Wireless Waffle - A whole spectrum of radio related rubbish
Goldilocks and the ITUsignal strength
Saturday 15 February, 2014, 14:01 - Spectrum Management
Posted by Administrator
When Goldilocks visited the house of the three bears, she tried their porridge and found one bowl too hot, one too salty but the third one just right. It seems that the ITU may have employed Goldilocks to help them put together their forecasts for mobile spectrum demand. Why? Read on...

esoa logoLeafing through the various responses to Ofcom's mobile data strategy consultation, one particular response raised more than an eyebrow. The response from the European Satellite Operators' Association (ESOA) points out that the model used by Ofcom to calculate the demand for spectrum for IMT (mobile broadband) services has a great big, whoppingly large, error in it. The model is based on that of the ITU which and is snappily titled 'ITU-R M.1768-1'. It was originally used at the 2007 World Radiocommunication Conference (WRC-07) to set expectations on how much spectrum would be required for mobile broadband services up to, and including, the year 2020.

At the time (2007), the ITU model predicted that by 2010, between 760 and 840 MHz of spectrum would be needed for IMT services. In reality, in most countries, little more than 400 MHz was actually available. And yet, ironically, the amount of data traffic being carried was far in excess of that which the ITU predicted. Not deterred by this apparent flaw in their logic, the model has been updated this year and a new set of results published. These new results show a demand for spectrum by 2020 of between 1340 and 1960 MHz.

real wireless logoWhat ESOA have spotted, is that if you apply the traffic densities which consultancy RealWireless have assumed in their work for Ofcom, or those developed by the ITU, the resulting total traffic for the UK would be orders of magnitude greater than the actual traffic forecasts. Figures 40 and 44 of their report clearly repeat these errors. The ESOA consultation response illustrates it quite nicely, as follows:

Traffic Density
Urban21030 - 1006300 - 21000
Suburban419010 - 2041900 - 83800
Rural2386000.03 - 0.37160 - 71600
Total23400055360 - 176400

What this shows it that the total monthly traffic for the UK, as calculated from the RealWireless traffic assumptions is between 55,360 and 176,400 PB (Peta Bytes) per month. Compare this to their traffic forecasts which show the total UK traffic reaching around 1000 PB/month by 2020 even in the 'high market setting' in the chart below.

realwireless traffic predic
Source: Figure 40 of 'Study on the future UK spectrum demand for terrestrial mobile broadband applications', 23 June 2013

So if the ITU and Ofcom models assume traffic levels of 100 times greater than reality, why is the resulting demand for spectrum which it outputs in line with many other industry predictions? Without digging deeply into the model (which is immensely complex), it's difficult to say, but it stands to reason that there must be some assumptions that have been 'adjusted' to make the results seem believable - fiddle factors as they're normally called.

goldilocks and the ituThis is where Goldilocks comes in:
  • If the ITU model produced a result which said that 20,000 MHz of spectrum was needed for mobile broadband by 2020 (which it ought to given the high data traffic it is trying to model), no one would believe it - too hot!
  • If it had said that 200 MHz of spectrum was needed it would equally have not been believed - too salty!
  • But as it produces a result around 2000 MHz it is seen as just right!
As the traffic forecasts are so far out, there must have been some tweaking of the fiddle factors to get the believable response. The model must be fusing the ridiculously high values of traffic with some other ridiculous values to produce the seemingly reasonable answer it does - there's no other logical explanation. Of course, it is in ESOA's interest to find a way to reduce the demand for mobile spectrum and take pressure off the push to use satellite spectrum (L-Band, S-Band and C-Band) for terrestrial mobile services but nonetheless, their logic in questioning the model seems sound.

Indeed the ITU themselves seem to recognise that there is some fiddling going on in a note they provide hidden deep in the annexes in their paper entitled ITU-R M.2290-2014 which says:
The spectrum efficiency values ... are to be used only for spectrum requirement estimation by Recommendation ITU-R M.1768. These values are based on a full buffer traffic model... They are combined with the values of many other parameters ... to develop spectrum requirement estimate for IMT. In practice, such spectrum efficiency values are unlikely to be achieved.

charlie eppes numb3rsWhat a 'full buffer traffic model' is, is anyone's guess but it seems to suggest that this factor, and others, may not be values that mobile operators or anyone else for that matter, would recognise. The problem with any complex model of this type is that it is difficult to understand except by the academic elite that prepared it (or by Charlie Eppes on Numb3rs), and equally difficult to sense-check. It seems that the sense checking has not taken place and what is left succumbs to the old computing law, "garbage in = garbage out". Many countries have done their own calculations and in many cases these have shown smaller figures than those espoused by the ITU, some have shown higher figures. Where such figures are based on the ITU model itself, they should, of course, now be taken with a very large pinch of salt.

verizon wireless logoTo take a real life example, Verizon Wireless in the USA claimed in June 2013 that:
57 percent of Verizon Wireless’ data is carried on its 4G LTE.

