What type of techniques can be applied in wireless transmission to reduce OPEX ?

There are many approaches like :

- Power amplifier improvement  / Techniques : CFR and DPD

- Time domain energy-efficient / Techniques : Unicast , DTX

- Cell switch on/off / Techniques : Increase ON cell radius

- Energy-efficient architectures / Techniques : Cell Zooming

- Transmission scheme /  Techniques : Reduce the number of antennae