Battary

LCD

LCD is a big consumer.
PTT Application must operate on LCD off.

Network

Transferring Data Without Draining the Battery

- Optimizing Downloads for Efficient Network Access
- Minimizing the Effect of Regular Updates
- Redundant Downloads are Redundant
- Modifying your Download Patterns Based on the Connectivity Type

Ref. https://developer.android.com/training/efficient-downloads/index.html

Keep Alive

In PTT, Keep-alive packets effect battary. So client and server need to consider that.

Audio device

PTT client need to open audio device on necessory. In case of VOX, it drain battary more.

Bluetooth

GPS

GPS has a very very slow communication channel. So bettary is also used for it.
Ref. Why does GPS use so much more battery than any other antenna or sensor in a smartphone?

Refferences

- Apple - Maximizing Battery Life and Lifespan
- iPhone5 : http://www.ilounge.com/index.php/reviews/entry/apple-iphone-5-16gb-32gb-64gb/P7