FFT/DWT/DCT OFDM channel estimation using EM algorithm in the presence of chaotic interleaving

This paper presents a new interleaving scheme for efficient data transmission with Orthogonal Frequency Division Multiplexing (OFDM) over fading channels. This approach is based on the chaotic Baker map. The binary data is interleaved with the proposed approach prior to the modulation step. In addition to improve the system performance in fading channel, the proposed chaotic interleaving approach adds a degree of encryption to the transmitted data. The performance of the proposed approach is tested on the conventional Fast Fourier Transform OFDM (FFT-OFDM), Discrete Wavelet Transform OFDM (DWT-OFDM), and Discrete Cosine Transform OFDM (DCT-OFDM) with and without chaotic interleaving. Expectation-Maximization (EM) algorithm is also proposed to efficiently estimate the channel impulse response (CIR) of such a system operating on a channel with multipath fading. Starting from the Maximum Likelihood (ML) principle, we derive an iterative estimation algorithm based on the (EM) algorithm. This algorithm is capable of improving the channel estimate. In the initialization phase of this iterative algorithm, the initial channel estimate is based on the observation of the pilot carriers only. Then the EM algorithm updates the channel estimates until convergence is reached, the resulting bit error rate essentially coincides with the case of the perfectly known channel. By simulations, the efficiency of these algorithms can be investigated with simulation and the results of estimation will come to a comparison.