Comtech EF Data CDM-500 Instrukcja Użytkownika Pobierz pdf (Strona 2)

CDM-625 Advanced Satellite Modem with DoubleTalk Carrier-in-Carrier

Modems

Advanced Communication Solutions

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 efficiency, DoubleTalk Carrier-in-Carrier

utilizing advanced signal processing techniques provides a new

dimension in bandwidth and power efficiency.

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. Alternatively, DoubleTalk Carrier-in-Carrier can

be used to achieve very high spectral efficiencies E.g.,

DoubleTalk Carrier-in-Carrier when used with 16-QAM approaches

the bandwidth efficiency of 256-QAM (8bps/Hz).

When combined with VersaFEC or LDPC/TPC, it can provide

unprecedented savings in transponder bandwidth and power

utilization. This allows for its successful deployment in bandwidth-

limited as well as power-limited scenarios as well as reduction in

Earth Station BUC/HPA power requirements.

VERSAFEC FORWARD ERROR CORRECTION

CDM-625 is the first modem to offer VersaFEC, a patented

(Covered by US Patents 7,353,444 and 7,415,659. Other patents

pending) system of high performance short-block low latency

LDPC codes designed to support latency-sensitive applications,

such as cellular backhaul over satellite. VersaFEC provides

excellent coding gain with lowest possible latency. VersaFEC’s

Eb/No performance is similar to that of DVB-S2 (short block) or

LDPC (16k block) with 70-90% lower latency. Compared to TPC,

VersaFEC can provide coding gain of 1.0 dB or more.

ADAPTIVE CODING & MODULATION (ACM)

Satellite users have traditionally relied on worst case link margin

to overcome rain fade which leads to significant inefficiencies.

ACM converts the fade margin into increased throughput – gain of

100% or more is possible. CDM-625 with VersaFEC was

specifically architected to support ACM for IP/Ethernet traffic.

ACM maximizes throughput under all conditions – rain fade,

inclined orbit satellite operation, antenna mispointing, noise,

interference and other impairments.

VersaFEC ACM can provide almost 85% reduction in latency

compared to DVB-S2 (short block).

ACM can also be used with DoubleTalk Carrier-in-Carrier.

LOW DENSITY PARITY CHECK CODES (LDPC) & TURBO

PRODUCT CODES (TPC)

CDM-625 offers an integrated LDPC and 2nd Generation TPC

codec. LDPC is an advanced Forward Error Correction technique

capable of providing performance much closer to Shannon limit.

The current LDPC implementation can provide 0.7 to 1.2 dB

additional coding gain compared to an equivalent TPC code.

In order to take full advantage of the increased coding gain

provided by LDPC, Comtech EF Data has developed a patented 8-

QAM modulation (US Patent 7,254,188) that allows for acquisition

and tracking at much lower Eb/No compared to 8-PSK.

DUAL BAND CAPABILITY

CDM-625 supports 70/140 MHz and L-Band capability in the same

unit with independently selectable transmit and receive IF. This

simplifies sparing and stocking in networks requiring 70/140 MHz

and L-Band units.

QUAD E1 INTERFACE (QDI) WITH ENHANCED D&I++

The CDM-625 supports a Quad E1 interface that can aggregate up

to 4 full or fractional E1s into a single carrier, with very low

overhead. This provides significant CAPEX savings by reducing

the number of modems and could possibly reduce the BUC/HPA

size by eliminating the multi-carrier backoff. A proprietary, closed

network Drop & Insert (D&I++) allows for Dropping or Inserting

any combination of 1 to 31 Time Slots on each E1. D&I++ is

supported for E1-CCS only.

For QDI operation, all E1s must have a common clock source.

IP SUB MULTIPLEXER

IP Sub Mux allows multiplexing IP/Ethernet traffic with serial or

G.703 traffic into a single carrier. This is particularly useful for

cellular backhaul when both E1 and IP backhaul is required. This

reduces the number of modems and could possibly reduce the

BUC/HPA size by eliminating the multi-carrier backoff.

4-PORT MANAGED ETHERNET SWITCH WITH VLAN & QOS

CDM-625 incorporates a 4-port 10/100 BaseT Managed Ethernet

Switch with VLAN capability and priority based Quality of Service

(QoS). Access (Native) Mode and Trunk Mode are supported.

Traffic can be prioritized using port based priority or VLAN

priority.

EDMAC & AUPC

The CDM-625 support EDMAC, EDMAC-2, EDMAC-3 and AUPC.

EDMAC/EDMAC-2/EDMAC-3 can be used to monitor and control

the distant end of a satellite link using a proprietary overhead

channel. EDMAC-3 is also used for SNMP management of the

distant end modem. AUPC enables automatic uplink power control

for a duplex link.

MANAGEMENT & SNMP PROXY

The modem can be managed via the front panel, the remote M&C

port (EIA-232/EIA-485), or the 10/100BaseT Ethernet port. With

support for SNMP, http and telnet, the modem can be easily

integrated into an IP based management system.

The CDM-625 can also act as SNMP proxy for the distant end

modem. This allows distant end modem management using SNMP

without requiring an end-to-end IP link.

CDM-600/CDM-600L EMULATION MODE

CDM-625 can be placed in CDM-600 or CDM-600L emulation

mode. This permits easy integration into an existing CDM-600/L

setup without changes to M&C platform or redundancy switches.

FEATURE ENHANCEMENTS

Enhancing the capability of CDM-625 in the field is easy. Features

that do not require additional hardware can be added on site,

using FAST access codes purchased from Comtech EF Data.

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