Research And Designation Of Modem In Military Digital Cryptogram Telephone

With the development of the informational society, everyone in different areas can share the achivemnents of it, but it also bring us a challeng-the security of the information.Because the digital cryptogram telephone can enctypt the voice on commen line, it has been used in many areas, such as in military, bank, and diplomatic communication.In military communication, the digital cryptogram telephone are often asked to be used in complex environments and to connect with others in a few seconds.But, today's digital cryptogram telephone can't satisfy to these demands because of its modem which uses the traditional protocols.Today's digital cryptogram telephone have two deficiencies: one is its long hand-shake time, and another is bad voice quality in bad environment.In order to fufil the requitment of the Digital Secure Telephone in military communication, this issue aims at the demands of the Digital Secure Telephone in army, and means to settle the disadvantage of long time hand-shake protocol and bad voice quality.The contents of this issue can be summarized as follows:1. It introduces modom's working theory, system constitutes, developing course and the situation of today's development, then it presents critical technologies in modems.2. It base on hand-shake's time to analys three hand-shake protocols:V.22bis, V.34 and V.90 combined with modulate and demodulate, then abstract what make up the time of hand-shake protocols througt test and analys.3. It puts forward a new hand-shake protocol of modem from the demand in military communication. Then it analyses the capability of this new protocol, and believe the new protocol can decrease the time of hand-shake.4. It compares some classic methods of error control in speech coding, and choose RCPC as channel channel coding. In order to resist mistake , it provides a new convolutional interleaving algorithm which has perfect quality in delay,storage occupied and mistake resistance.5. It realizes a hardware and software scheme which based on the new hand-shake protocol in modem and a method of error control.6. It tests and validates the new hand-shake protocol in modem and function of resist miatake through the logic channel annalyes instrument.In the end, we can conclude that the new modem can cut off the hand-shake time of military digital cryptogram telephone,and can provide good voice.