Asymmetrical loop timing & data source bit synchronization
Ethernet interface for remote control using HTTP, Telnet and Simple Network Management Protocol (SNMP)
EIA-485 and EIA-232 interface for remote control
Comtech SLM-5650A Satellite Modem
Comtech EF Data’s SLM-5650A Satellite Modem is compliant with the strict requirements defined in
MIL-STD-188-165A, modem types I, II, IV, V and VI for applications on DSCS, WGS and commercial
satellites. Data rates from 64 kbps to 155 Mbps and symbol rates from 32 ksps to 64 Msps are supported.
The modem provides standard MIL-STD-188-114 (EIA-530 / RS-422), and EIA-613 (HSSI) serial interfaces,
and can be optionally configured to support G.703 and Low Voltage Differential Signaling (LVDS) serial
interfaces. It can also optionally be equipped with a 4-port 10/100/1000Base-T Ethernet Network Processor
module that supports switching, routing and advanced Quality of Service protocols.
The SLM-5650A can be integrated with the Vipersat Management System (VMS) to provide fully automated
network and capacity management. An AES-256 TRANSEC module, compliant with the FIPS-140-2 NIST
standard is also available as an option. All traffic (including overhead and all VMS control traffic) is
encrypted when using the TRANSEC module.
Advanced forward error correction (FEC) capabilities are a Comtech EF Data standard feature. Viterbi,
Trellis, Concatenated Reed-Solomon, Sequential, and Turbo Product Codes are all supported.
Advanced FEC and modulation capabilities are integrated with the revolutionary DoubleTalk® Carrier-in-
Carrier® bandwidth compression allowing for maximum state-of-the-art performance under all conditions.
This combination of advanced technologies enables multi-dimensional optimization, allowing satellite
communications users to:
Minimize required satellite bandwidth
Maximize throughput without using additional transponder resources
Maximize availability (margin) without using additional transponder resources
Enable use of a smaller BUC/HPA and/or antenna
Or, a combination of the above to meet specific mission needs
SLM-5650A Sample Configuration
The SLM-5650A is interoperable with the OM-73, SLM-3650, MD-1352(P)/U (BEM-7650), SLM-7650, SLM-8650, CDM-570, CDM-
600/600L, CDM-625, CDD-562, CDD-564, DMD20, and DMD2050 satellite modems.
The modem supports EIA-530 (RS-422), EIA-612/613 (HSSI) as standard features. Optional interface modules are available to support
G.703, LVDS serial, or 4-port Gigabit Ethernet interfaces.
An optional transmission security (TRANSEC) module provides bulk AES-256 encryption/decryption in accordance with the FIPS-140-2
Level 2 specification. The TRANSEC module encrypts all traffic sent over the air, including data traffic, overhead channel and Vipersat
Management System messages (if present).
Turbo Product Coding
Turbo coding provides superior error correction performance over Viterbi, Trellis and Reed-Solomon FEC. The SLM-5650A TPC is
compatible with Intelsat IESS-315 and Comtech EF Data’s CDM-570, CDM-600, CDM-625, SLM-3650, SLM-7650, DMD20, and
DMD2050 Satellite Modems and the CDD-562/564 IP Demodulators.
ASYNC Overhead Channel / AUPC
An asynchronous overhead channel supporting 2- and 4-wire RS-485, as well as RS-232 can be optionally configured. This overhead
channel is typically used to support control and monitoring of equipment external to the modem in a remote network. The ASYNC
overhead channel can be provisioned in conjunction with any of the supported traffic interfaces (RS-422, HSSI, G.703, LVDS or
Ethernet). Automatic Uplink Power Control (AUPC) is available to maintain a desired Eb/No at the demodulator despite link fades due to
excessive rain or other power level variations.
The Network Processor (NP) module provides a wide variety of advanced Internet Protocol (IP) features including routing, switching,
Quality of Service, and Vipersat dynamic bandwidth control.
With the NP module installed, the modem can be configured as an Ethernet switch or as a high-speed router. Networking options include
configuration of a bridged point–to-multipoint network, which enables bridged network connectivity (desired in many satellite networks
carrying encrypted traffic) in a hub-spoke network architecture.
