Calculating The Required Satellite Bandwidth; Calculating The Basic Efficient D&I Rate; Calculating The Efficient D&I Rate With E1 Signaling - Comtech EF Data DMD50 Installation And Operation Manual

DMD50 Universal Satellite Modem
INBAND RATE
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I.3.1 Calculating the Required Satellite Bandwidth
In order to calculate the satellite bandwidth (i.e. the symbol rate), we must first calculate the
Efficient D&I Rate (i.e. the data rate plus the overhead required for Efficient Drop & Insert).
From there, the calculation of the required satellite bandwidth is identical to all other modes of
operation and simply takes into account modulation type and forward error correction.
In this section, we will cover the calculation of the basic Efficient D&I Rate, as well as, the two
cases that alter the basic rate.
I.3.2 Calculating the Basic Efficient D&I Rate
When E1 signaling is not required (all T1 and PCM31 cases) and Enhanced Async is not enabled
(the Earth Station to Earth Station link is the standard ES-ES), the Efficient D&I Rate for N
timeslots is as follows:
Efficient D&I Rate = Data Rate + (N * 250 bps)
In other words, the basic Efficient Drop & Insert Rate only requires 250 bps of overhead per slot,
while at the same time providing all of the functionality found in the Drop & Insert open network
standard plus Automatic Uplink Power Control. By comparison, the Drop & Insert open network
standard requires 4267 bps per slot, so by utilizing Efficient Drop and Insert, Radyne customers
can realize a bandwidth savings of over 4000 bps per slot.
I.3.3 Calculating the Efficient D&I Rate with E1 Signaling
When E1 signaling is enabled (PCM-30, PCM30C), an additional 2000 bps per slot are required
to carry the E1 signaling. So the Efficient D&I Rate for N timeslots is:
Efficient D&I Rate increase = N * 2000 bps
With the Drop & Insert open network standard requiring 4267 bps per slot, Efficient Drop and
Insert provides a bandwidth savings of over 2000 bps per slot when E1 signaling is required.
MN-DMD50– Revision 3
This menu is available when enhanced async is enabled. This
field allows the operator to select a desired Earth Station to Earth
Station in-band rate. This allows the user to optimize the In-
Band
Rate based on the amount of traffic that will pass over the.
satellite. In most cases, this should be set to the same rate or 4800
higher than the TX & RX Async/ ES port baud rate. When this 9600
rate is set lower than the ES port baud rate, the user must insure
that the actual ES to ES transmission rate does not exceed the
In-Band Rate, otherwise characters will be dropped.
Efficient Drop and Insert (D&I)
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