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DSCS Baseband Systems

The control segment of the DSCS provides the means for near-real-time allocation of satellite power, antenna orientation/ nulling, and terminal monitoring and control to ensure maximum performance under changing traffic conditions, natural or man-made stresses, disturbances, and equipment disruption. It consists of hardware distributed among control centers, satellites and earth terminals, and common software to evaluate the status of the system.

Overall operational control of the DCS, of which the DSCS is a subsystem, is exercised through DISA. Within DISA, the DSCS Operations Control System (DOCS) is responsible for DSCS control. The DOCS consists of the DISA Operations Center, two Regional Control Centers (RCC) (Wheeler Air Force Base, Hawaii, and Vaihingen, Germany) and a DSCS Operations Center (DSCSOC) for each satellite area (ELANT and WLANT, EPAC and WPAC, and IO). The RCCs are responsible for the day-to-day operation and control of all DSCS satellites and execute this task through the DSCSOCs. Specifically, the DSCSOCs provide network and communications control and provide backup spacecraft control. Special users who establish subnetworks via the DSCS are responsible for their own subnetwork control procedures, but interface with the DSCSOC to provide status and performance data and to receive operational direction. Navy terminals operating in the DSCS will be controlled by the subnetwork control terminal operating under the DSCSOC for the satellite area.


The control segment performs the functions of spacecraft control, payload control, and network control.

Spacecraft Control. Spacecraft functions provide for maintaining the satellites in assigned orbital positions, maintaining orientation, and supporting functions to ensure optimal operations. The Consolidated Space Operations Center (CSOC), the associated Remote Gateway Facilities (RGF), and auxiliary satellite control terminals (ASCT) are responsible for DSCS in-orbit tracking, telemetry, and spacecraft control. Backup spacecraft control is provided by the DSCSOCs.

Payload Control. Payload control functions control and configure the DSCS communications payload. DISA payload management decisions will be implemented through the shared satellite command capabilities of the DSCSOC, the Consolidated Space Test Center (CSTC), and the CSOC. Satellite Configuration Control Elements (SCCE) at each DSCSOC perform telemetry and command functions for the control of critical satellite payload functions. This includes configuration of MBAs, GDAs, and control of transpolar gain. The SCCE consists of a computer interface processor, secure telemetry equipment, and command communications equipment.

Network Control. Network control functions manage communications between operators and processors, generate and drive display formats, process operator data entries, and maintain and provide rapid access to the network database. Network control ensures efficient use of satellite power and bandwidth. The RCCs monitor the satellites to detect power and bandwidth violations and report these to the respective controlling authority of the offending terminal.

DSCS ECCM Network Control. Control of the ECCM networks is exercised through the ECCM network controller at the DSCSOCs. The designated NCT for each satellite area provides synchronization, control, and management of ECCM networks via the critical control circuit (CCC). Status and direction is distributed to the network terminals (NT) over this circuit. All NTs establish a return orderwire to the NCT. In the case of the AN/ USC-28( V) modem, the return orderwire is the return critical control orderwire. The NCTs notify the NTs via the CCC when the control units or receiver/ transmitter link margins are out of tolerance to initiate actions to maintain link efficiency and quality. The DSCS ECCM Control System (DECS) provides for network establishment, network configuration control, status reporting, and performance monitoring of the equipment and communications signals of the DSCS ECCM network. The DECS provides automation and flexibility in the execution of ECCM network control functions such as day-to-day network performance monitoring and status gathering, anomaly detection and resolution, and response to adverse operating conditions. Further information can be found in the classified DISA Circular 800-E70 series, such as DISA Circular 800-E70-12 (DSCS ECCM Operating and Control Procedures).



