Meshing Military And Commercial
It is no secret that the Pentagon needs more bandwidth and that the commercial satellite industry has taken on an important new role as far as the Defense Department (DoD) is concerned. For one thing, the Defense Information Systems Agency has tripled its budget for commercial satellite capacity throughout the past three years to just under $200 million annually in commercial transponder leases, with this amount expected to increase.
The DoD has its net-centric operations flag flying high, and the immense scale of the global operations of the U.S. military will result in a continued growth in bandwidth requirements and the need to determine what commercial and military satcom systems will be used to satisfy these requirements.
"The DoD's approach for the management of their satcom resources utilizes centralized administration with distributed management of all assets--ground and space," says Mark Casady, vice president and general manager at the Communications Systems Group of ITT Industries, Systems Division.
Casady points to the wideband milsatcom control segment embodied by the current Defense Satellite Communications System (DSCS) Operations Control System (DOCS) soon to be renamed the Wideband Satcom Operations Control System (WSOCS) with the launch of the Wideband Gapfiller Satellite (WGS) as a case in point.
"Elements of this control system are located at the worldwide level for long-term planning and administration of functionality. Distributed management occurs at the network operations centers within each of the satellite areas of operation for overall satcom network control and at each of the earth terminals," Casady says.
"ITT Industries is responsible for the operational support, maintenance and training for the DOCS. As far as control subsystems are concerned, ITT Industries built both the Satellite Configuration Control Element (SCCE) for managing the configuration of the communications payload on the spacecraft and the Integrated Monitoring and Power Control System (IMPCS) for fault, performance and configuration management of the ground segment resources, which includes the earth terminals and their communications gear.
Among other things, WGS stands out because, although it continues to use bent-pipe transponders rather than a processed payload, the channelization is done digitally, allowing for variable channel bandwidths. This provides a higher degree of onboard switching and recombining than traditional transponding satellites.
"Commercial satcom utilizes a different approach with control primarily applied at the satellite level by the satellite service provider. Network control such as spectrum monitoring, earth terminal control, monitor and alarm and some degree of Demand Assigned Multiple Access (DAMA) for Very Small Aperture Terminal (VSAT) type networks tends to be the responsibility of the ground segment provider," Casady says. "This may change if turnkey systems like Hughes' Spaceway are introduced in the commercial sector. If this happens, end-to-end service provisioning may open the door for a commercial version of IMPCS."
What also complicates the landscape is the question of how much of the control functionality should be on the satellite, where access and cost may be an issue, versus how much should be on the ground. Within the DoD there are differing philosophies as to how and where control of the overall satcom system should reside.
With the DoD already heavily invested in a full-blown hybrid fiber/wireless satellite network, Casady sees other unresolved issues that could have an effect on the current efforts by the DoD to complete the blueprints for its transformational communications architecture. The first cut at this is now expected to be finalized this coming summer.
"How the terrestrial segment will request service over the satcom segment is one of the key issues. What is the protocol that will be used for media access control (MAC)? Will this protocol be a derivative from existing techniques or will it have to be totally new in order to accommodate both segments being addressed?" asks Casady. "Will it use a circuit or packet-switched architecture or some combination of both? How will it support an end-to-end provisioning of QoS-based service level agreements? Resolution of these issues will require a more comprehensive and holistic approach to system management."
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