###### Abstract  
This paper presents an enhanced method for the transmission of 3D video in the Multi-view Video plus Depth (MVD) format over Two-Way Relay Channels (TWRC). Our approach addresses the unique challenges of MVD-based 3D video by combining Hierarchical Quadrature Amplitude Modulation (HQAM), a method that prioritizes data layers based on importance, and Inter-Layer Forward Error Correction (IL-FEC), which protects critical data from errors. These are specifically designed to handle the dual-layer data structure where color data and depth information require different levels of error protection, and it reduces transmission errors and enhances the quality of MVD-based 3D video over TWRC. In the TWRC scenario, the proposed scheme optimizes transmission by reducing the number of relayed bitstreams by half while maintaining high-quality requirements, as demonstrated by significant improvements in the Structural Similarity Index (SSIM) for virtually synthesized views. Furthermore, we identify and optimize the hierarchical modulation parameter (a), which controls the priority and protection levels of different data streams. Systematically varying \(\alpha\) reveals its substantial impact on the quality of the reconstructed 3D video, as measured by SSIM. Our results demonstrate that the proposed combination of HQAM and IL-FEC not only maintains the target SSIM of 0.9 for the virtually synthesized view under various relay conditions but also reveals the optimal \(\alpha\) value for balancing the error protection between the color and depth map data streams. Notably, while increasing \(\alpha\) enhances the protection of critical data (such as color video streams), it may concurrently degrade the quality of less important streams (like depth maps), highlighting the importance of fine-tuning \(\alpha\) to achieve the best overall video quality. These findings suggest that our method provides a flexible and effective solution for high-quality 3D video transmission in challenging communication environments, potentially advancing the development of future 3D video delivery systems. h 2024 14 8741 10.3390/app1498741 10. Quadrature Amplitude Modulation (HQAM) to prioritize data layers effectively and Inter-Layer Forward Error Correction (IL-FEC) to maintain data integrity in Two-Way Relay Channels (TWRC). With the increasing adoption of MVD content, the challenge of efficiently and reliably transmitting this complex, high-dimensional data becomes critical [3; 4]. TWRC offers a promising solution for facilitating bidirectional communication between nodes exchanging MVD content by enhancing spectral efficiency and reducing latency, which is crucial for high-bandwidth applications like real-time 3D video communication [5; 6; 7]. However, the inherent high data rates and susceptibility to transmission errors in MVD content posed challenges that our method addressed by optimizing advanced modulation (i.e., HQAM) and error correction techniques (i.e., IL-FEC) to maintain quality and reliability. HQAM presents a flexible approach to balancing data rate and robustness by organizing data hierarchically and prioritizing different information layers based on their importance [8; 9]. To further enhance the reliability of MVD transmission over TWRC, we propose integrating IL-FEC with Hierarchical QAM [10; 11; 12]. The IL-FEC technique provides targeted error protection within each hierarchical layer, effectively mitigating the impact of channel impairments and preserving the integrity of critical data. Previous works, such as those presented in [10; 12], have addressed the challenges associated with layered video coding, which creates multiple layers of varying importance to progressively enhance video quality. Meanwhile, the study in [11] focuses on issues related to conventional stereoscopic video (CSV) transmission, where left and right video streams are transmitted with one stream prioritized to ensure 2D service continuity.