DSCS FDMA Control System (DFCS)

DFCS is an automated system installed at heavy and medium earth terminal locations to enable automated control of the FDMA networks. DFCS replaces the manually operated Pilot Control System-Extension equipment. Specifically, DFCS is a highly sophisticated control and monitoring subsystem which provides automatic continuous monitoring of carrier transmit power and receive quality, equipment status reporting, and real-time power control for each point-to-point and fan link in the DSCS FDMA network. Each network consists of 2 NCTs and up to 48 NTs. One NCT is online in each network at all times. The NCT equipment (AN/ GSC-96) is located in the operations and equipment rooms of the DSCSOCs. The NT equipment (AN/ GSC-51( V) 1 or AN/ GSC-51( V) 2) is collocated with the AN/ FSC-78( V), AN/ GSC-39( V) 1, AN/ GSC-39( V) 2, AN/ GSC-39A( V) 1, AN/ GSC-39A( V) 2, AN/ GSC-52( V) 1, and AN/ GSC-52( V) 2.

Typical DFCS Network

NCT. The online NCT implements link carrier control through carrier definition data from the SATCOM network controller. This data is entered into the NCT database and identifies the carriers to be monitored by the network, the required link quality, and limits to be maintained by the network. When performance is determined to be outside desired limits, the NCT identifies the problem to the respective NT for adjustment. The NCT also monitors the FDMA transponder for saturation caused by excess uplink power and establishes net timing.

NT. The purpose of the NT is to interface directly with the Earth terminal (ET) for the collection of fault/ status data, to control uplink power, and to communicate with the NCT. It measures carrier-to-noise density, measures pseudo bit-error rate, and measures carrier and transmitter power levels. Additionally, it monitors the status of radio frequency terminal equipment and the Digital Communications Subsystem equipment (i. e., AN/ GSC-24( V), Integrated Digital Network Exchange [IDNX] multiplexers, OM-73 modems, etc). Performance data collected by the NT is passed to the NCT by means of the control data link in burst mode as the NCT polls the NT.

Demand Assigned Multiple Access (DAMA). DAMA is a DISA proposal that will be supported by FDMA SCPC circuits and will offer a broad range of messaging, director, port, internetwork, and billing services. It will support semipermanent fixed bandwidth and bandwidth-on-demand through user recognition.

FDMA Network Management System (FNMS). FNMS is a DSCS DAMA control system that will monitor and control links using standard FDMA modems. FNMS capabilities include login/ logout, orderwire, FDMA link setup and characterization, FDMA link maintenance and teardown, NCT handover, remote NCT operations, and Circuit Control TRANSEC protection. FNMS will eventually replace GMF Interim Tactical Orderwires and be incorporated into DFCS.

Demand Assigned Bandwidth System (DABS). DABS is a DISA service-on-demand initiative to provide users with various types of communications service when required. It is a system that makes efficient use of limited satellite bandwidth and power. DABS, an on-demand scheduled service, exploits the COTS technology of "Smart Muxs," such as the Automated Digital Multiplexer System (ADMS) TIMEPLEX Link/ 2+ ICS and the DISN Backbone IDNX 90. It consists of a DISA/ CFE-developed personal computer (PC)-based software for rapid channel reconfiguration of smart multiplexers and, through out-of-band signaling, modem reconfiguration for expanded throughput and bandwidth reallocation. The DABS software controls access and bandwidth to the Defense Information Infrastructure (DII)/ DISN wide area network from remote locations ashore and afloat. DABS allows any commander to make connections across DISN through rapid channel level interface between IDNX and TIMEPLEX.

DISN Tactical Extension Program (DTEP). DTEP is a DISA pilot network program that provides near-real-time bandwidth management of DSCS through DAMA. It provides the tactical warfighter access to DII/ DISN circuitry on demand from a remote location using DABS.

Interim Tactical Orderwire System (ITOS). ITOS is intended to be the universal, interim, satellite control capability for deployable terminals prior to the implementation of SHF DAMA. Its primary role is to fill the gap between the phase-out of the existing orderwire and the introduction of DAMA. ITOS equipment will be deployed at the DSCSOCs, tactical terminals, and STEP sites to coordinate DISN entry.

