Research On The LDPC Based On Respond Correlation Of Multicarrier

With the rapid development of communication techniques, data traffic of services increasingsharply and multimedia services emerging constantly,how to supply communication systems withmore business, fast speed and high quality in limited spectral resource becomes one of the mostpopular research directions of communications. In order to achieve this goal, wirelesscommunication techniques which are used in wireless communication system must be able totransmit wideband datas with high quality, that is,they can resist kinds of drawbacks in wirelesschannel,such as multipath fading and doppler shift, and this allows OFDM systems based onchannel coding to become a popular issues.Based on the relevant studies,this paper combinesLDPC codes and OFDM systems,and also take frequency domain correlation of the OFDM intoconsideration, and then put forward new decoding algorithm. This thesis research into the followingaspects:Firstly, in order to analyze the correlation in the frequency domain of the OFDM theoretically,series formulas are deduced,and then from probabilities perspective under different conditions ofparameters, the simulation proves the existence of this characteristic in OFDM systems.Secondly,taking advantage of this correlation thought, the concept of "crossing" is made use of in LDPCdecoding algorithm,and bit-flipping algorithm and BP algorithm are improved. At last, based on thetheoretical analysis,a LDPC-COFDM system model is set up,write relevant code, under the sameparameter conditions,and map out the performance curve of the relationship between BER andSNR.By contrast,some conclusions are drawn:the calculation at a time maybe a litter larger for theimproved decoding algorithm,but they can save decoding system time,and achieve the expectedstudy aim.