The dirty secret of 'half power' mobile phones

December 24, 2014 //By Jeremy Hendy, Nujira
It is one of the mobile industry's dirty secrets, but nearly all of today's 4G handsets do not transmit at full power. Instead, 4G handset manufacturers have been producing "half-power handsets," due partly to limitations of RF front-end components, but more often because of the mistaken belief that reducing transmit power is the best way to maximise battery life.

For end users, battery life is still one of the key metrics when selecting a handset. This is why, as more is asked of the battery in mobile handsets, manufacturers have been so keen to pursue any strategy that reduces current consumption. As a result, handset manufacturers have looked to minimise the peak handset transmit power wherever possible.

Ironically the fact is that, in the data-centric 4G world, far from extending battery life, backing off handset transmit power as far as possible is actually increasing the drain on batteries. Not only that, but "half power handsets" also significantly reduce network coverage and data rates for all users.

A new approach is needed to overcome these significant performance limitations and consign half-power handsets to history. It may seem counter-intuitive, but the best way to extend handset battery life is deceptively simple - turn the transmit power up to eleven.

Low power transmit problems in 4G

In the voice-centric 2G and 3G era, the strategy of backing off transmit power made good sense and fitted neatly with network bandwidth allocation strategies. Network bandwidth allocation in those networks tended to focus on two key metrics: number of simultaneous users, and latency for voice calls.

Figure 1: A handset power consumption comparison between 2G, 3G and 4G transmissions.

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