User's Manual

Company Confidential 17 Raveon Technologies
compromise. If after 5 times, the data does not get through, then there
probably is something seriously wrong with the channel or system.
The retried-transmissions are randomly spaced at intervals between
approximately 200mS and 400mS, increasing by 50mS for each attempted
transmission. Once the modem has sent its data the number of times the
user specified in the ATRB xx command, the data is discarded, and the
modem will continue to operate as normal.
It is very important that if one modem is configured to send ACK packets
(ATAK 1) that all other modems communicating with it are also set to expect
ACK packets using the ATRB xx command.
To disable ARQ (the default condition of the modem), disable ARQ with the
ATAK 0 and set retries to zero with the ATRB 0 command.
6.7 Store-and-Forward Repeating and Routing
The M7-UC modem has a built-in wireless repeater/router. Each M7-UC is
capable of not only sending and receiving data from/to its serial port, but also
re-transmitting over-the-air data. It is also able to re-transmit data that is
addressed to other modems in the system.
Figure 3 Overview of Repeater Operation
In the example shown in Figure 3 above, M7-UC A is will communicate with
all other modems in the system. It can directly communicate with B, H, and
F. Because of propagation limits, it cannot communicate reliable to E, D, C,
and G.