Wireless Waffle - A whole spectrum of radio related rubbish
Grotesquely Skewed Mathematical Analysessignal strength
Friday 22 May, 2015, 07:48 - Spectrum Management
Posted by Administrator
You may remember in this very month of last year, that Wireless waffle reported that various studies concerning the demand for radio spectrum for mobile services were replete with rather significant and obvious mathematical errors. It seems that these types of error which serve to highlight the poor plight of the mobile operators and their search for new spectrum may be systematic. This time it is the turn of Frontier Economics and their studies 'Economic assessment of C-band reallocation in the Arab States region' and 'Economic assessment of C-band reallocation in Africa'.

In them, they try and calculate the price of spectrum in a number of countries by considering the differences between the population density, average revenue per user (ARPU) and 3G penetration with a benchmark value derived from the price paid at auction in other countries. So where have they gone wrong?

feeding ducksImagine you are trying to calculate the overall appetite for bread to some ducks in a pond. The data you have tells you the density of ducks in the pond, the preference of the ducks for bread, and the area of the pond. Clearly:
  • if the density of ducks increases, the appetite for bread will increase in direct proportion (that is to say that if the density of ducks doubles, then the appetite for bread will double);
  • if the preference of the ducks for bread increases, similarly the appetite will increase in direct proportion, and
  • if the area of the pond increases, the appetite for bread will increase, and again it will be directly proportional.
If you want to take all these factors into account to determine the overall change in appetite, you just multiply them together. So if the density of ducks doubles, the preference for bread doubles and the area of the pond doubles, then the appetite for bread will increase by 800% (200% x 200% x 200%). And as a check on this logic, then if any of the factors is zero (i.e. there is no pond, no ducks in the pond, or the ducks don't like bread), then their appetite will be zero. Check!

So it may come as a surprise, that in their studies, Frontier Economics consider a similar set of factors but instead of multiplying them together, they average them as page 16 of their report on Africa demonstrates:
We first calculate the country's population density, 3G penetration rate and ARPU as a percentage of the auction sample's average population density, 3G penetration rate and ARPU respectively. We then take a simple average of these three proportions to obtain the final adjustment factor.

frontier calculationsSo if the ducks have the same preference for bread as the benchmark (e.g. the 'auction sample') and are just as densely packed, but the size of the pond is zero, the overall appetite should, of course, be zero. But if these factors are averaged, the result will not be zero. The average of 100%, 100% and 0% is... oh, come on now, the maths is pretty easy... 66%. Therefore, according to the economists at Frontier, the appetite for bread by NO ducks, is two-thirds of the benchmark value. And if the density, preference and area of the pond double and thus (as shown above) the appetite should increase by 800%, Frontier would no doubt claim that it only increases by a factor of 200% (the average of 200%, 200% and 200%, as it goes).

Of course there is an argument to say that the factors that the report is trying to apply are not mutually exclusive so that multiplying them is not the right approach. But whatever the right approach is, taking the average is unlikely to be one of them.

frontier comic onesMaybe Frontier Economics flunked the statistics module in their maths exams. This would tend to be hinted at by the slogan on their web-site:
We hope you'll find us a little different

What they mean by 'little' and 'different' may, of course, be in themselves a little different from someone else's understanding. Alternatively, the fact that they were being paid to do the calculations by the GSMA meant that they did them in a way that was 'a little different'. In either case a little different would seems to mean 'a little wrong'. So how does their slogan read now?

Whatever the cause, it seems that the mobile industry is replete with regulators, consultants and industry bodies who have forgotten how to use a calculator properly. As for the GSMA who should surely have checked for such glaringly self-evident miscalculated averages before publishing the reports, perhaps grotesquely skewed mathematical analyses are to their taste?
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How Not To Install A Satellite Dish (Part II)signal strength
Saturday 16 May, 2015, 15:38 - Satellites, Much Ado About Nothing
Posted by Administrator
In the last instalment of 'How Not To Install A Satellite Dish', we successfully installed and aligned a new satellite dish to point at 19.2 degrees East so as to be able to receive German language television (and a few French channels to boot). The next job was therefore to connect the new dish, and the old dish, to the satellite receiver so that the same receiver could be used to switch between the German channels and the English language channels received through the existing, and separate, dish pointing at 28.2 degrees East.

