Optimizing Semantic Spectral Efficiency in Wireless Image Transmission: A PPO-Driven Resource Allocation Scheme

To tackle spectrum scarcity in 6G networks, this letter introduces a semantic-oriented resource allocation scheme for wireless semantic image transmission (WSIT) systems. For the first time, we define the image semantic spectrum efficiency (ISSE) and consider it a crucial performance metric for assessing the image transmission efficiency. We propose an ISSE-driven proximal policy optimization (ISSE-PPO) algorithm to jointly optimize the compression ratio (CR), channel assignment, and power allocation in WSIT systems under the constraint of image transmission quality. The ISSE-PPO mechanism limits the magnitude of policy updates via a clipping operation, thereby ensuring effective and stable training. Experimental results reveal that the proposed ISSE-PPO approach significantly outperforms the baseline methods. The effectiveness and superiority of the proposed algorithm make it a promising technical solution for enhancing resource utilization efficiency in WSIT systems.