An efficient decoding erasure algorithm for the improvement of the decoding performance of the BCH code in the BeiDou satellite navigation system is proposed in this paper.The algorithm is used to construct a group of vectors on the basis of the reliability of each position in the hard-decision vector.Each group of vectors contains two erasure locations, and each vector is decoded by the decoding erasure algorithm.One obtained code word is select-ed as the output of the proposed algorithm in accordance with certain rules.To improve the efficiency of the algo-rithm, a termination mechanism is developed to decrease the number of decoded vectors.Simulation results show that the designed termination mechanism can effectively reduce the complexity of the proposed algorithm with little performance degradation.The proposed algorithm outperforms the traditional hard-decision decoding algorithm with a negligible increase in complexity.Therefore, the proposed algorithm achieves good tradeoff between decoding per-formance and complexity and is thus a good choice for practical navigation receivers.

In order to improve the performance of the traditional hard-decision decoding of BCH code in the BeiDou satellite navigation System, a low-complexity soft-decision decoder architecture is designed and implemented in this paper. The designed decoder is based on the syndrome-assisted soft-decision decoding algorithm. A non-uniform quantization scheme and a ROM reduction strategy based on cyclic property are proposed to reduce the hardware resources. Simulation results show that the performance of designed decoder is closed to that of the optimal soft-decision decoding. Compared with the traditional hard-decision decoder, the hardware resource increment is very small, which suggests the designed decoder is a suitable choice in practice.

To ensure fast acquisition of satellite signals in high dynamic applications , an improved algorithm was proposed for signal detection during acquisition by global navigation satellite system .The algorithm combined the advantages of the M-of-N and Tong detection algorithms .Through the multi-threshold detection mechanism , the de-tection and rejection speed accelerated whether the signals exist or not .Numerous real data tests show that the im-proved algorithm is three times faster than the M-of-N detection algorithm and one-third times faster than the Tong detection algorithm without any performance deterioration .

Soft-decision decoding of BCH code in the global navigation satellite system（ GNSS） is investigated in order to improve the performance of traditional hard-decision decoding. Using the nice structural properties of BCH code,a soft-decision decoding scheme is proposed. It is theoretically shown that the proposed scheme exactly performs maximum-likelihood（ ML） decoding,which means the decoding performance is optimal. Moreover,an efficient implementation method of the proposed scheme is designed based on Viterbi algorithm. Simulation results show that the performance of the proposed soft-decision ML decoding scheme is significantly improved compared with the traditional hard-decision decoding method at the expense of moderate complexity increase.

In the application of global satellite position system, signal adaptive acquisition strategies are required for various environment applications, such as weak signal, emergency moment, so fast and high sensitivity acquisition algorithms are important for the receiver process. This paper presents acquisition algorithms: coherent integration, non-coherent integration, differential coherent and differential non-coherent integration, and the differential integration are analyzed in both standard and pair-wise form, all of which are theoretically compared in their probability distribution with detailed analysis. And testing statics using Monte-Carlo with collected realistic various signal, considering the existence of carrier Doppler frequency and code phase shift in the objectives, give out that in certain probability of detection, differential standard coherent integration is the best detector, non-coherent integration is the second best; and differential pair-wise coherent, differential standard and pair-wise non-coherent integration give out almost the same performance; and the standard algorithm is more tolerable in residual Doppler environment than the pair-wise algorithm; the code phase shift will affect much more in the lower probability of detection; finally, in the theory analysis, the hypothesis of approximated gauss distribution and the IQ data completely independence with each other need to be revised in more accurate model to fit the actual data.

With the development of Global Navigation Satellite System (GNSS) and the emergence of multi-system joint positioning, the receiver is facing dilemma that both the amount of data processing and the hardware scale are becoming larger and larger in the restricted hardware resource. Great redundancy existing in the sampled data obtained by the classical Shannon-Nyquist sampling theorem is the fundamental cause. In recent years, as an emerging theory of signal sampling, compressed sensing (CS) provides a new method to solve this dilemma.Taking GNSS signal acquisition as a research object in this paper, a novel GNSS signal acquisition scheme based on CS and signal acquisition theoretical basis is proposed, aiming at the large hardware scale and the big amount of data processing problem. The new acquisition scheme adopts a single measurement orthogonal matching pursuit (OMP) algorithm to reconstruct the signal so as to simplify the signal recovery algorithm and reduce the complexity of the algorithm, and then theoretically analyze the effect of the measurement matrix to the acquisition performance. In proceeding, the conclusion that extra carrier-to-noise ratio (CNR) caused by CS loss and the compression ratio displaying inversely proportional is proved. Furthermore, two methods aiming at solving the problem of extra CNR caused by CS loss are proposed to improve the acquisition performance in this paper by increasing the compression ratio and enhance the input CNR. Finally, a series of tests toward the global positioning system (GPS) signal and the binary offset carrier (BOC) signal are simulated and verified in the following aspects, such as the choice of measurement matrix, the noise loss analysis, the acquisition probability and the CNR loss under different compression ratio. The simulation result consistent to theoretical analysis shows that the proposed algorithm can be effectively applied to the navigation applications, and can greatly reduce the hardware scale under the condition of certain guaranteed performance.

