Daily Archives: 19. October 2012

There are some interesting discussions on my group – Marine Telecom (Communications) – on LinkedIn.com:

http://www.linkedin.com/groups?home=&gid=3208547

Next generation satellite services aren’t base on frequency

Ku-band vs. Ka-band — What’s the Real Story? | Intelsat General

(the following is source = http://www.intelsatgeneral.com/blog/ku-band-vs-ka-band-whats-real-story?goback=%2Egmr_3208547%2Egde_3208547_member_176709747%2Egmr_3208547%2Egde_3208547_member_176577215)

Ku-band vs. Ka-band — What’s the Real Story?
October 10, 2012
Chris Hudson
 
Comparing Ku-band and Ka-band satellite capacity is a high interest topic right now in the satellite industry. In fact, a previous story we wrote on this topic is one of the best read pages on SATCOM Frontier.
 
A new study just released sheds new light on this important topic. Presented late last month at the International Conference on Satellite and Space Communications (ICSSC) 2012 in Rome, Italy, the study shows that the differences between Ku-band and Ka-band have much more to do with spot beam size than frequency band.
 
Ku-band currently dominates the aeronautical mobile satellite systems (AMSS) broadband market. The satellite bandwidth is leased by many companies from Fixed Satellite Service (FSS) providers like Intelsat and AMERICOM. These Ku-band satellites utilize continental scale wide beams.
 
New Ka-band systems coming onto the market promise to deliver substantially greater throughput than current Ku-band offerings. This fact has led some in the industry to conclude that Ka-band capacity is a superior evolution of Ku-band capacity.
 
However, this study demonstrates that the superior performance of Ka-band is the result of customized satellites and multiple spot beams. A Ku-band satellite using similarly sized spot beams can equal or exceed the performance of Ka-band satellites.
 
All this is not to say that one frequency is better or worse than the other. There are certainly scenarios in which Ka-band SATCOM is advisable. In fact, the new Intelsat EpicNG platform will offer C-, Ku- and Ka-band frequencies.
 
However, correcting the current misunderstanding of many around the performance characteristics of these frequencies is important. It could provide an evolution path to greater satellite capacity with current Ku-band satellites, thereby avoiding the need for expensive changes to terrestrial infrastructure.

* An excerp from the article cited above as “new study just released”

High Throughput Ku-band for
Aero Applications
Chris McLain* and Sunil Panthi†
Panasonic Avionics Corporation, Lake Forest, CA, 92630
and
James Hetrick‡
LinQuest Corporation, Los Angeles, CA 90056

Intelsat-29e
Panasonic and Intelsat have collaborated to tailor Intelsat-29e for AMSS service over North
America and the North Atlantic, which together represent the largest aviation market in the
world and the densest long haul air corridor. Panasonic has committed to up to 1 Gbps of
capacity on the Intelsat-29e. Intelsat has added spot beams over the North Atlantic air corridor
and a wide beam that will carry rebroadcast TV as well as serve low traffic density regions.
Intelsat-29e will support up to 200 Mbps of throughput in a single region (160 Mbps spot beam
and 40 Mbps wide beam) and up to 80 Mbps to a single aircraft. The high throughputs
supportable by Intelsat-29e exceed those of similar Ka-band systems, such as Inmarsat-5, as a
direct result of using spot beams smaller than 2 degrees. The relative performance of both is
shown in Table 1.

(I’m guessing that this is important for SOME marine VSAT as well … in particular it seems to be pretty important to KVH Industries, and I should say also Inmarsat.)

The skinny on all of this is that Inmarsat is coming out with its new Inmarsat-5 called Global Xpress … Global Xpress is Ka Band only … and Intelsat is a competing satellite operator to them. Therein is the rub or friction about the Ka vs Ku band … the frequencies and the satellite beam sizes … and all. See also:

http://www.spacenews.com/satellite_telecom/121015-inmarsat-intelsat-broadband-claims.html

* This article was also cited by intelsatgeneral.com above:

http://www.intelsatgeneral.com/blog/ka-band-or-ku-band-which-better-you

(a bit more technical … but still understandable by most [e.g. Yacht Engineers / Captains] and those in communications, like Alan Spicer)

Ka-band or Ku-band — Which is Better for You?
 

