Comtech EF Data DMD-2050E - Manual (Page 62)

DMD2050E Universal Satellite Modem Theory of Operation
MN-DMD2050E Revision 2 3–20
3.8 Ebem Framing Unit
The DMD2050E EBEM framing Unit provides the ability to multiplex both Serial (MIL-STD-188-
114A or Hgh Speed Serial Interface – HSSI) with Bridged Ethernet payload, overhead and
embedded channel data within the over-the-air transport stream.
3.8.1 DMD2050E Information Throughput Adpatation (ITA)
Refer to Appendix I for additional information.
3.8.2 Embedded Channel
The embedded channel is used for exchanging messages between DMD2050E units. ITA,
AUPC and TRANSEC traffic encryption/decryption key negotiation are typical examples of
messages sent through the DMD2050E embedded channel. The nominal rate of the embedded
channel is 4 kbps.
3.9 STANAG Turbo Coding
The DMD2050E provides STANAGE Turbo coding FEC for all specified baseband data rates (64
kbps to 52.0 Mbps) and modulation formats (BPSK, QPSK, 8-PSK, and 16-APSK) with the
following code rates: None, 1/2, 2/3, 3/4, 7/8, or 19/20. A decoding function for all Turbo encoded
data is also provided.
Turbo codes come extremely close to achieving the absolute maximum channel capacity, in bits
per second, for a given transmit power level. For traffic that can tolerate decoding delay and
require a low Bit Error Rate (BER) (i.e., 1×10–10), Turbo coding can be used. For traffic such as
speech, where excessive decoding delays cannot be tolerated and higher BER can be tolerated.
STANAG Turbo Block Sizes
Block Size (Bits) Total Composite Data Rate
1024
Data Rate =<1024 kbps
4096 1024 kbps < Data Rate < 4096 kbps
16384 Data Rate ≥ 4096 kbps