| In remote areas and special fields,paging system still plays an important role due to the lack or prohibition of communication networks.It can no longer satisfy the application needs of multimedia paging that traditional paging system can only support single business which is text message.Based on features of DMB(Digital Multimedia Broadcast)like digitalization,multimedia and high bit rate,this thesis studies digital multimedia paging system,which makes data transmission rate higher and paging content richer compared with traditional paging system.The research productions will extend the application mode of DMB and provide new technical means for special communication.This thesis first studies the structure and principle of DMB system,and then based on its data service channel and open interface,the thesis designs the framework of wireless digital multimedia paging system,which makes full use of the existing technologies and devices.Paging service module is designed at the transmitting end of DMB system,realizing functions of single paging,group paging and all paging.At the receiving end of DMB system,the multimedia paging message is decoded and displayed through hardware improvement and embedded software development.At the transmitting end of DMB multimedia paging system,Web technology is used to design a paging service module with friendly user interfaces,which can be used in conjunction with DMB transmitting software in the laboratory.The module is composed of paging service front-end,paging service back-end and paging service coding and transmitting service program.Paging messages flow from front-end of paging service to back-end,and then enter paging message queue in the database.Paging service coding and transmitting service program reads paging messages from queue,and encodes,groups,packs and sends paging messages to DMB system.At the receiving end of DMB multimedia paging system,two forms of paging terminals are designed.First is independent DMB paging terminal,which realizes functions of receiving,decoding and displaying paging message by embedded software development based on the existing DMB receiver.Second is Android mobile phone with plugging DMB receiving module.Through hardware design and driver development,DMB multimedia paging messages are displayed on the phone.Finally,every module and the whole system are tested.The results show that paging terminals can correctly display various kinds of multimedia paging messages;the system can support 9 paging channels at most at the same time,each paging channel can support 65536 paging terminals at most,and up to 256 paging users can initiate paging at the same time.For text paging messages,the transmitting time is less than 1 second;for voice messages,the transmitting time is usually less than 3 seconds;for image messsages,the transmitting time is usually less than 5 seconds.The system has well implemented the function of multimedia paging. |
