Also how many smart phone are connect to the same antenna plays a role on speed too.
I am a vendor and I travel all over working at fairground. In early morning or late at night when fairground is quiet, I can get my email or surf website or use data on my phone like Video Phone with excellent speed throughout.
But during the busiest hours where there thousands of people mean at the fairground which mean there 2x thousands of smart phones (remember is not only adults but also their children have smart phone now days) and I barely get any data traffic or surf the web sites take 100x longer to load but cannot use Video Phone at all period. Reason is because there too many smart phone tying up the antenna on one same tower.
So your Video Phone performance may varies depending on the time of the day, if there lots of active smart phones connect to the same tower antenna that your smart phone are connected to then you will see a poor performance hit even on 4G.
I had smart phone for many years now and as the year process I notice more and more performance hit when more people are using popular social sites like FaceBook or Google+ to share thousands of photo which mean thousand of photo uploading daily in the background.
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