Encoding And Decoding Alogrithem Of LDPC Code In Leo Satelite Communication

As the most promising satellite mobile communication system,LEO satellite communication system has the advantages of small delay,low path loss and wide coverage.It is an important development direction of global personal communications in the future.In the process of low earth orbit satellite and ground communication,the signal will be distorted because of the influence of attenuation,noise and interference.In the case of limited power,in order to reduce the error rate of channel encoding must use powerful error correcting ability.LDPC code can provide high coding gain while maintaining high coding efficiency,thus it's very suitable for LEO satellite communication.LEO satellite communication is different from ground communication.LEO satellite has a short time to pass,a limited communication time which requires a fast encoding speed.LEO satellites are generally small satellites,the hardware resources on the satellite are very limited,so the complexity of encoding and decoding can not be too high.However,most of the encoding and decoding algorithms of LDPC codes have high complexity,which limits the application of LDPC codes in Leo satellites.This paper proposes a low complexity encoding and decoding algorithm,which makes LDPC codes more suitable for LEO satellite communications.In view of the short time of LEO satellite communication and the limited hardware resources on the satellite,a low complexity LDPC encoding and decoding algorithm is proposed.Original(81767154)LDPC code has a high density of parity bits,which leads to a large number of addition operations in the encoding process.This subject improves the adjustment of the sub cyclic matrix of the parity check matrix,which makes the check bits of the generated matrix partially sparse,and reduces the computational complexity in the coding process.The simulation results show that the new encoding error rate is slightly worse than the original encoding.The traditional decoding algorithm in decoding failure,need to run to the maximum number of iterations to exit.In this paper,we propose an algorithm to stop iteration in advance,judge whether the decoding is successful in the iterative process and withdraw early when the failure occurs.In this paper,we improve the log domain decoding algorithm,and transform the multiplication in the process of updating the check nodes into additive and quantized operations one by one,which reduces the complexity of decoding algorithm hardware implementation.LEO satellite communication environment is complex,in addition to noise is Rician Fading interference and Doppler frequency shift.This topic simulates the interference factors in the LEO satellite communication simulation system,and tests the performance of the LDPC encoding and decoding algorithm.After a large number of simulation tests prove that the issue of the proposed algorithm can work in low orbit satellite communication environment,and the algorithm moves under the influence of the performance limit in Rician Fading and Doppler frequency,has practical significance for the application of LDPC codes in the low earth orbit satellite.