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Comtech EF Data CDM-625 Advanced Satellite Modem
- DoubleTalk Carrier-in-Carrier
- 70/140 MHz and L-Band capabilities
- Data Rates to 25 Mbps
- Extensive backwards compability
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Comtech CDM-625 Advanced Satellite Modem
The Comtech EF Data CDM-625 is the first modem to combine advanced FEC such as Low
Density Parity Check (LDPC) codes with the revolutionary
DoubleTalk® Carrier-in-Carrier® bandwidth compression
allowing for maximum savings under all conditions.
CDM-625 Advanced Satellite Modem builds on Comtech EF
Data’s legacy of providing the most efficient satellite modems.
It is the first modem to combine advanced FEC such as Low
Density Parity Check (LDPC) codes with the revolutionary
DoubleTalk® Carrier-in-Carrier® bandwidth compression
allowing for maximum savings under all conditions. This
combination of advanced technologies enables multidimensional
optimization, allowing satellite communications
users to:
- Minimize operating expenses (OPEX)
- Maximize throughput without using additional transponder
resources
- Maximize availability (margin) without using additional
transponder resources
- Minimize capital expenses (CAPEX) by allowing a smaller
BUC/HPA and/or antenna
- Or, a combination to meet specific business needs
The advanced technologies and features of CDM-625 are
covered by a number of U.S. patents including 7,254,188,
7,353,444, 7,415,659 and other pending patents.
Applications
- Cellular Backhaul
- G.703 Trunking
- IP Trunking
- Offshore & Maritime Communications
- Enterprise
- Communications on-the-Move
- Satellite News Gathering
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Typical Users
- Mobile Operators
- Telecom Operators
- Satellite Service
Providers
- Government & Military
- Enterprise
- Offshore
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CDM-625 Satellite Modem Key Features
- DoubleTalk Carrier-in-Carrier bandwidth compression
- Adaptive Coding and Modulation (ACM)
- IP Packet Processor with header compression, payload
compression and advanced Quality of Service (QoS)
- Dual Band Capability: 70/140 MHz and L-Band in same unit
- Data Rate: 18 kbps to 25 Mbps
- Symbol Rate: 18 ksps to 12.5 Msps
- Modulation: BPSK, QPSK/OQPSK, 8-PSK/8-QAM, 16-QAM
- FEC: Viterbi, Sequential, Concatenated Reed Solomon,
TCM, Turbo Product Code (TPC) (IESS-315 Compliant),
LDPC Code and VersaFEC (low-latency LDPC)
- Widest Range of Data Interfaces: EIA-422/530, V.35, G.703
T1, G.703 E1, G.703 T2, G.703 E2, Quad G.703 E1, ASI,
LVDS, HSSI, 4-port 10/100Base-T Ethernet
- 4-port Managed Ethernet Switch with VLAN and QoS
- Sub Mux to multiplex IP/Ethernet traffic with serial or G.703
traffic
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- Drop & Insert for T1/E1
- Enhanced D&I++ for Single T1/E1 & Quad E1
- Management: 10/100Base-T Ethernet with SNMP, Distant
End SNMP Proxy, HTTP ,Telnet and EIA-232/EIA-485
- Embedded Distant-end Monitor and Control (EDMAC)
- Automatic Uplink Power Control (AUPC)
- Engineering Service Channel (ESC/ESC++)
- Standard High Stability Internal Reference (± 6 x 10-8)
- 5-tap Adaptive Equalizer
- L-Band TX: 10 MHz reference for BUC, FSK communications
and optional BUC power supply
- L-Band RX: 10 MHz reference and LNB power supply
- Open Network Modes
- CDM-600/L emulation mode
- 1:1 and 1:10 redundancy switches available
- Backwards compatible with CDM-500/CDM-550, CDM-550T,
CDM-570/L and CDM-600/L Satellite Modems
- Interoperable with many Comtech EF Data Satellite
Modems: CDM-Qx/L, SDM-8000, 300A, and 300L3
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Doubletalk Carrier-in-Carrier
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.
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 efficiency, DoubleTalk Carrier-in-Carrier
utilizing advanced signal processing techniques provides a new
dimension in bandwidth and power efficiency.
DoubleTalk Carrier-in-Carrier allows satellite users to achieve
spectral efficiencies (i.e. bps/Hz) that cannot be achieved with
traditional links. E.g., 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.