To improve the gain of decoding BCH code message in satellite navigation system ,using structural properties of BCH codes ,a low complexity decoding scheme of soft information was designed .Considering the performance and computation through algorithm level simulation ,parameters that were suitable for information software decoding of satellite navigation system were chosen ,and hardware implementation was realized .The actual validation results show that the hardware scale becomes lar‐ger but in the acceptable range ,the performance of decoding soft information is greatly improved on the premise of increasing lit‐tle complexity .

The rotation vector of each update cycle being small enough is taken as precondition by the traditional rotation vector algorithm, while the carrier moving as the whirligig in the high speed up to 100 rad/s for example and the update frequency of the system limited as 100Hz for example make the rotation vector of each update cycle too large to be neglected in some places during the calculation which directly leads to error augment of the traditional rotation vector algorithm so as to make the traditional one not apply to the attitude calculation algorithm of the carrier moving as whirligig in the high speed. In this paper, an adaptive rotation vector estimated algorithm was proposed which real-time dynamically estimated the rotation vector according to the different rotation rate of the carrier. And it was proved by simulation that the improved algorithm for attitude update could effectively improve the accuracy in the condition of carrier rotating in a high speed with coning motion.

In inertial navigation system, some traditional calibration methods of accelerator mainly rely on turntable, other methods without the support of turntable have less accuracy. Therefore, this paper presents a high-accuracy calibration method of accelerator without the support of turntable. It only needs 12 static output data of accelerator to calibrate the bias, scale factor and misalignment. Experiment results indicate that this method has higher accuracy cnmDared with traditional calibration method without the support of turntable.

In the data fusion of tightly coupled GPS/Attitude Heading Reference System (AHRS), the calculation errors of traditional UKF resulted in a negative definite state of covariance. The results may ultimately reduce the accuracy of filter and even cause divergence of filters which lead to abnormality of the system. An improved adaptive SRUKF (square root unsensitive Kalman filter) provided in this paper, can help solve the problem of negative definite state covariance and lower calculation complexity. The filtering results of the simulation data show that, under the condition of unknown and real-time system noise statistics, the improved adaptive SRUKF in a tightly coupled integrated navigation system have better performance both in accuracy and in robustness.

Due to the uncertainty of measurement noise,the accuracy of the Kalman filter is affected seriously while measuring the vehicle attitude in the Attitude and Heading Reference System(AHRS).The sudden change of measurement noise brought by interference of the system even leads to filter divergence.An algorithm for the adaptive Kalman Filter used in AHRS is presented in this paper,which is able to estimate the measurement noise in real time according to observation data and improve the accuracy of the Kalman Filter.Simulation result shows that the results of the Kalman filter diverge clearly even though the measurement noise varies,and that the adaptive Kalman filter results converge very well.The system stability is markedly improved without significant increase in computing complexity.

The bandwidth characteristics of an extended Kalman filter were analyzed in order to study the filter's performance in tracking high dynamic signals,and a mathematic model was also established.According to the analysis,a modified tracking loop was proposed.The bandwidth characteristics of both algorithms were analyzed under various conditions,and the results show that the bandwidth of the modified method is much smaller than that of routine method from NASA.Both algorithms were simulated with high dynamic global navigation satellite system(GNSS) signals whose relative jerk achieves 100 g/s.Compared with a routine algorithm,the frequency error and probability of a loss-of-lock of novel algorithm are all markedly reduced,and the tracking sensitivity is increased by 1.3 dB.

The global navigation satellite system(GNSS) can position rapidly within one second if the sum of the initial position error,initial time error,and other factors is less than 150 km;that is,the initial time error can not be larger than 210 s even when the initial position error is zero.So the time to first fix(TTFF) of the GNSS could be within one second only in the instance of a hot start or Aided GNSS.To resolve the problem,a novel algorithm for rapid positioning using a Doppler-aided range fit was proposed.The algorithm can function in conditions other than a hot start and Aided GNSS.Analysis and tests in real data show that the proposed algorithm works correctly and achieves the TTFF within one second when the initial time error exceeds one thousand or even ten thousand seconds,as well as in the condition of an unknown initial position error.

This paper modifies the histogram bit synchronization algorithm. The expressions on probability of both synchronization and false alarm of histogram method have been deduced, and the quantity of measured bits as well as thresholds with best performance is acquired. Compared with results from relational literature, the average time of bit synchronization has almost been shortened by 40%.