WINNER II pdf - Final Report - Cept

WINNER II D1.1.2 V1.2
is divided to number of sub-intervals equal to maximum number of clusters within the channel segments.
During each sub-interval the power of one old cluster ramps down and one new cluster ramps up. Power
ramps are linear. Clusters from the old and new segments are coupled based on their power. If number of
clusters is different in the channel segments, the weakest clusters are ramped up or down without a pair
from other cluster.
amplitude
time
delay
Figure 3-8 Smooth transition between channel segments by power ramp-up and ramp-down of
clusters.
3.4.2 Markov process based method of time evolution
In [ZTL+05] the authors propose a dynamic channel model, where paths are arised and disappeared
according to a Markov process. The birth and death probabilities are specified from measurements. This
approach leads to a more realistic behaviour of the channel. However, to apply this approach, the birth
and death parameters are needed for all the channels, which are not available at the moment. Another
disadvantage is the variable number of instantaneous paths.
In spite of the drawbacks listed above this approach seems quite promising, and should be investigated
and adopted in a later stage, if the benefits are deemed more important than the disadvantages. One way
would be to use only the N strongest paths in the model based on the Markov process, where N is a
constant.
3.5 Nomadic channel condition
Propagation environment is called nomadic, if the transmitter and receiver locations are normally fixed
during the communication, but may have moved between different uses of the network [OVC06]. In such
conditions we have to assume that some of the scatterers may move. Actually this is quite typical in many
cases, like when there are people working in the vicinity of the transceiver. For the nomadic environment
it is also typical that an access point and especially user terminals can change place, e.g. in the room and
even go out from the room. However, the most important feature to be taken into account in channel
modelling is the moving scatterers. Nomadic channels can be regarded as a special case of the WINNER
generic model shown in eq. (3.3). In principle, nomadic channels can exist in all the WINNER
deployment scenarios, both in indoor and outdoor. For feeder links we assume that the LOS component is
strong enough, so that the reflections from moving objects can be neglected. Therefore we use nomadic
modelling only for the scenarios A1 Indoor and B4 Outdoor-to-indoor.
Traditionally these scenarios have been modelled using very low speed for the User Equipment. By
applying an approach using fixed links with moving scatterers, we can certainly get more accurate
channel model and parameters for the generation of the channel coefficient.
The idea of modelling nomadic (or fixed) environments has been introduced in some open literature. Here
we follow the approach introduced in [OP04, OC07, Erc+01, ESB+04]. Based on measurements, we can
define a temporal K-factor, for both LOS and NLOS connections. Based on the temporal K-factor,
pathloss model including shadow fading, cross polariztion discrimination etc., the channel coefficients
can be generated [ESB+04]. In [ESB+04], 2x2 MIMO was discussed from theory, measurements,
generation of channel coefficients, and validation of the channels, but without information of angular
domain.
The overall procedure is roughly as follows. Assume that we have generated initial channel parameters
(delays, powers, AoA/AoD etc.) for the nomadic situation. Then we draw the clusters that are moving.
Next we draw the Doppler frequencies for all moving rays in all the clusters containing movement. (Note
that all or only part of the rays are moving in those clusters.) Next we can simply generate the channel
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