Page 278 - GuideFWA

FWA/UPCS Coexistance 1910-1930 MHz

5-10E

4E 4E

4E 4E

4E 4E

4E 4E
4E 4E

4E 4E

FWA interferes less than another row of UPCS cells does. FWA site with
6 sector antenae arragement with totally 60E as an example.

2. ANALYSIS

Suppose the closest DECT Base is only 100m away and one side of a building is directly in the beam.
Since the base is so close by, we can assume that the contribution from other bases can be disregarded.
The power from the DECT base just inside the wall is:
24 dBm (Tx power)+ 12 dBm (antenna gain) -38 dB -40 dB (line of sight) + 15 dB (wall penetration) = -
57 dBm.

The power from an indoor cell will be:
20 dBm (PWT) + 3dB (antenna gain) -38 dB - 30logd. This indoor cell will give the same power as the
DECT base (-57 dBm) for d = 25 m. In an open indoor shopping centre d could approach 100m.

If every person in an office has a cordless phone, the traffic density will be about 0.2 E per 20 sqm. PWT
can support 4 E per base in an infinite grid. To provide this traffic density the PWT base station
separation will be 20 m in a rectangular grid, and cell radii of about 10 m. It is quite obvious that the
radiation from the FWA DECT system is lower that from a row of internal cells. Therefore interference
from FWA to Private office systems is not critical.

Similarly, interference from a private system to FWA will not be critical, since if a specific sector has a
high close by building full with cordless phone facing it, it will not be hard for this sector to find say 5
escape channels in the 1910 - 1920 MHz band where no private systems exist.

Inter-American Telecommunication Commission 259