Thankfully this does not (should not!) require the fitting of an additional downlead from the dish to the receiver, oh no. A system called DiSEqC (apparently pronounced 'die-seck' though in reality it should be pronounced 'diss-equck') comes to the rescue. This allows the receiver to select from multiple dishes connected on the same cable by sending control signals along the cable. All that is required is that a suitable DiSEqC switch is installed at the satellite end, connected to both dishes, and to the cable from the receiver.

2 way sat switchA 2 way sat-switch was duly purchased and installed as per the instructions. Back at the receiver (a trusty Foxsat HDR - though the original model, not the new one being sold now on Amazon), the secret menu that allows access to funky multi-satellite functions was accessed (by going into the Setup menu, then pressing red, green, yellow, blue, green, yellow and then blue in that order - or 🌑🌑🌑🌑🌑🌑🌑). Selecting 'DiSEqC 1' from the pull-down menu duly yielded signals from the original 28.2E dish. However, none of the other four DiSEqC inputs yielded anything from the 19.2E dish. Swapping the feeds at the dish end meant that channels from the 19.2E dish could be found on 'DiSEqC 1' but no signals from the 28.2E dish could be found on any setting. Grrr...

4 way sat switchThe DiSEqC settings in the receiver had four channels (e.g. 1, 2, 3 and 4) but the switch only had two. Could this be the problem? Only one way to find out, and so a second switch, this time a 4 way sat-switch was bought (which oddly is cheaper than the 2 way switch at the time of writing!) The original (28.2E) dish was duly connected to input 1 on the switch and the new 19.2E dish was connected to input 2. And guess what - this time success. Now the receiver would find signals from both satellites on the appropriate DiSEqC settings on the receiver.

It is unclear whether this was due to the fact that the first switch was faulty, but as the 4-way switch is (currently) cheaper than the 2-way switch, then anyone attempting this exercise might like to consider just getting the 4-way device to start with and thereby circumventing the tedious hours of failure that might otherwise present themselves.

freesat foxsat menuAnd so now, by switching the Foxsat receiver out of 'Freesat' mode, it was possible to access a wide range of German channels (and the UK ones) but without the help of the Freesat programme guide. Switching back to Freesat mode returned the box to the standard Freesat channel line-up and the programme guide. But surely there must be a way to add the German channels to the Freesat channel menu so that there's no need to go faffing around with multicoloured buttons in the settings menu to switch between them? Actually, there is and at least that part of the job went relatively easily, so stay tuned to Wireless Waffle for Part III of 'How Not To Install A Satellite Dish'...
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Adjø FM Radiosignal strength
Tuesday 28 April, 2015, 15:58 - Broadcasting, Licensed, Spectrum Management
Posted by Administrator
norway wave goodbyeThe Norwegian Communications Authority (NKOM) recently announced that FM radio is to be closed-down in Norway by the end of 2017. The closure will begin at the north of the country, and spread southwards. National broadcaster NRK will wave goodbye to FM radio first, followed by major commercial broadcasters. Some smaller, local broadcasters, will be allowed to continue broadcasting on FM but the rest will continue only on DAB or on other digital platforms (such as television or online).

The switch-over in Norway, follows a similar logic as that used by Ofcom in the UK (as previously discussed by Wireless Waffle). There are a number of specific criteria that the Norwegian government said had to be met for the switch-off to occur:
  • NRK's digital services have to have the same coverage as their FM service, and national commercial services need to cover 90% of the country.
  • There has to be an affordable solution for listening in cars.
  • At least 50% of listeners have to be listening to digital radio every day.
The regulator claims that these targets have been met but broadcaster claim that they haven't. The Norwegian Local Radio Association claims that only 19% of listeners use DAB and that other 'digital' listening is through other platforms. They also argue that an 'all digital Norway' would mean that any tourists driving from a neighbouring country who don't have a DAB radio would be unable to receive local traffic and weather information and that this could prove dangerous. Of course, if those tourists hired a car in Norway, presumably this problem would not occur.

radio snowBroadcasters also fear that driving people away from FM onto, for example, online radio would open up a much wider world of competition from the likes of Spotify. In this respect, FM radio represents a way of limiting listener choice and reducing competition so it is perhaps no wonder that broadcasters are keen to ensure the longevity of the medium.

