Plessey MDR2400-SR, Руководство пользователя

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MDR2400-SR, MDR5800-SR and Orion 5825-SR
Issue 10
Page 28
3.4 Interference Considerations
The ISM frequency bands are used by other devices that can cause interference to the
MDR / Orion radio systems. Interference can be avoided by careful planning of the
system installation. The available methods for providing isolation from interfering
radiators are the following:
l. Frequency
diversity
m. Antenna polarization
It is recommended to scan the proposed installation areas with a spectrum analyzer
prior to installation to establish the presence of interference. The spectrum analyzer
feature available on the NMS / GUI may also be used. If interference is detected on
the path, the GUI, via laptop connection, can be used to select a new channel plan (A,
B, or C) to “steer around the interferer, or to create a new custom channel plan (Plan
D) to avoid the interference. SNMP network architecture, if employed, may also be
used to make the frequency plan changes. The frequency spectrum should be
scanned over a sufficient time period to ensure that periodic transmissions are
recorded.
Interferers will cause problems if their amplitudes are not more than 20 dB below the
intended receive power level. A link path loss calculation should be performed to
determine the expected receive power level.
The procedure for selecting the optimum antenna polarization and system frequency
plan is the following:
n. Perform a spectral analysis at each site in the link direction using a high gain
antenna.
o. Repeat the spectral analysis for vertical and horizontal polarization.
p. Select the polarization with the lowest interfering levels as the system antenna
polarization.
q. Consult the MDR / Orion frequency channel plans as shown in section 2.2.1 and
select the frequency plan that would operate in an interference-free band.
r. Install the ‘High Band’ and ‘Low Band’ Outdoor Units at the sites where they would
experience the lowest interference in their respective receive bands.