Scattering Environment Aware Joint Multi-User Channel Estimation and Localization With Spatially Reused Pilots

The growing number of users leads to an increase in pilot overhead, while the constraint of limited pilot resources poses a challenge in supporting all users with orthogonal pilots. By exploiting the spatial characteristics of the multi-user (MU) environment, it is possible to reduce pilot costs and improve the channel estimation performance. In practical scenarios, nearby users often share the same scatterers, whereas users situated farther apart tend to exhibit orthogonal channels. This paper proposes a two-timescale approach for joint MU channel estimation and localization, modeling the MU channel in the 3-D location-domain. In the long-timescale phase, the positions of the scatterers are estimated through a scatterer association algorithm based on density-based spatial clustering of applications with noise (DBSCAN). This enables the base station to group users via a graph-coloring-based user grouping algorithm, achieving spatial division multiplexing of pilots and reducing overhead. In the short timescale phase, a low-complexity scattering environment aware location-domain turbo channel estimation (SEA-LD-TurboCE) algorithm integrates overlapping scatterer information to achieve precise MU channel estimation and localization under spatially reused pilots. Simulation results verify the superior channel estimation and localization performance of our proposed scheme over the baselines.