Baseband systems comprise the equipment necessary to process, format, and interface the user data channels between user equipment and the IF input/ output (I/ O) of satellite terminals. The equipment at the DSCS gateway includes the tactical baseband equipment necessary to interface with the DSCS. The DSCS is an all digital transmission system and the gateways are designated as single or dual terminal, depending on whether the gateway can access one or two satellite transponders simultaneously. The baseband equipment configuration depends on the type of interconnect facility used to transmit signals between the technical control facility (TCF) and the Earth terminals.

DSCS GMF Gateways

Croughton, UK Dual EASTLANT / IO
Landstuhl, Germany Triple WESTLANT / IO / EASTLANT
Lago Di Patria, Italy Dual EASTLANT / IO
Finegayan, Guam Single WESTPAC
Camp Zama, Japan Single WESTPAC
Ft. Buckner, Okinawa, Japan Dual IO / WESTPAC
Camp Roberts, CA Dual EASTPAC / WESTPAC
Northwest, VA Triple EASTLANT / WESTLANT

Digital Communications Subsystem (DCSS)

The DCSS includes the modulation, multiplexing coding, and processing equipment necessary for the assembly of various types of user data into a digital form suitable for transmission over a satellite link in the protected or unprotected modes. In the unprotected mode, the DCSS will utilize BPSK modulation. Transmission through the satellite will be accomplished in FDMA. Quadrature phase-shift keying (QPSK) modulation has been introduced into the system to provide greater spectrum conservation. At this time, both BPSK and QPSK types of modulation can be used for the unprotected mode. The protected mode will employ QPSK modulation. Transmission through the satellite will be accomplished by means of CDMA. The DCSS interfaces to the user at baseband data rates and with the satellite Earth terminal at the 70-or 700-MHz IF.

A DCSS will be installed at each Earth terminal and will be compatible with all terminals associated with the DSCS. At locations where the TCF is removed from the Earth terminal, portions of the DCSS will be located at both the TCF and Earth terminal, interconnected by a radio relay or cable.

Multiplex Equipment

AN/ FCC-98( V) 1. The AN/ FCC-98( V) 1 TDM/ demultiplexer is a full-duplex, 24-channel, telecommunications device with full transmit and receive capabilities. Each multiplexer is configured to specific communications systems requirements by the installation of selected combinations of voice, data, and data-timing plug-in modules. Once installed and operational in a communications system, the multiplexer/ demultiplexer generally requires only scheduled maintenance. Troubleshooting and corrective maintenance are completed to the module level by station forces with the unit in place. The output pulse-coded modulation (PCM) mission bit stream (MBS) can extend to 1.544 megabits per second (Mbps), dependent on the module configuration.

AN/ FCC-99( V). The AN/ FCC-99( V) multiplexer/ demultiplexer provides redundant, full-duplex second-level time division multiplexing and demultiplexing of I/ O data between first-level and third-level communications equipment primarily associated with shore installations. It accepts up to eight non-return-to-zero (NRZ) or bipolar data inputs, each operating at a nominal rate of 1.544 Mbps. Operational configuration provides additional NRZ data rate options of 3.088 Mbps per port and 6.176 Mbps per port. The multiplexer set operates in both synchronous and asynchronous modes with any combination of port data rates whose combined rate does not exceed 12.352 Mbps. Synchronous data is multiplexed into the MBS using a fixed-rate conversion. Asynchronous data is multiplexed using positive bit stuffing.

AN/ FCC-100( V) 1/ 2. The AN/ FCC-100( V) 1/ 2 low speed time-division multiplexer (LSTDM) operates with full-duplex capabilities at speeds up to and including 256 kilobits per second (kbps) providing a 16-port configuration capable of synchronous, asynchronous, isochronous (transitional encoded), and diphase data transmission. It is configured at the user's side of the communications system. A down-loading capability permits one operator to configure the local or the remote LSTDM from a single unit for system operation. Once configured, the LSTDM is capable of performing multiplexing, demultiplexing, timing, control, synchronization, framing, monitoring, and alarm reporting. Timing for the LSTDM is provided by a highly accurate, internal oscillator or by an external timing source. Local and remote data loopback capabilities allow for overall link testing and trouble isolation from a single LSTDM to the remote LSTDM. This multiplexer has been installed on selected flag-configured ships in the AN/ TSC-93B (modified) SHF QUICKSAT terminal.

