Blind Turbo Channel Estimation Exploiting Parity Check Equa- tions

This paper presents an iterative blind channel estimation algorithm that exploits the parity check equations of a channel code. While with conventional pilots prior data knowledge is used to estimate the channel, the idea here is to exploit prior knowledge of the parity check equations of the code. Furthermore, if an asymmetric code is used, the inherent phase ambiguity of blind systems is avoided. Hence, the channel can be blindly estimated to increase the spectral efficiency. An algorithm for iterating in a turbo fashion between channel estimator, equalizer and decoder is derived in such a way that the estimates of the channel are considerably refined throughout the iterations. The results of the proposed Blind Turbo Equalizer demonstrate that the Mean Square Error (MSE) of the estimated channel reaches the Cramer-Rao Lower Bound (CRLB) in a high SNR regime. In terms of BER, the blind Turbo equalizer reaches the performance of a Turbo Equalizer with perfect knowledge of the channel impulse response.