cnReach N500 User Guide
Tasks and Best Practices
phn-4673_002v000 (March 2018)
4-5
Optimizing Radio Settings
Modulation
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Lower modulations will have slower speeds, but offer better sensitivity. This equates to longer
links with better ability to propagate through clutter.
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In the case of cnReach, lower modulations also have smaller channel bandwidths, which gives
them higher noise immunity. This is because the narrow band has less chance of a bit becoming
corrupted. One corrupted bit causes the whole packet to be thrown out unless FEC is enabled.
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Higher modulations will have faster speeds, but with lower sensitivities they will be restricted to
shorter links.
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Higher modulations are more susceptible to noise as they have a larger bandwidth, although
using small packet sizes allows them to get on and off channels a lot faster than slower
modulations reducing the chance of noise affecting the signal in the time domain.
Payload Bytes
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cnReach N500 radio packet sizes can be set from 64 bytes to 1600 bytes.
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Smaller packet sizes will lead to lower throughput. This happens because each packet
regardless of size has the same amount of overhead such as network address.
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Larger packet sizes will offer better throughput from less overall overhead.
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Larger packet sizes are more susceptible to noise. This happens due to the fact that they are
modulated for a longer period of time which can result in corrupted bits.
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Dynamic allows the End Point to use as much as 512 bytes of an unused Access Point time slot.
Dynamic does not work with multispeed or MMS. Ideal packet size settings are 512 and 512 when
using dynamic.
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In PMP networks with multiple modulations selected ALWAYS confirm that the max payload
size is greater than the min max payload size of the tables in chapter 3.
Transmit Power
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Never use 100 mW or greater with positive dB gain antennas in close proximity. This will cause
dropped data, and can possibly damage the receiver.
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We recommend using 100 mW transmit power with a 20 dB attenuator for bench testing.
When doing indoor tests use no more than 100mW, especially if there is no attenuation. If you
have attenuation, tune the link to the proper receiver level mentioned below.
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RSSI levels should be between -40dBm to -80dBm depending on modulation.
Best Settings for Speed and Throughput
Speed and Throughput
32QAM or 16QAM with 1600 byte packet sizes (Only if power levels are tuned; QAM is very sensitive to
high RSSI levels above -40dBm.). 8PSK with 1600 byte packet sizes.
Reliable Modulation with High Sensitivity and Speed
QPSK with 512 byte packet sizes.
Turn dynamic on to increase throughput.
High Sensitivity with High Noise Immunity
MSK with 256 byte packet sizes.
Содержание cnReach N500
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