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Summary Massive multiple‐input, multiple‐output (MIMO) system is an effective technique to develop the spectral efficiency of the wireless communication systems. Since the number of users is much higher than the available number of orthogonal pilot sequences, the users in the neighboring cells can reuse the same pilots of the home cell. Thus, pilot contamination occurs, which restricts the system throughput. In this paper, Laplacian centralized scattering‐spatially correlated Rayleigh fading channel model with multi‐cell minimum mean square error (M‐MMSE) combining and precoding to mitigate pilot contamination and enhance cell throughput. This model gives a more accurate description, especially for cell‐edge users. It results in an accurate spatial channel correlation matrix calculation that enhances the channel estimation quality under pilot contamination. Simulation results indicate that the proposed Laplacian scattering‐spatially correlated Rayleigh fading model achieves better pilot contamination mitigation and larger spectral efficiency, as compared with both the one‐ring scattering‐spatially correlated Rayleigh fading and the uncorrelated Rayleigh fading channel models for different combining and precoding schemes at different pilot reuse factors. The cost of interference rejection and spectral efficiency enhancement is an increase in the system computational complexity.

This paper presents a newinterleaving 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.