AN/ FCC-100( V) 3. The AN/ FCC-100( V) 3 LSTDM operates with full-duplex capabilities at speeds from 1200 bps to 2.048 Mbps providing a 16-port configuration capable of synchronous, asynchronous, isochronous, and diphase data transmission. It is configured at the user's side of the communications systems. A down-loading capability permits one operator to configure the local or the remote LSTDM from a single unit for system operation. Once configured, the LSTDM is capable of performing multiplexing, demultiplexing, timing, control, synchronization, framing, monitoring, signaling information (i. e., request-to-send, clear-to-send), and alarm reporting. Timing for the LSTDM is provided by a highly accurate, internal oscillator or by an external timing source.

AN/ FCC-100( V) 4X. The AN/ FCC-100( V) 4X is an LSTDM with full-duplex capabilities. The AN/ FCC-100( V) 4X operates at speeds up to 256 kbps and provides 16 ports capable of handling any mix of synchronous, asynchronous, isochronous and diphase data transmission. The AN/ FCC-100( V) 4X is configured at the user's site to satisfy specific communications system requirements. The downline loading capability permits an operator to configure a remote AN/ FCC-100( V) 4X from a central unit, thereby eliminating the need for an operator at a remote site during reconfiguration. Once installed and configured, the AN/ FCC-100(V) 4X is capable of performing multiplexing, timing, control, synchronization, framing, monitoring, and alarm reporting. Timing for the AN/ FCC-100( V) 4X is provided by a highly accurate, internal oscillator or from an external timing source.

TD-1389( V). The TD-1389( V) is a microprocessor-controlled TDM. It is capable of accepting up to 12 channels of digital, analog, and frequency-shift keying (FSK) synchronous or asynchronous signals. The independent multiplexing/ demultiplexing operations can be configured so that user channel data of different and unrelated forms can be processed. The device can serve as a low rate multiplexer (LRM) or as a loop group multiplexer. The aggregate output can be up to 256 kbps. A remote option that duplicates all of the front panel functions (except power control) is available. This LRM is currently being installed in shore and SHF-configured platforms as a replacement for the TD-1251 multiplexer/ demultiplexer under the SATURN program.

TIMEPLEX LINK/ 2+. The LINK/ 2+ has become the primary full-or half-duplex, first-level multiplexer for Navy tactical SHF communications. The LINK/ 2+ is expandable to 54 module slots. It will replace or augment the AN/ FCC-100( V) in some applications. Navy SHF will use a basic 18-slot chassis, with the capability of an 18-slot-expansion chassis (two-nested) system. The LINK/ 2+ allows for greater I/ O (user) flexibility, advanced network management and versatility (i. e., automatic rerouting or self-healing) than the current first-level multiplexers (e. g., AN/ FCC-100( V) 1 through (V) 7). It is capable of processing digital data, voice (voice compression), and video by synchronous, asynchronous, isochronous, asymmetrical (different transmit and receive speeds on the same channel), and simplex signal processing. The LINK/ 2+ is capable of operating 12 trunks at aggregate data rates of 4.8 kbps to 2.048 Mbps each (not to exceed 7 T-1s, each at 1.544 Mbps). It also has the ability to interface with the Defense Information Systems Agency's DCSS Integrated Digital Network Exchange as a trunk and will allow for eventual worldwide connectivity (via the DCSS) for Navy SHF communications.

Sources and Resources

FAS | Space | Military | Programs | Communication |||| Index | Search | Join

Maintained by Robert Sherman
Originally created by John Pike
Updated Saturday, April 04, 1998 9:28:42 AM