  COST INTERACT working group (WG)1 aims at increasing the theoretical and
experimental understanding of radio propagation and channels in environments of
interest and at deriving models for design, simulation, planning and operation
of future wireless systems. Wide frequency ranges from sub-GHz to terahertz
(THz), potentially high mobility, diverse and highly cluttered environments,
dense networks, massive antenna systems, and the use of intelligent surfaces,
are some of the challenges for radio channel measurements and modeling for next
generation systems. As indicated in [1], with increased number of use cases
(e.g., those identified by one6G [2] and shown in Fig. 1) to be supported and a
larger number of frequency bands, a paradigm shift in channel measurements and
modeling will be required. To address the particular challenges that come with
such a paradigm shift, WG1 started the work on relevant topics, ranging from
channel sounder design, metrology and measurement methodologies, measurements,
modeling, and systematic dataset collection and analysis. In addition to the
core activities of WG1, based on the strong interest of the participants, two
sub-working groups (subWGs) have been initiated as part of WG1: i) subWG1.1 on
millimeter-wave (mmWave) and THz sounding (subWG THz) and ii) subWG1.2 on
propagation aspects related to reconfigurable intelligent surfaces (RIS) (subWG
RIS). This white paper has two main goals: i) it summarizes the state-of-theart
in radio channel measurement and modeling and the key challenges that the
scientific community will have to face over the next years to support the
development of 6G networks, as identified by WG1 and its subWGs; and ii) it
charts the main directions for the work of WG1 and subWGs for the remainder of
COST INTERACT duration (i.e., until October 2025).
