Abstract: A novel uplink sparse code multiple access (SCMA) detection framework with whitening processing is proposed to address the challenge of spatially colored interference in ultra-dense wireless networks. First, the whitening processing technique is applied to decorrelate the interference, and a whitening-based message passing algorithm (W-MPA) is developed to enhance detection performance. Second, to tackle the high complexity of W-MPA, a whitening-based decentralized expectation propagation algorithm (W-DEPA) is further introduced, which synergistically integrates a decentralized processing architecture with approximate distribution passing principles. Simulation results validate the effectiveness of the whitening technique in mitigating both co-channel and narrowband interference, and show that W-DEPA not only achieves comparable detection performance to W-MPA but also reduces computational complexity significantly.