Implementation Of Real-time GPS Software Receiver Based On ASIP

As indispensible equipment, GPS receiver helps the users to achieve positioning. With the development of digital technology, traditional GPS hardware receiver gradually gives place to GPS software receiver. Through receiving and processing the GPS positioning signals from satellites, GPS software receiver solves out information and shows it to the user. As the main operation unit of GPS receiver, signal synchronization estimates the C/A code phase and Doppler frequency shift to generate a local signal synchronized to the received signal, then the carrier and C / A code can be removed and the navigation data can be extracted for the follow-up positioning unit. Signal synchronization includes capturing and tracking. FFT and Bit-wise are the main operation units in the capturing process and tracking process respectively. Real-time data processing is always the key problem in GPS software design.This paper explores real-time GPS software receiver based on ASIP, and find out that frequent memory access in Bit-wise algorithm is the bottleneck in real-time operation. Therefore, reasonably designed and well performing memory is an effective way to solve real-time problems. According to the idea of memory access pattern, this paper carries out memory performance evaluation with different parameters on M5 simulator, and finally gives a group of optimized memory parameters for Bit-wise algorithm.In the evaluation of memory performance with different Cache size, the paper uses the idea and analyzing method of reuse distance. The program-independence and accurateness of reuse distance, and its relationship with Cache miss rate are fully displayed in this paper. With M5 platform, this paper obtains and analyzes the reuse distance histogram of Bit-wise algorithm, and finds out the optimized Cache size. Besides, based on MAR and miss rate evaluation standards, the paper carries out performance evaluation of memory with different block size, different associative and different frequency group, and get a group of optimized parameters. Finally, with the parameters, this paper designs a system structure for real-time GPS software receiver.The result shows that, based on the completed ASIP, when Cache size=64K, block size=64, associative=2, and the frequency proportion of CPU, BUS and memory is 1:1:0.333, the running time of GPS signal processing is shorter than the corresponding data length, and it finally achieves GPS software receiver real-time operation.