A Closer Look at High Throughput Satellites
Separating the Hype from the Real Benefits
The advent of high throughput satellite (HTS) technologies with unprecedented bandwidth and power have ushered in the potential for a new generation of communications and networking services for customers across a variety of markets.
No longer just tradeshow concepts, next generation high throughput satellites like Intelsat’s EPIC fleet and Inmarsat’s GlobalXpress are under construction and will be in orbit as early as 2014. EPIC and GlobalXpress each use high throughput spot beam technology enabling much higher data rates and access to greater amounts of overall bandwidth than traditional standard throughput satellites. Each system promises efficiency and capability not previously available in satellite networks. However EPIC and GlobalXpress take very different approaches to the implementation of HTS technology. EPIC relies on an open systems design, field proven Ku band systems and regional clusters of high throughput beams to provide concentrated services that maximize speed and link reliability. In contrast, GlobalXpress is a proprietary closed network designed entirely new from the ground up. It uses the higher Ka band frequency, and a mesh of larger Ka band spot beams to maximize global coverage. As with any technology, there are trade-offs to each approach. So which satellite technology is right for your network?
As the world’s largest commercial buyer of space segment and a provider of end-to-end managed satellite communications solutions, Harris CapRock continually analyzes new technologies and their integration into reliable high performance networks. Our customers expect Harris CapRock to serve as a neutral, trusted technology advisor. Whether the network includes Ku, C, L or Ka-band satellite technologies, the ultimate goal is to exceed current service level agreements and provide a resilient high-quality platform that grows along with our customers needs. Our independent perspective uniquely qualifies us to analyze emerging bandwidth technologies in an unbiased manner to develop conclusions from a customer viewpoint. In this article, we will analyze the basic capabilities, strengths and weaknesses of the emerging Ku and Ka-band HTS technologies and draw conclusions from the engineering of real-world end-to-end solutions.
As a quick introduction, it’s easiest to group Ka-band satellites into two classifications – small spot and large spot beam. Small spot Ka-band focuses the radio signals into small spots on the Earth’s surface, providing concentrated link performance in terms of data rate and availability. However, because the beam is focused on one narrow area, any performance gain is offset by a limited geographic coverage area. The reverse is true with large spot Ka-band satellites. The coverage area is much wider than with small spot beams, but the radio signals have a much looser concentration which directly limits data rates and availability. With existing technology and a limited number of Ka-Band HTS systems, the upcoming Ka-band satellites fail to strike a balance between high performance and global coverage.
Beyond the link performance and coverage trade-off, Ka-band HTS systems have a number of issues to consider:
Spot Beams and Costs
Spot beams allow both the Ku and Ka-band systems to achieve high spectrum efficiencies. When the question of coverage comes into play, Ka-band systems sacrifice link performance by increasing their spot beam size to roughly the same size as the Ku-band spot beam size. When comparing equal coverage areas between Ku and Ka-band assets, Ka-band is at a disadvantage due to weather related propagation affects. Therefore, when comparing the net impact to the end user between equal coverage Ku vs. Ka systems, a Ka-band solution would have a higher cost relative to Ku-band to achieve the same level of link availability.
If we consider an example customer who needs high availability service in a specific geographic region, we can compare an HTS Ka and Ku solution to determine which is most cost-effective. At the same link availability, and using cost per MHz assumptions, the cost per bit is lower with a Ku-band HTS system. The cost difference between small spot Ka and Ku does narrow as the availability requirements are reduced and in many cases, with the Ka-band small spot system achieves near parity with the Ku-band system for availabilities under 98%, and is impacted in rain fade regions. Ku-band has a distinct advantage for customers who demand very high service reliability and as availability needs increase to 99.5% and greater, the cost advantage grows rapidly in favor of a Ku solution. The large spot Ka-band HTS systems do not appear to be cost-competitive for providing services in any of the key regions in which Harris CapRock supports customer operations, especially when considering mission requirements for data rates at service availabilities at 99.5% and higher.
By their nature, spot beam systems are limited in coverage, with each spot covering at most a few thousand square kilometers. However, some HTS systems provide large fields of spot beams that collectively create continental and even global coverage, whereas others offer only a relatively small number of fixed or steerable spots in targeted areas. Ku-band spot beams and Ka-band large spot beams offer comparable coverage areas. Ka-band small spot beams, however, generally cover only about 10% or 15% of the area covered by a large spot beam, and these spacecraft tend to offer less total spot beam coverage.
Ability to Recover from Satellite Failure
Ka-band satellite capacity, due to its infancy, is relatively sparse. GlobalXpress specifically is a proprietary design with no comparable spacecraft available from other satellite fleet operators. In the event of a failure on a Ka-band HTS, a service provider will find it difficult if not impossible to migrate a customer’s affected service to another Ka-band satellite. Alternatively, the Ka-band service could be migrated to a backup service in Ku-band but this would require additional ground terminal hardware increasing service cost. Ku-band satellite services on the other hand, like Intelsat’s EPIC is available virtually everywhere in the world via traditional spacecraft. Affected service on one Ku-band system can be easily migrated directly from one HTS satellite to traditional standard throughput spacecraft – effectively making Ku HTS “backward compatible.”
Ka-band VSAT systems are less common in the marketplace and therefore can be more expensive than Ku-band systems of similar performance. It is also common to see Ka-band networks designed with larger antennas in heavy rain regions, but that represents a serious drawback for many customers who require smaller antenna solutions. Customers who aren’t bound by antenna size will find that larger VSATs make a Ku-Band solution equally advantageous to Ka.
New Spectrum Availability
One of the chief selling points for Ka-band satellite services is the relatively unused spectrum, while the lower frequency satellite bands are all heavily subscribed. The use of spot beams at any of these frequencies allows a much higher frequency reuse, which greatly multiplies the data throughput that can be achieved in the available bands.
Ka-band links are far more susceptible to disruption from weather and other atmospheric disturbances than Ku-band links. Where heavy rainfall is common, it’s more difficult and more expensive to provide high availability, reliable services with Ka-band than Ku. Many Ka providers are claiming that advanced modulation schemes will mitigate weather related issues, but the underlying link availability will still require additional satellite resources. In many high rain zone areas, the adoption to Ku band systems has not occurred due to the reliability of legacy C-band networks.
At Harris CapRock, we’re committed to meeting each of our customer’s unique needs with the most cost-effective solutions available. Considering the objectives and requirements of our industrial customers today, relative to the strengths of Ka and Ku-band systems, Ku service remains the superior-performing solution for our customers by almost every practical measure. Ka-band HTS systems can be competitive for mass market or consumer grade customers that do not require particularly high reliability and are willing to deal with some trade-offs in their communications solution.
For industrial customers in markets like energy, maritime and government whose remote operations depend on their communications as a literal lifeline – the new, HTS Ku implementation will prove to be the best-performing, most cost-effective reliable satellite network technology. For more information on our analysis, please contact your account executive.
Join Harris CapRock at SATCON, where we’re participating in a thought leadership forum on High Throughput Satellites
Luncheon Forum open to all SATCON attendees:
A Closer Look at High Throughput Satellites: What’s Right for Your Operation?
Moderator: Simon Bull, Senior Consultant, COMSYS
Lunch will be provided. For questions or to RSVP, please contact email@example.com.
Nov. 14, 2012 - 1:00 - 2:00 p.m., Room 5
COMSYS’ Simon Bull will moderate as thought leaders from organizations including Harris CapRock analyze the ability of HTS technologies to be integrated in new and innovative solutions. They will discuss some of the basic capabilities, strengths and weaknesses of emerging Ku- and Ka-band HTS technologies.