Design And Implementation Of Medium And Low Speed Converged Multimedia Trunking Terminal

According to different customer,communication networks can be divided into public networks and private networks.Since entering the information stage,China's public network communication technology has developed rapidly from 2G era to today's 5g era.However,due to various reasons,the development of dedicated communication technology has been significantly lagging behind.At this stage,my country's private network communication still uses voice-based digital trunking PDT(Police Digital Trunking)technology.Therefore,in order to realize the video service on the private network faster,this paper proposes a medium and low-speed integrated broadband multimedia trunking terminal solution.This integration method is modified on the existing PDT narrowband voice communication system terminal,which is compatible with the original Narrowband voice communication has added video communication,which is of great significance in the field of private network communication applications.In order to realize the video service on the PDT terminal,it is first necessary to establish a video acquisition and transmission channel on the PDT terminal.Therefore,the terminal designed in this paper is based on the PDT Trunking portable produced by Hytera Corporation,which integrates intelligent control modules and medium-speed data Transmission module.The intelligent control module adopts the Android operating system development simulation board to realize the collection and compression of video data,man-machine interface operation and call flow control.The medium-speed data transmission module adopts the data transmission module of Jiuhuaxin Company to transmit video IP data.Secondly,the original PDT standard did not stipulate the related signaling of the video service,so this article designed the video call signaling and call process,The transmission channels for service channel plane data transmission and call plane signaling are planned.Thirdly,because the interfaces between the PDT terminal,the intelligent control module and the medium-speed data transmission module are not unified,this paper designs the routing equipment and control signaling communication protocol to realize the connection of the various modules within the terminal.This paper also designed UI(User Interface)control software based on the Android operating system to realize business function interaction,and studied the H.264 algorithm to realize video capture,encoding and transmission,and support dynamic bit rate according to wireless channel status Adjustment.After testing,realized the functions of video single call and video group call,and the fusion terminal finally met the task requirements.The highlight of this article is the development of air interface agreements and procedures.The traditional PDT scheme can only satisfy low-speed voice transmission.Through the design of this article,in addition to voice and data transmission,business requirements such as image and video can also be achieved.For the future broadband and narrowband convergence of private network communications,provide important reference.