WINNER II pdf - Final Report - Cept

WINNER II D1.1.2 V1.2
of the relative positions of the system elements, as well as vectored description of their movements
(speeds). In general, positions (coordinates) of scatterers are unknown. Only exceptions are related to far
cluster scatterers (FCS) that are actually positioned in the same coordinate system as radio-stations. In
multi-link simulations spatial correlations of channel parameters are important. In order to establish
correlations between links at system level the LSPs have been generated with the desired correlation
properties. This has been described in the following subsection.
3.3.1 Correlations between large scale parameters
For single position of radio-stations (one link) we can describe inter-dependence of multiple control
parameters (LSP) with correlation coefficient matrix. Correlations of LSPs that are observed in measured
data are not reflected in joint power or probability distributions. Instead LSPs are estimated from
marginal power distributions (independently for angles and delays), and necessary dependence is reestablished
through cross-correlation measure:
where
Cxy
is the cross-covariance of LS parameters x and y.
xy
=
C
C
xx
xy
ρ , (3.4)
At system level two types of correlations could be defined: a) between MSs being connected to the same
BS and b) correlations of links from the same MS to multiple BSs (Figure 3-5). These correlations are
mostly caused by some scatterers contributing to different links (similarity of the environment).
C
yy
a) b)
Figure 3-5 Links toward common station will exibit inter-correlations: a) fixed common station, b)
mobile common station
In the first case WINNER models are using exponential correlation functions to describe dependence of
LSP changes over distance. In other words LSPs of two MSs links toward same BS would experience
correlations that are proportional to their relative distance d MS . As a consequence correlation coefficient
matrices for neighbouring links (for MSs at certain distance) are not independent and they also have to
reflect observed correlations over the distance dimension:
C
( =
( d
)
xy MS
ρ
xy
dMS
)
, (3.5)
CxxC
yy
For this reason elements of link cross-correlations coefficient matrix should reflect exponential decay
with distance, as shown in Figure 3-6
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