smooth variation of the signal-to-noise ratio (SNR), the additive Gaussian interference, and pulsed jamming. In most of the current communications systems, block-wise estimators are considered. However, for some applications such as GNSSs, symbol-wise estimators are available due to the low data rate. Usually, the noise variance is considered either perfectly known or available through symbol-wise estimators, leading to possible mismatched demodulation, which could induce errors in the decoding process. In this contribution, we first derive two closed-form expressions for LLRs in additive white Gaussian and Laplacian noise channels, under noise uncertainty, based on conjugate priors. Then, assuming those cases where the statistical knowledge about the estimation error is characterized by a noise variance following an inverse log-normal distribution, we derive the corresponding closed-form LLR approximations. The relevance of the proposed expressions is investigated in the context of the GPS L1C signal where the clock and ephemeris data (CED) are encoded with low-density parity-check (LDPC) codes. Then, the CED is iteratively decoded based on the belief propagation (BP) algorithm. Simulation results show significant frame error rate (FER) improvement compared to classical approaches not accounting for such uncertainty.

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GNSS data demodulation over fading environments: Antipodal andM‐ary CSK modulations

Cited by 6 publications

References 23 publications

Research on Tracking Technique Based on BPSK-CSK Signals

Research on Tracking Technique Based on BPSK-CSK Signals

A new real‐time cycle slip detection and repair approach based on BDS dual‐frequency carrier phase and Doppler observations

Low Complexity Robust Data Demodulation for GNSS

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