multiple tvs

“I have 3 tvs, 2 are not smart tvs.”

You can use one internet gateway with multiple connected/streaming devices. The T-Mobile GW does have restrictions for 64 devices but the Nokia defaults to 128 so I don't know how much T-Mobile polices the number of devices per gateway. You can't have 256 devices on the subnet as you can't use the upper and lower addresses of the range and you cant use the IP of the gateway. I have in the neighborhood of two dozen devices of various types and have never seen any major bandwidth issues. The number of simultaneous devices using the gateway will depend upon the data feed to each and the bandwidth available via the cellular connection. Knowing the speeds the gateway can deliver on the cellular connection helps to get a better understanding of what will and will not work well. Here we commonly see 120-150 Mbs on an n71 frequency for the download so having the Xbox, 2-3 iPads and a computer or two with streaming usually works just fine with no apparent issues. Each user situation is a little different as clean, strong signals with low noise perform much better than if there is noise. 

You can use speedtest.net and fast.com to start with and run some speed tests to see how the feed performs at different times of the day/night. If you understand the cellular metrics you can record those and use a reference table to determine the signal strength, signal quality, and signal to noise ratio. A clean strong signal will provide better performance and typically faster speeds. 

If you are streaming HD and 4K sure you need more bandwidth capability. If you see the TV stream stutter and stall you can take a speed test with a client to see how the delivery is at that time. If you are seeing buffering it is quite likely the speed has dropped down to 25-30 Mbs and the demand is more than the feed can properly do at the time. 

One way to get around lower bandwidth with streaming is to download a movie or series when the bandwidth is stronger/faster and then watch them offline in effect. Later in the evening or night is usually a better time to have more bandwidth. 

If you get the cellular metrics from the mobile application or the web interface of the gateway you can use the table below to better understand the signal and how good it is. If that is too much just post your metric values for the RSRP, RSRQ and SINR reporting and the community can help translate and set expectations. If the values are in the Good to Excellent range across the board you should be in pretty good shape.

IF you dont see the metrics or dont know how to get to them again users are here that can provide info on that. If you are seeing 4-5 bars on the gateway you have for the signal then you are probably in a pretty good place for a solid signal. Speed testing helps to confirm the expectations.