The U.S. Military Awaits More Ka-band Capacity
Today, the U.S. military relies on the Ka-band Global Broadcast Service from three of the Boeing-built fleet of eight operational UHF Follow-On satellites, F8 through F10. Each is equipped with 4X130-watt, 24 Mbps Ka-band transponders and three steerable downlink spotbeam antennas as well as one steerable and one fixed uplink antenna.
When the first of five WGS satellite activates late next year, WGS controllers will be required to dynamically and simultaneously focus required satellite coverage and capacity when and wherever needed by deployed forces. The decision to include Ka-band along with X-band on WGS opens the door to the many perceived advantages of Ka-band including greater bandwidth, increased data throughput and smaller receive antennas.
WGS involves conventional transponded (bent-pipe) satellites with all NMS on the ground. ViaSat is supplying the Enhanced Bandwidth Efficient Modem, while Titan Corp., which was recently acquired by L-3 Communications, is providing the U.S. Army with Ka-band Satcom Augmentation Terminals.
According to Mark Hayes, vice president and director of communications systems at ITT Industries, systems division, WGS network controllers located at the Wideband Satellite Operations Centers (WSOCs) must have immediate access to the status, performance and usage of all satellite, terminal and link resources. Using the Integrated Network Monitoring and Control Subsystem (IMPCS), controllers can exert positive control over all terminals accessing the WGS by interacting directly with the terminals through automated control circuits and secure voice order wires provided by the IMPCS.
"As the complexity of the satellites increases, so must the monitoring and control systems employed to manage these critical communications assets. The IMPCS is designed to provide integrated spectrum monitoring, signal characterization and link power control capable of sustaining communications through severe rain fades given one-way rain fade of 30 dB per minute at Ka-band frequencies," says Hayes.
When combined, X- and Ka-bands on each WGS satellite represent about 1500 MHz of bandwidth. However, the actual bandwidth supported by the WGS payload is much greater as portions of each frequency band will be reused in different coverage areas illuminating different portions of the earth.
"Circular polarization and spatial reuse of frequency results in a total of about 1800 MHz of X-band bandwidth and more than 2700 MHz of Ka-band bandwidth per satellite. This combination of antennas coupled with the WGS's ability to digitally route spectrum in 2.6 MHz sub-channels provides virtually unlimited flexibility," Hayes says.
The Spectrum Monitoring Subsystem, an integral component of IMPCS, enables controllers to continuously monitor the entire WGS spectrum or controller-selected portions of the satellite's X- and Ka-band coverage areas. It alerts the WSOC controllers to interference, unauthorized users and out-of-tolerance conditions.
"Since the WSOC will not be illuminated by all of the WGS spacecraft's separate downlink coverage areas, the WGS provides a spectrum tapping capability to sequentially sample the spectrum in 10-20 MHz bandwidth increments and downlink these samples to IMPCS," says Hayes. "IMPCS features a WGS synchronization receiver to reassemble the downlink at the WSOC for effective monitoring of the entire X- and Ka-band spectrum. IMPCS also provides C- and Ku-band interfaces to provide advanced monitor and control of all satellites operating in any of the four satellite communications bands."
No Turning Back
As for Ka-band developments in Europe and Asia, there is some confusion about what is really happening. Look at iPstar, for example. Anik F2, weighing in at 5200 kg, was the largest commercial satellite in the sky until the successful recent launch by Thailand-based Shin Satellite Plc. of iPstar-1 (Thaicom 4) - topping the scales at 6775 kg - with its Ka-/Ku-band payload at 120 degrees East.
An industry press release declared, among other things, that, "Thaicom 4 (iPstar) will use its seven on-board antennas to create 112 spot and regional beams in the Ku and Ka frequency bands."
We turned to Shin Satellite spokesman Richard Jones in Bangkok for help.
"It looks like there is a problem from the start as iPstar does not use Ka-band for connections to customers. We have minimal capacity for the uplink from the control centre to the satellite only. All our spot beams are Ku-band. I don't know how this misunderstanding came about, but iPstar is essentially a Ku-band satellite," says Jones.
As for New Skies Satellite NV's NSS 6, this uses Ka-band uplinks only, too. With Digital Multimedia Broadcasting via satellite now making headway in Japan and South Korea, thanks to MBsat, and with satellites with partial Ka-band payloads in the region including Koreasat-3, and, the SCC Superbird and Jsat Nstar satellites serving broadband markets in Japan, there is much to discuss. But it must wait.
Here in the United States, things like the Universal Service for the 21st Century Act (or S. 1583) and the recent decision by the Texas legislature to grant telcos a one-stop, statewide franchise will alter the Ka-band landscape again. On Capitol Hill, powerful senators with increasingly vocal and unserved rural constituents are saying enough is enough. Tired of waiting for an affordable broadband solution to penetrate the rural heartland, they introduced S. 1583 to amend the Telecommunications Act of 1996 and create a subsidized base of support for rural broadband service provider with an annual outlay that could amount to as much as $500 million.
Ka-band is maturing and now redefined as a video solution rather than a broadband vehicle only. This proves that the process of finding new revenue streams for Ka-band is just getting underway and the potential out there is enormous.
Peter Brown is Via Satellite's Senior Multimedia & Homeland Security Editor.
Email
Comments
Print
Reuse
