WAGshar(03)10
WAG Subgroup on Sharing/DFS
Source: BT
FSS Sharing with FWA Systems in the band 5725-5875 MHz:
Interim Report on Analysis of Interference from FWA Systems into
InterBelar-1 Satellite at 59.5o East
At the first WAG Sharing Subgroup meeting1 it was concluded that sharing between
high-elevation satellites (above ~ 20 degrees) and various types of FWA systems was
feasible in the band 5725-5875 MHz. Since the meeting, RA provided details of two
satellites at 53o East and 59.5o East, both of which use the whole of Band C and
subtend low elevation angles into north-west Europe.
This new information has required a different approach, as the satellites are illuminated
by the main elevation lobes of the FWA antennas. At present we are carrying out
studies to address interference into the lowest-elevation satellite (Interbelar-1 @ 59.5o
East) which subtends elevation angles into the UK in the range 4-11o.
In order to establish the number of FWA devices that can be deployed in the UK whilst
assuring protection of the Interbelar-1 satellite at 59.5 o East, the approach taken is as
follows:
1. Evaluate the maximum eirp on the surface of the Earth that will enable the
specified value of Tlink/Tlink to be met using the equations shown in our
previous contribution. A value of Tlink/Tlink of 6% was specified at the first
meeting of the WAG Sharing Subgroup.
2. Divide the land regions in the view of the satellite into segmental areas
based on i) elevation angle; ii) country. Figure 1 illustrates the way in
which this has been done.
3. Calculate the number of FWA systems in Region 1 countries (mesh, PMP
and a mixture of each type) that can be accommodated without causing
unacceptable interference into these satellites.
The key unknown here is the distribution of FWA devices across the UK and northwest Europe, and at present a conservative assumption using a uniform distribution is
leading to results that indicate that sharing is promising. This is in the absence of
information about typical deployment densities of FWA mesh and PMP systems in this
band. A more thorough analysis would take into account the rural, suburban and urban
population densities in Europe as well as the density of business premises (i.e. to a
much finer resolution). More information is also required on the near-in elevation
plane sidelobe characteristics of typical FWA antennas.
1
BT presented document WAGshar(02)02 at the first meeting on 9 December 2002
1
5o
10o
15o
20o
25o
Figure 1. Elevation Contours to Interbelar-1 Satellite @ 59.5o East
(1 degree intervals)
Table 1 shows the main parameters used in this calculation for a Tlink/Tlink of 6%.
This table is for all the satellites considered in this and the previous studies.
Satellite

Sub-satellite
longitude
Tlink
(K)
Gr
(dBi)
(dB)
Maximum permitted EIRP
from all FWA devices
(dBW per 20 MHz channel)
Telecom 3
8o West
870
32
0
29.5
Statsionar
Express 2
14o West
1680
26.5
1.2
36.6
INTELSAT
IX
31.5o West
1528
32.8
0
31.2
INTELSAT
VII
66o East
1528
32.8
0
31.6
Statsionar
Express-5
53o East
1680
26.5
1.2
37.0
59.5o East
165
34
-19.1
39.8
Interbelar-1
Table 1. Derivation of maximum EIRP from all FWA devices into various satellites
for Tlink/Tlink of 6%.