3G Vs 2G power consumption

Most people are aware of the increased power consumption requirements of 3G Vs 2G. In fact quite a lot of people "lock" their phones on 2G as a way of increasing battery life. For this post, I wanted to quantify the difference between the two but in a more novel way than the usual comparison charts. So I thought it would be a good idea to measure the current drain of a voice call in 3G then perform a handover to 2G while still measuring the current drain and then compare the two. So using Nokia's energy profiler and the right radio conditions the chart above was produced (x axis is seconds and y axis is current in mA)..

The various phases are:

1. UE is in idle mode on 3G, current drain is approx. 50mA

2. CS call is set up on 3G, current drain increases to approx. 220mA

3. Screen dims, current drain falls to 200mA

4. Radio conditions start to deteriorate. UE is instructed to power up while at the same time compressed mode is activated which requires higher transmit power due to the spreading factor reduction

5. UE performs a handover to 2G and current drain reduces to 80mA. Finally the call is terminated right at the end of the graph

Although battery life has improved through the years, it is some inherent differences between 2G and 3G that account for the increased current drain. The main one being that in 3G the UE is required to transmit/receive the DPCCH continuously while in 2G the UE is only required to transmit/receive one timeslot out of 8 (GSM TDMA frame structure) and shut down its transmitter/receiver in between. The differences in modulation scheme (GMSK Vs QPSK) also lead to a more efficient power amplifier in 2G. 

So what about LTE? Even though it is early days for voice calls over LTE, the actual implementation allows for DRX/DTX in connected mode so it is possible that current consumption actually improves over 3G. Lets see..