Site-specific radio channel representation for 5G and 6G

A site-specific radio channel representation (SSCR)
takes the surroundings of the communication system into account
by considering the environment geometry, including buildings,
vegetation, and mobile objects with their material and surface
properties. We present methods for an SSCR that is spatially
consistent, such that mobile transmitter and receiver cause a
correlated time-varying channel impulse response and closely
spaced antennas are correctly correlated. An SSCR is composed
of a dynamically varying number of multipath components solely
defined by the environment geometry and the material of the
environmental objects. Hence, the environment geometry is the
only natural scenario parameterization and specific calibration
procedures shall be avoided. 5G and 6G physical layer tech-
nologies are increasingly able to exploit the properties of a
wide range of environments from dense urban areas to railways,
road transportation, industrial automation, and unmanned aerial
vehicles. The channel impulse response in this wide range
of scenarios has generally non-stationary statistical properties,
i.e., the Doppler spectrum, power delay profile, K-factor and
spatial correlation are all spatially variant (or time-variant for
mobile receivers). SSCRs will enable research and development
of emerging 5G and 6G technologies such as distributed multiple-
input multiple-output systems, reconfigurable intelligent surfaces,
multi-band communication, and joint communication and sens-
ing. We highlight the state of the art and summarize research
directions for future work towards an SSCR.