@dryash u r getting low speeds due to 2.4g band.
The router u using it supports 2.4g band.
The 2.4g band is provides good range but speeds are low.
I UPGRADED my Airtel connection to FTTH last month.I faced same problem.
Then I bought TP-Link RE305 AC1200 Dual-Band Wi-Fi Range Extender
Now I m...