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 and 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 U.S. patents 7,353,444 and 7,415,659; other
patents pending) system of high performance short-block lowlatency
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. The 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
mis-pointing, 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 (U.S. 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.
4-PORT MANAGED ETHERNET SWITCH WITH VLAN & QoS
CDM-625 base modem incorporates a 4-port 10/100Base-T
managed Ethernet switch with VLAN capability and prioritybased
Quality of Service (QoS). Access (Native) Mode and
Trunk Mode are supported. Traffic can be prioritized using portbased
priority or VLAN priority. The maximum Ethernet frame
size is 1536 bytes.
IP PACKET PROCESSOR
The IP Packet Processor enables efficient IP networking and
transport over satellite by adding routing capability with very
low overhead encapsulation, header compression, payload
compression and Quality of Service to the CDM-625. The
advanced QoS combined with header and payload compression
ensures the highest quality of service with minimal jitter and
latency for real-time traffic, priority treatment of mission critical
applications and maximum bandwidth efficiency.
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Header Compression
The IP Packet Processor incorporates industry-leading header
compression for IP traffic. Header compression can reduce the
40 byte IP/UDP/RTP header to as little as 1 byte. For TCP/IP,
the 40 byte header is reduced to as little as 3 bytes. For
applications such as VoIP, header compression can provide
bandwidth savings exceeding 60%. E.g. the 8 kbps G.729 voice
codec requires 24 kbps of IP bandwidth once encapsulated into
an IP/UDP/RTP datagram. With header compression, the same
voice call needs about 8.5 kbps – a saving of almost 65%. And,
bandwidth requirements for typical Web/HTTP traffic can be
reduced by 10% or more with TCP/IP header compression.
Payload Compression
The IP Packet Processor incorporates industry-leading payload
compression for IP traffic. Implemented in the hardware for
maximum throughput and efficiency, payload compression can
reduce the required satellite bandwidth by as much as 40-50%.
Streamline Encapsulation (SLE)
The IP Packet Processor incorporates Comtech EF Data’s
patent-pending very low overhead Streamline Encapsulation
(SLE). SLE can reduce the encapsulation overhead by as much
as 65% compared to industry standard HDLC.
Advanced Quality of Service (QoS)
The IP Packet Processor incorporates multi-level QoS to
ensure the highest quality service with minimal jitter and
latency for real-time traffic, priority treatment of mission critical
applications and maximum bandwidth efficiency.
Supported modes are:
- DiffServ – Industry-standard method of providing QoS
enabling seamless co-existence in networks that implement
DiffServ
- Max/Priority – Provides multi-level traffic prioritization with
the ability to limit maximum traffic per priority class
- Min/Max – Provides a Committed Information Rate (CIR) to
each user defined class of traffic with the ability to allow a
higher burstable rate depending on availability
QUAD E1 INTERFACE (QDI) WITH ENHANCED D&I++
The CDM-625 supports a Quad E1 interface that can aggregate
up to four 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
The 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 multicarrier
backoff.
EDMAC & AUPC
The CDM-625 supports 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 10/100Base-T 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 the 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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System Specifications
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| Data Rate |
