Comtech EF Data CDD-56X Series Vipersat - Manual (Page 20)

Product Description MN/22137, rev 1
1-6 Vipersat CDD-56X Series User Guide
STDMA
The addition of STDMA capability to a Vipersat network allows multiple termi-
nals to share the same satellite resources that would be dedicated to a single
terminal in an SCPC configuration. This means that more terminals can be
added to the network with minimal additional cost in either satellite bandwidth
or Hub Terminal hardware.
Vipersat STDMA thus provides a low cost solution for medium to large sized
networks with generally moderate bandwidth requirements, while at the same
time providing all the features of the existing Vipersat systems, including the
availability of a switched pool of SCPC channels for occasional high bandwidth
traffic such as video conferences and large file transfers. Each STDMA
upstream channel from the remote terminals to the Hub uses an STDMA frame
operating at an aggregate data rate of from 16 kbps to 9.98 Mbps and can
support up to hundreds of remote terminals with multiple burst channel
inbounds.
Configured as a Hub terminal, the CDD-564/564L provides one demod for
receiving an upstream STDMA channel from the remotes, and three demods for
receiving three SCPC channels.
Single Hop On Demand
The CDD-56X is ideal for mesh applications such as Vipersat's Single Hop On
Demand (SHOD). With the CDD-56X, SHOD (meshed) circuits are easily and
economically established between remotes. SHOD provides significant and
dynamic connectivity between latency connections without suffering the high
costs associated with multiple carriers and/or 1-to-1 multi-receiver links.
Turbo Product Coding
The Comtech Vipersat CDD-56X incorporates a Turbo Product Codec (TPC)
error correction, delivering significant performance improvement when
compared to Viterbi with concatenated Reed-Solomon. TPC simultaneously
offers increased coding gain, lower decoding delay, and significant bandwidth
savings.
Header Decompression
Header compression reduces the required Voice over Internet Protocol (VoIP)
bandwidth by as much as 60%. Example: a G.729 voice codec operating at 8
kbps will occupy 32 kbps once encapsulated into IP framing on a LAN. Using
IP/UDP/RTP Header Compression, the same traffic only needs 10.8 kbps total
WAN satellite bandwidth to cross the link. The CDD-56X demods perform
header decompression prior to passing the data onto the LAN.