User's Manual

March 1, 2002 Page D4
interference if both hub antennas are transmitting on the same frequency, even though the
subscriber is receiving nominally the same signal from both hub antennas.
The solution for this is to ensure that adjacent hub antennas are never transmitting on the same
frequency. A minimum of two frequencies (and a maximum of six frequencies) is required for an
omnidirectional system employing six – 60 degree hub antennas. See Figure D1, following.
In a 10 Mbps hub, one WMTS downstream signal is utilized and two upconverters output the
same signal on frequency A and frequency B. In a 20 Mbps hub, two WMTS downstream signals
are utilized, each driving a separate upconverter A and upconverter B. A 30 Mbps hub can be
created by utilizing three upconverters in an ABCABC pattern. See figure D2.
A
B
A
B
B
A
Omnidirectional
Hub
6 sectors
Figure D1
WMTS
U
p
converter A
U
p
converter B
A
Antennas
B Antennas
10 Mb
p
s Hub
–
One Downstream
WMTS
U
p
converter A
U
p
converter B
A
Antennas
B Antennas
20 Mb
p
s Hub
–
Two Downstreams
Figure D2
Downstream Channel
Example