Grouped Annulus-Modulated Transceiver Is Almost Full DoF-Achieving for RIS-Assisted Symbiotic Radios Over Spatial-Correlated Channels. - Ruo-Qi Sun; Jianfeng Shi; Yonggang Zhu; Mingliang Xie; Kang Luo; Yifu Sun; Ru-Han Chen; Kang An 001 (CoRR, 2026)