A Text Information Distributing System Based On Analog Broadcasting Channel

Nowadays, the mobile communication network technology is generally used in the public text information distributing system in urban areas. The broadcasting system is mature now. If the analog broadcasting channel can be used to distribute the text information, the application fields of broadcast system will be expanded. At the same time, the wireless communication channel resources and communication cost can be saved.The paper is focused on the text information distributing technology based on the analog broadcasting channel. The text information is embedded in the radio signal while the basic structure of analog broadcasting system is not changed and the quality of radio signal is ensured. The real-time text information sending and receiving system is constructed.The whole system is composed of information embedding and extracting subsystems. The text information is embedded through digital watermark technology. Firstly by analyzing and comparing the technology for data transmission in the audio system, the digital watermark technology is concluded as the best for distributing text information in the analog broadcasting channel in the paper. A real-time audio watermark algorithm is simulated to verify its effect when the magnitude of the signal changes and the noise attacks the system. The algorithm is used to embed the text information in the analog radio signal. In the information embedding subsystem, a suitable starting point is set as the beginning of a frame. The watermark is added and the specific synchronization code and check code are embedded simultaneously. The buffer is designed as multi-pointer structure. The sliding sampling window is used to detect the synchronization code in the information extracting subsystem. Adding and extracting digital watermark is realized in real time. Then according to the above technology, a testing system is designed and completed. The paper discussesthe hardware and software of the system in detail. The hardware includes the MCU and its interfaces, audio interface and the FM transceiver circuit. The playback and sampling of audio signal, the structure audio data buffer, the FM modules and the transformation algorithm are introduced in the software part. At last, the testing result is given and the result indicates that the system is valid and possible to be realized.The technology can not only be used to distribute the text information in the analog broadcasting channel but also be used in some other fields, such as protecting the copyright of live programs.