DMD50 Universal Satellite Modem
Appendix H
TM118 – Rev. 1.1
H
-1
Drop and Insert (D&I)
H
H.0 Drop and Insert (D&I)
The Drop and Insert (D&I) function provides an interface between a full T1 or E1 Trunk whose
framing is specified in CCITT G.704 and a fractional Nx64 Kbps Satellite Channel. The Drop and
Insert functionality conforms to IBS, small IDR, and Radyne Proprietary Efficient D&I Framing
Structures. For information pertaining to Radyne proprietary Efficient Drop and Insert function,
refer to Appendix I.
The Drop function allows the user to select the terrestrial T1 or E1 timeslots that are to be
dropped off for transmission over the link in the specified satellite channels. The Insert function
allows the user to select the T1 or E1 timeslots into which the received satellite channels are to
be inserted. The two functions are completely independent allowing maximum flexibility in
choosing configurations. The four-port G.703 Interface allows one or more modems to be looped
together using the same T1 or E1 trunk.
The Transmit Data Trunk is brought into the modem via the Send Data In (SDI) Port. From there,
the TX Baseband Processor extracts the selected timeslots from the G.704 Frame and prepares
them for transmission. The original trunk data is sent out of the modem unaltered via the Send
Data Out (SDO) Port. The Receive Data Trunk is brought into the modem via the Insert Data In
(IDI) Port. The data is buffered inside the modem and the RX Baseband Processor inserts
satellite data into the selected timeslots in the G.704 Frame. The modified terrestrial trunk is then
output via the Receive Data Out (RDO) Port.
Figure H-1 shows two modems looped together. This configuration could be simplified to just use
one modem, or extended to use more than two modems. Figure H-2 shows an alternative
method of looping where all of the drop (transmit) data is processed prior to performing any insert
(receive) processing. In both configurations, the terrestrial trunk is providing the timing for the
satellite transmission and for the terrestrial receive.
Summary of Contents for DMD50
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