High-throughput satellites are the solution
- By Karl Fuchs
- Oct 25, 2012
The appetite for over-the-horizon bandwidth within the Defense Department has never been greater. Intelligence, surveillance and reconnaissance (ISR) missions and other full-motion, high-definition video feeds are the fastest growing bandwidth-consuming applications used by the warfighter. The Wideband Global SATCOM (WGS) constellation began to come on line in 2007, when WGS 1 was launched. Even though there are four WGS satellites in orbit today, with two more to follow, the military still needs to use commercial satellites to augment its satellite capacity in order to meet expanding bandwidth needs. Recent budget constraints, the rapidly changing profile of end users data and the proliferation of airborne communications-on-the-move (COTM) systems make the new high-throughput satellite (HTS) networks now being launched an attractive augmentation to the government’s existing resources. In fact, the pool of bandwidth available on HTS is projected to be 90 percent of all available bandwidth by 2015, according to Comsys.
The global coverage of HTS networks makes this system a perfect choice to augment mission coverage. The new HTS satellites are based on overlapping spot-beam architecture. Each spot beam features very high and uniform gain over temperature and equivalent isotropically radiated power and, in some cases, each beam can provide up to 50 Mbps. The overlapping spot beams and the consistent transmission profile make HTS ideal for airborne COTM missions. All of the new HTS being launched support Ka, while some support Ka and a mix of other bands. The use of Ka band, while it is the commercial portion of the band in HTS systems, enables the military to leverage some commonality of antenna and transmission equipment used on WGS Ka systems.
There are a number of challenges to designing a military satellite communications system that can seamlessly transition between a government-owned and operated network using WGS Ka bandwidth and a commercial HTS spot-beam offering. Chief among them is providing a modem that is capable of operating in both worlds while also meeting stringent government information assurance (IA) and transmission security (TRANSEC) requirements. Commercial HTS systems rely almost exclusively on proprietary waveforms, while the DOD is moving toward a standards-based platform. A modem with sufficient memory would be capable of supporting multiple operational images.
Another significant challenge is supporting both the commercial and military ranges of the Ka frequency band. Most commercial modems have an L band interface that covers approximately 1 GHz. The entire Ka range, including both military and commercial, spans well over 2 GHz. The challenge is to address both ends of the band using a single L band interface. One proposed solution would be to develop a Ka Block Up Converter (BUC) with two Local Oscillators (LO). A communication mechanism would be required between the modem and BUC to implement the LO change.
Other considerations that need to be addressed before HTS networks can be used to augment satellite bandwidth include the need for commercial satellite providers to provide a secure enclave within their teleports. Ultimately, the landed traffic will need to be transported to a secure terrestrial network, and the commercial satellite provider will have to meet stringent government requirements, such as Mission Assurance Category (MAC) II or even MAC I. A commercial provider’s teleport infrastructure will be subject to the same stringent IA requirements, including security content automation protocol hardening, as government teleports. Finally, a TRANSEC-enabled network may be required for some missions.
Despite the challenges, the benefits of the government using the new HTS global networks as either a primary or secondary choice to meet mission needs cannot be overstated. The architecture of the new satellite constellations provides remarkable amounts of satellite capacity, with beam characteristics that make it perfectly suited to support the newest high-data-rate applications. The global reach and ubiquitous always-on coverage can augment any currently deployed government network. Leveraging a shared infrastructure and tapping into such a fast-growing bandwidth pool will make using HTS a very cost-effective way to meet mission requirements in the years to come.