There has been a lot of talk about Ka band lately, but unfortunately also a lot of misinformation. At least nobody disputes that Ka band is important for the continued health of the satellite communications industry, by increasing both capacity and flexibility, while reducing costs. Ka band operates in the 26.5GHz to 40GHz frequency range, higher than the preceding C and Ku bands, opening up previously unused spectrum for communications. This overcomes the physical constraint on satellite capacity resulting from the fixed number of slots available in geostationary orbit. Ka band satellites can be positioned alongside existing C and Ku band satellites without interference to increase throughput.
Also, crucially, the higher frequencies enable faster communications at bit rates up to 20Mb/s, which in many locations is competitive with fixed broadband services. The higher frequencies also enable the size of the receiving dish to be reduced for a given level of performance. A 65cm Ka system is about equal in transmission capacity to a 1.2m Ku system, which translates into a big savings on the ground while also reducing the level of visual pollution.
But there is one drawback, and it is on this count that we start to run into the misinformation. This is the rain fade issue, since water absorbs electromagnetic radiation more strongly at the higher frequencies of Ka band. In wet weather, Ka band transmissions can suffer from delay as a result of dropped packets having to be resent, and this has led many to conclude that Ka band is much better suited to broadband Internet than broadcast TV. Such sentiments would come as a surprise to DirecTV and Dish Network, which have both been beaming TV over Ka band for several years right across the U.S. That includes states such as Florida and Louisiana, where torrential downpours do occur.
The fact is that Ka band does suffer from rain fade, but operators have gotten around this by developing more advanced FEC to reduce packet loss, coupled with techniques such as MPEG CoP3 FEC, developed by the ISO MPEG Working Group, to correct for the few packet losses that still occur. In any case, satellite platform operator Eutelsat has conducted tests on Ka band backed up by these techniques and found that its packet loss rate during rainy conditions is now virtually as low as for regular Ku satellites. So the rain fade issue is now rather a red herring.
The actual reason Ka band has not been used much in Europe for TV is that there is still plenty of capacity left in the Ku band, so there has been little demand for it from DTH operators. The situation in the U.S. was different because of the obligation upon DTH operators to transmit local channels across the whole country.
The U.S. is split into 210 local regions defined by Nielsen, the media measurement company, as designated market areas (DMAs), each one with separate local channels. DTH operators faced having to transmit all the local channels to the whole county, even though only people within one DMA would want to watch a given channel, so this was a highly inefficient use of capacity. However, Ka band supports spot beams more readily, which meant that DirecTV and Dish Network could serve local programming to all 210 DMAs with much less spectrum, reusing the same frequencies for successive spot beams each aimed as just one DMA.
This situation has not arisen in Europe, where there are a number of smaller countries, each with just a handful of regions. In that case, DTH operators can conveniently pack all the local channels into their multiplex and not worry about using spot beams to reuse spectrum. For Europe, therefore, Ka band is only likely to figure for TV when perhaps Ultra HD services come along with much higher spectrum requirements, when Ku capacity is likely to run out.
It is a different story though for broadband Internet, where Ka band is seen in Europe as having a crucial role in bridging the digital divide by making 20Mb/s available download, and around 6Mb/s upload, to homes outside the reach of cable TV or sufficiently fast DSL services. Depending on which analyst you believe, that amounts to about 20 million households in Europe, which includes both the “unserved” market comprising homes that have no broadband option at all, and the larger “underserved” market where service is available but not fast enough to deliver HD TV services. This brings us to the point that the distinction between TV and broadband has effectively ceased to exist, since increasingly the latter is used to deliver the former via OTT. Demand for higher broadband speeds is largely being driven by video these days.
At any rate, consumer broadband is the biggest driver for Ka band in Europe now, but an important related one is the home office market for professional IP services. People increasingly want to be able to work from home and also sometimes locations where they can stay in touch while on vacation, which is often quite remote places with no fast fixed broadband available.
Another fast-growing market is mobility, since satellite can be the only viable broadband option for ships, airplanes and trains, which will often be beyond the range of cellular services. Of greater interest though for broadcasting is the growing use of Ka band for satellite newsgathering. This is exploiting Ka band’s smaller dish size for a new generation of lightweight equipment, as in Eutelsat’s NewsSpotter service. This gives broadcasters and service providers the ability to transmit live HD or SD video from the field with fast set up within minutes. It is small enough to be fitted onto a small car for rooftop mounting and is capable of connecting mobile news crews to studios for transmission of live recordings, images and data.
So although Ka band may not be used for traditional DTH broadcast in Europe, it is finding plenty of application elsewhere in the TV and video ecosystem.
— Philip Hunter is a technology journalist specializing in the business and delivery of video and digital entertainment.
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