Dear Laouid,

If it help, look here:

http://research.ijcaonline.org/volume113/number19/pxc3902104.pdf

And if energy issue related to WSN is you R&D you may want to read also this:

http://www.sciencedirect.com/science/article/pii/S0168169908001257

Good Luck into your Research

Dear Laouid,

If it help, you may look here:

http://research.ijcaonline.org/volume113/number19/pxc3902104.pdf

And if WSNs energy harvesting is an important topic for you, you may look here also:

http://www.sciencedirect.com/science/article/pii/S0168169908001257

Good luck in your Research.

Signal Strength Measurement

Signal strength mesurement is more real

In order to measure energy (E), then: E=IVt. Sensor nodes have regulator, therefore V is fixed. Hence, you measure the current over time.