Research Of Hybrid Networking Mode In MCPTT System

MCPTT is an application layer broadband trunking communication protocol proposed by the 3GPP organization,which supports on-network and off-network modes.MCPTT system is a professional command and dispatch system based on MCPTT protocol,which is mainly used in public security,subway,government affairs and military departments and emergency communication scenarios.At present,the researches of MCPTT system focus on the optimization of on-network mode and the realization of off-network mode,and there is no solution of the hybrid networking mode in the MCPTT system.The single on-network mode in MCPTT system cannot be used in scenarios with poor network conditions,and the single off-network mode in MCPTT system is limited by communication distance and system capacity,which cannot fully meet the command and dispatch requirements of emergency communication scenarios.Therefore,the research on the hybrid networking mode in MCPTT system is of great significance.On the basis of reviewing the research status of the networking mode in the communication systems at home and abroad,this paper studies and realizes the hybrid networking mode in MCPTT system.The main work is as follows:1.An architecture of the hybrid networking MCPTT system is constructed.The communication process of the hybrid networking MCPTT system is analyzed,and the process of network mode handover and floor control is designed,which realizes the intercommunication of terminals in on-network and off-network modes.The architecture has the characteristics of strong portability,fast signaling processing and easy maintenance.2.A heterogeneous network handover algorithm LB-CWTOPSIS for the hybrid networking MCPTT system is proposed.The algorithm not only considers the directionality of on-network and off-network mode handover,but also comprehensively considers the effects of objective and subjective weights,and selects the best target network in combination with network load,which ensures the accuracy of network mode handover,low handover times and low handover blocking rate.3.A relay terminal selection mechanism and a floor control strategy for the hybrid networking MCPTT system are proposed.The mechanism selects the relay terminal according to the idea of separating the control and data plane,which realizes the communication of the hybrid talk group.The strategy decides the speaking right based on queuing,which ensures the consistency of the floor control results between the offnetwork mode terminal and the MCPTT core network,and realizes the management of floor control of the hybrid networking MCPTT system.4.Based on the Android operating system and using the Java programming language,the basic function,the hybrid group communication,and the signaling and media processing modules of the hybrid networking MCPTT system are developed,which realizes the functions of login,talk group formation and voice/video group call of hybrid networking MCPTT system.5.A verification platform for the hybrid networking MCPTT system was built,which is used to verify the functions of login,talk group formation and voice/video group call and the performances such as average handover delay,average handover blocking rate and average floor request delay of the hybrid networking MCPTT system.The verification results show that the implemented hybrid networking MCPTT system can meet the function and performance requirements of MCPTT system.