Research On Application Of Convolutional Code And RS Code In Wireless Communication Systems

In modern communication systems, Signals will be disturbed to varing degrees during the transmission because of the intrinsic noise and fading characteristic-and worse, makes the communication failed. As one of the channel coding technique, FEC is an effective way to improve the reliability of information transmission. Concatenated code which has better performance always take convolutional code as its internal code and take RS code as outer code.Convolutional code makes full use of the correlation among each code word and it is easy to realize optimal decoding. Viterbi decoding algorithm is a kind of maximum likelihood decoding algorithm. Reed-Solomon code is a kind of multiple codes with strong ability of correcting burst errors. Its operations are based on glories field.This paper discussed internal code(2, 1, 7) and outer code RS(255,223). Some improvements and optimizations are put forward when the both codes are designed and realized.(2, 1, 7) is considered to be the optimal decoding algorithm. Its structure is builded up with units of BMU, ACSU, and SMU-OUT. The parallel ACS structure is adopted to improve the throughput of data. The storage parts of input bits are removed from memory, which can reduce the storage space of RAM. It can accurately realize output just reads the last bit of survival state when tracingback decoding. For RS(255,223), although adopting soft-decision decoding algorithm will get 2~3d B performance advantage, but the complexity of structure of decoding is unaccepted. So the hard-decision decoding algorithm with low complexity is always applied in practical. The inverse Ri BM algorithm with correction reduces decoding delay; RS code of assembly line for the decoder design structure can improve data throughput. Convolutional interleaving technology is applied between the inernal and external codes in orde to improve the burst interference performance of whole communication system.The hardware description language VHDL is taken as the software design language for(2,1,7) and RS(255,223). The design is synthesized in software Xilinx Project Navigator and simulated by using Modelsim. Hardware debug is tested on Xilinx Virtex5 xc5vlx30. The result proves that the concatenated code is suitable for wireless communication systems.