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General Information
The following list shows what general information to list
with a scenario. Some information is mandatory, some is optional.
Optional information is marked by an asterisk ('*').
- Scenario identifier
- The scenario identifier must be unique among all scenarios. (By making the
identifier part of the file content rather than the file name, we can get
rid of the various restrictions imposed by file naming conventions of the
different operating systems used by the subgroup-members.)
- *Scenario annotation
- The contributor of a scenario may want to add some comments for the human
reader of the file. Useful comments can be a description of the scenario's
origin and what is problematic/typical about the scenario.
- Network type
- The network type indicates whether the scenario is a GSM900 or
GSM1800 network.
- Spectrum
- We assume that the spectrum is an interval. In case the set of available
channels is not an interval, the spectrum is the interval ranging from
the lowest available channel to the highest available channel. The channels
not available within that range are listed as globally blocked.
- *Globally blocked channels
- A channel is globally blocked if it is in the spectrum but not available
for frequency assignment for some reason.
- Co-site separation
- The co-site separation is the minimum separation necessary between channels
operated on carriers at the same site. We assume that the co-site
separation is the same for all sites.
- Default co-cell separation
- The co-cell separation is the minimum separation necessary between
[4]
channels
used by carriers in the same cell. Due to different transceiver technologies,
the co-cell separation may vary from cell to cell. Here, we define a
default minimum separation that should hold for most of the cells. In case
there are different requirements for some cells, those can be specified in the
corresponding cell descriptions.
- Handover separation
- There are handover relations between cells.
We have to specify what handover separation is required like it is done
in Table 4.
- *Minimal significant interference
- All known interference relation between cells should be listed in a scenario
description.
Hence, relations with very small interference ratings are included in the
list. This parameter will be used as a threshold to delete interference
ratings below its value prior to frequency planning. The reason for listing
small interference ratings anyway is that those relations will provide
additional structural information on the scenario.
- *Maximal tolerable interference
- The value of this parameter is used as an upper bound on the maximal
admissible interference. Interference ratings exceeding this threshold
are ruled out by introducing a separation requirement with a sufficiently
high value, i.e., a minimum separation of one is used to rule out co-channel
interference and a minimum separation of two is used to rule out co- and
adjacent-channel interference.
Again, ruling out intolerably high interference by inserting suitable
separation requirements should be done only prior to frequency planning,
since the interference ratings carry more information for structural
investigations than a separation requirement.
- Demand model
- For our scenario Tiny, the absolute number of carriers per
cell is given. This will be called the absolute demand model.
A more flexible approach is called
normalized traffic model [1]:
For each cell the expected traffic is
given. These traffic figures are used to derive the number of carriers per
cell. Since traffic data will often be confidential,
normalized traffic is used. The normalized traffic figures are
determined in such a way that the relations between the cells come out
right. The actual demand of carriers per cell depends on two parameters:
a scaling factor and a blocking rate. (Reasonable ranges for
values of these parameters can be given in the annotation.) The carrier demand
in a cell is computed by means of the Erlang-B formula [2]
where the scaled normalized
traffic and the blocking rate are inserted.
By changing the values of the scaling factor and the blocking rate, the
number of necessary carrier per cell changes.
(This happens in a more realistic way than by scaling the figures in the
absolute demand model.)
- Site locations
- For a graphical representation of a scenario, Cartesian coordinates of the
site locations are extremely helpful. The value of this parameter indicates
whether site locations are supplied. Some operators may not want to supply
the precise coordinates of their (projected) sites. Yet, the experience is
that a graphical representation of a network can be very useful in the
design of algorithms for frequency assignment and the structural analysis of
scenarios.
However, approximate coordinates are usually sufficient for our purposes.
Therefore, we strongly support
that scenarios are given including Cartesian coordinates of site
locations--possibly with the coordinates perturbed and/or translated.
Next: Cells
Up: Discussion of scenario parameters
Previous: Discussion of scenario parameters
Andreas Eisenblaetter
1998-02-25