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2. MICROCELL PLANNING 
Due to the growth of the subscribers of the D2 network, the 
resulting high traffic load and the use of low performance 
mobile phones the network has to be adjusted continuously. 
One possibility of expanding the capacity, that is to say 
more subscribers are able to set up calls at the same time, 
is the introduction of smaller cells with their own BTS. The 
capacity (Erlang/km?) is proportional to the number of cells 
within a specified area. 
The growing number of cells (and BTS) leads to a problem 
however. Each BTS uses a specified frequency for the 
connection to and from the mobile. The number of possible 
frequencies is limited however, therefore each frequency 
has to be used as often as possible. On the other hand the 
same frequencies sent from different BTS must not disturb 
each other to avoid interference problems and dropped 
calls. Therefore the knowledge of the topography is very 
important. 
Especially in the major cities the topographic data (100 m 
by 100 m pixelsize) which has been used up to now is no 
longer sufficient. In order to plan optimized coverage and 
capacity precise digital data of the terrain height including 
the location and the height of the buildings (city structure 
data) are currently needed. The knowledge of city 
structures is a presumption for the planning of further 
antenna locations for the microcells. The height above 
ground of these antennas will not project neighboring 
buildings and the coverage performance of a microcell will 
be within a radius of one kilometer. 
For modelling the urban areas sophisticated fieldstrength 
propagation models have been developed. Mannesmann 
Mobilfunk is using the Urban-Micro-Model (Cichon et al., 
1993), which describes multipath wave propagation by 
three components (vertical plane, transversal plane model 
and multipath scattering model caused by reflections). The 
computer-aided planning software bases on the use of 
precise raster data. 
3. DIGITAL CITY STRUCTURE 
To evaluate the requirements of the building data different 
procedures for providing data were initially tested and then 
subsequently the accuracy of the resulting data sets. A 
variety of different data sets were created from one testing 
Site and others were aquired. These sets were compared 
with a regard to their usability with the prediction model 
currently used (Feistel, Baier 1995). This test resulted in 
the following data requirements: 
- combined dataset of both terrain and building heights 
- pixelsize of 5x5 m? 
* horizontal accuracy of about half pizelsize, vertical 
accuracy *2m 
- generation of all buildings with a larger size than 50 m? 
and above ground height of more than 3 m 
- generation of the buildings as boxes with flat roofs 
(highest representative point) 
- perpendicular rise of heights between ground and 
building (height discontinuity) 
- division of building blocks into several parts, if the 
height differs by more than 3 m 
183 
  
  
Fig.1: Digital model of a city 
Moreover the data has to be generated or transformed to 
the same geocoded space as other data used at 
Mannesmann, that means Gauss-Kruger coordinates with 
Bessel ellipsoid and Potsdam datum, and they have to be 
transferable to the common used format within the 
company. 
After establishing the prerequisites the first orders for 
obtaining the 3-D building data for several German cities 
were placed. 
  
Fig. 2: Raster dataset of Berlin 
4. HARD- AND SOFTWARE ENVIRONMENT 
The planning of a cellular radio network is a very complex 
business that cannot be done without the extensive use of 
hard- and software. Within the headquarters planning 
department a huge UNIX-based network has been 
installed. Numerous SUN workstations are connected via 
FDDI or Ethernet. Different backup media like Jukeboxes, 
DAT and Exabyte are available. 2 Sparc Center 1000 for 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996