Monday 21 April, 2014, 19:34 - Spectrum Management
Posted by Administrator
Following the recent Wireless Waffle piece on Valles Marineris sized chasm in the values used by the ITU in predicting the demand for IMT spectrum in 2020 spotted by the European Satellite Operators Association in their response to Ofcom's mobile data consultation, others have noted similar gulfs. Posted by Administrator


Wireless Waffle has been able to get hold of a copy of the 'Speculator' and so exclusively for you, here are some of the values that are causing people such as ESOA, Mr Farrar and the EBU such consternation:
Parameter | Current Value | Notes |
---|---|---|
Spectrum Efficiency | For GSM/UMTS/LTE: 2 to 4 bits/second/Hz/cell. For LTE-Advanced: 4.5 to 7.3 bits/second/Hz/cell | These look like highly aspirational values! |
Call Blocking Rate | 1% | This represents the chance of not being able to make a call (i.e that there is a 99% chance of success). |
Population Density | Maximum of 222,333 per sq km | This occurs in 'SE2, SC12' which equates to interactive high multimedia use in offices in dense urban areas. |
Mean Service Bit Rate | SC6 (streaming super high multimedia): Up to 1 Gbps SC11 (interactive super high multimedia): Up to 1 Gbps | Really? 1 Gbps on average! |

A mean (average) service bit rate of 1 Gbps seems excessively excessive. If this was the peak service rate then, maybe, just maybe, this would be possible (and only possible on LTE-Advanced networks, not on the others). But to assume that it is an average seems just crazy.
Of course the big question is, what would the 'Speculator' say, if the values input to it were more realistic? To try and answer this question requires some kind of estimation of what realistic actually means. Whilst we make no claims for the realism of any of the values proposed below, here are some alternative values...
Parameter | New Value | Notes |
---|---|---|
Spectrum Efficiency | For GSM/UMTS/LTE: 0.55 to 1.5 bits/second/Hz/cell. For LTE-Advanced: 1.1 to 3 bits/second/Hz/cell | The values for LTE-Advanced are taken from the ITU's own Report M.2134. Those for GSM/UMTS/LTE are half the LTE-Advanced values (roughly in line with the original ratios). |
Call Blocking Rate | 2% | A value that more operators would recognise. |
Population Density | Reduced so that the weighted average values are the same as those in the ESOA report for the UK (e.g. ~11000 per sq km in Urban areas). | This should mean that running the ESOA calculations would at least yield the correct population for the UK. |
Mean Service Bit Rate | Capped at 100 Mbps. | Seems a little more reasonable based on the technologies likely to be in use by 2020. |
The big question is obviously therefore, what does this do to spectrum demand? The original and revised figures are shown in the table below.
Setting | GSM/UMTS/LTE | LTE-Advanced | Total | |||
---|---|---|---|---|---|---|
Original | Revised | Original | Revised | Original | Revised | |
Low | 440 MHz | 580 MHz | 900 MHz | 480 MHz | 1340 MHz | 1060 MHz |
High | 540 MHz | 660 MHz | 1420 MHz | 600 MHz | 1960 MHz | 1260 MHz |
What does this tell us? Oddly, in both cases, the demand for GSM/UMTS/LTE spectrum has increased. This is probably due to the lower spectrum efficiency that these technologies have been assumed to achieve. Conversely, the total spectrum demand has dropped significantly and all of this reduction has come from spectrum for LTE-Advanced.
But what is most striking about these calculations is not necessarily the differences in the results, but the simplicity with which it is possible to present alternative values and find a different outcome. For example, no effort has been made in the above analysis to check the way in which the ITU model apportions traffic between the 2G/3G networks and the LTE-Advanced network. Could, for example, it be argued that by 2020 major carriers in advanced markets (e.g. USA) will have moved all of their data traffic to LTE-Advanced and that only 2G will remain for legacy voice services.

The fact is that any model of this kind, no matter how many brains were employed in developing it, can never be more than a 'best guess', especially when looking 7 to 10 years into the future. Weather forecasters struggle to predict the level of precipitation 7 to 10 days into the future and no-one in their right mind would decide if they needed to carry an umbrella a week next Tuesday based on their forecast. Nor should the vast wireless community take decisions based on this one forecast, it would be irresponsible of them to do so and if the weather changes, they may end up getting soaked!
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