Putting this in perspective, Verizon has around 40% of the US market and is using just 20 MHz of spectrum for its LTE network. This means that with an LTE network using 5 times as much spectrum (i.e. 100 MHz), it ought to be possible to carry the whole of the US's mobile data traffic today. Allowing for growth in data traffic of 33% per year (a figure which both Vodafone and Telefonica have cited as their actual data growth in 2013), and by 2020 the US would need a total of 740 MHz of spectrum for mobile data, a far cry from the 1960 MHz being demanded by the ITU. And the 740 MHz figure does not take into account any additional savings that might be realised using more efficient technology such as LTE-Advanced.

The inexorable growth in demand for mobile data is not in question, though at some point it will become too expensive to deliver the 'all you can eat' packages that people expect. Who is going to pay US$10 to download one film on their mobile when the subscription to Netflix for the whole month is less than that, and they could use their home WiFi and do it for next to nothing? What is now in question is how much spectrum you need to deliver it. Maybe a good starting point would be to stop where we are and wait a few years for things to settle down, and then see what the real story is. Maybe Goldilocks will have run into the forest to hide from the ITU, and a new bowl of porridge will have been made that tastes a whole lot better.
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"London to be underwater by 2019" says eminent scientistsignal strength
Tuesday 11 February, 2014, 19:09 - Much Ado About Nothing
Posted by Administrator
Given the current extreme weather battering the UK, the time seemed very apt to give a plug to an excellent novel whose plot-line is chillingly familiar.

flood - stephen baxterFlood by British hard-fiction author Stephen Baxter begins with the River Thames flooding in London and leads to a tale of global catastrophe. The follow-up, Ark, continues the story as the human race battles for survival.

The hard-fiction genre of books aim to use existing scientific theories but weave them into a piece of fiction. They're not about visits from aliens, or interstellar war, but instead focus on 'what might happen' by developing current scientific thinking. At the end of many stories, the author will divulge which bits of the book are real and which are made-up - and the bits that are real are often more incredulous than the fictitious bits.

If you have never read a science fiction book of any kind, Steven Baxter's books come highly recommended by Wireless Waffle and in many cases may not remain fiction for that much longer!
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90 years of the 'time pips'signal strength
Friday 7 February, 2014, 13:43 - Broadcasting, Licensed, Much Ado About Nothing
Posted by Administrator
What a disappointment it was to find a recording called 90 years of the time pips, to discover that it is a special version of the pips¹ designed to celebrate their 90th birthday.

Wouldn't it have been more fun to have calculated how many pips there have been in 90 years and then created audio that just pipped (or beeped continuously) through all 90 years? How many pips would that be?

90 years × 365.25 days × 24 hours = 788,940 hours²

The first 5 pips have a duration of a tenth of a second, and the final pip has a duration of half a second, so the total duration of the pips each hour is exactly 1 second (5 × 0.1 + 0.5). A constant tone of duration 788,940 seconds (which is 9 days, 3 hours and 9 minutes precisely) would therefore represent '90 years of the time pips' much more accurately.

So here for your listening pleasure, is the Wireless Waffle tribute to the pips... 90 years of pips compressed into 9 days, 3 hours and 9 minutes.

play 90 years of the pips
Just click the play button, sit back and enjoy!

gladys knight and the pips¹ Not to be confused with Gladys Knight's backing group who, whilst also played on the BBC from time-to-time, are not the pips in question here.

² Of course the pips have not been broadcast every hour over that period. Other time signals (such as the chimes of Big Ben) are used on some hours. Equally the BBC has not always been a 24 hour service, so this figure is probably a significant over-estimate.
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Local TV test transmissions on-airsignal strength
Wednesday 29 January, 2014, 11:01 - Licensed
Posted by Administrator
It's a surprise that there haven't been more reports of this, but it seems that the Local TV services licensed by Ofcom last year are beginning to come online. The video clip below shows test of one of the two national channels that will be operated by Comux (to try and generate enough profit to run the transmitters) as received in Clacton, Essex. The signal comes from the Crystal Palace transmitter in London.

There doesn't yet seem to be placeholder for London Live which will launch in the capital in March on channel 8 on Freeview, but the two national channels awaiting launch and currently sat on channels 791 and 792 so you can check whether you will be able to receive it (a re-tune may be necessary).

The first of the new raft of local TV stations on the air was Estuary TV in Grimsby, whose transmitter also does a pretty good job of covering nearby Kingston-upon-Hull.

Wireless Waffle previously reported on the lessons to be learnt from the failed attempts at local TV in the UK in the past, and on the uncanny similarity between Comux (the local TV network operator) and Arqiva (who are providing the transmitters to Comux.

There are still a large number of local TV transmitters to be put on-air, so keep checking your set-top-boxes for new channels. Oh, and whilst you're at it, see if you can get the additional Freeview HD multiplexes that have quietly launched around the UK providing such excitement as BBC4 HD and Al Jazeera HD. Why couldn't they have put something useful in HD such as Dave or Film4?

You can check the channel line up on Freeview at your location by using the handy form below.

Your Postcode
House Number or Name
(Providing a house name or number is not essential but makes your results more accurate)

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