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Chptr 5 Multichannel Control System

Chapter 5

Multichannel Control System

5-1. System Description

a. With multichannel TACSAT communications terminals in use by the Army, Air Force, and Marine Corps, the DSCS controller cannot accommodate the increased number of users. The ground mobile forces satellite communications (GMFSC) system operates as a subnetwork providing its own control system. This prevents interference degradation for other users of the DSCS SHF satellites.

b. The GMF satellite communications control centers (GMFSCCC), AN/MSQ-114 and AN/FSQ-124, provide mobile and fixed control facilities. The USAISC's operation and control procedures contain specific information and instructions on GMFSC planning control, management, and terminal user procedures. (These procedures are currently being revised.)

c. Specially trained US Army GMF controllers provide GMFSC control for the terminals deployed by the multiservice (Army, Air Force and Marine Corps) GMFSC system. The GMF controllers continuously monitor the downlink signals for all terminals in their networks to control uplink signals. They direct changes as necessary. The controller ensures that all terminals operate within the proper limits of frequency, power, and channel capacity. Should any discrepancies take place, the controller communicates by orderwire to initiate the changes necessary.

d. The GMFSCCC operates in the SHF frequency range of 7.9 to 8.4 GHz transmit and 7.25 to 7.75 GHz receive. Orderwire and AJ/CM units are used for communicating with terminals under their control. The satellite automatic monitoring system (SAMS) is used to monitor downlink frequencies of all terminals. This provides control over uplink power and frequency.

5-2. Deployment

The AN/MSQ-114 is usually deployed one unit per theater of operation. Since the AN/MSQ-114 is a limited production item, its deployment is rigidly controlled. The AN/MSQ-114 can support forward deployed forces, nonforward deployed forces, or contingency operations. Nonforward deployment usually refers to the home location of the GMFSSCCC (either AN/MSQ-114 or AN/FSQ-124). The control system must be within the respective satellite footprint, which usually is the NC/AC antenna footprints for DSCS II or the GDA footprint for the DSCS III satellites. (See Figures 5-1 through 5-4.) Using DSCS II, a GMFSCCC located in Korea can control GMF terminals in CONUS, provided the control system and GMF terminals are within the NC/AC footprints on that satellite. (See Figure 5-3.) On DSCS III, the control system and GMF terminals must be within the GDA footprint. If the NC/AC or GDA footprint is moved to support a mission so that the control system falls outside the footprint, the AN/MSQ-114 would be deployed into a footprint to allow control coverage of the GMF mission.

5-3. Employment

a. In their normal employment, the AN/MSQ-114 and the AN/FSQ-124 can control a number of GMFSC terminals. The exact number of terminals being controlled depends on the network configuration and the mission requirement. A point-to-point configuration is used when connectivity between two low capacity terminals is desired. The hub-spoke configuration uses a multichannel terminal as the hub. Up to four low capacity terminals are used as the spokes. When at least two hub terminals are connected by communications and each operates with up to three spoke terminals, a hybrid configuration is derived. The control terminal can monitor and control any configuration that may be active within the control area.

b. In the networks designated for control by an AN/MSQ-114 terminal, the controller--

The first step in the start procedure after the AN/MSQ-114 is on station at a new location is to activate the control orderwire to the DSCS controller. Frequencies to be transmitted and received are authorized by the GMF manager from an allotment granted to the GMFSC system by DCA. Other system parameters that are determined prior to start are transmit power, number of channels, and type of modulation coding priority. The GMF controller accesses each tactical terminal using the control terminal (CT) orderwire. The controller then directs the adjusting of transmit power to achieve planned link performance. Measurements are made and entered into the SAMS for real-time monitoring of the link.

c. To evaluate link parameters, the SAMS monitors the network for out of tolerance conditions. Manual spectrum analyzers and user reports are also used to evaluate link parameters. Bad weather, equipment, operator errors, satellite problems, and intentional or unintentional interference may cause problem conditions. The GMF controller detects and analyzes network problems. The next step is to direct work-around solutions. These solutions may be temporary power adjustments, reduction-in-link capacity (drop out by priority) or instructions to operators. In some cases, it may be necessary to interrupt service for major maintenance actions. The GMF controller maintains a log of all problems and terminal faults. A network status display printout is also maintained. The status display printouts that are available in the SAMS data base are status and statistics reports. These reports are available as a hard copy, a cathode ray tube (CRT) display, both on command, or at regularly timed intervals.