18 kbps to 25 Mbps, in 1 bps steps (Modulation, FEC & Data
Interface dependant) |
| Symbol Rate |
18 ksps to 12.5 Msps |
| Operating Frequency |
50 – 180 MHz (Standard) AND 950 – 1950 MHz (Option), 100 Hz
Resolution, Independent TX and RX operation |
| Major Operating Modes |
Open Network, per IESS-308 / 309 / 310 / 314
Transparent, Closed Network per IESS-315
LDPC / TPC Codec (Optional Plug-in Module)
EDMAC Framed with/without AUPC
RS Outer Codec
High Rate ESC / Enhanced ESC (ESC++)
Drop & Insert (D&I) /Enhanced D&I++
Quad E1 Drop & Insert (QDI)
DoubleTalk Carrier-in-Carrier |
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FEC Options
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| None |
Uncoded BPSK/QPSK/OQPSK |
| Viterbi: k=7, per IESS-308/309 |
Rate 1/2 BPS/QPSK/OQPSK
Rate 3/4 QPSK/OQPSK
Rate 7/8 QPSK/OQPSK |
| Viterbi with Reed Solomon |
Rate 3/4 16-QAM
Rate 7/8 16-QAM |
| Reed Solomon |
Open Network and Closed Network modes |
| TCM (Per IESS-310) |
8-PSK/TCM Rate 2/3 |
Integrated LDPC and TPC
(2nd Gen) Codec
(Optional Plug-in Module) |
LDPC Code Rates
Rate 1/2 BPSK/QPSK/OQPSK
Rate 2/3 QPSK/OQPSK/8-PSK/8-QAM
Rate 3/4 QPSK/OQPSK/8-PSK/8-QAM/16-QAM
TPC Code Rates
Rate 5/16 BPSK
Rate 21/44 BPSK/QPSK/OQPSK
Rate 3/4 QPSK/OQPSK/8-PSK/8-QAM/16-QAM
Rate 7/8 QPSK/OQPSK/8-PSK/8-QAM/16-QAM
Rate 0.95 QPSK/OQPSK/8-PSK/8-QAM |
| Scrambling |
IDR Mode, no RS, - per ITU V.35 (Intelsat variant)
IBS mode, no RS - per IESS-309, externally frame synchronized
Transparent Closed Network mode, no RS or TPC/LDPC - per ITU V.35
(Intelsat variant)
EDMAC mode, no RS coding - externally frame synchronized (proprietary)
TPC/LDPC modes - externally frame synchronized (proprietary)
All RS modes - externally frame synchronized per IESS-308/309/310 |
| Management |
10/100 BaseT Ethernet with SNMP, HTTP and Telnet support,
EIA-232, EIA-485 (2- or 4-wire) |
| Form C Relays |
Hardware fault, Rx and Tx Traffic Alarms, Open Network
Backward Alarms |
External Reference
(Input OR Output) |
BNC Connector
Input: 1, 2, 5, or 10 MHz, -6 dBm to +10 dBm, 50Ω/75Ω (nominal)
Output: 10 MHz, 2.7 V peak-to-peak ± 0.4 V, Low Impedance Output |
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Modulator
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| Frequency Stability |
±0.06 ppm (±6 x 10-8), 0° to 50°C (32° to 122° F)
with Internal Reference |
| Transmit Filtering |
Per IESS-308 |
| Harmonics and Spurious |
Better than -60 dBc/4 kHz (typically <-65 dBc/4kHz)
Measured from 1 to 500 MHz (50-180 MHz band)
Measured F0 ± 500 MHz (950-1950 MHz band) |
| Transmit On/Off Ratio |
-60 dBc minimum |
| Output Phase Noise |
< 0.480° rms double sided, 100 Hz to 1MHz
(Minimum 16 dB better overall than the INTELSAT IESS-308/309
requirements)
| dB/Hz |
Frequency Offset |
| -63.0 |
100 Hz |
| -73.0 |
1 kHz |
| -83.0 |
10 kHz |
| -93.0 |
100 kHz |
Fundamental AC line spurious is -42 dBc or lower
The sum of all other single sideband spurious, from 0 to 0.75 x symbol
rate, is -48 dBc or lower |
| Output Power |
50-180 MHz: 0 to -25 dBm, 0.1 dB steps
(0 to -20 dBm in CDM-600 emulation mode)
950-1950 MHz: 0 to -40 dBm, 0.1 dB steps
(0 to -45 dBm in CDM-600L emulation mode, but power accuracy and
spurious only guaranteed to -40 dBm) |
| Power Accuracy |
50-180 MHz:
±0.5 dB over frequency, data rate, modulation type and temperature
range of 15 to 35° C
±0.8 dB over frequency, data rate, modulation type and temperature
range of 0 to 50° C
950-1950 MHz:
±0.7 dB over frequency, data rate, modulation type and temperature
range of 15 to 35° C
±1.0 dB over frequency, data rate, modulation type and temperature
range of 0 to 50° C |
Output Impedance
& Return Loss |
50-180 MHz: 50Ω/75Ω, 16 db minimum return loss (18 dB
typical), BNC Connector
950-1950 MHz: 50Ω, 19 db minimum return loss (21 dB typical), Type-N
Connector |
| Clocking Options |
