Research On VoIP Implementation Technology In Tactical Internet

As the core technology of the next-generation network,VoIP is mainly applicated in the field of the fixed network.Due to wireless communication,the link of the tactical internet is not stable and the bandwidth is limited,so there are many difficulties in applying VoIP services on the tactical internet.Based on the Doubango and Asterisk technologies,this thesis studied on some important technologies of VoIP in bad communication environments,including the technology of adaptive voice transmission,the mechanism of terminal KeepAlive,the implementation technology of group call service and streaming video business,and ultimately realized the tactical internet VoIP communication system.The main contents are as follows:(1)This thesis introduced the topology and network model of the tactical internet,designed the structure of tactical internet communication system based on the SIP protocol,and analyzed the signaling process and signaling content of the tactical internet VoIP system.(2)In order to adjust the sending rate of speech stream according to the network quality,with the deeply analysis of fixed rate speech encoding algorithm,combined with the QoS feedback mechanism in RTCP and adaptive rate speech encoding model,this thesis proposed an adaptive speech transmission algorithm based on the quality of network.Simulation demonstrated that the packet loss rate and network delay parameters of the proposed algorithm were better than the fixed rate speech encoding algorithm.(3)In order to realize the KeepAlive of terminal equipment and vehicle base station,the terminal re-registration mechanism based on PING packet was designed,which solved the problem that the VoIP SIP protocol stack could not rotate to the normal state caused by the wireless link instability.Without changing the existing network structure,group call service was designed and implemented,which could extend the existing point-to-point communication model.In addition,the H.264 video codec technology was used to realize the video streaming service in the condition of sufficient bandwidth,extending the single service of voice call.(4)A VoIP server was built by using of Asterisk PBX platform.What's more,the soft switch function of VoIP was completed by analyzing the architecture,call flow and controlflow of Asterisk platform.Furthermore,the SIP soft terminal was designed by using of Doubango technology and the implementation of the low-level SIP protocol stack was analyzed.Testing results demonstrated that the VoIP system had the advantages of correct signaling,smooth service and strong network convergence,which is suitable for tactical internet environment.