Digi is activating its 900MHz spectrum for 4G use in July, and has published a video explaining why this matters for its customers. The idea is that the lower frequency allows for better indoor coverage, which is generally how radiowaves work.
The video itself does a good idea of explaining the difference between the 900MHz spectrum and the existing 1800MHz and 2600MHz spectrums. Benefits include things like less signal degradation when penetrating solid objects and a longer transmission range.
However, it doesn’t point out that the lower frequency also results in slower connections. Although, this will likely still be comparable with the higher frequency connections and is far more stable. Digi is also mixing the frequencies, so customers on a whole will be seeing improvements to their connections while inside buildings.