Based On The Coding Structure Of The Channel Estimation Algorithm And Its Application

As a result of digital communication technique development, channel estimation is used in many engineering areas. For example, The SNR estimation is used in CDMA power control and in some iteration decoding (such as BP and BF decoding algorithm for LDPC code).At present, most of the estimation algorithms are implemented by the training sequence by which the characteristics of the sequence was known by the receiver. Maximum likelihood estimation or the projection of training sequence is frequently used to estimate the SNR. But these techniques will increase the complexity of the reciever.This thesis has improved the original estimation algorithm gave by Mr Zhou, and exended to the estimation of the SNR of AWGN channel and Rayleigh fading channel. By comparing this algorithm with (3,2) and (7,6) parity check code, we find that the performance of short code is better than that of the longer one. When more than 10 6 (3,2) parity check codes are used to estimate the SNR of AWGN channel and Rayleigh fading channel, the estimation error is less than 1%. And if the number of codes are less, the multi-thresholds demodulation can be applied to increasing the estimation performance.Although the estimation algorithm is carried out by parity check code, but it is also applicable in general linear block codes to estimate the channel's parameter. The iterative decoding of LDPC code must use the noise variance, so the variance estimation is important for the LDPC code decoding. By the computer simulation, we find that the impact of the estimation algorithm for the LDPC code performance is less than 0.2dB.