  Going from theory to practice in fog networking raises the question of the
optimum number of fog nodes that will be upgraded from the existing nodes. This
paper finds the optimum number of fog nodes for a given total number of
ordinary nodes residing in the area of interest for different channel
conditions. Determining the optimum number of fog nodes is quite beneficial,
because it can strongly affect the SINR, and thus the average data rate and
transmission delay. The numerical results indicate that the average data rate
increases nearly an order of magnitude for an optimized number of fog nodes in
case of shadowing and fading. It is further shown that the optimum number of
fog nodes does not increase in direct proportion to the increase in the total
number of nodes. Furthermore, the optimum number of fog nodes decreases when
channels have high path loss exponents. These findings suggest that the fog
nodes must be selected among those that have the highest computation capability
for densely deployed networks and high path loss exponents channels.
