For this method, we're going to use the LTEview app (by @ProAsm) to switch from Rains default band B3 to B38.
You require these in order for the band switch to work.
1. A compatible Huawei router (Supports TDD B38 or B41 2500/2600Mhz).
Huawei routers that will work (Not all are listed)...
With a compatible router, external antennas, and a tower that broadcasts the B38 band, you can get the "Up to 10Mbps" speeds.
Rain operates on B3 and B38.
B3 is the default and is always congested, which is why most users get terrible speeds.
B38 is less congested, however does not...
If you have the compatible hardware, try switching bands for better 4g speeds. If there's a tower that's broadcasting B38 within line of sight then you may be lucky. My B3 tower is 230m away but congested. B38 tower is 3.4km away, getting just over 10Mbps.
Forced it to B38 2500.
Tested with internal antennas only and DL speed was 1Mbps.
I used the standard antennas (comes with the router) and got 7Mbps.
Then I used the external/outdoor antenna (Poynting Xpol6) and got 14Mbps.
Its not the greatest speeds but it is an improvement.