power required of broadcast transmission

Hi all,

I want to know the power required by node i to broadcast its data to 2 nodes is it the sum of power ofrequired for each node separetly ??

No. If the antenna is omnidirectional, then ideally the power per unit area at a given distance in any direction is the same.

David83 said:

No. If the antenna is omnidirectional, then ideally the power per unit area at a given distance in any direction is the same.

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thanks for the response,

the nodes are distante from the source by d1 and d2 .Since the power is function of the distance how the power is the same ??

What David83 is saying is an omnidirectional source produces a spherical radiation pattern. The strength decreases as the distance increases but the signal is there at all locations at all times. How much of it you receive is a proportional to the distance the to receiver location but one receiver does not influence what another picks up.

Brian.

What David83 is saying is an omnidirectional source produces a spherical radiation pattern. The strength decreases as the distance increases but the signal is there at all locations at all times. How much of it you receive is a proportional to the distance the to receiver location but one receiver does not influence what another picks up..

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If the emission pattern is spherically symmetric, the signal strength decreases as the inverse square of the distance. In other words, the signal strength (W/m2) will be 1/4 at twice the distance.

If the emission is confined to a circular plane, the signal strength decreases as the inverse of the distance: the signal will be half as weak at twice the distance.

If the emission is confined to a parallel beam (pencil), the signal strength is independent of the distance.

Of course these are idealizations and are far from reality. You will mostly find that the signal always decreases as the inverse square of the distance (even if the beam has been focussed, it still has some divergence). That is where the directional pattern of the particular antenna comes in the picture.

hmayna said:

thanks for the response,

the nodes are distante from the source by d1 and d2 .Since the power is function of the distance how the power is the same ??

Click to expand...

I said (ideally) the power at any given distance in any direction is the same. What power a node receives doesn't affect the power the other node receives. A node receives a power that's proportional to its distance from the transmitter. It doesn't matter how many nodes there are as receivers.

David83 said:

I said (ideally) the power at any given distance in any direction is the same. What power a node receives doesn't affect the power the other node receives. A node receives a power that's proportional to its distance from the transmitter. It doesn't matter how many nodes there are as receivers.

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But I talk about the transmit power of node i to node j which is proportional to the distance of transmission. In the equation (1) of this paper https://people.rennes.inria.fr/Olivier.Sentieys/publications/2007/NBS07.pdf is the transmit power of the source to a destination D which distant d ,when we have a destination D1 distant d1 from the source, the transmit power is simply we remplace d by d1 .But when the source broadcast to D and D1 what is the transmit power ??