Research on the Navigation Message Broadcast Mode for COMPASS

In the satellite navigation system,the message is defined as the information carried by the navigational signal.For the independent receivers,the broadcast mode has a significant impact on their working sensitivity,first fix-position time,and positioning accuracy,etc.In the recent years,several new forms of messages have been proposed along with the modernization process of GPS,as well as the developing of Galileo system.The newly proposed broadcast modes introduce a lot of benefits compared to the traditional GPS message forms.However,the remaining problems include the conflict between working sensitivity and information capacity,as well as the first fix-position time.Compass navigation system has its own uniqueness,such as different satellite orbits,construction stages,market applications,and other issues which should be considered when designing the broadcast mode of its message.Some principles should be followed when designing the broadcast mode of the message,which include the characteristics of different satellite orbits and different frequencies,the different characteristics of different satellite system,and the working sensitivity.A multi-rate broadcast mode is proposed in this paper based on the importance of different messages and their requirements for repeat cycle,and also,the higher broadcast rate and lower ones have their own advantages and disadvantages,respectively.By employing this mode,the broadcast rate can be changed on a single signal according to some factors,such as the content of information and regional environment,in so doing,a trade-off was reached between the working sensitivity and the first fix-position time,as well as the information capacity.Finally,the broadcasting and receiving method,as well as the performance analysis of this broadcast mode are given in this paper.