Wi-Fi tower's range

Ah so you are referring to the cellular signals. If you are, as I suspect, referring to the bars on the LED screen then one bar is really poor. You need to take the gateway on a walkabout and see where it gets a better cellular signal. If it is one of the newer ones get a long extension cord and carry it about the house  to see if you can find a location where there are more bars reported. If your home has stucco exterior keep in mind there is wire mesh under the cement so you might live in a shielded box. Windows with specific coatings can also knock down the cellular frequencies. Metal screens, metal roofs etc… there are dense materials that knock cellular signals down or reflect them. Take the gateway to the four sides of the house near windows and experiment a bit to find a better location.

If you cannot find improvement with the gateway it might be that an external antenna would be the only real solution to make significant improvement. External antennas can be aded but it takes a bit of technical expertise and lots of patience and extreme care as the connectors the antenna leads connect to are very delicate and small thus easy to break. It is NOT supported by T-Mobile but is possible. Some people do this and companies like Waveform.com provide some excellent solutions and assistance.

You can use your phone and the TMO home internet mobile application to see and record the cellular metrics. If you post the metrics to the community it can help as others can also respond and help you understand those if you do not. Most people don’t so it takes a bit of translation with a chart. Those can be found on the internet with a search for “cellular metrics”. The RSRP, RSRQ, and SINR acronyms can all be made clear with a search on the web. If you have questions, and you probably will, just post them to the community and I know you can get more answers.