Research On Navigation Receiver Real-Time Scheduling Key Technology

In the process of R&D(Researching and Developing) our new generation satellite navigation receivers, which are classified into different categories in order to meet different requirements in applications, receivers must not only have multi-frequency and multi-channel satellite signal receiving functions, but also be inevitably of applicable functions, such as multipath suppression, antijamming, high dynamic carrier navigation, information encryption and decryption, and so on. Some top-class receiver even has all the above functions and need complicated timing control. Also, design demand often changes, which requires adding new modules. Traditional R&D methods focus on module-stage design. Adding tested modules directly into receiver task set lacks for controllable quantificational scheduling optimization and performance evaluation methods. This cannot troubleshoot the potential task timing conflict in time, which costs much especially at the late stage, and results in low efficiency.Considering real-time scheduling at the design stage can greatly improve the R&D efficiency. Navigation receivers adopt well-appointed fixed priority scheduling kernel. Designers only need to use it, and then pay attention to the off-line optimization of task execution time, priority, period and deadline, so that every task is scheduable, and reduce receiver's power consumption, which is just the key of this dissertation. This dissertation focuses on navigation receiver task set scheduling optimization method and performance evaluation technology. The main contributions of this dissertation are as follows:The off-line optimization technology of navigation receiver task parameters is studied. The fixed priority scheduling performance evaluation method is proposed, where the quantitative analyses of task execution time, priority, period and deadline are considered. The determinant rule for receiver scheduling with limited priority levels is proposed and proved analytically. Traditional R&D methods lack for controllable quantificational scheduling optimization, subjective decision often results in low efficiency. An execution time dichotomy optimization off-line method is proposed based on equilibrium rule, aimed at troubleshooting timing conflict potentially aroused by demand changes. Deadline monotonic ordered saturated assignment is proved to have the least priority levels, which is much quicker than those tradional priority assignment algorithms. An energy-saving scheduling method based on decreasing frequency is proposed to reduce receivers'power consumption, still maintaining taskset schedulability. The above researches provide important theoretical principle for receiver task scheduling. Optimization design of common navigation functions is one of the important methods to guarantee task set schedulable and reduce receiver's power consumption. As for execution time optimization design of navigation tasks, an optimizing method based on Differential Evolution is proposed to find optimal approximating polynomial coefficients of baseband digital signal processing tasks, such as signal estimation, discriminator, and navigation calculation. In contrast, direct calculation of the above processing costs too much, and tradional progression approximating methods need to improve their computing precision. Take arc tangent PLL discriminator as an example, the calculation complexity of our method is approximately 1/2 of Chebyshev progression approximating, and 1/1700 of Taylor progression approximating, with the same precision.Checking peripheral device scheduling at the design stage can greatly improve receiver's R&D efficiency. This dissertation analytically proves that the circular buffer schedulablity requires the ratio of the total response time of the peripheral device to total time be less than 1, which is the sufficient and necessary condition. An off-line numerical method is proposed to calculate the minimal space of the circular buffer. And an improved word-oriented march test algorithm is proposed to diagnose all the static unlinked fault of the peripheral memory. The above researches provide important principle for receiver peripheral device scheduling.As for multi-precision redundancy scheduling of navigatin task, a time redundancy scheduling method with predictable Deadline Miss Ratio is proposed, which eliminates the domino effect of continuous deadline missing. Further improving approach is presented, and Deadline Miss Ratio can be effectively reduced by adopting traditional time redundancy techniques based on off-line checkpointing analysis. The techniques studied in this dissertation have been successfully applied to the real-time scheduling design of high quality navigation receivers.