Cambium Networks cnReach N500, User Manual

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cnReach N500 User Guide System Configuration
phn-4673_003v000 (November 2018)
2-17
Note
Some older 900 MHz MAS radios have a software limit set to 3W. If your radio limits you to
setting 3000 mW maximum, contact support for a patch to increase this to 4000 mW
maximum.
mW can be converted to dBm using this online calculator .
Attention
RF performance is often more problematic at higher RSSI levels. When the Transmit
Power is set too high, the receiving radio RSSI may be too high and the overall noise floor
in the area will increase.
Transmit Power should be
tuned
to provide enough SNR on the receiving Radio.
Please refer to the
RSSI
and
Sensitivity & Minimum SNR per Modulation
sections .
When lab testing with an optional 0 dBi whip antenna it is recommended to install 20 dB
coaxial attenuators and adjust the transmit power to 100 mW.
Channel Sizes
As a software defined radio, cnReach supports a wide variety of channel bandwidths. From 6.25 kHz up
to 250 KHz depending on the band and regulatory requirements. Refer to Chapter 3: Technical
Reference and individual specification sheets to determine which channel bandwidths are available for
each band. LINKPlanner is also a good resource when planning networks.
In addition the FCC or other regulatory body license will state what channel size can be utilized.
Transmit Rates
Transmit Rates (or modulations) are configured by selecting one or more modes from the available list.
The faster the speed the more complex the modulation but the more complex the modulation the
higher the signal level needs to be relative to the noise floor of the link. Therefore, the network design
should select modulations that deliver the necessary capacity but with enough fade margin to ensure a
reliable link. LINKPlanner is an excellent tool for designing cnReach networks based on need for
capacity and availability.
The lists below are representative of 900 MHz. Other bands will have different channel sizes and
different modulations.
There are several rules to keep in mind when selecting these modulations. Primarily they are:
1. Don’t select more than four modulations
2. All selected modulations should be adjacent in the table. For example, if you select 10kbps MSK and
23 kbps QPSK below, don’t skip 19 kbps 4FSK.
3. The exact same set of modulations must be selected for all radios in the same network (PTP or PMP
cluster)