Multicast traffic forwarding is supported via static multicast addressing, dynamic multicast address learning through IGMP router and
IGMP Proxy, and via the bridged point-to-multipoint mode of operation.
Flow Control is supported via Ethernet pause frames (IEEE 801.3)
Dynamic Routing Protocol using OSPF
OSPF based interior gateway protocol (IGP) is supported in split-path topology.
Proxy ARP is supported to enable transparent subnets.
Quality of Service (QoS)
The NP module supports multi-level QoS to reduce jitter and latency for real time traffic, provide priority treatment to mission critical
applications and allow non-critical traffic to use the remaining bandwidth. Supported functionality includes differentiated services code
point (DSCP) in accordance with RFCs 2474 and 2475, Expedited Forwarding in accordance with RFC 3246, and Per Hop Behavior in
accordance with RFC 3247.
VMS Bandwidth Management
The Vipersat Management System (VMS) is the engine that provides dynamic Single Carrier per Channel (dSCPC) bandwidth
management of the space segment.
When a remote in the network has an application to transport over the satellite link, dSCPC technology provides the mechanism to
automatically establish the SCPC carrier for that transmission. dSCPC resizes the carrier based on the increase or decrease in
applications being sent over the link, and it returns the remote to its home state once the application is completed. dSCPC yields true
bandwidth-on-demand, giving the user the low-latency, low-jitter dedicated SCPC connection when it is needed for real-time applications,
such as Voice over IP (VoIP), video conference, broadcasts and large applications (file or image transfers).
VMS automates bandwidth utilization while optimizing space segment efficiency. It allows intelligent management of satellite networks
through port and system configuration and alarm management of the protocol, modem, RF equipment and IP broadband networking. The
graphical user interface of VMS enables centralized network configuration and management. It provides auto-detection of satellite
modems, configuration and monitoring of the modems, and real-time views of network health and transmission quality. These allow
operators to easily configure and monitor dynamically controlled networks. The VMS can be configured to dynamically allocate satellite
network capacity in a variety of ways. Supported modes for capacity allocation include:
1. Entry channel mode, which allows a modem to automatically enter/exit a network, sets a fixed capacity for the terminal when in
2. Load: Capacity allocation based on load demand of terminals on the network.
3. Type of Service (ToS): Type and priority based allocation using DiffServ Code Point (DSCP) fields.
Both shared forward link and multiple point-to-point hub-spoke architectures can be configured and dynamically controlled by the VMS.
Supports lossless, low-latency antenna handover in conjunction with the CRS-311-AH antenna handover switch controller.
Expanded Dynamic Range
The modem exceeds the MIL-STD-188-165A input signal dynamic range requirements by extending the low signal input level
requirement of –55 dBm to down to –70 dBm for lower baud rate carriers.
Ultra high reliability, redundant configurations are supported in conjunction with Comtech EF Data’s CRS-311 and CRS-300 switches.
The CRS-311 can be configured to support 1:1 redundancy for any SLM-5650A configuration. The CRS-300 provides the same
functionality for 1:N redundant system architectures.
Network Management / Remote Control
The modem supports access to network management information via HTTP using a standard web browser. SNMP and Telnet remote
control is also supported. The modem includes separate Ethernet and EIA-485/EIA-232 remote control interfaces. Remote control can
also be accomplished via the Ethernet ports of the optional Network Processor. Secure network management via Secure Sockets Layer
(SSL), Secure Shell (SSH) and SNMPv3 are available as options.
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
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
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 8-PSK, 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
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:
Demodulation Only & Asymmetric Data Rates
In order to cost-effectively enable hub-spoke networks, two cost saving configurations are supported. First, the SLM-5650A is available
in a demodulation-only version (SLM-5650AD). This configuration is often used as a hub demodulator. Hub-spoke networks using the
CDD-564 multi-channel demodulators are also supported.
There is also a reduced cost configuration option that allows the remote modems to receive a large shared outbound and transmit a
smaller return channel.