Page 45 - ITU Journal: Volume 2, No. 1 - Special issue - Propagation modelling for advanced future radio systems - Challenges for a congested radio spectrum

ITU Journal: ICT Discoveries, Vol. 2(1), December 2019

scatterer locations are defined by their coordinates lifetimes are best described by a log-normal
in the simulation area rather than their directions distribution for the radii of the MPC visibility
with respect to the base station and user equipment regions. For a smooth onset of the activation of a
antennas. As the model output is the transfer specific MPC the relative contribution of each MPC
function matrix between the base station antenna is modeled by a gain function, with a Gaussian
array and the antennas of the user equipment, any profile as in (4) which multiplies the complex
kind of digital, hybrid or analog beamforming is amplitude of each MPC. Thus, the weight of a
supported. particular MPC depends on the Euclidean distance
Massive MIMO extensions: Visibility regions are between the user equipment position and the
center of the -th MPC visibility.
used at the base station to model the appearance
and disappearance of clusters along a physically
large array as a death-birth process along the array.
The appearance/disappearance of new clusters are
modeled by a Poisson process along the array with
intensity new clusters per meter. The number of
observed base station visibility regions for an array
spanning the interval to is given by (4):
1
2
( , ) ∈ { ( − ) + ( )} (4)
1
2
1
2
0
where E(Y) is the scenario dependent mean length
of the visibility area at the base station [7]. Fig. 2
shows a measurement example with a 7.5 m Fig. 3 – The distance on the y-axis is the propagation distance
uniform linear array in a line-of-sight (LOS) for the MPCs, whereas the time on the x-axis indicates the
different channel snapshots.
scenario at 2.6 GHz. Over the whole array the
median value of clusters is 23, but not all of them The lifetime of the MPC, determined by the width of
are visible at the same spot of the array. Six clusters the Gaussian profile, is controlled by , and is
can (in the median) be seen over the whole array, modeled as a log-normal parameter as in (5) [7].
and 17 clusters at some parts. 2
2
, ( ) = ⁡(− ( − ) /2 ) (5)
,

The COST IRACON massive MIMO extension is
parameterized and validated based on
measurements for physically large outdoor arrays
at 2.6 GHz in LOS and non-LOS (NLOS), and with
indoor and outdoor measurements for closely
located users at 2.6 GHz. A detailed model
description can be found in [7].

Fig. 2 – Visibility regions over a large array. N(x1,x2) is the 4. VEHICLE TO VEHICLE
number of observed visibility regions (or clusters), Nnew is
the number of appearing visibility regions and Nalive is the In this section, we analyze the radio channel for
number of already existing visibility regions.
vehicle-to-vehicle (V2V) communication from the
The gain function describes the appearance and sub-6 GHz to the mm-wave band. We investigate the
disappearance of individual multipath components. challenging cases of propagation characteristics in a
The lifetime, or the length of the spatial region transition from LOS to NLOS in a corner scenario
within the visibility region where a MPC has a and an urban crossroad.
significant contribution, is a random parameter
determining the radius of the MPC visibility region 4.1 Corner scenario at mm-waves
and the corresponding width of the gain function. Here we focus on the effect of the transition from
Fig. 3 shows an example of MPC lifetime from a LOS LOS to NLOS in a corner scenario. Simultaneous
measurement in an indoor sports hall [9]. Many of measurements at 30 GHz, 60 GHz and 6.75 GHz
the MPCs have relatively short lifetimes with a few were conducted using the multiband approach in
MPCs observed over the whole route of the user. [10]. To emulate the transition of (V2V)
These sports hall measurements show that MPC communication from LOS to obstructed line of sight

© International Telecommunication Union, 2019 29