International Research Journal of Innovations in Engineering and Technology - IRJIET International Open Access, Monthly, Peer Reviewed, Reputed Journal ISSN (online): 2581-3048

Impact Factor (2025): 6.9

DOI Prefix: 10.47001/IRJIET

Hybrid LS-MMSE Channel Estimation for OFDM Systems Over Frequency-Selective Rayleigh Fading Channel

Abstract

To achieve reliable orthogonal frequency division multiplexing (OFDM) communications in frequency-selective fading channels, accurate channel estimation is critical. The traditional least squares (LS) estimator enhances noise at pilot locations, whereas the traditional pilot-only minimum mean square error (MMSE) estimator adds residual interpolation error that remains independent of signal-to-noise ratio (SNR). This paper suggests an Adaptive Full-Band Hybrid LS-MMSE channel estimator which removes both of the limitations by a one-step linear minimum mean square error (LMMSE) Wiener filter of size NxNP analytically computed based on the complete channel frequency-domain cross-correlation matrix using the exponential power delay profile (PDP). The proposed estimator directly interpolates all pilot measurements to estimates in the entire frequency band in a single step, ensuring the Hybrid MSE results better than LS and MMSE results at any SNR. Monte Carlo simulated 16-QAM OFDM system with N = 64 subcarriers, NP = 16 pilots and L = 6 tap Rayleigh fading channel show consistent performance improvements. The proposed method has a NMSE of -18.21 dB (4.83 dB gain over LS and 3.14 dB gain over MMSE) and a BER of 0.0649, and spectral efficiency of 8.4 bits/s/Hz at SNR = 28 dB. The estimator is computationally tractable, and it achieves the Cramer-Rao Lower Bound at high SNR, making it a high-performance solution to 5G and beyond OFDM systems.

Country : Iraq

1 Mustafa Ghanim2 Ayman N. Muhi3 Mohaimen Q. Algburi

  1. College of Communication Engineering, University of Technology- Iraq
  2. College of Communication Engineering, University of Technology- Iraq
  3. College of Communication Engineering, University of Technology- Iraq

IRJIET, Volume 10, Issue 4, April 2026 pp. 276-286

doi.org/10.47001/IRJIET/2026.104040

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