Performance Evaluation of Uncoded and Convolutionally Coded Alamouti MIMO Systems for Image Transmission over Rayleigh Fading Channels

Abstract

Reliable wireless image transmission over fading channels remains a significant challenge due to the combined effects of multipath propagation and additive noise, which degrade both transmission reliability and reconstructed image quality. This paper presents and evaluates an integrated 2×2 Alamouti multiple-input multiple-output (MIMO) image transmission framework that combines spatial diversity, rate-1/2 convolutional channel coding, and three digital modulation schemes to improve communication reliability over Rayleigh fading channels. Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), and 16-Quadrature Amplitude Modulation (16-QAM) are investigated to analyze the trade-off between transmission reliability and spectral efficiency. System performance is evaluated through bit error rate (BER) analysis over a wide range of signal-to-noise ratio (SNR) values, while the quality of the reconstructed images is assessed using the Peak Signal-to-Noise Ratio (PSNR) and the Structural Similarity Index Measure (SSIM). The simulation results demonstrate that the combination of Alamouti space-time block coding and convolutional coding significantly enhances transmission reliability over Rayleigh fading channels. Among the investigated modulation schemes, BPSK achieves the lowest BER together with the highest image reconstruction quality, yielding a PSNR of 58.38 dB and an SSIM of 0.9996 at an operating SNR of 10 dB, whereas comparable image quality is maintained at an SNR of 2 dB when convolutional coding is employed. QPSK provides an effective compromise between transmission reliability and spectral efficiency, whereas 16-QAM offers the highest spectral efficiency at the expense of increased sensitivity to channel impairments. Overall, the obtained results demonstrate that the integration of Alamouti STBC and convolutional coding provides a reliable and computationally efficient approach for wireless image transmission and offers practical design guidelines for selecting appropriate modulation schemes according to application requirements