December 6, 2011
 
Chris Hudson
 
As the economics of providing Ka-band satellite communication services drive several new satellite deployments around the world, customers have been asking the question: Ka-band versus Ku-band — which is better? The answer to that question depends on the customer’s needs and the trade-offs that can be accepted.
 
Let’s start with an example customer who needs a certain geographic region covered by a single satellite. Must the coverage be provided by one beam or can it be multiple beams? Using just a single beam, if both the Ka-band and Ku-band satellites have equal-sized amplifiers, the beam’s power as it leaves the satellite is the same. This is called the Effective Isotropic Radiated Power, or EIRP.  The “isotropic” power is focused the same amount for both, so the signal strength directed to Earth is the same.
 
If the Ku and Ka-band receiving Earth stations are the same size, the reflector gain will be greater for a Ka-band signal.  This is because the reflector gain is proportional to the frequency squared and the higher Ka-band frequencies benefit. However, this additional gain is exactly equal to Ka-band’s worse path loss from satellite to Earth. Path loss is also proportional to the frequency squared.  The net result is that the carrier power level out of the antenna reflector is identical for both Ka and Ku-band.
 
Carrier strength is one factor but, the quality of a signal is the ratio of carrier to noise.  At the Ka-band frequencies, noise is higher than at Ku-band. So, in this example, with equal coverage on the ground and equal size receive antennas, the quality of the signal will be better at Ku-band.
 
Proponents of Ka-band capacity point out that the Ka-band beams usually have higher EIRP values than Ku-band.  This is true, but it is because the Ka-band beam is more focused.  A better-focused beam automatically results in a smaller coverage on the ground.  With smaller satellite beams, a satellite operator then needs multiple beams to cover the same area.
 
There is nothing inherently wrong with this. Multiple, smaller ‘spot’ beams can be aggregated to provide the desired coverage. However, it does introduce a potential challenge to the customer’s needs. Can the customer accept having multiple satellite beams to cover the desired region of operation? Due to the close proximity of the spot beams, i.e. being side-by-side, each beam will have a different polarization and/or frequency range within the Ka band. Is this acceptable to the customer?
 
Multiple spot beams may also create operational issues. To mimic single beam coverage, can a transmission in one spot beam be seen in its own beam as well as in all the other spot beams in the region of operation? Can this occur automatically or only by re-transmission from a gateway?  Most importantly, does the mitigation meet all the customer’s needs?
 
The example above, where the signal quality was better at Ku than at Ka-band, assumed no adjacent satellite interference, ASI, and no rain degradation.  Ka-band typically has the upper hand with ASI.  Ku-band satellites can be, and often are, spaced only 2 degrees apart from each other. The closer the adjacent satellite, the higher its interference can be. Today, Ka-band satellites are typically spaced further apart, and thus have less ASI.
 
A final consideration, and the one you hear most about, is rain fade. Atmospheric rain, snow or ice will absorb radio frequency signals above 11 GHz, and a Ka-band signal suffers more degradation than a Ku-band signal.  This is a win for Ku if there is sufficient rain in the region.
 
Both rain and ASI degradations vary greatly depending on a customer’s specific situation (e.g. satellite and terminal locations) so you can’t really make generalizations about either factor.
 
In conclusion, the advantages and disadvantages of either band can be mitigated. But not all concerns can be addressed for all customers at all times.  The underlying needs must be known and trade-offs made to arrive at the optimal choice of Ku or Ka-band.

—

Alan Spicer Marine Telecom

+1 954 683 3426

communications @ marinetelecom.net