"WINNER II Channel Models", ver 1.1, Sept
"WINNER II Channel Models", ver 1.1, Sept
"WINNER II Channel Models", ver 1.1, Sept
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<strong>WINNER</strong> <strong>II</strong> D<strong>1.1</strong>.2 V<strong>1.1</strong><br />
Let us assume we have M LSPs per link and K correlated links, i.e. K MSs linked to the same BS site at<br />
locations (x k ,y k ), where k = 1,…,K. Auto-correlation is generated to the LSPs the following way. At first<br />
we generate a uniform grid of locations based on co-ordinates of the K MSs. Size of the grid is<br />
( max( xk ) − min( xk<br />
) + 2D) x ( max( yk<br />
) − min( yk<br />
) + 2D)<br />
. To each grid node we assign M Gaussian iid<br />
~N(0,1) random numbers, one for each LSP. Then the grid of random numbers is filtered with a two<br />
dimensional FIR filter to generate exponential auto-correlation. Impulse response of the filter for the mth<br />
LSP is<br />
⎛ d<br />
( ) ⎟ ⎞<br />
h ⎜<br />
m<br />
d = exp − , (3.12)<br />
⎝ ∆<br />
m ⎠<br />
where d is distance and ∆ m is the correlation distance both in meters (see Table 4-5). Each of the M<br />
random numbers in nodes of the grid, representing M LSPs, is filtered with a specific filter, because the<br />
correlation distances may be different in Table 4-5. After filtering the correlated random numbers<br />
ξ x , y ) at K grid nodes (K MS locations) are saved and the redundant grid nodes are discarded.<br />
M<br />
(<br />
k k<br />
Cross-correlation is generated independently to the LSPs of K links by linear transformation<br />
where elements of correlation matrix<br />
are defined in Table 4-5.<br />
~<br />
s ( x , y ) = C (0) ξ ( x , y ) , (3.13)<br />
k<br />
k<br />
MxM<br />
M<br />
k<br />
⎡ C~ ⎤<br />
s ~ (0)<br />
~ ~ (0)<br />
1s<br />
L C<br />
1<br />
s1sM<br />
⎢<br />
⎥<br />
C<br />
MxM<br />
(0) = ⎢ M O M ⎥<br />
(3.14)<br />
⎢ ~ ~<br />
⎥<br />
⎣<br />
Cs<br />
(0)<br />
~ ~ (0)<br />
M s<br />
L C<br />
1<br />
sM<br />
sM<br />
⎦<br />
k<br />
3.4 Concept of channel segments, drops and time evolution<br />
<strong>Channel</strong> segment represents a period of quasi-stationarity during which probability distributions of lowlevel<br />
parameters are not changed noticeably. During this period all large-scale parameters, as well as<br />
velocity and direction-of-travel for mobile station (MS), are practically constant. To be physically<br />
feasible, the channel segment must be relatively confined in distance. The size depends on the<br />
environment, but it can be at maximum few meters. Correlation distances of different parameters describe<br />
roughly the proper size of the channel segment, see the paragraph 4.4.<br />
Allowing the channel segment length go to zero, we specify a drop: In a drop all parameters are fixed,<br />
except the phases of the rays. Motion within a drop is only virtual and causes fast fading and the Doppler<br />
effect by superposition of rotating phasors, rays. It can be said, that a drop is an abstract representation of<br />
a channel segment, where the inaccuracies caused by the change of the terminal location have been<br />
removed. In a simulation, the duration of a drop can be selected as desired. It is a common practice to use<br />
drops in the simulations. The main advantage is the simplicity of the simulation, because successive<br />
simulation runs do not need to be correlated. The drawback is that it is not possible to simulate cases,<br />
where variable channel conditions are needed. Howe<strong>ver</strong>, the drop-based simulation is the main method of<br />
simulations in <strong>WINNER</strong> projects I and <strong>II</strong>. In the final <strong>WINNER</strong> <strong>II</strong> <strong>Channel</strong> Models there is also an<br />
alternative for the drop-based simulation, i.e. simulation with time evolution., where correlated drops are<br />
used<br />
In the <strong>WINNER</strong> <strong>II</strong> models the propagation parameters may vary o<strong>ver</strong> time between the channel segments.<br />
In the multi segment modelling two options are available, either drops (stationary channel segments like<br />
in <strong>WINNER</strong> I) or continuous channel evolution with smooth transitions between segments. There are two<br />
approaches for time evolution modelling discussed below. First is the one that is proposed to be<br />
implemented, due to the simplicity of the method. Second is a method using Markov process that can be<br />
regarded as a more advanced method and it requires parameters that have not been determined yet.<br />
3.4.1 Basic method for time-evolution<br />
In this report time evolution of propagation parameters is modelled like depicted in Figure 3-8. The route<br />
to be modelled is co<strong>ver</strong>ed by adjacent channel segments. The distance between segments is equal to the<br />
stationarity interval. Transition from segment to segment is carried out by replacing clusters of the “old”<br />
segment by the clusters of the “new” segment, one by one. The route between adjacent channel segments<br />
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