Final report on link level and system level channel models - Winner

h
WINNER D5.4 v. 1.4
the properties and usefulness of communication schemes in case of large-scale deployment. Hence, we
follow the stochastic channel modeling approach in our analysis.
4.1.3 Interference modeling
Interference modelling is an application subset of channel models that deserves additional consideration.
Basically, communication links that contain interfering signals are to be treated just as any other link.
However, in many of today’s communication systems these interfering signals are not treated and
processed in the same way as the desired signals and thus modelling the interfering links with full
accuracy is inefficient.
A simplification of the channel modelling for the interference link is often possible but closely linked
with the communication architecture. This makes it difficult for a generalized treatment in the context of
channel modelling. In the following we will thus constrain ourselves to giving some possible ideas of how
this can be realised. Note that these are all combined signal and channel models. The actual
implementation will have to be based on the computational gain from computational simplification versus
the additional programming overhead.
AWGN interference
The simplest form of interference is modelled by additive white Gaussian noise. This is sufficient for
basic C/I (carrier to interference ratio) evaluations when coupled with a path loss and shadowing model. It
might be extended with e.g. on-off keying (to simulate the non-stationary behaviour of actual transmit
signals) or other techniques that are simple to implement.
Filtered noise
The possible wideband behaviour of an interfering signal is not reflected in the AWGN model above. An
implementation using a complex SCM or WIM channel, however, might be unnecessarily complex as
well because the high number of degrees of freedom does not become visible in the noise-like signal
anyway. Thus we propose something along the lines of a simple, sample-spaced FIR filter with Rayleighfading
coefficients.
Prerecorded interference
A large part of the time-consuming process of generating the interfering signal is the modulation and
filtering of the signal, which has to be done at chip frequency. Even if the interfering signal is detected
and removed in the communication receiver (e.g., multi-user detection techniques) and thus rendering a
PN generator too simple, a method of precomputing and replaying the signal might be viable. The
repeating content of the signal using this technique is typically not an issue as the content of the interferer
is discarded anyway.
4.1.4 Framework
MIMO channel characterization, which takes into account directional characteristics at the transmitter and
receiver sides, is widely known as double directional channel modelling. We separate the effective radio
channel in effects from wave propagation on one hand and antenna response on the other hand to develop
antenna independent MIMO channel model. By using the far-field, narrowband, discrete wave, and
geometric diffraction assumption, the effect of the antennas can be reduced to the effect of field pattern
and to a phase shift based on the angle of the impinging wave, its wavelength, and the geometry of the
antennas. This means that any antenna configuration, orientation, and pattern of antenna elements at both
ends can be inserted in the model. In multipath environment, each ray can be described by its path delay
(τ), azimuth departure angle (φ), elevation departure angle (θ), azimuth arrival angle (ϕ ), elevation
arrival angle (ϑ ) and complex amplitude (α ) of the wave and polarisation information matrix. The
framework of the generic channel model is for all scenarios where one terminal is mobile while the other
is fixed. It is based on principles of existing work presented in [3GPP SCM], [SV87], [Cor01], [GEYC],
[PMF00], [Fle00], [AlPM02], and generalized to MIMO case with elevation angles at both ends. The
generic model of MIMO channel for non-stationary environment can be described by channel impulse
response with horizontal and vertical polarisation between antenna element s at transmitter and antenna
element u at receiver as:
u,
s
L(
t)
Mn(
t)
( t;
τ,
φ,
θ,
ϕ,
ϕ)
=∑ ∑
e
v
T,
s
( φn,
m,
θn
, m)
( φ , θ )
vv
n,
m
j k( φ ( t) , θ ( t )),
xT
, s j k( ϕ ( t) , ϑ ( t)
),
x
T
vv vh
vh
( jΦn,
m
) κn , m
exp( jΦn , m
)
hv hh
hh
( jΦ
) κ exp( jΦ
)
h
hv
h
n= 1 m=
1 ⎢ T,
s n,
m n,
m ⎥ ⎢ n,
m n,
m n,
m
n,
m ⎥⎢
R,
u n,
m n,
m
n,
m
⎛
⎜⎡F
⎜⎢
F
⎝⎣
n,
m
e
n,
m
⎤ ⎡κ
⎥ ⎢
⎦ ⎣κ
n,
m
R,
u
exp
exp
e
j2πνn,
mt
δ
( τ −τ
) δ( φ −φ
) δ( θ −θ
) δ( ϕ −ϕ
) δ( ϑ −ϑ
)
n
n,
m
⎤⎡F
⎥⎢
⎦⎣F
v
R,
u
( ϕn , m,
ϑn,
m
) ⎤
⎥ •
( ϕ , ϑ ) ⎥⎦
n,
m
n,
m
n,
m
(4.1)
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