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DoubleTalk® Carrier-in-Carrier® Bandwidth Compression

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DoubleTalk Carrier‑in‑Carrier, based on patented “Adaptive Cancellation” technology, allows transmit and receive carriers of a duplex link to share the same transponder space.  DoubleTalk Carrier‑in‑Carrier is complementary to all advances in modem technology, including advanced FEC and modulation techniques. As these technologies approach theoretical limits of power and bandwidth efficiencies, DoubleTalk Carrier‑in‑Carrier utilizing advanced signal processing techniques provides a new dimension in bandwidth efficiency.

Figure 1 shows the typical full-duplex satellite link, where the two carriers are adjacent to each other. Figure 2 shows the typical DoubleTalk Carrier-in-Carrier operation, where the two carriers are overlapping, thus sharing the same spectrum.

When observed over a spectrum analyzer, only the Composite is visible. Carrier 1 and Carrier 2 are shown in Figure 2 for reference only.

Without DoubleTalk Carrirer-in-Carrier Scope ImageWith DoubleTalk Carrier-in-Carrier Scope Image

DoubleTalk Carrier-in-Carrier allows satellite users to achieve spectral efficiencies (i.e. bps/Hz) that cannot be achieved with traditional links. For example, DoubleTalk Carrier-in-Carrier when used with 16-QAM approaches the bandwidth efficiency of 256-QAM (8bps/Hz).

As DoubleTalk Carrier-in-Carrier allows equivalent spectral efficiency using a lower order Modulation and/or FEC Code, it can simultaneously reduce CAPEX by allowing a smaller BUC/HPA and/or antenna.

DoubleTalk Carrier-in-Carrier can be used to save transponder bandwidth and/or transponder power thereby allowing successful deployment in bandwidth-limited as well as power-limited scenarios. The following example illustrates the typical process for implementing DoubleTalk Carrier-in-Carrier in a power-limited scenario:

The conventional link is using 8PSK, TPC 3/4
Spread the signal by switching to a lower order modulation and/or FEC code – say QPSK, TPC 7/8. This increases the total transponder bandwidth, while reducing the total transponder power
Now using DoubleTalk Carrier-in-Carrier, the second QPSK, TPC 7/8 carrier can be moved over the first carrier – thereby reducing the total transponder bandwidth and total transponder power when compared to the original side-by-side 8PSK, TPC 3/4 carriers

Supported Products

DoubleTalk Carrier-in-Carrier is currently available in the following form factors:

CDM-760 Product Image CDM-760 Advanced High-Speed Trunking Modem
CDM-750 Product Image CDM-750 Advanced High-Speed Trunking Modem
CDM-625A Product Image CDM-625A Advanced Satellite Modem
CDM-625A Product Image CDM-625A-EN Advanced Satellite Modem
CDM-625 Product Image CDM-625 Advanced Satellite Modem
CDM-625 Product Image CDM-625-EN Advanced Satellite Modem
CDM-570A/L Product Image CDM-570A & CDM-570AL Satellite Modems
SLM-5650A Product Image SLM-5650A Satellite Modem
DMD2050E Product Image DMD2050E Universal Satellite Modem
DMD2050 Product Image DMD2050 Universal Satellite Modem
CDM-Qx/L Product Image CDM-Qx and CDM-QxL Multi-Channel Satellite Modems
DMD20 Universal Satellite Modem DMD20 Universal Satellite Modem
DMD20 LBST L-Band Satellite Modem and ODU Driver DMD20 LBST L-Band Satellite Modem
DMD50 Universal Satellite Modem DMD50 Universal Satellite Modem
CLO-10 Link Optimizer CLO-10 Link Optimizer (modem agnostic)

Award-Winning Technology

World Teleport Association CDM-625 Advanced Satellite Modem – Wins 2010 Teleport Technology of the Year Award by World Teleport Association
World Teleport Association DoubleTalk Carrier-in-Carrier– Wins 2007 Teleport Technology of the Year Award by World Teleport Association


Learn More About


Carrier-in-Carrier® is a Registered Trademark of Comtech EF Data
DoubleTalk® is a Registered Trademark of Raytheon Applied Signal Technology