d. Often, during network operations, it may be necessary to reconfigure a real-time link or the whole network. Some of the causes for reconfiguration are:

e. Reconfiguration by adding or deleting terminals is done by the GMF controller. This involves changes to the SAMS data base and coordination with the tactical terminal by orderwire. Terminal relocation requires immediate action by the controller to coordinate the movement. New system parameters and look angles must be provided and the SAMS data base updated. Adding a new type earth terminal and using a new satellite also requires reconfiguration. The GMF controller has the authority to reconfigure the network until changes in satellite power or new frequency assignments are required; then, the GMF manager must be informed of the change required. The DSCS controller is responsible for the DSCS satellite communications network. Since the GMF network is only a subnet, the GMF controller must interface with the DSCS controller when any action that takes place might impact on network performance. Coordination is normally required--

f. A more serious condition is when the DSCS controller informs the GMF controller that violations have taken place in the GMFSC network. As mentioned previously, a major duty of the GMF controller is to monitor the uplink and downlink characteristics of the GMFSC network for out of tolerance conditions. The result of this monitoring is to help TACSAT communications terminal operators find stations that are at fault and correct the problems. In severe cases, such as satellite failure or interference, the DSCS controller must help pinpoint and rectify the problem. The GMF controller, closely coordinating with the DSCS controller, directs and implements network antijamming plans.

5-4. Control and Management

TACSAT communications links are not independent, unlike conventional radio communications such as HF or LOS. All links in a network use the same satellite transponder. Each of the users must carefully configure their link with reference to other users and keep uplink power within an allotted level. Failure to follow these guidelines will have harmful consequences on all other users. The increase of power on one link improves the quality of that link but intermodulation products increase and cause interference on the other links. A large increase in power causes the downlink carriers on other links to be suppressed. Control of all links using the same satellite transponder is important. While the GMF controller is a major player in the operation, overall control is distributed among six activities. Those responsible for controlling the GMF/TACSAT communications resources are described in the following paragraphs.

a. The planner plans the action and provides the following information when establishing a communications link using a DSCS satellite:

b. The GMF manager is responsible for managing the satellite resources allocated to the GMFSC. The manager combines all requests and coordinates any conflicting requirements by--

c. The DSCS controller is responsible for the DSCS network. This encompasses all users including GMF terminals working a particular satellite. The DSCS controller--

d. The GMF controller operates under the direct supervision of the GMF manager. The controller operates and maintains the control and monitoring equipment. The GMF controller--

e. The TACSAT communications terminal operator interfaces directly with the GMF controller. The user or operator follows instructions and reports status and performance of the TACSAT communications terminal. The operator--

5-5. System Configuration

a. The GMFSCCC is deployed in a number of different system configurations depending on the mission and theater of operations. The simplest configuration is point-to-point, where the GMF controller monitors over two TACSAT communications terminals each used as a point. The slightly more complex network is the hub-spoke configuration. Each low capacity terminal becomes one of the spokes operating with either the AN/TSC-85( ) or AN/TSC-100A. The hybrid configuration deals with a number of hub-spoke configurations with the hubs communicating with each other as well as the spokes in their configuration. A DSCS terminal (a fixed station satellite communications facility called gateway) can replace a low capacity GMF terminal. In these configurations, the AN/MSQ-114 has an orderwire control link with all the TACSAT communications terminals and a monitor link to the satellite. The AN/MSQ-114 can communicate with a DSCS terminal via the terrestrial critical control circuit (TCCC) network using either an established terrestrial link or a communications circuit via the satellite. To make DSCS terminals compatible with GMFSC terminals, additional equipment must be included in the digital communications subsystem (DCSS) of the DSCS terminal. The GMF contingency rack 20 low rate initial production (LRIP) and GMF contingency rack 20A are single racks giving limited operational capabilities to the DSCS terminals in the GMF network. To enhance the capabilities, additional racks are added to produce the DSCS/GMF gateway racks. Included are encryption devices, antijamming modems, LRMs, and patch panels. The complement of racks is increased to six in this configuration.

b. The AN/MSQ-114 terminal consists of an environmentally controlled 34-foot semitrailer, two power generators, a 20-foot parabolic antenna, prime movers, and a shelter for maintenance and storage of spare parts. The AN/FSQ-124 consists of four electrical racks, a roll-around cart, and a control console in the facilities of the host terminal.

