| VHF radio station,as the relay station,terminal station and mobile station in the tactical communication system,is a kind of common equipment in the field of military communication.It features excellent anti-interference performance and broad communication band.Conventional VHF radio stations take voice communication and simple data transmission as its core functions.However,voice communication cannot be used to describe the battlefield situation in details.In addition,its data transmission requires a computer which leading to poor portability.So,it's hard for VHF radio stations to adapt to modern battlefield communication.Therefore,this thesis proposed stricter design requirements on the transmission function of VHF radio station.This thesis designed a multi-media transmission system based on real battlefields,making it able to transmit images,texts and videos which significantly improved its portability and practicality.This system adopts an Android smartphone APP to collect multi-media information and encode the information for data compression.According to a special transfer protocol,the information can be sent to the VHF radio station via Wi-Fi.Then,the VHF radio station will send the information to the receiving station via radio-frequency signals.At last,the received information will be decoded in real time by the upper computer software on the PC terminal.At first,this thesis introduced relevant background and current research conditions of this subject.In addition,Android system architecture,H.264/AVC Video Coding Standard and JPEG image compression algorithms were studied,and also the simulation analysis of the full search motion estimation,the diamond search,hexagon search algorithm.Secondary,the hardware structure and data transmission characteristics of the VHF radio station were introduced.Then,the overall system architecture was designed based on the VHF radio station.For all links of the overall system,layered modeling was carried out.After analysis of transmission characteristics of VHF radio station,User Datagram Protocol(UDP)was adopted for data transmission.In addition,the stop-and-wait protocol and pipeline transmission method in the TCP protocol were studied,based on which the picture transfer protocol(RDTP protocol)suitable for VHF radio stations was established,enabling reliable transmission.In terms of video transmission protocol,after comparison of traditional RTP encapsulation solutions,a frame length-based RTP encapsulation solution was adopted.In the process of design and implementation,this thesis designed an Android system-based APP,which enables not only image and text information collecting,but also JPEG compression coding and H.264 coding for images.Text and picture data is transmitted in accordance with RDTP protocol,while the real-time video stream data is transmitted in accordance with RTP/UDP protocol.In addition,this thesis also designed and implemented an embedded Wi-Fi interface module,on which the ?C/OS-II was transplanted.Then,a program was written on this module to enable wireless communication between the VHF radio station and the smartphone and PC terminal.At last,the upper computer software with a friendly UI was designed on the PC terminal to receive data and display texts,images and video in a real-time manner.After system testing,the results showed that this multi-media system is in compliance with design requirements and can realize transmission of images,texts and real-time video on the VHF radio station. |
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