Comtech EF Data CDM-Qx Manual de usuario descargar pdf (Pagina 2)

Doubletalk Carrier-In-Carrier

DoubleTalk Carrier-in-Carrier is based on patented bandwidth compression technology originally developed by Applied Signal

Technology, Inc. Using “Adaptive Cancellation” it allows transmit and receive carriers of a two-way link to share the same transponder

space.

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

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.

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:

EDMAC & AUPC

The CDM-Qx/QxL support EDMAC, EDMAC-2, and AUPC. EDMAC/AUPC is compatible with CDM-600/600L and CDM-570/570L.

EDMAC-2/AUPC is compatible with CDM-570/570L.

Monitoring & Control

The CDM-Qx/QxL provide a range of options for local and remote management. The modem can be managed via the front panel, the

remote M&C port (EIA-232/EIA-485), or the 10/100Base-T Ethernet port. With support for SNMP, HTTP and Telnet, the modems can be

easily integrated into an IP-based management system.

Figure 1 Figure 2

A B

B A

Carrier-in-Carrier

is a Registered Trademark of Comtech EF Data

DoubleTalk

is a Registered Trademark of Raytheon Applied Signal Technology

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Comtech EF Data CDM-Qx Manual de usuario Pagina 2