基于循环冗余校验码的卫星导航电文增强纠错方案

为使用错误导航电文改善卫星导航性能，提出一种基于循环冗余校验码的增强纠错方法.使用CRC-24检错编码纠正卫星导航电文中的1 bit错误模式，利用数学分析和计算机搜索方法证明了最小码重和纠正错误能力，基于电文格式和错误比特分布模型分析了增强纠错方案对导航电文的改善，给出了一种低复杂度查表实现. 以GPS CNAV电文数据为实例验证增强纠错方法的性能，结果表明导航接收机使用CRC辅助纠错可以降低导航电文的帧错误率1~2个数量级，增强纠错在不改变信号结构的条件下可改善导航数据可靠性. 

Enhanced Error Correction for Satellite Navigation Message Based on CRC Codes

To improve the performance of satellite navigation by using error messages, an enhanced error correcting method based on CRC code was proposed. The CRC-24 error checking code of navigation message was used to correct one-bit error pattern. The minimum hamming weight and error correcting capability of CRC-24 code were proved by mathematical analysis and computer searching. The performance improvement of navigation using CRC correction was analyzed based on message format and the model of error bit distribution. A low complexity implementation was schemed based on looking-up table. The performance of enhanced error correcting was simulated with GPS CNAV navigation message. The results show that the CRC-assisted correction can reduce frame error ratio by 1~2 orders of magnitude. Without changing the signal structure of navigation message, the reliability of navigation is improved by using the enhanced correction.