how is located the main traffic spot compared to your site ? (which timing advance, which dl and ul rxlev ?)
according to what you’re explaining, it seems your subscribers do not receive a good coverage (DL RXLEV < -90dBm) In this situation, you can either re-positionate your antenna (so they are aligned with the area they are meant to cover), change your antenna (more gain, more directivity). Are you using Rx-diversity ? You cannot increase coverage by tweaking parameters though, all solutions needs to be more "physical". You can try "synthetized frequency hopping" or "radio hopping", maybe you'll get benefit from "frequency diversity". It can add up to 3dB to your UL and DL, by lessen the fast fading attenuation.