But we also believe that the 700 will be good for a lot of those existing rural broadband sites and we will be adding those in over the next five years.
1800MHz will be our capacity layer and in predominantly urban areas. And the 700MHz spectrum will be a nation-wide coverage layer. We also have 2600MHz and that will be predominantly used for small cells and urban hotspots. So between now and the next 18 months, expect to see carrier aggregation dual band and tri-band. Tri-band aggregation will bring together 2600, 1800 and 700 and that's when you start talking about 500MBps to the device or more capacity for multiple users.
We are starting to see a re-farming of other spectrums across the world. Vodafone has other spectrum holdings. We have 5 blocks of 2100Mhz. Some of that could and would be freed up for 4G, and likewise, you have seen in other parts of the world 900MHz, 2100MHz and TDD 2300. So there are lots and lots and lots of blocks of spectrum that we own that we can ultimately group for 4G.
You will be seeing the vast majority of our spectrum holdings being used for 4G.
Q: When are we likely to reach 100 per cent national coverage with 4G? What are the challenges you encounter in ensuring that?
TB: The probability of us getting 100 per cent population coverage with existing terrestrial-based, cellular-based technology is unlikely. The probability of us getting to 99 per cent population coverage is achievable. The last 1-2 per cent is going to be very difficult in NZ because of population density.
But there are other technologies. For instance we have been testing and have available small cell sites with satellite. We could put in a satellite uplink and have a small cell off that. We will be doing that for spot coverage and also for emergencies, when they need coverage at short notice. We can get to 100 per cent coverage by using other backhaul technologies like satellite.
The limitations to having a 100 per cent would be the geography of NZ, power supplies, wind power, solar power. We have done a site in Great Barrier Island which is all green power. But that cost half a million dollars for the infrastructure alone leave alone the tower and — this was just electricity, batteries, wind, solar all of that cost a significant amount of money. You need to see that green energy costs for power coming down for these far remote sites.
For the furthest reaches of the network we use satellite, then we start using microwave. But with microwave you don't necessarily get the same bandwidth over long distances in a rural environment as you would in a city.
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