Double Block Zero Padding Research Articles

弱信号环境下的双块补零改进捕获技术研究

弱信号环境下的双块补零改进捕获技术研究

A Large Doppler Weak Direct Spread Signal Acquisition Algorithm and Optimization Method

For satellite receivers, on the one hand, large Doppler frequency will cause accumulation loss for a long-term accumulation acquisition algorithm, which leads to the problem of correlation peak broadening; on the other hand, searching within a larger Doppler uncertainty range will consume more logic resources. Thus, this paper first analyses the impact of large Doppler frequency on coherent accumulation and non-coherent accumulation based on the traditional Double Block Zero Padding (DBZP) algorithm. Secondly, an improved DBZP algorithm is designed in combination with the Keystone transform of the transform domain, and simplify the variable-scale DFT to reduce the amount of calculation. Then, the key parameters of the algorithm are extracted to establish the optimization objective function, the algorithm parameters are optimized through genetic algorithm without reducing the performance of the algorithm. Finally, the simulation verifies that the optimized and improved DBZP algorithm can effectively solve the problem of code phase walking.

Joint Acquisition Estimator of Modern GNSS Tiered Signals Using Block Pre-Correlation Processing of Secondary Code.

Objective is a joint primary and secondary code (SC) acquisition estimator of tiered Global Navigation Satellite Systems (GNSS) signals. The estimator is based on the Parallel Code Search algorithm (PCS) combined with the Single-Block-Zero-Padding (SBZP) and the Pre-correlation Coherent Accumulation (PCA). The PCA realizes the extension of the coherent integration time in front of the PCS. However, the PCS with the SBZP and the PCA is affected by a navigation/SC bit transition problem due to its cyclic property of a computed Cross-Ambiguity Function (CAF). This CAF is degraded by diverse parasitic fragments and is not directly applicable for an acquisition. A novel analysis of this mechanism and its impact is presented. Then, the proposed modified SBZP (mSBZP) modified PCA (mPCA) PCS estimator is constructed, which does not degrade the CAF. The mSBZP allows the use of the PCS algorithm in the presence of SC bit transition, while the mPCA decreases the number of PCS algorithm calculations by a factor of SC chip count due to SC pre-correlation processing. The algorithm has the same detection performance in comparison with conventional Double-Block-Zero-Padding (DBZP). However, it allows using the PCS of half-length with longer latency up to a factor of SC chip count.

Weak GPS signal acquisition method based on DBZP

Double block zero padding (DBZP) is a widely used but costly method for weak global positioning system (GPS) signal acquisition in software receivers. To improve the computational efficiency, this paper proposes an algorithm based on the differential DBZP algorithm and the discrete cosine transform (DCT) domain filtering method. The proposed method involves using a differential correlator after the DBZP operation. Subsequently, DCT domain low pass filtering (LPF) and inverse DCT (IDCT) reconstruction are carried out to improve the signal to noise ratio (SNR). The theoretical analysis and simulation results show that the detection algorithm can effectively improve the SNR of the acquired signal and increase the probability of detection under the same false alarm probability.

Efficient BeiDou DBZP‐based weak signal acquisition scheme for software‐defined receiver

Modulation with high-rate Neumann-Hoffman (NH) code in BeiDou signals increases the complexity and calculation load in acquisition as the data bit transitions are more frequent and there is no pilot component for synchronisation which is used in other constellations. Among the current state of the art, double block zero padding (DBZP) method has great potential in reducing the calculation. However, traditional DBZP is very sensitive to bit transition and the misalignment of bit edge will cause serious power loss. To relieve the calculation load and acquire the weak signal successfully, an efficient BeiDou DBZP-based scheme is proposed. The proposed scheme is optimised in two aspects: the NH code phase searching and correlation integration. The step size of the proposed NH code searching method is half an NH code bit which means the number of searches in one navigation message bit is only 40 and the computation load can be reduced greatly. Additionally, the proposed inherited correlation integration establishes a tight inherited structure between adjoining coherent integrations which can reduce the calculation burden further. The experiment results show that the proposed scheme can acquire as weak as 22 dBHz with only about 12% computation time of the traditional DBZP method.

Amelioration of Acquisition of a Degraded Signal in a GNSS Receiver Embeded in an Observation Satellite by Using Double Bloc Zero Padding Method (DBZP)

In this paper, we study the acquisition of signal in a GPS (Global Positioning System) receiver on board of an observation satellite that receives information on a carrier wave L1 frequency 1575.42 MHz .We simulated GPS signal acquisition. This allowed us to see the behavior of this type of receiver in AWGN channel. Block Zero-Padding (DBZP) acquisition method, known for his efficiency, is deeply analyzed to highlight the acquisition of the modernized GNSS signals can be seriously degraded by the presence of bit sign transitions at each spreading code period. It appears clear that there is a need to use an acquisition method which is bit sign transition insensitive. To tackle this problem an improved and innovative acquisition method, the Double-Block Zero-Padding. Besides this major improvement, other developments are proposed to limit losses on the acquisition performance, in. This paper we will focus on the study of the acquisition of weak signals. The performance study and the results point out the efficiency of this method for the acquisition signals, in comparison with a classical acquisition method which is also data insensitive.

