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Mobile Spectrum Demand: The Last Word?signal strength
Sunday 31 August, 2014, 12:28 - Spectrum Management
Posted by Administrator
Yet another challenge to the seemingly overinflated forecast demand for IMT spectrum has been raised. This time, a paper entitled, 'Overestimating Wireless Demand: Policy and Investment Implications of Upward Bias in Mobile Data Forecasts' which has been written by Aalok Mehta of the University of Southern California and J. Armand Musey of Goldin Associates.

http   www allbum it  zager evans in the year 2525 2Rather than do the maths on what their paper says, Wireless Waffle thought that it might be better to take a different approach and try and estimate how much spectrum may be needed in the far future, say in the year 2525. How much data could each person possibly consume? If it is assumed that each person lives in a totally immersive environment where there visual, audio and maybe even sensory experience is completely connected (a bit like a man-made version of The Matrix!) the question is how much data would this take?

There are three things to consider:
  • Firstly how much data is needed for such an immersive experience;
  • Secondly, how much progress will have been made on the various audio and video codecs which squish the raw data into a more manageable form; and
  • How spectrally efficient will the mobile technology be?

Video is currently the main bandwidth hog and whilst touch, feel and smell may turn out to be equally hungry for connectivity, let's focus on the video requirements first. If it is assumed that 3D video using ultra-high definition is required, today this would require a connection of 40 Mbps or faster. With improvements in coding technology, this could easily drop to 10 Mbps. If audio and other sensory data (including any personal machine-to-machine communications detecting, for example, heartbeat, ambient temperature and so on) doubles this, then a working assumption that a constant 20 Mbps of connectivity would allow a fully immersive experience would seem about right.

Finally we need to think about spectrum efficiency - how much spectrum would be needed to deliver this 20 Mbps. Current technologies such as LTE can deliver many bits per second per Hz of spectrum but performance becomes worse the futher away from the centre of a cell a user is. The ITU's model uses values of up to 5 bits per second per Hz in a 2020 timeframe, though other forecasts show values ranging from 2 to 15. By 2525, it ought to be possible to at least achieve the 5 bits per second per Hz value that the ITU forecasts is feasible by 2020, even as an average across a cell, and even those at the edge of coverage. This means that (whilst awake and living in the immersive environment) our mobile subscriber of 2525 would require around 4 MHz of spectrum dedicated to their sole usage.

How much spectrum is needed is therefore simply dictated by how many simultaneous users there are in each cell. Looking at this from a different direction, with around 1 GHz of mobile spectrum (not that different from the amount available today), 250 users could be supported in each cell. This seems perfectly realistic. Of course this amount of data would not be required by anyone who is asleep, and those at home or in an office could surely connect to the WiFi of the future and offload their data to an alternative service so 250 users per cell does not seem unreasonable.

So... even in a futuristic world in which everyone is immersed in a fully interactive environment for every waking hour, given developments in technology, 1000 MHz of spectrum dedicated to mobile networks seems sufficient. This result ties in with an interesting result posited by the Australian spectrum regulator ACMA in its report 'Towards 2020 - Future spectrum requirements for mobile broadband' (Figure 4.3) which indicates that spectrum demand may decrease in the future as the spectrum efficiency of newer technologies and improved coding techniques outpace the exponential growth in demand for data.

It therefore seems possible that we are going through a period in which spectrum demand for mobile broadband is at its peak as we phase out older mobile technologies and bring in the new and that in the long-term future, the amount of spectrum already available today will be enough to meet requirements. With this (albeit rather simplistic) analysis, we can now close the door on all the debate over spectrum for mobile services and instead focus on something more interesting...
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