The Research And Implement Of The Channel Code In HF Communication System

HF communication is the ancestor of radio communication. It has some incomparable advantages. Although the developments of the Software Wireless communication are VHF radio communication, microwave and higher frequency, short-wave communication still plays a very important role in many ways. HF channel is a complicated and changeable channel. After transmission in the HF channel, shortwave signal will be affected by multipath effect, fading and doppler shift. Without strong correction coding technology, it is. difficult to achieve the target reliable transmission. With the help of computer simulation, we analyzed and compared a variety of channel coding scheme and choose the best performing channel coding applying to our communication system.To study of different channel coding technologies’performance in the HF channel, we firstly choose a suitable HF channel model. With analyzing and comparing a variety of popular shortwave channel models, we select the broadband shortwave channel model-ITS model as the subject of the HF channel model. Owing to HF channel being a multipath fading channel, channel estimation and equalization must be conducted. After briefly comparing two overcome multipath fading technologies, OFDM and SC-FDE, we select the SC-FDE technology to resist the bad influence from HF channel. In order to select a suitable channel coding with good performance in HF channel, we have studied three channel codes. They are convolution code that the MIL-STD-188-110C standard of US proposed, LDPC code that the IEEE802.16e standard recommended, and TPC code which is composed with the (32,26,4) extended Hamming code as subcodes. On the basis of suitable for engineering implementation, we selected the channel coding pattern, encoding and decoding algorithms for the three channel codes. Then with simulation of the selected specific channel codes, we got their BER curves in AWGN channel and HF channel. After comprehensive analysis of the three channel coding technologies’ performance and implementation complexity, we choose TPC code as the further research and engineering objects. To carry out the project realization, the paper further explores the impact of various factors that may affect the process of encoding and decoding performance on the TPC code, performance optimization in the algorithm level and code level to apply it on our current communication platform. In the end, we proposed a complete and concrete solution of how to apply the TPC to a parallel computing platform.