  Channel charting is an emerging self-supervised method that maps channel
state information (CSI) to a low-dimensional latent space, which represents
pseudo-positions of user equipments (UEs). While this latent space preserves
local geometry, i.e., nearby UEs are nearby in latent space, the
pseudo-positions are in arbitrary coordinates and global geometry is not
preserved. In order to enable channel charting in real-world coordinates, we
propose a novel bilateration loss for multipoint wireless systems in which only
the access point (AP) locations are known--no geometrical models or
ground-truth UE position information is required. The idea behind this
bilateration loss is to compare the received power at pairs of APs in order to
determine whether a UE should be placed closer to one AP or the other in latent
space. We demonstrate the efficacy of our method using channel vectors from a
commercial ray-tracer.
