  In this paper, the zero-forcing and regularized zero-forcing schemes
operating in crowded extra-large MIMO (XL-MIMO) scenarios with a fixed number
of subarrays have been emulated using the randomized Kaczmarz algorithm (rKA).
For that, non-stationary properties have been deployed through the concept of
visibility regions when considering two different power normalization methods
of non-stationary channels. We address the randomness design of rKA based on
the exploitation of spatial non-stationary properties. Numerical results show
that, in general, the proposed rKA-based combiner applicable to XL-MIMO systems
can considerably decrease computational complexity of the signal detector by
paying with small performance losses.