c. The AN/MSQ-114 antenna is a 20-foot parabolic antenna type AS-3199/TSC. It has a limited motion of ħl0° cross elevation and a full 90° in elevation. Antenna control can be from inside of the van or remote. The modes of operation provided are manual, acquisition, and auto-track. To acquire a satellite, the antenna must be implaced with the azimuth look angle very close to the bore sight of the feed system.

d. The AN/FSQ-124 is a component of a DSCSOC which is collocated with a host earth terminal. The host earth terminal can be an AN/GSC-39, an AN/GSC-52, or an AN/FSC-78. The AN/FSQ-124 consists of a remote orderwire console and four equipment racks that contain up- and down-converters, SAMS, IPAs, and orderwire modems. The AN/FSQ-124 is operated and maintained by a specially trained operator who is one of the five individuals normally on shift in the DSCSOC.

5-6. Antijamming and ECCM Techniques

a. The AN/MSQ-114, acting as the NCT, has the AJ/CM (MD-1133) that belongs to a family of spread spectrum modem equipment designed to provide the GMFSC terminals with ECCM capability for operation in a stressed environment. The spread spectrum link provided by the AJ/CM is more difficult to jam. This signal can coexist with the FDMA links by sharing the same frequency spectrum and presenting the appearance of not even being there. This link may well be the last ditch signal available in a stressed environment.

b. The MD-1133 used in the AN/MSQ-114 consists of one chassis assembly, the NCU. The NCU has a control and bus logic which provides functional terminal modem organization, execution, and control. The NCU control processor directs external programmable up-/down-converter synthesizer frequency control. The NCU requires a precise frequency and time reference from an external cesium beam standard. Redundant frequency standards (HP5061A), which are part of the AN/MSQ-114, provide the required time and frequency references. The NCU provides buffering for time and frequency reference signals for computational and code use. Software is modularized to specific terminal operations and functions. Terminal tasks are modularly executed through combinations of software modules, operator control, and fixed microprocessor hardware logic. Network control and status functions are provided on the NCU front panel along with monitor test and fault isolation functions. The AJ/CM replaces the RT-1287 nonsecure FM orderwire. It operates as an orderwire between the NT in addition to its communications function. In a jammed environment, the AJ/CM equipment provides the antenna tracking signal instead of normal communications tracking.

5-7. Data Entry

a. The SAMS element of the AN/MSQ-114 and the AN/FSQ-124 provides the data base for planning GMF resources. The SAMS also provides the monitor facilities for managing the GMFSC network. The SAMS supports the GMF controller in translating satellite communications (SATCOM) requirements into channel capacities, time schedules, transmitter power, RF frequency assignments, and modes of operation. The SAMS monitors and measures the technical performance of deployed GMF ground terminals. This allows missions to be accomplished with a minimum assignment of available RF power and bandwidth. It also helps determine compliance of GMF ground terminal with assignments.

b. Network management is done by the SAMS software which consists of various resource planning, measuring, calculating, and report generating programs. These programs present to the GMF controller a real-time description of the satellite downlink.

c. The major parameters to be measured and calculated include carrier-to-noise density (analog and digital signals received by the AN/MSQ-114 and AN/FSQ-124 terminals), operating noise temperature, and percentage of satellite power usage. Alarm conditions and statistical data are also presented to the controller as conditions dictate and/or as required. A real-time operating system controls the SAMS software modules and data bases.

d. The SAMS uses all of the hardware, under control of computer programs, to perform the following required functions:

e. The GMF controller makes SAMS data base entries which are directly related to the AN/MSQ-114 and the AN/FSQ-124 functions. These functions are monitoring and controlling the GMFSC networks. The information to be entered comes from the DCA planner and the GMF manager in the DSCS-GMF SAA. This information is entered into the SAMS data base via the keyboard or by prepared cassette tape(s). The following examples of an SAR, sample report 1 (Figure 5-5), and DSCS-GMF SAA, sample report 2 (Figure 5-6), are the worksheets from which data to be entered into the SAMS is taken. The SAR must be in accordance with Defense Communications Agency operations center (DCAOC) contingency/exercise plan. (All entries on these worksheets are fictitious although representative of actual data.)