| After the capability of the system (the number of users) reaches a certain degree, the low baud rate(300 B) is one of the direct reasons that network congestion for "the inshore fishery correspondence net for safe salvage" (IFCNSS), and also affects the communication probability and dependable of tone continue as well as the development of the followed increasing services and the maximum function of IFCNSS. Therefore, it is the most basic and most important tache in existent irregularity of IFCNSS.When ship station make a call , the time to establish one communieation process will be much more , so the call times that the control channel handle are much less in unit time .When the number of ship stations which make calls is far more larger than the number of users which the system can allow to handle, the weak channel control ability will lead to network congestion , so the baud rate and the communication protocol of current IFCNSS can not adapt a large-scale fishery busywork.For improving the baud rate of system, this text adopts the GMSK (Gauss ian Filtered Minimum Shift Keying) modulation method to replace ASK (Amplitude Shift Keying) modulation method of current IFCNSS. Then , we will proceed the experiment of serial communication, transmitting data with the velocity 9.6 kbit/ s , and get the very excellent experiment result , and rewrite the new protocol according to the new modulation method .Thus the time which establish once communication process will be shortened obviously .It establishes stability foundation for further solving the network congestion.In the case of satisfying normal and usual communication and safety communication , at the premise of the acceptable error code rate , it is important to increase the baud rate and mend the protocol of the systemfor improve the network congestion of JPCNSS . This improvement wi 1 1 produce the profound influence for technique improvement of IFCNSS , network upgrade and the followed increment services.
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