Hi Beecart, i'll try and answer as best I can although I'm not an expert. I am technical, but I don't work as a transmission engineer.
Originally Posted by beecart:
“Which network offers the most resilient 2G and 3G coverage and why ?”
This is difficult to answer as it varies across the country and really the best network is the best network for an individuals circumstances.
Vodafone and O2 are both extremely strong for 2G. Three is very good for 3G, but when you don't have it you may not get any 2G, also you may notice more dropped calls on Three, It's a much better data network, but a slightly weaker call and text network. Value wise it's a good choice and so is Giffgaff but for different reasons, for example giffgaff if you just want calls and texts and good 2G coverage and aren't too bothered about high speed reliable data outside of towns and cities.
Originally Posted by beecart:
“What are your thoughts on 3G 900 utilised by O2- will this just mean capacity gets reached quicker or not ?”
I think it's a good thing, it will mean that they have a much grater 3G coverage area without having to put in a lot of new cell sites. They need a lot less masts than Three to achieve the same result.
As for the capacity, it may be the case that they have less capacity if they have less cells per area as each cell has a microwave dish or a fibre connection, that will be a congestion point and if the cell is serving an area potentially twice as large as Three then there could be a capacity issue. However the benefit is much greater 3G coverage even in rural areas if they invest. If they put extra cells in just for capacity then it could be a brilliant solution. 900Mhz 3G meaning brilliant 3G coverage, lower capex and then add extra sites in cities for capacity (they probably have these anyway).
At those frequencies it also cuts in to buildings much better. If O2 do it right it could be a rock solid 3G network, same with Vodafone.
Originally Posted by beecart:
“Why doesn't 3g want to be a tall mast ? What's the technical reason ?
Thanks”
Because 3G on Three / T-mobile etc always uses 1800 - 2100 Mhz and around 32 dBW or less, it will only cover a few mile radius at best. So you want only want it to be just over roof height because there will be other cells in each direction within a few miles to cover the neighbouring areas.
If you put it too high then potentially it could interfere with cells further away that are high up and actually reduce coverage due to frequency clashes. The whole 3G design is based upon re-using frequencies over and over in a honeycomb cell structure, and you only want to cover things within a certain locality, the plan isn't to put it as high as possible, it's to only cover a specific zone and then you get handed off to your cell neighbours as you move from one to the next.
Frequencies are re-used over and over throughout the network and need to be as clear as possible. Very high cells are more likely to interfere.
Cell handoff works by your phone constantly monitoring what cells it can receive and measuring the signal of each cell it can see, it reports this to your active cell. When the netowrk MSCs see a cell that you would be better suited to it will organise a cut over to the new cell, all this is done with no call interruption.
If lots of 3G cells were all on high structures the reception as you move around would be all over the place, signal levels with be max one second and then gone the next and the result would be more dropped calls. 3G is more about lower cells and more localised coverage areas.
However in rural flat areas there are cases for putting 3G on higher structures and I think that makes a lot less difference.
If there are any network engineers that read this forum feel free to confirm or correct, but that's the way I understand it.