  Reconfigurable intelligent surfaces (RISs) are one of the foremost
technological enablers of future wireless systems. They improve communication
and localization by providing a strong non-line-of-sight path to the receiver.
In this paper, we propose a pilot transmission method to enable the receiver to
separate signals arriving from different RISs and from the uncontrolled
multipath. This facilitates channel estimation and localization, as the channel
or its geometric parameters can be estimated for each path separately. Our
method is based on designing temporal phase profiles that are orthogonal across
RISs without affecting the RIS beamforming capabilities. We take into
consideration the limited resolution of the RIS phase shifters and show that in
the presence of this practical limitation, orthogonal phase profiles can be
designed based on Butson-type Hadamard matrices. For a localization scenario,
we show that with our proposed method the estimator can attain the theoretical
lower bound even with one-bit RIS phase resolution.
