  A site-specific radio channel representation considers the surroundings of
the communication system through the environment geometry, such as buildings,
vegetation, and mobile objects including their material and surface properties.
In this article, we focus on communication technologies for 5G and beyond that
are increasingly able to exploit the specific environment geometry for both
communication and sensing. We present methods for a site-specific radio channel
representation that is spatially consistent, such that mobile transmitter and
receveiver cause a correlated time-varying channel impulse response. When
modelled as random, this channel impulse response has non-stationary
statistical properties, i.e., a time-variant Doppler spectrum, power delay
profile, K-factor and spatial correlation. A site-specific radio channel
representation will enable research into emerging 5G and beyond technologies
such as distributed multiple-input multiple-output systems, reconfigurable
intelligent surfaces, multi-band communication, and joint communication and
sensing. These 5G and beyond technologies will be deployed for a wide range of
environments, from dense urban areas to railways, road transportation,
industrial automation, and unmanned aerial vehicles.
