WINNER II pdf - Final Report - Cept

WINNER II D1.1.2 V1.2
In the example figure above the signal from MS1 to BS3 is transmitted via MS3 and BS2 act as a
repeater for BS1. These scenarios can be generated by introducing a BS-MS pair into position of a
single BS serving as a relay or into position of a single MS serving as a multihop repeater. In these
cases one can apply path-loss models of feeder scenarios described in section 3.2.4. The resulting
procedure is as follows.
1. Set base station BS1 to BS3 locations and array orientations according to layout.
2. Set mobile locations MS1 to MS3 and array orientations according to layout.
3. Add extra base station BS4 to position of MS3 and extra mobile MS4 to position of BS2 with
same array orientations and array characteristics as MS3 and BS2 respectively.
4. Set the BSxMS pairing matrix to
⎡0
⎢
⎢
1
A =
⎢0
⎢
⎣0
0
0
0
1
0
0
1
0
1⎤
0
⎥
⎥
0⎥
⎥
0⎦
5. Generate all the radio links at once.
6. Simulate the channel segments in parallel.
5.1.4 Interference
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 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 noiselike
signal anyway. Thus we propose something along the lines of a simple, sample-spaced FIR filter
with Rayleigh-fading coefficients.
Pre-recorded 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 pre-computing 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.
Exact interference by multi-cell modelling
Interference situations are quite similar to multi-cell or multi-BS situations, except that in this case the
other BSs transmit a non-desired signal which creates interference.
Page 54 (82)