The High Gain Codes And The Modulation Technology Based On The Software Radio Studies

Software radio is one kind of realization wireless correspondence architecture which was proposed in 1990s,which was considered as the third generation radio communications technology which continues the analog communications and the digital communication. Its central thought is to structure one open style, standardized, the modular general hardware platform, each kind of function like numerical information code, the decoding, the modulation, the demodulation needs the software to complete. This article studies the high gain code and the modulation technology from the software aspect, and take the key research on the latter. Chooses the LDPC code as object of study in the high gain code aspect, it is one kind based on the sparse check matrix linear grouping code, which can guarantee the very good performance under the low signal-to-noise ratio. Chooses the OFDM as object of study in the modulation technology aspect, it is more than one kind of carrier modulating technology modulating technique, which has the very high frequency band use factor, the strict synchronization in the practical application was needed, because it is extremely sensitive to the system synchronization error.This article was consist of two parts:LDPC code and OFDM system. In the first part, several kinds of LDPC codes arrange the decoding algorithm was researched in detail, then made the analysis to the LDPC code performance optimization, and finally carried on the simulation and the analysis under the different code length condition to the LDPC code performance's influence. In the second part, at first the basic principle and the characteristic of OFDM technology was introduced, the synchronization error to the system performance influence in theory was analyzed, and then, several kinds based on the training symbol's synchronized algorithm was compared,at last, the article decided to choose half and half the same symbol synchronized algorithm to carry on simulation and the analysis to the OFDM synchronized system, the result confirmed this algorithm to have the better synchronized performance under the white gauss noise channel.