The transmitter would be the one which would be using the max power in any cellphone.
In that case, make the antenna directional.
But then, we do *not* know the direction to which I have to sent the signal.
That can be done by maybe -
1. Changes needed for Towers
Sent downstream a small pilot signal of the same freq as the upstream signal which the phone emits for that call.
2. Changes needed in the Cell
Have a direction sensor in your mobile for this pilot signal. Once direction the highest amp for the pilot signal is obtained, sent the signal back in the same direction.
Instead of the wasted signal going all around, we have a signal which has very good directional properties. Thus the power of the signal to be sent can be reduced to maybe even 1/10th or 1/100th.
Thus the battery life also will have a propotional increase.
Adv of this system -
1.We dont care how many changes in direction the signal took and all.. Since the pilot came this way, my signal (almost the same freq, so almost the same refractive/reflective properties)will reach the tower proper.
2. Worries about your head getting fried by signal now over. Supposing that your head occupies 90 degrees of the phone directionality, now there is 1/4th time the power goes through you. In anycase, I dont think there is a high probability of the max amp pilot signal coming through your head.. So much less say1/10th of the time upstream signal goes through you.
Changes needed in all towers.
Is a antenna which can change direction depending on a signal already there ? If not the idea wont work at all.
Just an idea.