Zhang Yeqing, Wang Meiling, Li Yafeng
School of Automation, Beijing Institute of Technology, Beijing 100081, China.
Sensors (Basel). 2018 Feb 24;18(2):678. doi: 10.3390/s18020678.
For the objective of essentially decreasing computational complexity and time consumption of signal acquisition, this paper explores a resampling strategy and variable circular correlation time strategy specific to broadband multi-frequency GNSS receivers. In broadband GNSS receivers, the resampling strategy is established to work on conventional acquisition algorithms by resampling the main lobe of received broadband signals with a much lower frequency. Variable circular correlation time is designed to adapt to different signal strength conditions and thereby increase the operation flexibility of GNSS signal acquisition. The acquisition threshold is defined as the ratio of the highest and second highest correlation results in the search space of carrier frequency and code phase. Moreover, computational complexity of signal acquisition is formulated by amounts of multiplication and summation operations in the acquisition process. Comparative experiments and performance analysis are conducted on four sets of real GPS L2C signals with different sampling frequencies. The results indicate that the resampling strategy can effectively decrease computation and time cost by nearly 90-94% with just slight loss of acquisition sensitivity. With circular correlation time varying from 10 ms to 20 ms, the time cost of signal acquisition has increased by about 2.7-5.6% per millisecond, with most satellites acquired successfully.
为了从根本上降低信号采集的计算复杂度和时间消耗，本文探索了一种适用于宽带多频全球导航卫星系统（GNSS）接收机的重采样策略和可变循环相关时间策略。在宽带GNSS接收机中，重采样策略通过以低得多的频率对接收到的宽带信号的主瓣进行重采样来作用于传统采集算法。可变循环相关时间被设计用于适应不同的信号强度条件，从而提高GNSS信号采集的操作灵活性。采集阈值被定义为载波频率和码相位搜索空间中最高相关结果与第二高相关结果的比值。此外，信号采集的计算复杂度通过采集过程中的乘法和加法运算量来表示。对四组不同采样频率的真实GPS L2C信号进行了对比实验和性能分析。结果表明，重采样策略能够在采集灵敏度仅有轻微损失的情况下，有效降低计算量和时间成本近90%-94%。当循环相关时间从10毫秒变化到20毫秒时，信号采集的时间成本每毫秒增加约2.7%-5.6%，并且大多数卫星都能成功采集。
