User's Manual

28 Document Number: 0100SM1401 Issue: 05-15
ChannelShare+™ Example 2
This flow chart shows the C/A operation in a remote
radio with the following configuration:
• C/A: ChannelShare+
• Backoff Method: Delay Before Tx attempt
• Backoff time:
- Max Slots: 16
- Slot Time: 20ms
• Data Priority: Tx Data
Data waiting to be
transmitted
Wait a random
time
Is C/A busy
flag set?
Transmit data to
C/A master
No
Yes
Rx data ‘Priority’:
In PTMP/R system topologies, where the Entry Point radio is half duplex, the configuration of Rx data priority may be required.
This is particularly useful for asynchronous traffic, such as a combination of SCADA exception reporting and polling. In this
scenario, the probability that a data packet currently being receive by the Entry Point radio is for the Entry Point radio and not
for a remote, is high. Therefore, without Rx data priority, incoming packets to the Entry Point radio would be lost if priority was
given to transmitting packets.
The primary difference when compared to example 1, is that the radio applies the random wait time before any attempt is
made to check the C/A busy flag.
This collision avoidance configuration provides maximum radio channel efficiency when there is synchronous data traffic on
the radio channel (i.e. GPS timing, synchronous exception reports) .
When data is ready to be transmitted, the remote radio
waits a random time before checking the C/A busy flag
to see if it is set (i.e. is the C/A master receiver busy). If
the C/A busy flag is clear, the data is transmitted to the
C/A master. If the C/A busy flag is set, the radio repeats
the wait time and tries again.
Part D – Feature Detail