”Invisible airwaves crackle with life
Bright antennae bristle with the energy
Emotional feedback, on timeless wavelength
Bearing a gift beyond price – almost free”
– Rush – The Spirit of Radio –
Marine and all VSAT (Satellite Systems) can be involved in this discussion. I’m glad I’m a Ham Radio Operator … because it teaches you things about radio frequency bands and propagation. Of course when you are sending a signal from the earth and bouncing it off the ionosphere it’s quite different from sending signals too and from Geosynchronous Orbit out in space. The issue of frequency comes up though in Ham Radio – because we use many many frequency bands as well. The average ham (not extraordinary ones operating in the higher Ghz bands) operates from 3 Mhz to 400 Mhz Range. But we know from VHF and UHF that those frequencies don’t get very far without being repeated … with the exception of some special propagation effects that occur naturally (and without our control.) We have a fair number of occassions each year to talk DX – distant … on 50 Mhz (some guys on 144 and 440 Mhz) when we get conditions like Sporadic-E that create an atmospheric Tunnel or Duct for the radio waves to travel through. It’s a lot of fun and it’s challenging and sometimes just plain luck of being on the air on the right band at the right time.
Anyway that having been said … some end users of satellite systems for TV or Internet may be aware of the bands being used and some “issues” with those bands. The most common these days are Ku Band and Ka bands. I personally have had DirecTV which operates satellites in both Ku and Ka bands and have seen the effects of Rain Fade on HD channels which are sent over Ka band … while SD channels are sent over Ku band. I could still watch the Ku band channels … when the Ka band channels dropped out due to heavy weather like rain.
I knew already that there was a buzz going on from 2011 and 2012 about Inmarsats Global Xpress that’s coming with the launch of their V5 satellites. And other satellite provider have challenged them on the fact that it is Ka band based system. I had not heard about newer High Throughput Satellites (HTS) until I noticed something in an email from Via Satellite in a newsletter referring to an article and some information from CapRock. So I went to see that and also looked it up a bit on Google.com.
The link was http://kafactcheck.com/ and the PDF download is a “Download the white paper” tab – link near the top left.
HTS Ka or HTS Ku? What’s right for you? – Is the title of the web page, but … the title of the PDF doc is
Not All Bands Are Created Equal A Closer Look at Ka & Ku High Throughput Satellites
INTRODUCTION
The advent of high-throughput satellites (HTS) enables network service providers to offer a new
generation of communications solutions. HTS systems combine the exceptional spectrum efficiency and
performance of spot-beam antennas with ultra-wideband transponders to enable unprecedented levels of
bandwidth and throughput. Each spot beam reuses frequencies in multiple carriers so that a single HTS
spacecraft can provide five to ten times the capacity of traditional satellites. For the customer, this
provides the potential to dramatically increase data rates, upwards of 100Mbps to a single site, and
improve application performance compared to traditional satellite based communications.
Despite this tremendous potential, there is a great deal of misperception and lack of understanding about
these new technologies among both customers and the industry at large. This is compounded by
marketing exuberance from some satellite fleet operators with their own specific and often proprietary
flavors of these emerging technologies. Customers and satellite network service providers alike need an
unbiased engineering perspective on the features, benefits and trade-offs of emerging HTS technologies.
ENGINEERING ANALYSIS OF HTS SYSTEMS
In order to better understand the real potential and practical application
of this new generation of HTS spacecraft, Harris CapRock
Communications, conducted an in-depth engineering analysis of
several HTS systems.
(more in the document from CapRock at the link above.)
The developers of HTS systems must balance their geographic coverage needs against the superior link
performance that small-spot beams can provide. The coverage/performance trade off is particularly
important for Ka-band HTS systems, where the links are especially susceptible to propagation
impairments due to rain and other atmospheric disturbances. Antennas size scales inversely with the
square of the frequency. Therefore, using very narrow spot beams to mitigate these propagation
impairments is particularly attractive in Ka-band. On the other hand, the number of transponders, the
payload complexity, and the spacecraft power requirements all scale directly with the number of beams
on the satellite, so very small beams also limit the available service area of the HTS.
At lower frequencies (such as Ku-band) where the links require smaller margins to overcome propagation
impairments, HTS systems have tended to use only wider spot beams, and the small-spot/large-spot
classification is less useful. The remainder of this white paper will compare three classes of HTS systems:
Ka-band small spot beam systems, Ka-band large spot beam systems and Ku-band spot beam systems.
Like most modern satellite systems, HTSs are often multi-purpose designs. HTS antennas may provide
large regional and hemispherical beams as well as spot beams. HTS payloads may include transponders
for several different satellite bands. This paper will focus exclusively on spot beam services in the fixed
satellite service bands in Ku-band and Ka-band.
This is one of the slides / images in the article … I like it because it shows the bands and their designation letters – so you can see how much higher Ka band is than Ku. I believe I did an article awhile back where I cited that Ku means “K Under” and Ka means “K Above”, and thusly there is a “K” for them to be above or below.
High Throughput Satellite Systems pertains to both Ku and Ka band systems and the engineering discussion is no doubt about which one is better … again with the rain fade … but there may be certain situations and certain configurations where Ka is better? It has also been said that a lot of excitement has been generated about Ka HTS systems … mostly by the organizations or companies trying to sell them. Without customers Inmarsat might become Inmar What? * Did anybody notice what I just noticed? In the image above, the wording … “Downlink … 11 Ghz vs 20 Ghz … 11 Ghz would be X band not Ku band, wouldn’t it? 20 Ghz would be K band not Ka band, wouldn’t it? And if I was talking computer binary programming I would say the wording is Big Endian “Ka than Ku” and Little Endian in the parenthesis where they compare the frequencies. In other words the two sets of descriptions don’t match up by which one they are talking about. If you say “Ka is worse than Ku”, for example, you should list frequencies as “Ka Frequency vs Ku Frequency”. Ka … than Ku = 20 Ghz vs 11 Ghz. Ka … than Ku = 30 Ghz vs 14 Ghz. … But who cares right?
It looks like Ku Band Spot service is the overall winner for provider and customer … with Ku current style (read the whole PDF doc!) running a close second. Ka small and large spot though I’m sure will have their places … especially with Ka Spot backup satellites.
And the cost comparison with the stipulation that this is about industrial environments. I’m not sure what that says about marine platforms. On yachts would the gear be considered industrial or more heavy duty? Anyway LNB, BUC prices go up for Ka band. And the cost of Teleport (not an end user expense) goes up also for Ka band. Sounds like you are trying to talk us out of Ka band.
There was another link in the CapRock pdf doc: http://www.harriscaprock.com/enewsletter/august_2012/industry_perspective.html worth looking at also.
—
Alan Spicer Marine Telecom
+1 954 683 3426
communications @ marinetelecom.net