Does gateway use only primary or only secondary or both.

dilbert wrote:

How does the primary and secondary work?

Does it use both of them together or does it use only one at a time  

If only one, how does it choose which one to use? 

Good questions! I hope someone can give a more technical answers than me. I've looked for answers to these online several times and they are hard to find. I mean it's confusing. If you search for them, there are a few hour-long podcasts where experts discuss 5G, and the technology behind it. I've got to start listening to more of those. Often they talk too much about mmWave, since it is so fast, but that is in relatively few places, and is so problematic right now I can't see it coming to my rural area within the next five years or more.

I've read that T mobile had a standalone 5G test project a year ago, but it wasn't as fast a speed range as provided by the non-standalone pair many T mobile users get currently in the mid-frequency n41 5G pairing with a 4G signal. Standalone 5G is used some in China, I believe, and they are working to develop it here and believe it will one day be the standard.

Right now, during the transition between 4G and 5G, it's convenient and cost effective to have the equipment on the same tower, and helpful since the signals work in a non-standalone pair for 5G, and can still function as standalone 4G LTE. The 3G has been around for 19 years and they are trying to phase it out now, so 4G is likely to be around for quite a while still.

I've heard the working relationship of the 4G/5G (primary/secondary) non-standalone 5G pair described that the 4G is an on-ramp to initiate the 5G signal. I don't know what that means in technical terms and am not even sure if it's accurate.

Practically, and from my own experience of getting the B2/n41 or B66/n41, the 3X the upload speed I get on the former pair suggests the 4G part of the pairing determines or handles the upload. And this is what was said by an expert in this field in an article from Forbes two years ago. I found that article while searching for answers to the questions you pose.

Basically, band pairs are selected dynamically and seamlessly, since the system is designed to function as you, for example, travel between towers on your phone in a car. Until I got a 4G just this year, I  didn't know that when I'm standing in my yard, in one position, sometimes the signal switches to a tower 10 miles away from the one that's 5 miles away. You can watch this happen in tower mapper software.

But as of yet, there is no band-locking to prevent it from doing this.

The third question, how does it choose band pairs. It's choosing on what's the strongest signal, but there's also some traffic management that goes on during high congestion, in which case you could be shifted to a signal pair that gives you slower speeds. Lastly, there can be priorities given to users on a more expensive phone plan. They more often get the fastest or perhaps more stable signals.

That said, with TMHI, a lot depends on your orientation in relation to various towers near you, how close you are, how directly you are in their transmission fan pattern, what equipment they have, what power the tower is transmitting at, the efficiency of their backhaul setup, and level of obstructions between you and the tower.

Oh, and one more thing. When you get a primary signal only, that means you are on 4G LTE. The 4G is a standalone signal always. Likewise, when getting primary and secondary, you are on 5G, or rather the current state of the 4G/5G non standalone 5G.