That heavily depends on your application.

What is the goal of your application?

Do you process audio and/or video?

What kind of processing shall be done (recording, motion detection, tracking, localization,....)?

What kind of wireless connection do you plan to use? There are plenty of surveys concerning the energy demand of wireless links but it depends on the technology you use (bluetooth, wifi, zigbee,...)

Hello Bernhard,

First of all thanks for you interest in it

i am processing on video.

record video using camera, little processing like comparison of current frame with previous frame so i need little bit memory on board for store the 10 -20 frames of video and process on it. if any event detect then network manager send that stream video.

I want to use wifi or zigbee any one of them is relevant for my application.   

Dear Berhard

You have to  evaluate the nodes as a hole package, because it is not common to get a configurable sensor boars where you can choose microcontroler, memory and devices as separates options.

For example a classical WSN node like the TelosB sensor model has a surprising 10kBytes of RAM depending on your frame size could be difficult to fit them on that ammount of RAM, and remmenber that you have to share that space with your programs.

You also need to do some Math to get what could be a suitable node for yours requirement. Using the frame size, the number of fps and what you what to transmit to the network. In the Math  you could fill a network frame and add the frame overhead to th enetwork speed to get some aproximation, or at least an upper bound of the real speed that you could possible get.

It is possible that a Zigbee comunicaton option could be a little slow for the video . It has a speed of 250kbps. And this is the theoretical max speed, if you got collisions or because of the overhead of the use of a MAC algorithm you could not reach in the real life this max speed. Maybe a node with WiFi interface card could be a better option.

Ricardo Gonzalez