星基增强系统接收机中的导航比特同步设计与性能仿真

Bit Synchronization Design and Performance Simulation of Satellite Based Augmentation System(SBAS) Receiver

星基增强系统(SBAS)中导航电文速率为500符号/秒,针对其弱信号时找导航比特边界难的特点,提出了基于最大似然算法的比特同步算法,给出了在SBAS接收机中比特同步的应用公式和实现方法,并进一步创新性地设计了包含有软判决和多次判决的比特同步综合流程;最后在多种导航比特分布的情形下,对最大似然比特同步算法进行了不同载噪比下的性能仿真,确认了此算法在接收信号很弱时仍然有效。

The navigation bit rate of SBAS （ Satellite Based Augmentation System） equals 500 symbols per second, which has difficulty in finding bit boundaries when operating with a very weak received signal. So, a maximum - likelihood bit synchronization algorithm is proposed, and its application formula and implementation method in the SBAS receiver are given. Meanwhile, to reduce the probability of false alarm, an integrated bit synchronization flow procedure is designed in which a soft decision and multi - time decision is considered. Finally, in the case of variable navigation bit probability and different carrier to noise ratio, the performance of maximum -likelihood bit synchronization algorithm is simulated, and the results prove the availability of this algorithm when the received signal is very weak.