cnReach N500 User Guide
Technical Reference
phn-4673_002v000 (March 2018)
3-7
Adaptive Modulation
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The user may enable multiple bit rate/modulation modes, via the web GUI or the radio menu.
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The same set of modes must be enabled on all radios in the network.
•
The master radio always transmits in one fixed mode (the master transmit mode), which can also be
indicated via the GUI or radio menu. The master transmit mode is one of the enabled modes.
•
Radios determine the slot period based on the maximum payload length for master and slave, at the
highest-speed enabled mode.
•
At lower speeds, maximum payload lengths are reduced from the maximum, to keep the slot time constant
regardless of the mode.
•
A slave transmits its request for master attention in the lowest-speed mode. Each packet’s header contains
a field indicating the mode in which the slave will transmit the next packet, after the current packet is
acknowledged.
•
Each slave independently determines the mode it transmits in, based on the acknowledge rate it observes
over multiple master attention sessions.
•
A slave transmits its request for master attention in the lowest-speed mode.
•
If no slave has master attention, an acknowledging slave transmits the acknowledge packet in the lowest-
speed mode.
•
If one slave has master attention and wishes to acknowledge a master packet, it transmits the acknowledge
packet in the mode established for the current attention session.
When configured as part of a cnReach N500 PMP network, End Point radios are not required to
communicate at the same data transmit rate. This enables remote End Point radios that are closer to
the Access Point or in a better RF environment to communicate at faster data-rates than remotes that
are further away or in high-noise areas.
Since transmissions from the Access Point radio in a PTMP network must be received by all remotes
irrespective of distance or RF conditions, the Access Point radio is limited to a single AP data transmit
rate. Remote End Point radios must also be configured with the data transmit rate the Access Point will
use to communicate.
Remote End Point radios in a PTMP network independently and dynamically select the optimal data
rate. The list of data rates is selected by checking the corresponding check-boxes on the remote radio.
Data rates which remote End Point radios may use to communicate must also be defined on the Access
Point radio, therefore the configuration should match between the Access Point radio and each of the
remote End Point radios.
Frequency Hopping (900 MHz ISM Only)
Frequency hopping is used with 900 MHz cnReach radios using the ISM unlicensed band. With
frequency hopping, the radio never dwells very long on a given channel but instead ‘hops’ on a pattern
defined in the configuration thereby avoiding interference. Note that for licensed channels
Summary of Contents for cnReach N500
Page 1: ...User Guide cnReach N500 System Release 01 30 900 MHz 700 MHz 450 MHz 220 MHz ...
Page 17: ...Chapter 1 Product Description cnReach N500 Radio Module ...
Page 70: ...cnReach N500 User Guide System Configuration phn 4673_003v000 November 2018 2 38 ...
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