Performance Evaluation of the Structure of GNSS Navigation Message

Based on the analysis of the factors which have influence on performance of navigation message and must be considered in the navigation message structure design,some criterion and methods of the performance evaluation of the structure of navigation message are proposed.The criterion and methods include the total number of data bits,the time to first user receiver position fix,the time for user receiver to acquire a set of almanac data,the flexibility and expansibility of navigation massage structure and the utilization ratio of the satellite communication channel.As an application example,the navigation message structure performances of GPS and GLONASS are analyzed.