RF-Link NL6000 - Manual (Page 24)

RF Neulink NL6000 User Guide 24
Best Choice: Mobile Data Mode
Because you expect a corrupt channel, use the mode that has the greatest
amount of error control. Mobile Data mode includes three types of error
control, Reed-Solomon forward error correction, error detection, and a block
interleaver. This mode provides for maximum transmission reliability on a
corrupt channel. Since the packet size is large, any data added to the packet
to fill the interleaver is insignificant.
Because you are more likely to recover from transmission errors with Mobile
Data mode, you can use a large Maximum Packet Size. A larger packet size
can compensate for the lower percentage of user data in each packet and
provide good throughput on a corrupt channel.
Why not use Basic Telemetry Mode for this scenario? Basic Telemetry
mode is not useful when you expect a corrupt channel because it uses error
detection only. Basic Telemetry mode cannot recover data errors, so
throughput would be poor.
Why not use Enhanced Telemetry Mode for this scenario? Enhanced
Telemetry mode provides error correction, but if both the signal strength and
path are poor, you might need to reduce the Maximum Packet Size to
increase reliability. With Mobile Data mode you can increase the Maximum
Packet Size and get better throughput on a very corrupt channel.
5.6.2. Maximum Packet Size
The NL6000 transmits a data packet on the radio channel when the amount of
data in the input buffer is equal to the Maximum Packet Size or when there is
a timeout on the serial port. The maximum packet size is the largest amount of
user data in one RF packet.
5.6.3. Over-the-Air Data Rates
The NL6000 supports two over the air data rates: 12,000 bps or 22,050 bps.
Select the data rate you want to use depending upon the bandwidth you
occupy and your license.
5.6.4. Acknowledgements
The NL6000 can request an acknowledgement (ACK) from the destination
modem with each transmission. If this option is enabled, the unit will
retransmit a packet up to a specified number of times if it does not receive an
ACK. If it does not receive an ACK after the final retry, the unit will transmit the
next packet. You specify the desired maximum number of retries with the Max
Retries option.
Note: When acting as a repeater, the unit never generates an ACK. ACKs
are end-to-end and do not affect the repeater unit.