In this paper, we propose a proxy-based SNR scalable error tracking framework for real-time video transmission where the server is wired connected to Internet and the client is connected to Internet through wireless broadband networks. We assume that all errors (packet losses) result from wireless links, and wired links are assumed to be error-free. The client sends back NACKs with the information about base layer lost packets to the proxy via a feedback channel. Once the NACK is received, the proxy uses the motion data and the side information received from the streaming server to perform error tracking. We compare our approach to the original proxy-based error tracking scheme without scalability support at the same bitrate and bit error rate. Experimental results show that the proposed method can effectively improve performance.