Algorithm Implementation And Improvement For Senging Part Of Serial Modem For Shortwave Communication

The ionosphere is used by the shortwave communication as the relay station for the electromagnetic paths. For the characteristics of this media, shortwave signal can be transmitted between a long distance and is not easy to be destroyed. Shortwave communication plays an important part in the war and military communications. In the recent years, the transceiver for shortwave communication with higher bit rate and better quality is needed and being developed around the world. The innovation is imperative under the situation12.In the shortwave wireless channel, many factors, such as noise, multi-path effect and Doppler effect, affect the communication quality. The modulation technology is a mainay to resolve the problem. There are mainly two kinds of modulation schemes:the serial modem and parallel modem12. For the reason that the single-tone serial modem is able to work with higher bit rate and lower peak-mean power ratio, it performs much better than the parallel one12. The purpose of this thesis is to implement the scheme for the sending part of the baseband serial modem, and optimize and improve the scheme.There are two logical parts of the thesis, each describing the modem from a different aspect.The first part of it is mainly about the algorithms and its realization. In this part it will use C programming language to implement and optimize a set of baseband processing algorithm applied to serial modem, which includes the FEC, interleaving, the code shaping, MGD, the scrambling and so on, under the development enviroment 'KeilC' of SCM. Also in this part it will describle the developement and opmtimization for the interleaving module to improve its effct.The second part of the thesis concentrates on the implementation for the real time control about trasmittion on the sending part of the short-wave serial modem, based on the real-time system transplated into the MCU. In this part will analyze the characteristic ofμC/OS-II, a real-time system and describe the control for the synchronization of the rate and the real time about transmittion through the communication between the tasks by semaphore and data sharing.