Internal, ±0.06 ppm (SCT)
External, locking over a ±100 ppm range (TT)
Loop timing (Rx satellite clock) - supports asymmetric operation
External Clock |
| External Tx Carrier Off |
By TTL 'low' signal or external contact closure |
| BUC Reference (10 MHz |
Via TX IF center conductor, 10.0 MHz ± 0.06 ppm (With
internal reference), selectable ON/OFF, 0.0 dBm ± 3 dB |
BUC Power Supply
(HW Option) |
24VDC, 4.17 Amps max., 90 W @ 50° C
48VDC, 3.125 Amps max., 150W @ 50° C (180 W @ 30° C)
Supplied through Tx IF center conductor and selectable ON/OFF via M&C
control. |
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Demodulator
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Input Power Range,
Desired Carrier |
50-180 MHz: -105 + 10 log (symbol rate) to -70 + 10 log
(symbol rate) dBm
950-1950 MHz: -130 + 10 log (symbol rate) to -80 + 10 log (symbol
rate) dBm |
Max Composite
Operating Level |
50-180 MHz:
94 - 10 log (symbol rate, desired carrier) dBc, +10 dBm max, with the
additional requirement that within ±10 MHz of the desired carrier the
composite power is ≤ +30 dBc
950-1950 MHz:
102 - 10 log (symbol rate, desired carrier) dBc, +10 dBm max, with the
additional requirement that within ±10 MHz of the desired carrier the
composite power is ≤ +30 dBc |
| Absolute Maximum |
+20 dBm |
| Adaptive Equalizer |
5-tap design, selectable ON/OFF |
| Acquisition Range |
Programmable in 1kHz increments
Below 32 ksymbols/sec: ±1 kHz to ± (Rs) kHz, where Rs = symbol rate in
ksymbols/sec
Between 32 and 389 ksymbols/sec: ±1 kHz to ±32 kHz Above 389
ksymbols/sec: ±1 kHz to ± (0.1 * Rs) kHz, up to a maximum of ± 200 kHz
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| Acquisition Time |
Highly dependent on data rate, FEC rate, and demodulator
acquisition range. E.g.: 120 ms average at 64 kbps, R1/2 QPSK, ±10 kHz
acquisition sweep range, 6 dB Eb/No |
Plesiochronous/
Doppler Buffer |
Selectable from 64 to 262,144 bits, in 16-bit steps
(Additional limitations for G.704 frame boundaries) |
| Receive Clock |
Rx Satellite, Tx Terrestrial, External Reference |
| Clock Tracking |
± 100 ppm minimum |
| LNB Reference (10 MHz) |
Via RX IF center conductor, 10.0 MHz ± 0.06 ppm (With
internal reference), selectable ON/OFF, -3.0 dBm ± 3 dB |
| LNB Voltage |
Selectable ON/OFF, 13 VDC, 18 VDC per DiSEq 4.2 and 24 VDC at
500 mA maximum |
| Monitor Functions |
Eb/N0 estimate, Corrected BER,
Frequency offset, Buffer fill state, Receive signal level |
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Doubletalk Carrier-In-Carrier
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| Delay Range |
0 to 330 ms |
Power Spectral
Density Ratio |
–7 dB to +11 dB (Interferer to Desired) |
| Eb/N0 Degradation |
0 dB Power Spectral Density Ratio
BPSK/QPSK/OQPSK: 0.3 dB
8-QAM: 0.4 dB
8-PSK: 0.5 dB
16-QAM: 0.6 dB
+10 dB Power Spectral Density Ratio
Additional 0.3 dB |
| Satellite Restrictions |
Satellite in “loop-back” mode (i.e., the Transmit Station can
receive itself)
“Non-processing” satellite (i.e., does not demodulate/remodulate the
signal) |
| Environmental And Physical |
| Temperature |
Operating: 0 to 50ºC (32 to 122°F)
Storage: -25 to 85ºC (-13 to 185ºF) |
| Power Supply |
100 - 240 VAC, +6%/-10%, 50/60 Hz, Auto sensing
-48 VDC (HW Option) |
| Power Consumption |
48 watts (typical with TPC/LDPC Codec and Carrier-in-Carrier
module installed), 55 watts (max.)
280 watts (typical with TPC/LDPC Codec, Carrier-in-Carrier module and
48 VDC BUC power supply installed), 300 watts (max.) |
| Physical Dimensions (1RU) |
1.75H x 19.0W x 17.65D inches
(4.4H x 48W x 44.8D cm) approximate |
| Weight |
10.5 lbs (4.8 kgs) maximum, with all option modules and 48
VDC BUC power supply installed |
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See Datasheet for more specifications and Options
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