Software Development For Digital Terminal Of SW Radio Stations

Short-wave (SW) communication over the years has been widely used in military, weather, marine, government, business and other departments, as important as satellite communications, microwave communications and wired communications. However, traditional SW radio transmission, due to its poor quality, vulnerable to interference and other defects, have been unable to adapt to the current electromagnetic environment, the influence of the traditional SW communication was declining. The use of SW broadcasting in vast, sparsely populated region is still the preferred mode of information transmission. Therefore SW communication must increase the data rate and anti-jamming capability, the digital SW broadcast which can make up the defect, making SW communication regain its former Young vitality. As an international standard, the DRM is currently the most mature digital broadcasting technology.This technology can make some improvements on the basis of analog S W radio equipment. The transmission of digital information can be achieved without having to replace equipment, making the promotion of cost reduction which takes on great potential.This paper describes the realization of digital SW radio terminal software to follow the DRM digital broadcasting standards and software transformation program based on virtual radio technology. Its transmitting terminal works as SW radio station and the receiving terminal is SW radio, which applies to half-duplex SW radio station. In this paper, we completed its work in the following three aspects:Firstly, analyze theoretically the digital SW radio terminal system and introduce the transmission system, channel model and receiving system. The transmission system is analyzed from source coding, multilevel coded modulation and orthogonal frequency division multiplexing (OFDM) modulation and a mathematical channel model is provided. For receiving system, the details of the synchronization techniques are mainly introduced, and given the main mathematical derivation. These derivations provide a theoretical basis for the working principle and software design of digital SW radio terminal.Secondly, Audio Codec of digital SW radio terminal system has not chosen AAC codec in DRM shortwave broadcasting standards, but manual switching Opus and Speex. The Speex Audio Codec is adapted in the need of bit-rate reduction, while the Opus Audio Codec is required to ensure better quality in the case of high bit-rate. The Opus and Speex audio encoding module, eventually, are integrated into the Audio Codec Module.Finally, introduce digital SW radio terminal system software implementation. Digital SW radio terminal software is based on the Android platform developing with the Qt framework. In this paper, the overall design of SW radio is circumfused with the software life cycle, software business logic and data transfer, describing the specific implementation details between transmitter and receiver.