User's Manual
Configuration using proAtoN
Page 36
The transceiver is now configured to report message #21 on channel 1 every 6th minute, and on channel 2
every 6th minute, but offset by three minutes from channel 1. This results in a transmission of message #21
every three minutes on alternating channels. The actual start slot selected for each channel will depend on the
FATDMA allocations in the area of operation.
7.3.4 RATDMA Schedule configuration
Using the RATDMA (Random Access TDMA) access scheme the time for each transmission made by the
transceiver is specified. The transceiver will determine the actual slots used for transmission based on internal
knowledge of the AIS environment gained from the AIS receivers.
The parameters required for an RATDMA schedule are as follows.
Channel 1 start UTC
This is the hour and minute of the frame in which transmission will occur on channel 1. The slot used within this
frame will be determined by the transceiver.
Channel 1 interval
This is the interval in minutes between transmissions on channel 1. A typical value is 6 minutes.
Channel 2 start UTC
This is the hour and minute of the frame in which transmission will occur on channel 2. The slot used within this
frame will be determined by the transceiver.
Channel 2 interval
This is the interval in minutes between transmissions on channel 1. A typical value is 6 minutes.
Example RATDMA schedule
A typical transmission schedule requires that the AIS AtoN transceiver transmit AIS message #21 every three
minutes on alternating channels. The transmission schedule is presented diagrammatically in Figure 20.
Figure 20 Example RATDMA schedule
This schedule can be configured using the following values:
● Channel 1 start UTC = 00:00 (the first minute of every hour)
● Channel 1 interval = 6 minutes
● Channel 2 start UTC = 00:03 (the third minute of every hour)
● Channel 2 interval = 6 minutes
T3
T3+S
Channel 1
00:01
00:02
00:03
00:04
00:05
00:06
00:07
00:08
00:09
00:10
00:11
00:12
00:00
hh:mm
Channel 1 interval
6 minutes
Channel 2
00:01
00:02
00:03
00:04
00:05
00:06
00:07
00:08
00:09
00:10
00:11
00:12
00:00
hh:mm
Channel 2 interval
6 minutes
Overall interval
(3 minutes)