Users Manual

120 MDS™ Master Station MDS 05-6399A01, Rev. G
7.0 SPECIAL CONFIGURATIONS
7.1 Migrating “A” Modem Networks
Mitigation strategy for mixed SDx/x710 repeater networks using the “A” modem
One key aspect of the MPRS MDS Master Station is that it’s backward compatible with the
9790. In many respects, in fact, the Master Station’s performance is superior to that of the 9790.
For example, the sensitivity of the Master Station is better than that of the 9790. However, one
performance aspect in which the Master Station lags the 9790 is latency in both the receiver and
the transmitter.
In many applications, this latency hit of the Master Station is barely noticeable. A point to mul-
tipoint network is one of these applications. In other applications, such as streaming repeater ap-
plications, however, this latency hit needs to be addressed via user configuration in order to get
the radio network up and running.
Note that in most repeater network cases, the latency effect of the Master Station after this addi-
tional configuration will still be comparable to that of point to multipoint networks. Having said
that, there are a few cases where additional delay will be required.
In regards to the aforementioned user configuration, it’s worth noting that streaming repeater ap-
plications that employ Packet-with-MAC mode don’t need to worry about this configuration.
Also, users migrating from x710/transparent to Packet-with-MAC mode don’t need to worry
about resetting this configuration, since all the parameters involved are ignored in Packet-
with-MAC mode.
User Configuration 1: Non-CKEY Repeater Network Case
The following parameters need to be configured in the order in which they are described below.
1. SCD := A soft carrier dekey delay of greater than 0 needs to be configured on the polling
remote and on the remotes to prevent the remotes from hearing their own transmissions.
2. PTT := If serial flow control isn’t available at the remote sites (excluding polling remote
site) and the O.T.A rate is faster than the effective baud rate, a push to talk delay may be
required such that the Master Station repeater latency remains constant across back-to-
back 9710 transmissions. Note that the effective baud rate of 8E1 is smaller than that of
8N1.
3. BUFF := A custom BUFF delay may need to be configured if there are still large gaps in
the data received O.T.A by the polling remote and the remotes. Multiples of 10ms should
be used as a rule of thumb.
Note that for modem 9600, baud 9600, a custom BUFF delay should not be required.
The following table provides the appropriate SCD values for all the A modems that may be em-
ployed on a mixed SDx/x710 repeater network. Note that PR stands for polling remote. Note also
that these values will work whether the remotes are keyed on RTS, DATA or both. These values
do assume that flow control is either available or not available throughout the radio network.
Note that the values are not symmetrical because of the transmit waveform differences between
the SDx and the 9710 despite having the same configuration.