Gnss Signal Processing in Gpu

ABSTRACT Signal processing of the global navigation satellite systems (GNSS) is a computationally demanding task due to the wide bandwidth of the signals and their complicated modulation schemes. The classical GNSS receivers therefore utilize tailored digital signal processors (DSP) not being flexible in nature. Fortunately, the up-to-date parallel processors or graphical processing units (GPUs) dispose sufficient computational power for processing of not only relatively narrow band GPS L1 C/A signal but also the modernized GPS, GLONASS, Galileo and COMPASS signals. The performance improvement of the modern processors is based on the constantly increasing number of cores. This trend is evident not only from the development of the central processing units (CPUs), but also from the development of GPUs that are nowadays equipped with up to several hundreds of cores optimized for video signals. GPUs include special vector instructions that support implementation of massive parallelism. The new GPUs, named as general-purpose computation on graphics processing units (GPGPU), are able to process both graphic and general data, thus making the GNSS signal processing possible. Application programming interfaces (APIs) supporting GPU parallel processing have been developed and standardized. The most general one, Open Computing Language (Open CL), is now supported by most of the GPU vendors. Next, Compute Unified Device Architecture (CUDA) language was developed for NVidia graphic cards. The CUDA language features optimized signal processing libraries including efficient implementation of the fast Fourier transform (FFT). In this paper, we study the applicability of the GPU approach in GNSS signal acquisition. Two common parallel DSP methods, parallel code space search (PCSS) and double-block zero padding (DBZP), have been investigated. Implementations in the C language for CPU and the CUDA language for GPU are discussed and compared with respect to the acquisition time. It is shown that for signals with long ranging codes (with 10230 number of chips - Galileo E5, GPS L5 etc.). Paper presented at the "European Navigation Conference 2012", held in Gdansk, Poland

Computational Efficiency Improvement for Unaided Weak GPS Signal Acquisition

Acquisition of unaided weak Global Positioning System (GPS) signals requires long coherent integration time and thus all the possible navigation data bit combination paths have to be searched. In this paper, to improve the computational efficiency, the Improved Fast Modified Double-Block Zero Padding (IFMDBZP) algorithm using the Optimal Path Search Method (OPSM) is proposed instead of the FMDBZP algorithm using the All Paths Search Method (APSM). The proposed method consists of unlikely data bit combination path elimination by applying the Viterbi algorithm during each coherent integration step to improve the FMDBZP algorithm. The analyses show that the proposed OPSM can reduce the computation calculations and save memory space without suffering any loss compared to the APSM. And the longer the coherent integration time is, the more benefit one can gain from the proposed method. The simulation results also show that the IFMDPZP algorithm using the proposed OPSM has the same acquisition performance as the APSM.

Partial-correlation-result reconstruction technique for weak global navigation satellite system long pseudo-noise-code acquisition

In global navigation satellite system (GNSS), the signals are very weak. In particular, when the signals are interfered by other signals or shadowed by heavy vegetation, mountains, buildings etc., they will be significantly attenuated and become much weaker. In the situation, for GNSS pseudo-noise (PN)-code acquisition, detection performance is critical. In the study, to improve the detection performance of the previously published double block zero-padding (DBZP) method for weak GNSS long PN-code signals, the authors propose to reconstruct the correlation results of DBZP. Taking the advantage of utilising the correlation results that correspond to part of received signal aligning with local signal and are discarded by DBZP, the technique expands coherent integration time. The effect of the proposed technique on detection and mean acquisition time performance is analysed. It is shown that after reconstructing correlation results the proposed technique expands coherent integration time to twice, improves detection performance about 1.3 dB and consequently further shortens mean acquisition time, whereas it does not increase the implementation complexity of a GNSS receiver. The technique is also applicable to other GNSS long PN-code acquisition methods such as the previously published direct average method and the overlap average method.

Implementation and Testing of an Unaided Method for the Acquisition of Weak GPS C/A Code Signals

Fast Modified Double Block Zero Padding (FM-DBZP) is presented as a method for unaided acquisition of weak GPS C/A signals. FM-DBZP uses frequency-domain techniques for coherent integration over integer multiples of the data bit period to perform a search in code delay, Doppler frequency, bit combination, and bit edge. The FFT operation count grows linearly with coherent integration time. The Zoom FFT (ZFFT) further reduces the multiplication count by 28% and the addition count by 37%. The coherent integration time is set to minimize the total computational cost, given a specified acquisition threshold. Successful acquisition, at a design C/N0 of 15 dB-Hz, is demonstrated using a GPS signal simulator. The signal is further attenuated until the algorithm failed to acquire a satellite with a success rate better than 50%. This occurs at a C/N0 of 12.5 dB-Hz.