Comtech EF Data OM20 - Manual (Page 202)

OM20 Universal Outdoor Modem Appendix F
MN-OM20– Revision 5 F–4
F.3.4 Calculating the Efficient D&I Rate with Enhanced Asynchronous
Overhead
The amount of overhead required to carry the Enhanced Async is driven by the in-band baud
rate. The calculation is a two step process involving the in-band baud rate and the number of
slots as follows:
X = Truncation of (In-Band Baud Rate / (N * 125))
Efficient D&I Rate increase = X * N * 125 bps
Because of the truncation, this increase in bandwidth is guaranteed to be less than the baud rate
itself.
Summary and Examples:
The following examples further illustrate how to calculate the Efficient D&I rate which can be
summarized for N timeslots as:
Efficient D&I Rate
= Data Rate + (N * 250 bps)
With E1 signaling add
N * 2000 bps
With Enhanced Async add
(Truncation (In-Band Baud / (N * 125))) * (N * 125) bps
Example 1a:
5 Drop Slots with T1-D4 framing, standard ES to ES overhead
For 5 Drop Slots, the Data Rate would be 5 * 64000 or 320000 bps
The Efficient D&I Rate would be 320000 + (5 * 250) bps = 321250 bps
The Open Network rate is over 20,000 bps higher at 341333 bps.
Example 1b:
Change to E1-PCM30 framing (E1 Signaling), standard ES to ES overhead
Add 5 * 2000 bps to our previous calculation gives 331250 bps
Still saving over 10,000 bps compared to the open network standard.