Norway was one of the first countries to complete the switch from analogue to digital television and is no doubt hoping that it's bold decision to close FM radio will give it similar kudos. However there were good reasons for a digital television switch-over, including the greater choice and higher quality recption that digital offered and, perhaps most importantly from the perspective of the regulator and government, the ability to free up some radio spectrum which could then be sold of to mobile operators for lots of money. Wireless Waffle estimates that the sale of the digital dividend spectrum in the auction that took place in 2013 raised around GBP75 million, which is not that much compared to the very large prices paid in other countries.

nkom trailblazingThe FM band is a different proposition though, because other than for radio broadcasting, there are no other (harmonised) uses for the band. It could be used for mobile radio (e.g. walkie talkies) but there aren't any available that operate in that frequency range. It could be used to extend the aeronautical band (which begins at 108 MHz). It could be used for some, as yet uninvented wireless service. But unless neighbouring countries (and the local FM broadcasters in Norway who continue to use the band) also switch off their transmitters, the levels of interference from these stations would be too high to make the spectrum of any real value.

So what is the real benefit of switching to digital? For Norway, perhaps, a chance to be a trailblazer. For any other country, perhaps none at all.
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Polar Foil - virtually not antennas at all?signal strength
Wednesday 1 April, 2015, 11:01 - Spectrum Management
Posted by Administrator
It is almost a law of physics, that the best way to increase the coverage of a transmitter is not simply to turn up the power, but better still to increase the height of the transmitting antenna. Wireless Waffle has discussed the relationship between height, power and coverage before. It is, however, almost a law of nature, that increasing the height of an antenna through building a taller mast will incur the wrath of residents and environmental protestors and as such, there is a political limit to just how high antennas can be mounted.

birds antennaWouldn't it be great if someone invented invisible, or nearly invisible antennas? One option might be to use atom thin superconducting graphene tubes that were self-supporting but so thin as to be virtually invisible. The only downside of such an antenna would be that any bird that flew into it would be immediately sliced in two as the antenna would have almost infinitely sharp edges.

Another option could be to use multiple beams to project and focus energy at a specific point to materialise a virtual antenna. If force (thrust) can be generated by electromagnetic waves in an EmDrive, then could a similar principal be used to project an antenna at a point away from the source of the physical beams? This far-fetched idea is being considered by Professor Nisan Sakasi at the Communications and Spectrum Management Research Centre at the University of Bilkent, in Turkey.

By focussing very narrow microwave beams which cross in a specific quadrifilar pattern, the air atoms at that point can be ionised to become electrically conductive and with careful tuning,quadrifilar radiation can project a virtual antenna at a point separated from the microwave transmitters by several metres. Professor Sakasi has called the antennas 'polar foil', because the area where the virtual antenna is formed, if viewed from polar angles, glints a little like aluminium foil. Of course at night they are completely invisible.

The difficulty for the team at Bilkent is now to find a way of feeding the polar foil with RF energy so that it can actually radiate useful signals. The team believe that with the right beamforming, a 'virtual feeder' could also be created permitting injection of RF signals from a lower point. A secondary problem is that the amount of electricity needed to feed the microwave transmitters which generate the polar foil is 'in the region of kiloWatts', meaning that the power required to form the virtual antennas is currently far more than that required to generate the radio signals that would feed into them.

The advantages of such a system is that, with tighter beamforming, it may be possible to generate the polar foil not just metres away from the microwave transmitters but tens of metres away. As such, antennas could be virtualised far above the ground, without the need to build masts at all. The fact that the antennas are virtual, and not real, means that problems like slicing a bird in half as it flies into the antenna are virtually unreal and thus no damage would be caused.

A spokesperson for the Royal Society for the Protection of Birds, told Wireless Waffle that:
We are very concerned about the idea of superconducting graphene antennas being erected across the country, however we think that many birds would like the idea of a network of virtual feeders!

polar foil beams
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